From 37a3884ee29823252d84c5abf1fa22f4e0f25508 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Sat, 5 Jun 2021 15:22:56 -0400
Subject: [PATCH 01/22] Initial commit of multicursor. Next step is to
 investigate how multicursor works on various other IDEs and ape those.

---
 data/core/commands/doc.lua | 245 +++++++++++++++++++++----------------
 data/core/doc/init.lua     | 124 +++++++++++++------
 data/core/docview.lua      |  69 +++++++----
 3 files changed, 270 insertions(+), 168 deletions(-)

diff --git a/data/core/commands/doc.lua b/data/core/commands/doc.lua
index c8c27509..ae67d5e1 100644
--- a/data/core/commands/doc.lua
+++ b/data/core/commands/doc.lua
@@ -24,13 +24,19 @@ local function get_indent_string()
 end
 
 
-local function doc_multiline_selection(sort)
-  local line1, col1, line2, col2, swap = doc():get_selection(sort)
-  if line2 > line1 and col2 == 1 then
-    line2 = line2 - 1
-    col2 = #doc().lines[line2]
+local function doc_multiline_selections(sort)
+  local iter = doc():get_selections(sort)
+  return function() 
+    local idx, line1, col1, line2, col2 = iter()
+    if not idx then
+      return
+    end
+    if line2 > line1 and col2 == 1 then
+      line2 = line2 - 1
+      col2 = #doc().lines[line2]
+    end
+    return idx, line1, col1, line2, col2
   end
-  return line1, col1, line2, col2, swap
 end
 
 local function append_line_if_last_line(line)
@@ -76,46 +82,51 @@ local commands = {
   end,
 
   ["doc:newline"] = function()
-    local line, col = doc():get_selection()
-    local indent = doc().lines[line]:match("^[\t ]*")
-    if col <= #indent then
-      indent = indent:sub(#indent + 2 - col)
+    for idx, line, col in doc():get_selections() do
+      local indent = doc().lines[line]:match("^[\t ]*")
+      if col <= #indent then
+        indent = indent:sub(#indent + 2 - col)
+      end
+      doc():text_input("\n" .. indent, idx)
     end
-    doc():text_input("\n" .. indent)
   end,
 
   ["doc:newline-below"] = function()
-    local line = doc():get_selection()
-    local indent = doc().lines[line]:match("^[\t ]*")
-    doc():insert(line, math.huge, "\n" .. indent)
-    doc():set_selection(line + 1, math.huge)
+    for idx, line in doc():get_selections() do
+      local indent = doc().lines[line]:match("^[\t ]*")
+      doc():insert(line, math.huge, "\n" .. indent)
+      doc():set_selections(idx, line + 1, math.huge)
+    end
   end,
 
   ["doc:newline-above"] = function()
-    local line = doc():get_selection()
-    local indent = doc().lines[line]:match("^[\t ]*")
-    doc():insert(line, 1, indent .. "\n")
-    doc():set_selection(line, math.huge)
+    for idx, line in doc():get_selections() do
+      local indent = doc().lines[line]:match("^[\t ]*")
+      doc():insert(line, 1, indent .. "\n")
+      doc():set_selections(idx, line, math.huge)
+    end
   end,
 
   ["doc:delete"] = function()
-    local line, col = doc():get_selection()
-    if not doc():has_selection() and doc().lines[line]:find("^%s*$", col) then
-      doc():remove(line, col, line, math.huge)
+    for idx, line, col in doc():get_selections() do
+      if not doc():has_selection(idx) and doc().lines[line]:find("^%s*$", col) then
+        doc():remove(line, col, line, math.huge)
+      end
+      doc():delete_to(idx, translate.next_char)
     end
-    doc():delete_to(translate.next_char)
   end,
 
   ["doc:backspace"] = function()
-    local line, col = doc():get_selection()
-    if not doc():has_selection() then
-      local text = doc():get_text(line, 1, line, col)
-      if #text >= config.indent_size and text:find("^ *$") then
-        doc():delete_to(0, -config.indent_size)
-        return
+    for idx, line, col in doc():get_selections() do
+      if not doc():has_selection(idx) then
+        local text = doc():get_text(line, 1, line, col)
+        if #text >= config.indent_size and text:find("^ *$") then
+          doc():delete_to(idx, 0, -config.indent_size)
+          return
+        end
       end
+      doc():delete_to(idx, translate.previous_char)
     end
-    doc():delete_to(translate.previous_char)
   end,
 
   ["doc:select-all"] = function()
@@ -128,75 +139,92 @@ local commands = {
   end,
 
   ["doc:select-lines"] = function()
-    local line1, _, line2, _, swap = doc():get_selection(true)
-    append_line_if_last_line(line2)
-    doc():set_selection(line1, 1, line2 + 1, 1, swap)
+    for idx, line1, _, line2 in doc():get_selections(true) do
+      append_line_if_last_line(line2)
+      doc():set_selections(idx, line1, 1, line2 + 1, 1, swap)
+    end
   end,
 
   ["doc:select-word"] = function()
-    local line1, col1 = doc():get_selection(true)
-    local line1, col1 = translate.start_of_word(doc(), line1, col1)
-    local line2, col2 = translate.end_of_word(doc(), line1, col1)
-    doc():set_selection(line2, col2, line1, col1)
+    for idx, line1, col1 in doc():get_selections(true) do
+      local line1, col1 = translate.start_of_word(doc(), line1, col1)
+      local line2, col2 = translate.end_of_word(doc(), line1, col1)
+      doc():set_selections(idx, line2, col2, line1, col1)
+    end
   end,
 
   ["doc:join-lines"] = function()
-    local line1, _, line2 = doc():get_selection(true)
-    if line1 == line2 then line2 = line2 + 1 end
-    local text = doc():get_text(line1, 1, line2, math.huge)
-    text = text:gsub("(.-)\n[\t ]*", function(x)
-      return x:find("^%s*$") and x or x .. " "
-    end)
-    doc():insert(line1, 1, text)
-    doc():remove(line1, #text + 1, line2, math.huge)
-    if doc():has_selection() then
-      doc():set_selection(line1, math.huge)
+    for idx, line1, _, line2 in doc():get_selections(true) do
+      if line1 == line2 then line2 = line2 + 1 end
+      local text = doc():get_text(line1, 1, line2, math.huge)
+      text = text:gsub("(.-)\n[\t ]*", function(x)
+        return x:find("^%s*$") and x or x .. " "
+      end)
+      doc():insert(line1, 1, text)
+      doc():remove(line1, #text + 1, line2, math.huge)
+      if doc():has_selection(idx) then
+        doc():set_selections(idx, line1, math.huge)
+      end
     end
   end,
 
   ["doc:indent"] = function()
-    doc():indent_text(false, doc_multiline_selection(true))
+    for idx, line1, col1, line2, col2 in doc_multiline_selections(true) do
+      local l1, c1, l2, c2 = doc():indent_text(false, line1, col1, line2, col2)
+      if not l1 then
+        doc():set_selections(idx, l1, c1, l2, c2)
+      end
+    end
   end,
 
   ["doc:unindent"] = function()
-    doc():indent_text(true, doc_multiline_selection(true))
+    for idx, line1, col1, line2, col2 in doc_multiline_selections(true) do
+      local l1, c1, l2, c2 = doc():indent_text(true, line1, col1, line2, col2)
+      if not l1 then
+        doc():set_selections(idx, l1, c1, l2, c2)
+      end
+    end
   end,
 
   ["doc:duplicate-lines"] = function()
-    local line1, col1, line2, col2, swap = doc_multiline_selection(true)
-    append_line_if_last_line(line2)
-    local text = doc():get_text(line1, 1, line2 + 1, 1)
-    doc():insert(line2 + 1, 1, text)
-    local n = line2 - line1 + 1
-    doc():set_selection(line1 + n, col1, line2 + n, col2, swap)
+    for idx, line1, col1, line2, col2 in doc_multiline_selections(true) do
+      append_line_if_last_line(line2)
+      local text = doc():get_text(line1, 1, line2 + 1, 1)
+      doc():insert(line2 + 1, 1, text)
+      local n = line2 - line1 + 1
+      doc():set_selections(idx, line1 + n, col1, line2 + n, col2, swap)
+    end
   end,
 
   ["doc:delete-lines"] = function()
-    local line1, col1, line2 = doc_multiline_selection(true)
-    append_line_if_last_line(line2)
-    doc():remove(line1, 1, line2 + 1, 1)
-    doc():set_selection(line1, col1)
+    for idx, line1, col1, line2, col2 in doc_multiline_selections(true) do
+      append_line_if_last_line(line2)
+      doc():remove(line1, 1, line2 + 1, 1)
+      doc():set_selections(idx, line1, col1)
+    end
   end,
 
   ["doc:move-lines-up"] = function()
-    local line1, col1, line2, col2, swap = doc_multiline_selection(true)
-    append_line_if_last_line(line2)
-    if line1 > 1 then
-      local text = doc().lines[line1 - 1]
-      doc():insert(line2 + 1, 1, text)
-      doc():remove(line1 - 1, 1, line1, 1)
-      doc():set_selection(line1 - 1, col1, line2 - 1, col2, swap)
+    for idx, line1, col1, line2, col2 in doc_multiline_selections(true) do
+      append_line_if_last_line(line2)
+      if line1 > 1 then
+        local text = doc().lines[line1 - 1]
+        doc():insert(line2 + 1, 1, text)
+        doc():remove(line1 - 1, 1, line1, 1)
+        doc():set_selections(idx, line1 - 1, col1, line2 - 1, col2)
+      end
     end
   end,
 
   ["doc:move-lines-down"] = function()
-    local line1, col1, line2, col2, swap = doc_multiline_selection(true)
-    append_line_if_last_line(line2 + 1)
-    if line2 < #doc().lines then
-      local text = doc().lines[line2 + 1]
-      doc():remove(line2 + 1, 1, line2 + 2, 1)
-      doc():insert(line1, 1, text)
-      doc():set_selection(line1 + 1, col1, line2 + 1, col2, swap)
+    for idx, line1, col1, line2, col2 in doc_multiline_selections(true) do
+      append_line_if_last_line(line2 + 1)
+      if line2 < #doc().lines then
+        local text = doc().lines[line2 + 1]
+        doc():remove(line2 + 1, 1, line2 + 2, 1)
+        doc():insert(line1, 1, text)
+        doc():set_selections(idx, line1 + 1, col1, line2 + 1, col2)
+      end
     end
   end,
 
@@ -205,28 +233,29 @@ local commands = {
     if not comment then return end
     local indentation = get_indent_string()
     local comment_text = comment .. " "
-    local line1, _, line2 = doc_multiline_selection(true)
-    local uncomment = true
-    local start_offset = math.huge
-    for line = line1, line2 do
-      local text = doc().lines[line]
-      local s = text:find("%S")
-      local cs, ce = text:find(comment_text, s, true)
-      if s and cs ~= s then
-        uncomment = false
-        start_offset = math.min(start_offset, s)
-      end
-    end
-    for line = line1, line2 do
-      local text = doc().lines[line]
-      local s = text:find("%S")
-      if uncomment then
+    for idx, line1, _, line2 in doc_multiline_selections(true) do
+      local uncomment = true
+      local start_offset = math.huge
+      for line = line1, line2 do
+        local text = doc().lines[line]
+        local s = text:find("%S")
         local cs, ce = text:find(comment_text, s, true)
-        if ce then
-          doc():remove(line, cs, line, ce + 1)
+        if s and cs ~= s then
+          uncomment = false
+          start_offset = math.min(start_offset, s)
+        end
+      end
+      for line = line1, line2 do
+        local text = doc().lines[line]
+        local s = text:find("%S")
+        if uncomment then
+          local cs, ce = text:find(comment_text, s, true)
+          if ce then
+            doc():remove(line, cs, line, ce + 1)
+          end
+        elseif s then
+          doc():insert(line, start_offset, comment_text)
         end
-      elseif s then
-        doc():insert(line, start_offset, comment_text)
       end
     end
   end,
@@ -350,26 +379,30 @@ local translations = {
 }
 
 for name, fn in pairs(translations) do
-  commands["doc:move-to-" .. name] = function() doc():move_to(fn, dv()) end
-  commands["doc:select-to-" .. name] = function() doc():select_to(fn, dv()) end
-  commands["doc:delete-to-" .. name] = function() doc():delete_to(fn, dv()) end
+  commands["doc:move-to-" .. name] = function() doc():move_to(nil, fn, dv()) end
+  commands["doc:select-to-" .. name] = function() doc():select_to(nil, fn, dv()) end
+  commands["doc:delete-to-" .. name] = function() doc():delete_to(nil, fn, dv()) end
 end
 
 commands["doc:move-to-previous-char"] = function()
-  if doc():has_selection() then
-    local line, col = doc():get_selection(true)
-    doc():set_selection(line, col)
-  else
-    doc():move_to(translate.previous_char)
+  for idx, line, col in doc():get_selections(true) do
+    if doc():has_selection(idx) then
+      doc():set_selections(idx, line, col)
+    end
+  end
+  if not doc():has_selection() then
+    doc():move_to(nil, translate.previous_char)
   end
 end
 
 commands["doc:move-to-next-char"] = function()
-  if doc():has_selection() then
-    local _, _, line, col = doc():get_selection(true)
-    doc():set_selection(line, col)
-  else
-    doc():move_to(translate.next_char)
+  for idx, _, _, line, col in doc():get_selections(true) do
+    if doc():has_selection(idx) then
+      doc():set_selections(idx, line, col)
+    end
+  end
+  if not doc():has_selection() then
+    doc():move_to(nil, translate.next_char)
   end
 end
 
diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index 88f63a68..63a4225b 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -46,7 +46,7 @@ end
 
 function Doc:reset()
   self.lines = { "\n" }
-  self.selection = { a = { line=1, col=1 }, b = { line=1, col=1 } }
+  self.selections = { 1, 1, 1, 1 }
   self.undo_stack = { idx = 1 }
   self.redo_stack = { idx = 1 }
   self.clean_change_id = 1
@@ -131,9 +131,20 @@ function Doc:set_selection(line1, col1, line2, col2, swap)
   assert(not line2 == not col2, "expected 2 or 4 arguments")
   if swap then line1, col1, line2, col2 = line2, col2, line1, col1 end
   line1, col1 = self:sanitize_position(line1, col1)
+  line2, col2 = self:sanitize_position(line2 or line1, col2 or col1) 
+  self.selections = { line1, col1, line2, col2 }
+end
+
+function Doc:set_selections(idx, line1, col1, line2, col2, swap)
+  assert(not line2 == not col2, "expected 3 or 5 arguments")
+  if swap then line1, col1, line2, col2 = line2, col2, line1, col1 end
+  line1, col1 = self:sanitize_position(line1, col1)
   line2, col2 = self:sanitize_position(line2 or line1, col2 or col1)
-  self.selection.a.line, self.selection.a.col = line1, col1
-  self.selection.b.line, self.selection.b.col = line2, col2
+  local target = (idx - 1)*4 + 1
+  self.selections[target] = line1
+  self.selections[target+1] = col1
+  self.selections[target+2] = line2
+  self.selections[target+3] = col2
 end
 
 
@@ -147,22 +158,53 @@ end
 
 
 function Doc:get_selection(sort)
-  local a, b = self.selection.a, self.selection.b
   if sort then
-    return sort_positions(a.line, a.col, b.line, b.col)
+    return sort_positions(self.selections[1], self.selections[2], self.selections[3], self.selections[4])
+  end
+  return self.selections[1], self.selections[2], self.selections[3], self.selections[4]
+end
+
+function Doc:get_selection_count()
+  return #self.selections / 4
+end
+
+function Doc:get_selections(sort)
+  local idx = 1
+  return function()
+    if idx >= #self.selections then
+      return
+    end
+    idx = idx + 4
+    if sort then
+      return ((idx - 5) / 4) + 1, sort_positions(self.selections[idx - 4], self.selections[idx - 3], self.selections[idx - 2], self.selections[idx - 1])
+    else
+      return ((idx - 5) / 4) + 1, self.selections[idx - 4], self.selections[idx - 3], self.selections[idx - 2], self.selections[idx - 1]
+    end
   end
-  return a.line, a.col, b.line, b.col
 end
 
 
-function Doc:has_selection()
-  local a, b = self.selection.a, self.selection.b
-  return not (a.line == b.line and a.col == b.col)
+function Doc:has_selection(idx)
+  if idx then
+    local target = (idx-1)*4+1
+    return 
+      self.selections[target] ~= self.selections[target+2] or
+      self.selections[target+1] ~= self.selections[target+3]
+  end
+  for target = 1, #self.selections, 4 do
+    if self.selections[target] ~= self.selections[target+2] or
+      self.selections[target+1] ~= self.selections[target+3] then
+      return true
+    end
+  end
+  return false
 end
 
 
 function Doc:sanitize_selection()
-  self:set_selection(self:get_selection())
+  for idx, line1, col1, line2, col2 in self:get_selections() do
+    self:set_selections(idx, line1, col1, line2, col2)
+  end
 end
 
 
@@ -348,13 +390,16 @@ function Doc:redo()
 end
 
 
-function Doc:text_input(text)
-  if self:has_selection() then
-    self:delete_to()
+function Doc:text_input(text, idx)
+  for sidx, line, col in self:get_selections() do
+    if not idx or idx == sidx then
+      if self:has_selection(sidx) then
+        self:delete_to(sidx)
+      end
+      self:insert(line, col, text)
+      self:move_to(sidx, #text)
+    end
   end
-  local line, col = self:get_selection()
-  self:insert(line, col, text)
-  self:move_to(#text)
 end
 
 
@@ -380,29 +425,38 @@ function Doc:replace(fn)
 end
 
 
-function Doc:delete_to(...)
-  local line, col = self:get_selection(true)
-  if self:has_selection() then
-    self:remove(self:get_selection())
-  else
-    local line2, col2 = self:position_offset(line, col, ...)
-    self:remove(line, col, line2, col2)
-    line, col = sort_positions(line, col, line2, col2)
+function Doc:delete_to(idx, ...)
+  for sidx, line1, col1, line2, col2 in self:get_selections(true) do
+    if not idx or sidx == idx then
+      if self:has_selection(sidx) then
+        self:remove(line1, col1, line2, col2)
+      else
+        local l2, c2 = self:position_offset(line, col, ...)
+        self:remove(line1, col1, l2, c2)
+        line1, col1 = sort_positions(line1, col1, l2, c2)
+      end
+      self:set_selections(sidx, line1, col1)
+    end
   end
-  self:set_selection(line, col)
 end
 
 
-function Doc:move_to(...)
-  local line, col = self:get_selection()
-  self:set_selection(self:position_offset(line, col, ...))
+function Doc:move_to(idx, ...)
+  for sidx, line, col in self:get_selections() do
+    if not idx or sidx == idx then
+      self:set_selections(sidx, self:position_offset(line, col, ...))
+    end
+  end
 end
 
 
-function Doc:select_to(...)
-  local line, col, line2, col2 = self:get_selection()
-  line, col = self:position_offset(line, col, ...)
-  self:set_selection(line, col, line2, col2)
+function Doc:select_to(idx, ...)
+  for sidx, line, col, line2, col2 in self:get_selections() do
+    if not idx or idx == sidx then
+      line, col = self:position_offset(line, col, ...)
+      self:set_selections(sidx, line, col, line2, col2)
+    end
+  end
 end
 
 
@@ -439,7 +493,7 @@ end
 --   inserts the appropriate whitespace, as if you typed them normally.
 -- * if you are unindenting, the cursor will jump to the start of the line,
 --   and remove the appropriate amount of spaces (or a tab).
-function Doc:indent_text(unindent, line1, col1, line2, col2, swap)
+function Doc:indent_text(unindent, line1, col1, line2, col2)
   local text = get_indent_string()
   local _, se = self.lines[line1]:find("^[ \t]+")
   local in_beginning_whitespace = col1 == 1 or (se and col1 <= se + 1)
@@ -455,9 +509,9 @@ function Doc:indent_text(unindent, line1, col1, line2, col2, swap)
     l1d, l2d = #self.lines[line1] - l1d, #self.lines[line2] - l2d
     if (unindent or in_beginning_whitespace) and not self:has_selection() then
       local start_cursor = (se and se + 1 or 1) + l1d or #(self.lines[line1])
-      self:set_selection(line1, start_cursor, line2, start_cursor, swap)
+      return line1, start_cursor, line2, start_cursor
     else
-      self:set_selection(line1, col1 + l1d, line2, col2 + l2d, swap)
+      return line1, col1 + l1d, line2, col2 + l2d
     end
   else
     self:text_input(text)
diff --git a/data/core/docview.lua b/data/core/docview.lua
index 070ee0c4..edde4c55 100644
--- a/data/core/docview.lua
+++ b/data/core/docview.lua
@@ -276,7 +276,18 @@ function DocView:on_mouse_moved(x, y, ...)
     local l1, c1 = self:resolve_screen_position(x, y)
     local l2, c2 = table.unpack(self.mouse_selecting)
     local clicks = self.mouse_selecting.clicks
-    self.doc:set_selection(mouse_selection(self.doc, clicks, l1, c1, l2, c2))
+    if keymap.modkeys["ctrl"] then
+      if l1 > l2 then
+        l2 = l1
+      end
+      local idx = 1
+      for i = l1, l2 do
+        idx = idx + 1
+        self.doc:set_selections(idx, i, math.min(c1, #self.doc.lines[i]), i, math.min(c1, #self.doc.lines[i]))
+      end
+    else
+      self.doc:set_selection(mouse_selection(self.doc, clicks, l1, c1, l2, c2))
+    end
   end
 end
 
@@ -340,46 +351,50 @@ end
 
 
 function DocView:draw_line_body(idx, x, y)
-  local line, col = self.doc:get_selection()
-
   -- draw selection if it overlaps this line
-  local line1, col1, line2, col2 = self.doc:get_selection(true)
-  if idx >= line1 and idx <= line2 then
-    local text = self.doc.lines[idx]
-    if line1 ~= idx then col1 = 1 end
-    if line2 ~= idx then col2 = #text + 1 end
-    local x1 = x + self:get_col_x_offset(idx, col1)
-    local x2 = x + self:get_col_x_offset(idx, col2)
-    local lh = self:get_line_height()
-    renderer.draw_rect(x1, y, x2 - x1, lh, style.selection)
+  for lidx, line1, col1, line2, col2 in self.doc:get_selections(true) do 
+    if idx >= line1 and idx <= line2 then
+      local text = self.doc.lines[idx]
+      if line1 ~= idx then col1 = 1 end
+      if line2 ~= idx then col2 = #text + 1 end
+      local x1 = x + self:get_col_x_offset(idx, col1)
+      local x2 = x + self:get_col_x_offset(idx, col2)
+      local lh = self:get_line_height()
+      renderer.draw_rect(x1, y, x2 - x1, lh, style.selection)
+    end
   end
-
-  -- draw line highlight if caret is on this line
-  if config.highlight_current_line and not self.doc:has_selection()
-  and line == idx and core.active_view == self then
-    self:draw_line_highlight(x + self.scroll.x, y)
+  for lidx, line1, col1, line2, col2 in self.doc:get_selections(true) do 
+    -- draw line highlight if caret is on this line
+    if config.highlight_current_line and not self.doc:has_selection(lidx)
+    and line1 == idx and core.active_view == self then
+      self:draw_line_highlight(x + self.scroll.x, y)
+    end
   end
-
+  
   -- draw line's text
   self:draw_line_text(idx, x, y)
 
   -- draw caret if it overlaps this line
   local T = config.blink_period
-  if line == idx and core.active_view == self
-  and (core.blink_timer - core.blink_start) % T < T / 2
-  and system.window_has_focus() then
-    local lh = self:get_line_height()
-    local x1 = x + self:get_col_x_offset(line, col)
-    renderer.draw_rect(x1, y, style.caret_width, lh, style.caret)
+  for _, line, col in self.doc:get_selections() do 
+    if line == idx and core.active_view == self
+    and (core.blink_timer - core.blink_start) % T < T / 2
+    and system.window_has_focus() then
+      local lh = self:get_line_height()
+      local x1 = x + self:get_col_x_offset(line, col)
+      renderer.draw_rect(x1, y, style.caret_width, lh, style.caret)
+    end
   end
 end
 
 
 function DocView:draw_line_gutter(idx, x, y)
   local color = style.line_number
-  local line1, _, line2, _ = self.doc:get_selection(true)
-  if idx >= line1 and idx <= line2 then
-    color = style.line_number2
+  for _, line1, _, line2 in self.doc:get_selections(true) do 
+    if idx >= line1 and idx <= line2 then
+      color = style.line_number2
+      break
+    end
   end
   local yoffset = self:get_line_text_y_offset()
   x = x + style.padding.x

From 93670a314d1c34e4d8f0973b0e159fa976f36e79 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Sat, 5 Jun 2021 15:36:26 -0400
Subject: [PATCH 02/22] Changed iterator behaviour to avoid allocating a
 closure each time.

---
 data/core/doc/init.lua | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index 63a4225b..21ee3f5c 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -169,18 +169,17 @@ function Doc:get_selection_count()
 end
 
 function Doc:get_selections(sort)
-  local idx = 1
-  return function()
-    if idx >= #self.selections then
+  return function(selections, idx)
+    local target = idx*4 + 1
+    if target >= #selections then
       return
     end
-    idx = idx + 4
     if sort then
-      return ((idx - 5) / 4) + 1, sort_positions(self.selections[idx - 4], self.selections[idx - 3], self.selections[idx - 2], self.selections[idx - 1])
+      return idx+1, sort_positions(selections[target], selections[target+1], selections[target+2], selections[target+3])
     else
-      return ((idx - 5) / 4) + 1, self.selections[idx - 4], self.selections[idx - 3], self.selections[idx - 2], self.selections[idx - 1]
+      return idx+1, selections[target], selections[target+1], selections[target+2], selections[target+3]
     end
-  end
+  end, self.selections, 0
 end
 
 

From a7f39017ffd8dae6b94a7100466f9860fef556ba Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Sat, 5 Jun 2021 16:06:21 -0400
Subject: [PATCH 03/22] Fixed undo stack.

---
 data/core/doc/init.lua | 16 ++++++++++------
 data/core/docview.lua  |  5 ++---
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index 21ee3f5c..7dc34c4c 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -159,9 +159,16 @@ end
 
 function Doc:get_selection(sort)
   if sort then
-    return sort_positions(self.selections[1], self.selections[2], self.selections[3], self.selections[4])
+    local result = {}
+    for sidx, line1, col1, line2, col2 in self:get_selections(true) do
+      table.insert(result, line1)
+      table.insert(result, col1)
+      table.insert(result, line2)
+      table.insert(result, col2)            
+    end
+    return result
   end
-  return self.selections[1], self.selections[2], self.selections[3], self.selections[4]
+  return unpack(self.selections)
 end
 
 function Doc:get_selection_count()
@@ -292,14 +299,11 @@ local function pop_undo(self, undo_stack, redo_stack, modified)
   if cmd.type == "insert" then
     local line, col, text = table.unpack(cmd)
     self:raw_insert(line, col, text, redo_stack, cmd.time)
-
   elseif cmd.type == "remove" then
     local line1, col1, line2, col2 = table.unpack(cmd)
     self:raw_remove(line1, col1, line2, col2, redo_stack, cmd.time)
-
   elseif cmd.type == "selection" then
-    self.selection.a.line, self.selection.a.col = cmd[1], cmd[2]
-    self.selection.b.line, self.selection.b.col = cmd[3], cmd[4]
+    self.selections = { unpack(cmd) }
   end
 
   modified = modified or (cmd.type ~= "selection")
diff --git a/data/core/docview.lua b/data/core/docview.lua
index edde4c55..477cee48 100644
--- a/data/core/docview.lua
+++ b/data/core/docview.lua
@@ -278,12 +278,11 @@ function DocView:on_mouse_moved(x, y, ...)
     local clicks = self.mouse_selecting.clicks
     if keymap.modkeys["ctrl"] then
       if l1 > l2 then
-        l2 = l1
+        l1, l2 = l2, l1
       end
       local idx = 1
       for i = l1, l2 do
-        idx = idx + 1
-        self.doc:set_selections(idx, i, math.min(c1, #self.doc.lines[i]), i, math.min(c1, #self.doc.lines[i]))
+        self.doc:set_selections(i - l1 + 1, i, math.min(c1, #self.doc.lines[i]), i, math.min(c1, #self.doc.lines[i]))
       end
     else
       self.doc:set_selection(mouse_selection(self.doc, clicks, l1, c1, l2, c2))

From 08ab6cba05133576abc78cfb02597f6fd104af58 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Sat, 5 Jun 2021 16:37:45 -0400
Subject: [PATCH 04/22] Added in multiple clipboard line buffers.

---
 data/core/commands/doc.lua | 34 +++++++++++++++++++++++++---------
 data/core/doc/init.lua     | 10 +++++++++-
 2 files changed, 34 insertions(+), 10 deletions(-)

diff --git a/data/core/commands/doc.lua b/data/core/commands/doc.lua
index ae67d5e1..edba731e 100644
--- a/data/core/commands/doc.lua
+++ b/data/core/commands/doc.lua
@@ -45,7 +45,6 @@ local function append_line_if_last_line(line)
   end
 end
 
-
 local function save(filename)
   doc():save(filename and core.normalize_to_project_dir(filename))
   local saved_filename = doc().filename
@@ -63,22 +62,39 @@ local commands = {
   end,
 
   ["doc:cut"] = function()
-    if doc():has_selection() then
-      local text = doc():get_text(doc():get_selection())
-      system.set_clipboard(text)
-      doc():delete_to(0)
+    local full_text = ""
+    for idx, line1, col1, line2, col2 in doc():get_selections() do
+      if line1 ~= line2 or col1 ~= col2 then
+        local text = doc():get_text(line1, col1, line2, col2)
+        doc():delete_to(idx, 0)
+        full_text = full_text == "" and text or (full_text .. "\n" .. text)
+        doc():set_cursor_clipboard(idx, text)
+      else
+        doc():set_cursor_clipboard(idx, "")
+      end
     end
+    system.set_clipboard(full_text)
   end,
 
   ["doc:copy"] = function()
-    if doc():has_selection() then
-      local text = doc():get_text(doc():get_selection())
-      system.set_clipboard(text)
+    local full_text = ""
+    for idx, line1, col1, line2, col2 in doc():get_selections() do
+      if line1 ~= line2 or col1 ~= col2 then
+        local text = doc():get_text(line1, col1, line2, col2)
+        full_text = full_text == "" and text or (full_text .. "\n" .. text)
+        doc():set_cursor_clipboard(idx, text)
+      else
+        doc():set_cursor_clipboard(idx, "")
+      end
     end
+    system.set_clipboard(full_text)
   end,
 
   ["doc:paste"] = function()
-    doc():text_input(system.get_clipboard():gsub("\r", ""))
+    for idx, line1, col1, line2, col2 in doc():get_selections() do
+      local value = doc():get_cursor_clipboard(idx) or system.get_clipboard()
+      doc():text_input(value:gsub("\r", ""), idx)
+    end
   end,
 
   ["doc:newline"] = function()
diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index 7dc34c4c..9fa22351 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -47,6 +47,7 @@ end
 function Doc:reset()
   self.lines = { "\n" }
   self.selections = { 1, 1, 1, 1 }
+  self.cursor_clipboard = {}
   self.undo_stack = { idx = 1 }
   self.redo_stack = { idx = 1 }
   self.clean_change_id = 1
@@ -126,6 +127,12 @@ function Doc:get_change_id()
   return self.undo_stack.idx
 end
 
+function Doc:get_cursor_clipboard(idx)
+  return self.cursor_clipboard[idx]
+end
+function Doc:set_cursor_clipboard(idx, value)
+  self.cursor_clipboard[idx] = value
+end
 
 function Doc:set_selection(line1, col1, line2, col2, swap)
   assert(not line2 == not col2, "expected 2 or 4 arguments")
@@ -133,6 +140,7 @@ function Doc:set_selection(line1, col1, line2, col2, swap)
   line1, col1 = self:sanitize_position(line1, col1)
   line2, col2 = self:sanitize_position(line2 or line1, col2 or col1) 
   self.selections = { line1, col1, line2, col2 }
+  self.cursor_clipboard = {}
 end
 
 function Doc:set_selections(idx, line1, col1, line2, col2, swap)
@@ -171,7 +179,7 @@ function Doc:get_selection(sort)
   return unpack(self.selections)
 end
 
-function Doc:get_selection_count()
+function Doc:get_cursor_count()
   return #self.selections / 4
 end
 

From 6c0d12441088414fa4beca1900789f3132fb00c3 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Sat, 5 Jun 2021 21:18:05 -0400
Subject: [PATCH 05/22] Allows for rectangular selections with ctrl; also fixed
 tabbing.

---
 data/core/commands/doc.lua | 51 ++++++++++++++++++--------------------
 data/core/doc/init.lua     |  4 +--
 data/core/docview.lua      |  7 ++----
 3 files changed, 28 insertions(+), 34 deletions(-)

diff --git a/data/core/commands/doc.lua b/data/core/commands/doc.lua
index edba731e..1331901b 100644
--- a/data/core/commands/doc.lua
+++ b/data/core/commands/doc.lua
@@ -25,9 +25,10 @@ end
 
 
 local function doc_multiline_selections(sort)
-  local iter = doc():get_selections(sort)
+  local iter, state, idx = doc():get_selections(sort)
   return function() 
-    local idx, line1, col1, line2, col2 = iter()
+    local line1, col1, line2, col2
+    idx, line1, col1, line2, col2 = iter(state, idx)
     if not idx then
       return
     end
@@ -52,6 +53,23 @@ local function save(filename)
   core.log("Saved \"%s\"", saved_filename)
 end
 
+local function cut_or_copy(delete)
+  local full_text = ""
+  for idx, line1, col1, line2, col2 in doc():get_selections() do
+    if line1 ~= line2 or col1 ~= col2 then
+      local text = doc():get_text(line1, col1, line2, col2)
+      if delete then
+        doc():delete_to(idx, 0)
+      end
+      full_text = full_text == "" and text or (full_text .. "\n" .. text)
+      doc():set_cursor_clipboard(idx, text)
+    else
+      doc():set_cursor_clipboard(idx, "")
+    end
+  end
+  system.set_clipboard(full_text)
+end
+
 local commands = {
   ["doc:undo"] = function()
     doc():undo()
@@ -62,32 +80,11 @@ local commands = {
   end,
 
   ["doc:cut"] = function()
-    local full_text = ""
-    for idx, line1, col1, line2, col2 in doc():get_selections() do
-      if line1 ~= line2 or col1 ~= col2 then
-        local text = doc():get_text(line1, col1, line2, col2)
-        doc():delete_to(idx, 0)
-        full_text = full_text == "" and text or (full_text .. "\n" .. text)
-        doc():set_cursor_clipboard(idx, text)
-      else
-        doc():set_cursor_clipboard(idx, "")
-      end
-    end
-    system.set_clipboard(full_text)
+    cut_or_copy(true)
   end,
 
   ["doc:copy"] = function()
-    local full_text = ""
-    for idx, line1, col1, line2, col2 in doc():get_selections() do
-      if line1 ~= line2 or col1 ~= col2 then
-        local text = doc():get_text(line1, col1, line2, col2)
-        full_text = full_text == "" and text or (full_text .. "\n" .. text)
-        doc():set_cursor_clipboard(idx, text)
-      else
-        doc():set_cursor_clipboard(idx, "")
-      end
-    end
-    system.set_clipboard(full_text)
+    cut_or_copy(false)
   end,
 
   ["doc:paste"] = function()
@@ -187,7 +184,7 @@ local commands = {
   ["doc:indent"] = function()
     for idx, line1, col1, line2, col2 in doc_multiline_selections(true) do
       local l1, c1, l2, c2 = doc():indent_text(false, line1, col1, line2, col2)
-      if not l1 then
+      if l1 then
         doc():set_selections(idx, l1, c1, l2, c2)
       end
     end
@@ -196,7 +193,7 @@ local commands = {
   ["doc:unindent"] = function()
     for idx, line1, col1, line2, col2 in doc_multiline_selections(true) do
       local l1, c1, l2, c2 = doc():indent_text(true, line1, col1, line2, col2)
-      if not l1 then
+      if l1 then
         doc():set_selections(idx, l1, c1, l2, c2)
       end
     end
diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index 9fa22351..1be09824 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -518,14 +518,14 @@ function Doc:indent_text(unindent, line1, col1, line2, col2)
         unindent and rnded:sub(1, #rnded - #text) or rnded .. text)
     end
     l1d, l2d = #self.lines[line1] - l1d, #self.lines[line2] - l2d
-    if (unindent or in_beginning_whitespace) and not self:has_selection() then
+    if (unindent or in_beginning_whitespace) and not has_selection then
       local start_cursor = (se and se + 1 or 1) + l1d or #(self.lines[line1])
       return line1, start_cursor, line2, start_cursor
     else
       return line1, col1 + l1d, line2, col2 + l2d
     end
   else
-    self:text_input(text)
+    self:insert(line1, col1, text)
   end
 end
 
diff --git a/data/core/docview.lua b/data/core/docview.lua
index 477cee48..081c7966 100644
--- a/data/core/docview.lua
+++ b/data/core/docview.lua
@@ -277,12 +277,9 @@ function DocView:on_mouse_moved(x, y, ...)
     local l2, c2 = table.unpack(self.mouse_selecting)
     local clicks = self.mouse_selecting.clicks
     if keymap.modkeys["ctrl"] then
-      if l1 > l2 then
-        l1, l2 = l2, l1
-      end
-      local idx = 1
+      if l1 > l2 then l1, l2 = l2, l1 end
       for i = l1, l2 do
-        self.doc:set_selections(i - l1 + 1, i, math.min(c1, #self.doc.lines[i]), i, math.min(c1, #self.doc.lines[i]))
+        self.doc:set_selections(i - l1 + 1, i, math.min(c1, #self.doc.lines[i]), i, math.min(c2, #self.doc.lines[i]))
       end
     else
       self.doc:set_selection(mouse_selection(self.doc, clicks, l1, c1, l2, c2))

From 316671e5b7c9b514a397ceb85669f19a2de7c363 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Sat, 5 Jun 2021 21:23:24 -0400
Subject: [PATCH 06/22] Fixed tabbing spaces.

---
 data/core/doc/init.lua | 1 +
 1 file changed, 1 insertion(+)

diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index 1be09824..f5bfbe57 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -526,6 +526,7 @@ function Doc:indent_text(unindent, line1, col1, line2, col2)
     end
   else
     self:insert(line1, col1, text)
+    return line1, col1 + #text, line1, col1 + #text
   end
 end
 

From b42708fe56f8749e46fddf5ea089cbeef51ab6ed Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Sun, 6 Jun 2021 20:30:09 -0400
Subject: [PATCH 07/22] Cleaned up functions.

---
 data/core/commands/doc.lua |  51 +++++++---------
 data/core/common.lua       |  20 +++++++
 data/core/doc/init.lua     | 120 +++++++++----------------------------
 data/core/docview.lua      |   2 +-
 4 files changed, 70 insertions(+), 123 deletions(-)

diff --git a/data/core/commands/doc.lua b/data/core/commands/doc.lua
index 1331901b..27da949a 100644
--- a/data/core/commands/doc.lua
+++ b/data/core/commands/doc.lua
@@ -25,14 +25,10 @@ end
 
 
 local function doc_multiline_selections(sort)
-  local iter, state, idx = doc():get_selections(sort)
+  local iter, state, idx, line1, col1, line2, col2 = doc():get_selections(sort)
   return function() 
-    local line1, col1, line2, col2
     idx, line1, col1, line2, col2 = iter(state, idx)
-    if not idx then
-      return
-    end
-    if line2 > line1 and col2 == 1 then
+    if idx and line2 > line1 and col2 == 1 then
       line2 = line2 - 1
       col2 = #doc().lines[line2]
     end
@@ -62,9 +58,9 @@ local function cut_or_copy(delete)
         doc():delete_to(idx, 0)
       end
       full_text = full_text == "" and text or (full_text .. "\n" .. text)
-      doc():set_cursor_clipboard(idx, text)
+      doc().cursor_clipboard[idx] = text
     else
-      doc():set_cursor_clipboard(idx, "")
+      doc().cursor_clipboard[idx] = ""
     end
   end
   system.set_clipboard(full_text)
@@ -89,7 +85,7 @@ local commands = {
 
   ["doc:paste"] = function()
     for idx, line1, col1, line2, col2 in doc():get_selections() do
-      local value = doc():get_cursor_clipboard(idx) or system.get_clipboard()
+      local value = doc().cursor_clipboard[idx] or system.get_clipboard()
       doc():text_input(value:gsub("\r", ""), idx)
     end
   end,
@@ -121,18 +117,18 @@ local commands = {
   end,
 
   ["doc:delete"] = function()
-    for idx, line, col in doc():get_selections() do
-      if not doc():has_selection(idx) and doc().lines[line]:find("^%s*$", col) then
-        doc():remove(line, col, line, math.huge)
+    for idx, line1, col1, line2, col2 in doc():get_selections() do
+      if line1 == line2 and col1 == col2 and doc().lines[line1]:find("^%s*$", col1) then
+        doc():remove(line1, col1, line1, math.huge)
       end
       doc():delete_to(idx, translate.next_char)
     end
   end,
 
   ["doc:backspace"] = function()
-    for idx, line, col in doc():get_selections() do
-      if not doc():has_selection(idx) then
-        local text = doc():get_text(line, 1, line, col)
+    for idx, line1, col1, line2, col2 in doc():get_selections() do
+      if line1 == line2 and col1 == col2 then
+        local text = doc():get_text(line1, 1, line1, col1)
         if #text >= config.indent_size and text:find("^ *$") then
           doc():delete_to(idx, 0, -config.indent_size)
           return
@@ -167,7 +163,7 @@ local commands = {
   end,
 
   ["doc:join-lines"] = function()
-    for idx, line1, _, line2 in doc():get_selections(true) do
+    for idx, line1, col1, line2, col2 in doc():get_selections(true) do
       if line1 == line2 then line2 = line2 + 1 end
       local text = doc():get_text(line1, 1, line2, math.huge)
       text = text:gsub("(.-)\n[\t ]*", function(x)
@@ -175,7 +171,7 @@ local commands = {
       end)
       doc():insert(line1, 1, text)
       doc():remove(line1, #text + 1, line2, math.huge)
-      if doc():has_selection(idx) then
+      if line1 ~= line2 or col1 ~= col2 then
         doc():set_selections(idx, line1, math.huge)
       end
     end
@@ -183,6 +179,7 @@ local commands = {
 
   ["doc:indent"] = function()
     for idx, line1, col1, line2, col2 in doc_multiline_selections(true) do
+      print("LINE", line1, col1, line2, col2)
       local l1, c1, l2, c2 = doc():indent_text(false, line1, col1, line2, col2)
       if l1 then
         doc():set_selections(idx, l1, c1, l2, c2)
@@ -398,25 +395,21 @@ for name, fn in pairs(translations) do
 end
 
 commands["doc:move-to-previous-char"] = function()
-  for idx, line, col in doc():get_selections(true) do
-    if doc():has_selection(idx) then
-      doc():set_selections(idx, line, col)
+  for idx, line1, col1, line2, col2 in doc():get_selections(true) do
+    if line1 ~= line2 or col1 ~= col2 then
+      doc():set_selections(idx, line1, col1)
     end
   end
-  if not doc():has_selection() then
-    doc():move_to(nil, translate.previous_char)
-  end
+  doc():move_to(nil, translate.previous_char)
 end
 
 commands["doc:move-to-next-char"] = function()
-  for idx, _, _, line, col in doc():get_selections(true) do
-    if doc():has_selection(idx) then
-      doc():set_selections(idx, line, col)
+  for idx, line1, col1, line2, col2 in doc():get_selections(true) do
+    if line1 ~= line2 or col1 ~= col2 then
+      doc():set_selections(idx, line2, col2)
     end
   end
-  if not doc():has_selection() then
-    doc():move_to(nil, translate.next_char)
-  end
+  doc():move_to(nil, translate.next_char)
 end
 
 command.add("core.docview", commands)
diff --git a/data/core/common.lua b/data/core/common.lua
index b7dd61db..548b5faa 100644
--- a/data/core/common.lua
+++ b/data/core/common.lua
@@ -61,6 +61,26 @@ function common.color(str)
 end
 
 
+function common.splice(t, at, remove, insert)
+  insert = insert or {}
+  local offset = #insert - remove
+  local old_len = #t
+  if offset < 0 then
+    for i = at - offset, old_len - offset do
+      t[i + offset] = t[i]
+    end
+  elseif offset > 0 then
+    for i = old_len, at, -1 do
+      t[i + offset] = t[i]
+    end
+  end
+  for i, item in ipairs(insert) do
+    t[at + i - 1] = item
+  end
+end
+
+
+
 local function compare_score(a, b)
   return a.score > b.score
 end
diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index f5bfbe57..80c8e5de 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -16,26 +16,6 @@ local function split_lines(text)
   return res
 end
 
-
-local function splice(t, at, remove, insert)
-  insert = insert or {}
-  local offset = #insert - remove
-  local old_len = #t
-  if offset < 0 then
-    for i = at - offset, old_len - offset do
-      t[i + offset] = t[i]
-    end
-  elseif offset > 0 then
-    for i = old_len, at, -1 do
-      t[i + offset] = t[i]
-    end
-  end
-  for i, item in ipairs(insert) do
-    t[at + i - 1] = item
-  end
-end
-
-
 function Doc:new(filename)
   self:reset()
   if filename then
@@ -127,91 +107,48 @@ function Doc:get_change_id()
   return self.undo_stack.idx
 end
 
-function Doc:get_cursor_clipboard(idx)
-  return self.cursor_clipboard[idx]
-end
-function Doc:set_cursor_clipboard(idx, value)
-  self.cursor_clipboard[idx] = value
-end
-
-function Doc:set_selection(line1, col1, line2, col2, swap)
-  assert(not line2 == not col2, "expected 2 or 4 arguments")
-  if swap then line1, col1, line2, col2 = line2, col2, line1, col1 end
-  line1, col1 = self:sanitize_position(line1, col1)
-  line2, col2 = self:sanitize_position(line2 or line1, col2 or col1) 
-  self.selections = { line1, col1, line2, col2 }
-  self.cursor_clipboard = {}
-end
-
 function Doc:set_selections(idx, line1, col1, line2, col2, swap)
   assert(not line2 == not col2, "expected 3 or 5 arguments")
   if swap then line1, col1, line2, col2 = line2, col2, line1, col1 end
   line1, col1 = self:sanitize_position(line1, col1)
   line2, col2 = self:sanitize_position(line2 or line1, col2 or col1)
-  local target = (idx - 1)*4 + 1
-  self.selections[target] = line1
-  self.selections[target+1] = col1
-  self.selections[target+2] = line2
-  self.selections[target+3] = col2
+  common.splice(self.selections, (idx - 1)*4 + 1, 4, { line1, col1, line2, col2 })
 end
 
+function Doc:set_selection(line1, col1, line2, col2, swap)
+  self.selections = {}
+  self:set_selections(1, line1, col1, line2, col2, swap)
+  self.cursor_clipboard = {}
+end
 
 local function sort_positions(line1, col1, line2, col2)
-  if line1 > line2
-  or line1 == line2 and col1 > col2 then
-    return line2, col2, line1, col1, true
+  if line1 > line2 or line1 == line2 and col1 > col2 then
+    return line2, col2, line1, col1
   end
-  return line1, col1, line2, col2, false
+  return line1, col1, line2, col2
 end
 
-
 function Doc:get_selection(sort)
-  if sort then
-    local result = {}
-    for sidx, line1, col1, line2, col2 in self:get_selections(true) do
-      table.insert(result, line1)
-      table.insert(result, col1)
-      table.insert(result, line2)
-      table.insert(result, col2)            
-    end
-    return result
-  end
-  return unpack(self.selections)
-end
-
-function Doc:get_cursor_count()
-  return #self.selections / 4
+  local idx, line1, col1, line2, col2 = self:get_selections(sort)(self.selections, 0)
+  return line1, col1, line2, col2
 end
 
 function Doc:get_selections(sort)
   return function(selections, idx)
     local target = idx*4 + 1
-    if target >= #selections then
-      return
-    end
+    if target >= #selections then return end
     if sort then
-      return idx+1, sort_positions(selections[target], selections[target+1], selections[target+2], selections[target+3])
+      return idx+1, sort_positions(unpack(selections, target, target+4))
     else
-      return idx+1, selections[target], selections[target+1], selections[target+2], selections[target+3]
+      return idx+1, unpack(selections, target, target+4)
     end
   end, self.selections, 0
 end
 
 
-function Doc:has_selection(idx)
-  if idx then
-    local target = (idx-1)*4+1
-    return 
-      self.selections[target] ~= self.selections[target+2] or
-      self.selections[target+1] ~= self.selections[target+3]
-  end
-  for target = 1, #self.selections, 4 do
-    if self.selections[target] ~= self.selections[target+2] or
-      self.selections[target+1] ~= self.selections[target+3] then
-      return true
-    end
-  end
-  return false
+function Doc:has_selection()
+  local line1, col1, line2, col2 = self:get_selection(false)
+  return line1 ~= line2 or col1 ~= col2
 end
 
 
@@ -341,7 +278,7 @@ function Doc:raw_insert(line, col, text, undo_stack, time)
   lines[#lines] = lines[#lines] .. after
 
   -- splice lines into line array
-  splice(self.lines, line, 1, lines)
+  common.splice(self.lines, line, 1, lines)
 
   -- push undo
   local line2, col2 = self:position_offset(line, col, #text)
@@ -365,7 +302,7 @@ function Doc:raw_remove(line1, col1, line2, col2, undo_stack, time)
   local after = self.lines[line2]:sub(col2)
 
   -- splice line into line array
-  splice(self.lines, line1, line2 - line1 + 1, { before .. after })
+  common.splice(self.lines, line1, line2 - line1 + 1, { before .. after })
 
   -- update highlighter and assure selection is in bounds
   self.highlighter:invalidate(line1)
@@ -402,12 +339,12 @@ end
 
 
 function Doc:text_input(text, idx)
-  for sidx, line, col in self:get_selections() do
+  for sidx, line1, col1, line2, col2 in self:get_selections() do
     if not idx or idx == sidx then
-      if self:has_selection(sidx) then
+      if line1 ~= line2 or col1 ~= col2 then
         self:delete_to(sidx)
       end
-      self:insert(line, col, text)
+      self:insert(line1, col1, text)
       self:move_to(sidx, #text)
     end
   end
@@ -415,11 +352,8 @@ end
 
 
 function Doc:replace(fn)
-  local line1, col1, line2, col2, swap
-  local had_selection = self:has_selection()
-  if had_selection then
-    line1, col1, line2, col2, swap = self:get_selection(true)
-  else
+  local line1, col1, line2, col2 = self:get_selection(true)
+  if line1 == line2 and col1 == col2 then
     line1, col1, line2, col2 = 1, 1, #self.lines, #self.lines[#self.lines]
   end
   local old_text = self:get_text(line1, col1, line2, col2)
@@ -429,7 +363,7 @@ function Doc:replace(fn)
     self:remove(line1, col1, line2, col2)
     if had_selection then
       line2, col2 = self:position_offset(line1, col1, #new_text)
-      self:set_selection(line1, col1, line2, col2, swap)
+      self:set_selection(line1, col1, line2, col2)
     end
   end
   return n
@@ -439,10 +373,10 @@ end
 function Doc:delete_to(idx, ...)
   for sidx, line1, col1, line2, col2 in self:get_selections(true) do
     if not idx or sidx == idx then
-      if self:has_selection(sidx) then
+      if line1 ~= line2 or col1 ~= col2 then
         self:remove(line1, col1, line2, col2)
       else
-        local l2, c2 = self:position_offset(line, col, ...)
+        local l2, c2 = self:position_offset(line1, col1, ...)
         self:remove(line1, col1, l2, c2)
         line1, col1 = sort_positions(line1, col1, l2, c2)
       end
diff --git a/data/core/docview.lua b/data/core/docview.lua
index 081c7966..15ecb838 100644
--- a/data/core/docview.lua
+++ b/data/core/docview.lua
@@ -361,7 +361,7 @@ function DocView:draw_line_body(idx, x, y)
   end
   for lidx, line1, col1, line2, col2 in self.doc:get_selections(true) do 
     -- draw line highlight if caret is on this line
-    if config.highlight_current_line and not self.doc:has_selection(lidx)
+    if config.highlight_current_line and (line1 == line2 and col1 == col2)
     and line1 == idx and core.active_view == self then
       self:draw_line_highlight(x + self.scroll.x, y)
     end

From 2475b1624f6becb052f023658f9732490b6c0ea2 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Mon, 7 Jun 2021 08:25:10 -0400
Subject: [PATCH 08/22] Fixed error.

---
 data/core/doc/init.lua | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index 80c8e5de..09816e4d 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -361,7 +361,7 @@ function Doc:replace(fn)
   if old_text ~= new_text then
     self:insert(line2, col2, new_text)
     self:remove(line1, col1, line2, col2)
-    if had_selection then
+    if line1 == line2 and col1 == col2 then
       line2, col2 = self:position_offset(line1, col1, #new_text)
       self:set_selection(line1, col1, line2, col2)
     end

From 75658b4f3f3ffb0b98cff88118032bd4e2c02e80 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Mon, 7 Jun 2021 08:26:49 -0400
Subject: [PATCH 09/22] Removed unecessary elses.

---
 data/core/doc/init.lua | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index 09816e4d..b448bbd4 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -455,13 +455,11 @@ function Doc:indent_text(unindent, line1, col1, line2, col2)
     if (unindent or in_beginning_whitespace) and not has_selection then
       local start_cursor = (se and se + 1 or 1) + l1d or #(self.lines[line1])
       return line1, start_cursor, line2, start_cursor
-    else
-      return line1, col1 + l1d, line2, col2 + l2d
     end
-  else
-    self:insert(line1, col1, text)
-    return line1, col1 + #text, line1, col1 + #text
+    return line1, col1 + l1d, line2, col2 + l2d
   end
+  self:insert(line1, col1, text)
+  return line1, col1 + #text, line1, col1 + #text
 end
 
 -- For plugins to add custom actions of document change

From 858f7a2a5070f7838ddf4d976b3612d6100a2928 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Tue, 8 Jun 2021 23:09:09 -0400
Subject: [PATCH 10/22] Added in missing boolean.

---
 data/core/commands/doc.lua | 56 ++++++++++++++++++++++++++++++++------
 data/core/doc/init.lua     | 16 ++++++-----
 data/core/keymap-macos.lua |  2 ++
 data/core/keymap.lua       |  2 ++
 4 files changed, 60 insertions(+), 16 deletions(-)

diff --git a/data/core/commands/doc.lua b/data/core/commands/doc.lua
index 27da949a..ca293393 100644
--- a/data/core/commands/doc.lua
+++ b/data/core/commands/doc.lua
@@ -55,7 +55,7 @@ local function cut_or_copy(delete)
     if line1 ~= line2 or col1 ~= col2 then
       local text = doc():get_text(line1, col1, line2, col2)
       if delete then
-        doc():delete_to(idx, 0)
+        doc():delete_to(0)
       end
       full_text = full_text == "" and text or (full_text .. "\n" .. text)
       doc().cursor_clipboard[idx] = text
@@ -66,6 +66,25 @@ local function cut_or_copy(delete)
   system.set_clipboard(full_text)
 end
 
+local function split_cursor(direction)
+  local new_cursors = {}
+  for _, line1, col1 in doc():get_selections() do
+    local exists = false
+    for _, line2, col2 in doc():get_selections() do
+      if line1+direction == line2 and col1 == col2 then
+        exists = true
+        break
+      end
+    end
+    if not exists and line1 > 1 and line1 < #doc().lines then
+      table.insert(new_cursors, { line1 - 1, col1 })
+    end
+  end
+  for i,v in ipairs(new_cursors) do
+    doc():set_selections(#doc().selections/4 + 1, v[1], v[2])
+  end
+end
+
 local commands = {
   ["doc:undo"] = function()
     doc():undo()
@@ -121,7 +140,7 @@ local commands = {
       if line1 == line2 and col1 == col2 and doc().lines[line1]:find("^%s*$", col1) then
         doc():remove(line1, col1, line1, math.huge)
       end
-      doc():delete_to(idx, translate.next_char)
+      doc():delete_to_cursor(idx, translate.next_char)
     end
   end,
 
@@ -130,11 +149,11 @@ local commands = {
       if line1 == line2 and col1 == col2 then
         local text = doc():get_text(line1, 1, line1, col1)
         if #text >= config.indent_size and text:find("^ *$") then
-          doc():delete_to(idx, 0, -config.indent_size)
+          doc():delete_to_cursor(idx, 0, -config.indent_size)
           return
         end
       end
-      doc():delete_to(idx, translate.previous_char)
+      doc():delete_to_cursor(idx, translate.previous_char)
     end
   end,
 
@@ -146,6 +165,16 @@ local commands = {
     local line, col = doc():get_selection()
     doc():set_selection(line, col)
   end,
+  
+  
+  ["doc:indent"] = function()
+    for idx, line1, col1, line2, col2 in doc_multiline_selections(true) do
+      local l1, c1, l2, c2 = doc():indent_text(false, line1, col1, line2, col2)
+      if l1 then
+        doc():set_selections(idx, l1, c1, l2, c2)
+      end
+    end
+  end,
 
   ["doc:select-lines"] = function()
     for idx, line1, _, line2 in doc():get_selections(true) do
@@ -366,6 +395,15 @@ local commands = {
     os.remove(filename)
     core.log("Removed \"%s\"", filename)
   end
+
+  ["doc:create-cursor-previous-line"] = function()
+    split_cursor(-1)
+  end,
+  
+  ["doc:create-cursor-next-line"] = function()
+    split_cursor(1)
+  end,
+
 }
 
 
@@ -389,9 +427,9 @@ local translations = {
 }
 
 for name, fn in pairs(translations) do
-  commands["doc:move-to-" .. name] = function() doc():move_to(nil, fn, dv()) end
-  commands["doc:select-to-" .. name] = function() doc():select_to(nil, fn, dv()) end
-  commands["doc:delete-to-" .. name] = function() doc():delete_to(nil, fn, dv()) end
+  commands["doc:move-to-" .. name] = function() doc():move_to(fn, dv()) end
+  commands["doc:select-to-" .. name] = function() doc():select_to(fn, dv()) end
+  commands["doc:delete-to-" .. name] = function() doc():delete_to(fn, dv()) end
 end
 
 commands["doc:move-to-previous-char"] = function()
@@ -400,7 +438,7 @@ commands["doc:move-to-previous-char"] = function()
       doc():set_selections(idx, line1, col1)
     end
   end
-  doc():move_to(nil, translate.previous_char)
+  doc():move_to(translate.previous_char)
 end
 
 commands["doc:move-to-next-char"] = function()
@@ -409,7 +447,7 @@ commands["doc:move-to-next-char"] = function()
       doc():set_selections(idx, line2, col2)
     end
   end
-  doc():move_to(nil, translate.next_char)
+  doc():move_to(translate.next_char)
 end
 
 command.add("core.docview", commands)
diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index b448bbd4..ef9e1f2e 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -130,7 +130,7 @@ end
 
 function Doc:get_selection(sort)
   local idx, line1, col1, line2, col2 = self:get_selections(sort)(self.selections, 0)
-  return line1, col1, line2, col2
+  return line1, col1, line2, col2, sort
 end
 
 function Doc:get_selections(sort)
@@ -342,10 +342,10 @@ function Doc:text_input(text, idx)
   for sidx, line1, col1, line2, col2 in self:get_selections() do
     if not idx or idx == sidx then
       if line1 ~= line2 or col1 ~= col2 then
-        self:delete_to(sidx)
+        self:delete_to_cursor(sidx)
       end
       self:insert(line1, col1, text)
-      self:move_to(sidx, #text)
+      self:move_to_cursor(sidx, #text)
     end
   end
 end
@@ -370,7 +370,7 @@ function Doc:replace(fn)
 end
 
 
-function Doc:delete_to(idx, ...)
+function Doc:delete_to_cursor(idx, ...)
   for sidx, line1, col1, line2, col2 in self:get_selections(true) do
     if not idx or sidx == idx then
       if line1 ~= line2 or col1 ~= col2 then
@@ -384,18 +384,19 @@ function Doc:delete_to(idx, ...)
     end
   end
 end
+function Doc:delete_to(...) return self:delete_to(nil, ...) end
 
-
-function Doc:move_to(idx, ...)
+function Doc:move_to_cursor(idx, ...)
   for sidx, line, col in self:get_selections() do
     if not idx or sidx == idx then
       self:set_selections(sidx, self:position_offset(line, col, ...))
     end
   end
 end
+function Doc:move_to(...) return self:move_to_cursor(nil, ...) end
 
 
-function Doc:select_to(idx, ...)
+function Doc:select_to_cursor(idx, ...)
   for sidx, line, col, line2, col2 in self:get_selections() do
     if not idx or idx == sidx then
       line, col = self:position_offset(line, col, ...)
@@ -403,6 +404,7 @@ function Doc:select_to(idx, ...)
     end
   end
 end
+function Doc:select_to(...) return self:select_to_cursor(nil, ...) end
 
 
 local function get_indent_string()
diff --git a/data/core/keymap-macos.lua b/data/core/keymap-macos.lua
index ccbb102a..3db4d4f7 100644
--- a/data/core/keymap-macos.lua
+++ b/data/core/keymap-macos.lua
@@ -101,6 +101,8 @@ local function keymap_macos(keymap)
     ["cmd+shift+end"] = "doc:select-to-end-of-doc",
     ["shift+pageup"] = "doc:select-to-previous-page",
     ["shift+pagedown"] = "doc:select-to-next-page",
+    ["cmd+shift+up"] = "doc:create-cursor-previous-line",
+    ["cmd+shift+down"] = "doc:create-cursor-next-line"
   }
 end
 
diff --git a/data/core/keymap.lua b/data/core/keymap.lua
index 84bcd770..0bd153b8 100644
--- a/data/core/keymap.lua
+++ b/data/core/keymap.lua
@@ -202,6 +202,8 @@ keymap.add_direct {
   ["ctrl+shift+end"] = "doc:select-to-end-of-doc",
   ["shift+pageup"] = "doc:select-to-previous-page",
   ["shift+pagedown"] = "doc:select-to-next-page",
+  ["ctrl+shift+up"] = "doc:create-cursor-previous-line",
+  ["ctrl+shift+down"] = "doc:create-cursor-next-line"
 }
 
 return keymap

From c6f7e473f0ed26ccab57630c546e2e0505e0aa23 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Wed, 9 Jun 2021 17:14:34 -0400
Subject: [PATCH 11/22] That's what I get for not testing after a 'simple'
 refactor.

---
 data/core/commands/doc.lua | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/data/core/commands/doc.lua b/data/core/commands/doc.lua
index ca293393..fff081a9 100644
--- a/data/core/commands/doc.lua
+++ b/data/core/commands/doc.lua
@@ -77,7 +77,7 @@ local function split_cursor(direction)
       end
     end
     if not exists and line1 > 1 and line1 < #doc().lines then
-      table.insert(new_cursors, { line1 - 1, col1 })
+      table.insert(new_cursors, { line1 + direction, col1 })
     end
   end
   for i,v in ipairs(new_cursors) do

From d3b3f263169b05db1ea49c390b30b7f67362f9f1 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Wed, 9 Jun 2021 17:59:19 -0400
Subject: [PATCH 12/22] Added in cursor merging behaviour.

---
 data/core/doc/init.lua | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index ef9e1f2e..4c326f95 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -121,6 +121,18 @@ function Doc:set_selection(line1, col1, line2, col2, swap)
   self.cursor_clipboard = {}
 end
 
+function Doc:merge_cursors(idx)
+  for i = (idx or (#self.selections - 3)), (idx or 5), -4 do
+    for j = 1, i - 4, 4 do
+      if self.selections[i] == self.selections[j] and
+        self.selections[i+1] == self.selections[j+1] then
+          common.splice(self.selections, i, 4)
+          break
+      end
+    end
+  end
+end
+
 local function sort_positions(line1, col1, line2, col2)
   if line1 > line2 or line1 == line2 and col1 > col2 then
     return line2, col2, line1, col1
@@ -383,6 +395,7 @@ function Doc:delete_to_cursor(idx, ...)
       self:set_selections(sidx, line1, col1)
     end
   end
+  self:merge_cursors(idx)
 end
 function Doc:delete_to(...) return self:delete_to(nil, ...) end
 
@@ -392,6 +405,7 @@ function Doc:move_to_cursor(idx, ...)
       self:set_selections(sidx, self:position_offset(line, col, ...))
     end
   end
+  self:merge_cursors(idx)
 end
 function Doc:move_to(...) return self:move_to_cursor(nil, ...) end
 
@@ -403,6 +417,7 @@ function Doc:select_to_cursor(idx, ...)
       self:set_selections(sidx, line, col, line2, col2)
     end
   end
+  self:merge_cursors(idx)
 end
 function Doc:select_to(...) return self:select_to_cursor(nil, ...) end
 

From c494d52caf48406b109576ff602247c9582e8830 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Wed, 9 Jun 2021 18:08:22 -0400
Subject: [PATCH 13/22] Used an inappropriate function in a selection loop.

---
 data/core/commands/doc.lua | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/data/core/commands/doc.lua b/data/core/commands/doc.lua
index fff081a9..0157962c 100644
--- a/data/core/commands/doc.lua
+++ b/data/core/commands/doc.lua
@@ -55,7 +55,7 @@ local function cut_or_copy(delete)
     if line1 ~= line2 or col1 ~= col2 then
       local text = doc():get_text(line1, col1, line2, col2)
       if delete then
-        doc():delete_to(0)
+        doc():delete_to_cursor(idx, 0)
       end
       full_text = full_text == "" and text or (full_text .. "\n" .. text)
       doc().cursor_clipboard[idx] = text

From 0f229b039d6425ef9db6d9ffa8cd6c6c1eca3691 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Thu, 10 Jun 2021 11:26:39 -0400
Subject: [PATCH 14/22] Fixed merging. Fixed selection undo stack.

---
 data/core/commands/doc.lua | 2 ++
 data/core/doc/init.lua     | 4 ++--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/data/core/commands/doc.lua b/data/core/commands/doc.lua
index 0157962c..7644e11b 100644
--- a/data/core/commands/doc.lua
+++ b/data/core/commands/doc.lua
@@ -398,10 +398,12 @@ local commands = {
 
   ["doc:create-cursor-previous-line"] = function()
     split_cursor(-1)
+    doc():merge_cursors()
   end,
   
   ["doc:create-cursor-next-line"] = function()
     split_cursor(1)
+    doc():merge_cursors()
   end,
 
 }
diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index 4c326f95..b9cfca5b 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -294,7 +294,7 @@ function Doc:raw_insert(line, col, text, undo_stack, time)
 
   -- push undo
   local line2, col2 = self:position_offset(line, col, #text)
-  push_undo(undo_stack, time, "selection", self:get_selection())
+  push_undo(undo_stack, time, "selection", unpack(self.selections))
   push_undo(undo_stack, time, "remove", line, col, line2, col2)
 
   -- update highlighter and assure selection is in bounds
@@ -306,7 +306,7 @@ end
 function Doc:raw_remove(line1, col1, line2, col2, undo_stack, time)
   -- push undo
   local text = self:get_text(line1, col1, line2, col2)
-  push_undo(undo_stack, time, "selection", self:get_selection())
+  push_undo(undo_stack, time, "selection", unpack(self.selections))
   push_undo(undo_stack, time, "insert", line1, col1, text)
 
   -- get line content before/after removed text

From b065b52067694195a60eb68e4b6091d4ee7ccd38 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Thu, 10 Jun 2021 11:29:21 -0400
Subject: [PATCH 15/22] Ensured that textual inputs sort cursors so that we
 don't get *real* weird behaviour.

---
 data/core/doc/init.lua | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index b9cfca5b..c8b541e9 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -351,7 +351,7 @@ end
 
 
 function Doc:text_input(text, idx)
-  for sidx, line1, col1, line2, col2 in self:get_selections() do
+  for sidx, line1, col1, line2, col2 in self:get_selections(true) do
     if not idx or idx == sidx then
       if line1 ~= line2 or col1 ~= col2 then
         self:delete_to_cursor(sidx)

From 6915d86d5901ba5d5f332cd6877f88a92ba6c199 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Thu, 10 Jun 2021 12:29:55 -0400
Subject: [PATCH 16/22] Introduced the constraint that all cursors must be in
 order.

---
 data/core/commands/doc.lua |  3 +-
 data/core/doc/init.lua     | 91 ++++++++++++++++++++++----------------
 data/core/docview.lua      |  1 +
 3 files changed, 55 insertions(+), 40 deletions(-)

diff --git a/data/core/commands/doc.lua b/data/core/commands/doc.lua
index 7644e11b..b4036e69 100644
--- a/data/core/commands/doc.lua
+++ b/data/core/commands/doc.lua
@@ -110,7 +110,7 @@ local commands = {
   end,
 
   ["doc:newline"] = function()
-    for idx, line, col in doc():get_selections() do
+    for idx, line, col in doc():get_selections(false, true) do
       local indent = doc().lines[line]:match("^[\t ]*")
       if col <= #indent then
         indent = indent:sub(#indent + 2 - col)
@@ -208,7 +208,6 @@ local commands = {
 
   ["doc:indent"] = function()
     for idx, line1, col1, line2, col2 in doc_multiline_selections(true) do
-      print("LINE", line1, col1, line2, col2)
       local l1, c1, l2, c2 = doc():indent_text(false, line1, col1, line2, col2)
       if l1 then
         doc():set_selections(idx, l1, c1, l2, c2)
diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index c8b541e9..f44b0ebf 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -107,18 +107,56 @@ function Doc:get_change_id()
   return self.undo_stack.idx
 end
 
-function Doc:set_selections(idx, line1, col1, line2, col2, swap)
+-- Cursor section. Cursor indices are *only* valid during a get_selections() call.
+-- Cursors will always be iterated in order from top to bottom. Through normal operation
+-- curors can never swap positions; only merge or split, or change their position in cursor
+-- order.
+function Doc:get_selection(sort)
+  local idx, line1, col1, line2, col2 = self:get_selections(sort)({ self.selections, sort }, 0)
+  return line1, col1, line2, col2, sort
+end
+
+function Doc:has_selection()
+  local line1, col1, line2, col2 = self:get_selection(false)
+  return line1 ~= line2 or col1 ~= col2
+end
+
+function Doc:sanitize_selection()
+  for idx, line1, col1, line2, col2 in self:get_selections() do
+    self:set_selections(idx, line1, col1, line2, col2)
+  end
+end
+
+local function sort_positions(line1, col1, line2, col2)
+  if line1 > line2 or line1 == line2 and col1 > col2 then
+    return line2, col2, line1, col1
+  end
+  return line1, col1, line2, col2
+end
+
+function Doc:set_selections(idx, line1, col1, line2, col2, swap, rm)
   assert(not line2 == not col2, "expected 3 or 5 arguments")
   if swap then line1, col1, line2, col2 = line2, col2, line1, col1 end
   line1, col1 = self:sanitize_position(line1, col1)
   line2, col2 = self:sanitize_position(line2 or line1, col2 or col1)
-  common.splice(self.selections, (idx - 1)*4 + 1, 4, { line1, col1, line2, col2 })
+  common.splice(self.selections, (idx - 1)*4 + 1, rm == nil and 4 or rm, { line1, col1, line2, col2 })
+end
+
+function Doc:add_selection(line1, col1, line2, col2, swap)
+  local l1, c1 = sort_positions(line1, col1, line2, col2)
+  local target = #self.selections / 4 + 1
+  for idx, tl1, tc1 in self:get_selections(true) do
+    if l1 < tl1 or l1 == tl1 and c1 < tc1 then
+      target = idx
+      break
+    end
+  end
+  self:set_selections(target, line1, col1, line2, col2, swap, 0)
 end
 
 function Doc:set_selection(line1, col1, line2, col2, swap)
-  self.selections = {}
+  self.selections, self.cursor_clipboard = {}, {}
   self:set_selections(1, line1, col1, line2, col2, swap)
-  self.cursor_clipboard = {}
 end
 
 function Doc:merge_cursors(idx)
@@ -133,43 +171,20 @@ function Doc:merge_cursors(idx)
   end
 end
 
-local function sort_positions(line1, col1, line2, col2)
-  if line1 > line2 or line1 == line2 and col1 > col2 then
-    return line2, col2, line1, col1
-  end
-  return line1, col1, line2, col2
-end
-
-function Doc:get_selection(sort)
-  local idx, line1, col1, line2, col2 = self:get_selections(sort)(self.selections, 0)
-  return line1, col1, line2, col2, sort
-end
-
-function Doc:get_selections(sort)
-  return function(selections, idx)
-    local target = idx*4 + 1
-    if target >= #selections then return end
-    if sort then
-      return idx+1, sort_positions(unpack(selections, target, target+4))
-    else
-      return idx+1, unpack(selections, target, target+4)
-    end
-  end, self.selections, 0
-end
-
-
-function Doc:has_selection()
-  local line1, col1, line2, col2 = self:get_selection(false)
-  return line1 ~= line2 or col1 ~= col2
-end
-
-
-function Doc:sanitize_selection()
-  for idx, line1, col1, line2, col2 in self:get_selections() do
-    self:set_selections(idx, line1, col1, line2, col2)
+local function selection_iterator(invariant, idx)
+  local target = invariant[3] and (#invariant[1] - 3 - idx * 4) or (idx*4 + 1)
+  if idx * 4 >= #invariant[1] then return end
+  if invariant[2] then
+    return idx+1, sort_positions(unpack(invariant[1], target, target+4))
+  else
+    return idx+1, unpack(invariant[1], target, target+4)
   end
 end
 
+function Doc:get_selections(sort_intra, reverse)
+  return selection_iterator, { self.selections, sort_intra, reverse }, 0
+end
+-- End of cursor seciton.
 
 function Doc:sanitize_position(line, col)
   line = common.clamp(line, 1, #self.lines)
diff --git a/data/core/docview.lua b/data/core/docview.lua
index 15ecb838..1cccb486 100644
--- a/data/core/docview.lua
+++ b/data/core/docview.lua
@@ -278,6 +278,7 @@ function DocView:on_mouse_moved(x, y, ...)
     local clicks = self.mouse_selecting.clicks
     if keymap.modkeys["ctrl"] then
       if l1 > l2 then l1, l2 = l2, l1 end
+      self.doc.selections = { }
       for i = l1, l2 do
         self.doc:set_selections(i - l1 + 1, i, math.min(c1, #self.doc.lines[i]), i, math.min(c2, #self.doc.lines[i]))
       end

From dfc57bd8848d4a20d572b6d38d0c2730b2c5e80a Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Thu, 10 Jun 2021 12:32:33 -0400
Subject: [PATCH 17/22] Used routine to add cursors in order correctly.

---
 data/core/commands/doc.lua | 4 +---
 data/core/doc/init.lua     | 2 +-
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/data/core/commands/doc.lua b/data/core/commands/doc.lua
index b4036e69..b67a1e7a 100644
--- a/data/core/commands/doc.lua
+++ b/data/core/commands/doc.lua
@@ -80,9 +80,7 @@ local function split_cursor(direction)
       table.insert(new_cursors, { line1 + direction, col1 })
     end
   end
-  for i,v in ipairs(new_cursors) do
-    doc():set_selections(#doc().selections/4 + 1, v[1], v[2])
-  end
+  for i,v in ipairs(new_cursors) do doc():add_selection(v[1], v[2]) end
 end
 
 local commands = {
diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index f44b0ebf..4091482a 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -143,7 +143,7 @@ function Doc:set_selections(idx, line1, col1, line2, col2, swap, rm)
 end
 
 function Doc:add_selection(line1, col1, line2, col2, swap)
-  local l1, c1 = sort_positions(line1, col1, line2, col2)
+  local l1, c1 = sort_positions(line1, col1, line2 or line1, col2 or col1)
   local target = #self.selections / 4 + 1
   for idx, tl1, tc1 in self:get_selections(true) do
     if l1 < tl1 or l1 == tl1 and c1 < tc1 then

From b5cbe3a2fb3f8b3c806d240ee4725b784320b722 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Fri, 11 Jun 2021 18:14:24 -0400
Subject: [PATCH 18/22] Added in the ability to iterate through cursors
 backwards.

---
 data/core/commands/doc.lua |  4 ++--
 data/core/doc/init.lua     | 10 +++++-----
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/data/core/commands/doc.lua b/data/core/commands/doc.lua
index b67a1e7a..02f7551a 100644
--- a/data/core/commands/doc.lua
+++ b/data/core/commands/doc.lua
@@ -118,7 +118,7 @@ local commands = {
   end,
 
   ["doc:newline-below"] = function()
-    for idx, line in doc():get_selections() do
+    for idx, line in doc():get_selections(false, true) do
       local indent = doc().lines[line]:match("^[\t ]*")
       doc():insert(line, math.huge, "\n" .. indent)
       doc():set_selections(idx, line + 1, math.huge)
@@ -126,7 +126,7 @@ local commands = {
   end,
 
   ["doc:newline-above"] = function()
-    for idx, line in doc():get_selections() do
+    for idx, line in doc():get_selections(false, true) do
       local indent = doc().lines[line]:match("^[\t ]*")
       doc():insert(line, 1, indent .. "\n")
       doc():set_selections(idx, line, math.huge)
diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index 4091482a..17a82d88 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -172,17 +172,17 @@ function Doc:merge_cursors(idx)
 end
 
 local function selection_iterator(invariant, idx)
-  local target = invariant[3] and (#invariant[1] - 3 - idx * 4) or (idx*4 + 1)
-  if idx * 4 >= #invariant[1] then return end
+  local target = invariant[3] and (idx*4 - 7) or (idx*4 + 1)
+  if target > #invariant[1] or target <= 0 then return end
   if invariant[2] then
-    return idx+1, sort_positions(unpack(invariant[1], target, target+4))
+    return idx+(invariant[3] and -1 or 1), sort_positions(unpack(invariant[1], target, target+4))
   else
-    return idx+1, unpack(invariant[1], target, target+4)
+    return idx+(invariant[3] and -1 or 1), unpack(invariant[1], target, target+4)
   end
 end
 
 function Doc:get_selections(sort_intra, reverse)
-  return selection_iterator, { self.selections, sort_intra, reverse }, 0
+  return selection_iterator, { self.selections, sort_intra, reverse }, reverse and (#self.selections / 4) + 1 or 0
 end
 -- End of cursor seciton.
 

From 02102645529d5ca256985a0708a61866c1a49895 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Fri, 11 Jun 2021 18:51:14 -0400
Subject: [PATCH 19/22] Made get_selections a bit more flexible.

---
 data/core/doc/init.lua | 53 +++++++++++++++++++-----------------------
 1 file changed, 24 insertions(+), 29 deletions(-)

diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index 17a82d88..836d9370 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -173,7 +173,7 @@ end
 
 local function selection_iterator(invariant, idx)
   local target = invariant[3] and (idx*4 - 7) or (idx*4 + 1)
-  if target > #invariant[1] or target <= 0 then return end
+  if target > #invariant[1] or target <= 0 or (type(invariant[3]) == "number" and invariant[3] ~= idx - 1) then return end
   if invariant[2] then
     return idx+(invariant[3] and -1 or 1), sort_positions(unpack(invariant[1], target, target+4))
   else
@@ -181,8 +181,11 @@ local function selection_iterator(invariant, idx)
   end
 end
 
-function Doc:get_selections(sort_intra, reverse)
-  return selection_iterator, { self.selections, sort_intra, reverse }, reverse and (#self.selections / 4) + 1 or 0
+-- If idx_reverse is true, it'll reverse iterate. If nil, or false, regular iterate. 
+-- If a number, runs for exactly that iteration.
+function Doc:get_selections(sort_intra, idx_reverse)
+  return selection_iterator, { self.selections, sort_intra, idx_reverse }, 
+    idx_reverse == true and ((#self.selections / 4) + 1) or ((idx_reverse or -1)+1)
 end
 -- End of cursor seciton.
 
@@ -366,14 +369,12 @@ end
 
 
 function Doc:text_input(text, idx)
-  for sidx, line1, col1, line2, col2 in self:get_selections(true) do
-    if not idx or idx == sidx then
-      if line1 ~= line2 or col1 ~= col2 then
-        self:delete_to_cursor(sidx)
-      end
-      self:insert(line1, col1, text)
-      self:move_to_cursor(sidx, #text)
+  for sidx, line1, col1, line2, col2 in self:get_selections(true, idx) do
+    if line1 ~= line2 or col1 ~= col2 then
+      self:delete_to_cursor(sidx)
     end
+    self:insert(line1, col1, text)
+    self:move_to_cursor(sidx, #text)
   end
 end
 
@@ -398,27 +399,23 @@ end
 
 
 function Doc:delete_to_cursor(idx, ...)
-  for sidx, line1, col1, line2, col2 in self:get_selections(true) do
-    if not idx or sidx == idx then
-      if line1 ~= line2 or col1 ~= col2 then
-        self:remove(line1, col1, line2, col2)
-      else
-        local l2, c2 = self:position_offset(line1, col1, ...)
-        self:remove(line1, col1, l2, c2)
-        line1, col1 = sort_positions(line1, col1, l2, c2)
-      end
-      self:set_selections(sidx, line1, col1)
+  for sidx, line1, col1, line2, col2 in self:get_selections(true, idx) do
+    if line1 ~= line2 or col1 ~= col2 then
+      self:remove(line1, col1, line2, col2)
+    else
+      local l2, c2 = self:position_offset(line1, col1, ...)
+      self:remove(line1, col1, l2, c2)
+      line1, col1 = sort_positions(line1, col1, l2, c2)
     end
+    self:set_selections(sidx, line1, col1)
   end
   self:merge_cursors(idx)
 end
 function Doc:delete_to(...) return self:delete_to(nil, ...) end
 
 function Doc:move_to_cursor(idx, ...)
-  for sidx, line, col in self:get_selections() do
-    if not idx or sidx == idx then
-      self:set_selections(sidx, self:position_offset(line, col, ...))
-    end
+  for sidx, line, col in self:get_selections(false, idx) do
+    self:set_selections(sidx, self:position_offset(line, col, ...))
   end
   self:merge_cursors(idx)
 end
@@ -426,11 +423,9 @@ function Doc:move_to(...) return self:move_to_cursor(nil, ...) end
 
 
 function Doc:select_to_cursor(idx, ...)
-  for sidx, line, col, line2, col2 in self:get_selections() do
-    if not idx or idx == sidx then
-      line, col = self:position_offset(line, col, ...)
-      self:set_selections(sidx, line, col, line2, col2)
-    end
+  for sidx, line, col, line2, col2 in self:get_selections(false, idx) do
+    line, col = self:position_offset(line, col, ...)
+    self:set_selections(sidx, line, col, line2, col2)
   end
   self:merge_cursors(idx)
 end

From 3541ab4aa1cec6ee77c4be8f8a39c189e62bae56 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Fri, 11 Jun 2021 19:01:43 -0400
Subject: [PATCH 20/22] Removed unecessary check.

---
 data/core/commands/doc.lua | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/data/core/commands/doc.lua b/data/core/commands/doc.lua
index 02f7551a..d54eb059 100644
--- a/data/core/commands/doc.lua
+++ b/data/core/commands/doc.lua
@@ -69,14 +69,7 @@ end
 local function split_cursor(direction)
   local new_cursors = {}
   for _, line1, col1 in doc():get_selections() do
-    local exists = false
-    for _, line2, col2 in doc():get_selections() do
-      if line1+direction == line2 and col1 == col2 then
-        exists = true
-        break
-      end
-    end
-    if not exists and line1 > 1 and line1 < #doc().lines then
+    if line1 > 1 and line1 < #doc().lines then
       table.insert(new_cursors, { line1 + direction, col1 })
     end
   end

From 292c98935cd4b44e7e66232cc4aa2f207acd3918 Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Mon, 14 Jun 2021 20:11:40 -0400
Subject: [PATCH 21/22] Fixed recursion error.

---
 data/core/doc/init.lua | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/data/core/doc/init.lua b/data/core/doc/init.lua
index 836d9370..0c5ba8fb 100644
--- a/data/core/doc/init.lua
+++ b/data/core/doc/init.lua
@@ -411,7 +411,7 @@ function Doc:delete_to_cursor(idx, ...)
   end
   self:merge_cursors(idx)
 end
-function Doc:delete_to(...) return self:delete_to(nil, ...) end
+function Doc:delete_to(...) return self:delete_to_cursor(nil, ...) end
 
 function Doc:move_to_cursor(idx, ...)
   for sidx, line, col in self:get_selections(false, idx) do

From 704e04396fe809d3f4f1f9de3e2a05c84e6a2b9f Mon Sep 17 00:00:00 2001
From: Adam Harrison <adamdharrison@gmail.com>
Date: Thu, 17 Jun 2021 19:17:24 -0400
Subject: [PATCH 22/22] Rebased, and added the ability for ctrl to just create
 new cursors.

---
 data/core/commands/doc.lua | 4 ++--
 data/core/docview.lua      | 6 +++++-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/data/core/commands/doc.lua b/data/core/commands/doc.lua
index d54eb059..b428cc74 100644
--- a/data/core/commands/doc.lua
+++ b/data/core/commands/doc.lua
@@ -384,7 +384,7 @@ local commands = {
     end
     os.remove(filename)
     core.log("Removed \"%s\"", filename)
-  end
+  end,
 
   ["doc:create-cursor-previous-line"] = function()
     split_cursor(-1)
@@ -394,7 +394,7 @@ local commands = {
   ["doc:create-cursor-next-line"] = function()
     split_cursor(1)
     doc():merge_cursors()
-  end,
+  end
 
 }
 
diff --git a/data/core/docview.lua b/data/core/docview.lua
index 1cccb486..446cf574 100644
--- a/data/core/docview.lua
+++ b/data/core/docview.lua
@@ -256,7 +256,11 @@ function DocView:on_mouse_pressed(button, x, y, clicks)
     end
   else
     local line, col = self:resolve_screen_position(x, y)
-    self.doc:set_selection(mouse_selection(self.doc, clicks, line, col, line, col))
+    if keymap.modkeys["ctrl"] then
+      self.doc:add_selection(mouse_selection(self.doc, clicks, line, col, line, col))
+    else
+      self.doc:set_selection(mouse_selection(self.doc, clicks, line, col, line, col))
+    end
     self.mouse_selecting = { line, col, clicks = clicks }
   end
   core.blink_reset()