Add IME support (#991)

data/core/doc/init.lua

@@ -456,6 +456,18 @@ function Doc:text_input(text, idx)
   end
 end
 
+
+function Doc:ime_text_editing(text, start, length, idx)
+  for sidx, line1, col1, line2, col2 in self:get_selections(true, idx or true) do
+    if line1 ~= line2 or col1 ~= col2 then
+      self:delete_to_cursor(sidx)
+    end
+    self:insert(line1, col1, text)
+    self:set_selections(sidx, line1, col1 + #text, line1, col1)
+  end
+end
+
+
 function Doc:replace_cursor(idx, line1, col1, line2, col2, fn)
   local old_text = self:get_text(line1, col1, line2, col2)
   local new_text, res = fn(old_text)

data/core/docview.lua

@@ -4,6 +4,7 @@ local config = require "core.config"
 local style = require "core.style"
 local keymap = require "core.keymap"
 local translate = require "core.doc.translate"
+local ime = require "core.ime"
 local View = require "core.view"
 
 ---@class core.docview : core.view
@@ -60,6 +61,7 @@ function DocView:new(doc)
   self.doc = assert(doc)
   self.font = "code_font"
   self.last_x_offset = {}
+  self.ime_selection = { from = 0, size = 0 }
 end
 
 
@@ -292,13 +294,42 @@ function DocView:on_text_input(text)
   self.doc:text_input(text)
 end
 
+function DocView:on_ime_text_editing(text, start, length)
+  self.doc:ime_text_editing(text, start, length)
+  self.ime_selection.from = start
+  self.ime_selection.size = length
+
+  -- Set the composition bounding box that the system IME
+  -- will consider when drawing its interface
+  local line1, col1, line2, col2 = self.doc:get_selection(true)
+  local x, y = self:get_line_screen_position(line1)
+  local h = self:get_line_height()
+  local col = math.min(col1, col2)
+
+  local x1, x2 = 0, 0
+
+  if length > 0 then
+    -- focus on a part of the text
+    local from = col + start
+    local to = from + length
+    x1 = self:get_col_x_offset(line1, from)
+    x2 = self:get_col_x_offset(line1, to)
+  else
+    -- focus the whole text
+    x1 = self:get_col_x_offset(line1, col1)
+    x2 = self:get_col_x_offset(line2, col2)
+  end
+
+  ime.set_location(x + x1, y, x2 - x1, h)
+  self:scroll_to_make_visible(line1, col + start)
+end
 
 function DocView:update()
   -- scroll to make caret visible and reset blink timer if it moved
   local line1, col1, line2, col2 = self.doc:get_selection()
   if (line1 ~= self.last_line1 or col1 ~= self.last_col1 or
       line2 ~= self.last_line2 or col2 ~= self.last_col2) and self.size.x > 0 then
-    if core.active_view == self then
+    if core.active_view == self and not ime.editing then
       self:scroll_to_make_visible(line1, col1)
     end
     core.blink_reset()
@@ -399,17 +430,45 @@ function DocView:draw_line_gutter(line, x, y, width)
 end
 
 
+function DocView:draw_ime_decoration(line1, col1, line2, col2)
+  local x, y = self:get_line_screen_position(line1)
+  local line_size = math.max(1, SCALE)
+  local lh = self:get_line_height()
+
+  -- Draw IME underline
+  local x1 = self:get_col_x_offset(line1, col1)
+  local x2 = self:get_col_x_offset(line2, col2)
+  renderer.draw_rect(x + math.min(x1, x2), y + lh - line_size, math.abs(x1 - x2), line_size, style.text)
+
+  -- Draw IME selection
+  local col = math.min(col1, col2)
+  local from = col + self.ime_selection.from
+  local to = from + self.ime_selection.size
+  x1 = self:get_col_x_offset(line1, from)
+  if from ~= to then
+    x2 = self:get_col_x_offset(line1, to)
+    line_size = style.caret_width
+    renderer.draw_rect(x + math.min(x1, x2), y + lh - line_size, math.abs(x1 - x2), line_size, style.caret)
+  end
+  self:draw_caret(x + x1, y)
+end
+
+
 function DocView:draw_overlay()
   if core.active_view == self then
     local minline, maxline = self:get_visible_line_range()
     -- draw caret if it overlaps this line
     local T = config.blink_period
-    for _, line, col in self.doc:get_selections() do
-      if line >= minline and line <= maxline
+    for _, line1, col1, line2, col2 in self.doc:get_selections() do
+      if line1 >= minline and line1 <= maxline
       and system.window_has_focus() then
-        if config.disable_blink
-        or (core.blink_timer - core.blink_start) % T < T / 2 then
-          self:draw_caret(self:get_line_screen_position(line, col))
+        if ime.editing then
+          self:draw_ime_decoration(line1, col1, line2, col2)
+        else
+          if config.disable_blink
+          or (core.blink_timer - core.blink_start) % T < T / 2 then
+            self:draw_caret(self:get_line_screen_position(line1, col1))
+          end
         end
       end
     end

data/core/ime.lua

@@ -0,0 +1,83 @@
+local core = require "core"
+
+local ime = { }
+
+function ime.reset()
+  ime.editing = false
+end
+
+---Convert from utf-8 offset and length (from SDL) to byte offsets
+---@param text string @Textediting string
+---@param start integer @0-based utf-8 offset of the starting position of the selection
+---@param length integer @Size of the utf-8 length of the selection
+function ime.ingest(text, start, length)
+  if #text == 0 then
+    -- finished textediting
+    ime.reset()
+    return "", 0, 0
+  end
+
+  ime.editing = true
+
+  if start < 0 then
+    -- we assume no selection and caret at the end
+    return text, #text, 0
+  end
+
+  -- start is 0-based, so we use start + 1
+  local start_byte = utf8.offset(text, start + 1)
+  if not start_byte then
+    -- bad start offset
+    -- we assume it meant the last byte of the text
+    start_byte = #text
+  else
+    start_byte = math.min(start_byte - 1, #text)
+  end
+
+  if length < 0 then
+    -- caret only
+    return text, start_byte, 0
+  end
+
+  local end_byte = utf8.offset(text, start + length + 1)
+  if not end_byte or end_byte - 1 < start_byte then
+    -- bad length, assume caret only
+    return text, start_byte, 0
+  end
+
+  end_byte = math.min(end_byte - 1, #text)
+  return text, start_byte, end_byte - start_byte
+end
+
+---Forward the given textediting SDL event data to Views.
+---@param text string @Textediting string
+---@param start integer @0-based utf-8 offset of the starting position of the selection
+---@param length integer @Size of the utf-8 length of the selection
+function ime.on_text_editing(text, start, length, ...)
+  if ime.editing or #text > 0 then
+    core.root_view:on_ime_text_editing(ime.ingest(text, start, length, ...))
+  end
+end
+
+---Stop IME composition.
+---Might not completely work on every platform.
+function ime.stop()
+  if ime.editing then
+    -- SDL_ClearComposition for now doesn't work everywhere
+    system.clear_ime()
+    ime.on_text_editing("", 0, 0)
+  end
+end
+
+---Set the bounding box of the text pertaining the IME.
+---The IME will draw its interface based on this info.
+---@param x number
+---@param y number
+---@param w number
+---@param h number
+function ime.set_location(x, y, w, h)
+  system.set_text_input_rect(x, y, w, h)
+end
+
+ime.reset()
+return ime

data/core/init.lua

@@ -6,6 +6,7 @@ local style = require "colors.default"
 local command
 local keymap
 local dirwatch
+local ime
 local RootView
 local StatusView
 local TitleView
@@ -657,6 +658,7 @@ function core.init()
   command = require "core.command"
   keymap = require "core.keymap"
   dirwatch = require "core.dirwatch"
+  ime = require "core.ime"
   RootView = require "core.rootview"
   StatusView = require "core.statusview"
   TitleView = require "core.titleview"
@@ -1051,6 +1053,8 @@ end
 
 function core.set_active_view(view)
   assert(view, "Tried to set active view to nil")
+  -- Reset the IME even if the focus didn't change
+  ime.stop()
   if view ~= core.active_view then
     if core.active_view and core.active_view.force_focus then
       core.next_active_view = view
@@ -1215,6 +1219,8 @@ function core.on_event(type, ...)
   local did_keymap = false
   if type == "textinput" then
     core.root_view:on_text_input(...)
+  elseif type == "textediting" then
+    ime.on_text_editing(...)
   elseif type == "keypressed" then
     did_keymap = keymap.on_key_pressed(...)
   elseif type == "keyreleased" then

data/core/keymap.lua

@@ -1,6 +1,7 @@
 local core = require "core"
 local command = require "core.command"
 local config = require "core.config"
+local ime = require "core.ime"
 local keymap = {}
 
 ---@alias keymap.shortcut string
@@ -177,6 +178,10 @@ end
 -- Events listening
 --------------------------------------------------------------------------------
 function keymap.on_key_pressed(k, ...)
+  -- In Windows during IME composition, input is still sent to us
+  -- so we just ignore it
+  if ime.editing then return false end
+
   local mk = modkey_map[k]
   if mk then
     keymap.modkeys[mk] = true

data/core/rootview.lua

@@ -334,6 +334,9 @@ function RootView:on_text_input(...)
   core.active_view:on_text_input(...)
 end
 
+function RootView:on_ime_text_editing(...)
+  core.active_view:on_ime_text_editing(...)
+end
 
 function RootView:on_focus_lost(...)
   -- We force a redraw so documents can redraw without the cursor.

data/core/view.lua

@@ -238,6 +238,10 @@ function View:on_text_input(text)
   -- no-op
 end
 
+function View:on_ime_text_editing(text, start, length)
+  -- no-op
+end
+
 ---@param y number
 ---@return boolean
 function View:on_mouse_wheel(y)

src/api/system.c

@@ -249,6 +249,23 @@ top:
       lua_pushstring(L, e.text.text);
       return 2;
 
+    case SDL_TEXTEDITING:
+      lua_pushstring(L, "textediting");
+      lua_pushstring(L, e.edit.text);
+      lua_pushinteger(L, e.edit.start);
+      lua_pushinteger(L, e.edit.length);
+      return 4;
+
+#if SDL_VERSION_ATLEAST(2, 0, 22)
+    case SDL_TEXTEDITING_EXT:
+      lua_pushstring(L, "textediting");
+      lua_pushstring(L, e.editExt.text);
+      lua_pushinteger(L, e.editExt.start);
+      lua_pushinteger(L, e.editExt.length);
+      SDL_free(e.editExt.text);
+      return 4;
+#endif
+
     case SDL_MOUSEBUTTONDOWN:
       if (e.button.button == 1) { SDL_CaptureMouse(1); }
       lua_pushstring(L, "mousepressed");
@@ -425,6 +442,23 @@ static int f_get_window_mode(lua_State *L) {
   return 1;
 }
 
+static int f_set_text_input_rect(lua_State *L) {
+  SDL_Rect rect;
+  rect.x = luaL_checknumber(L, 1);
+  rect.y = luaL_checknumber(L, 2);
+  rect.w = luaL_checknumber(L, 3);
+  rect.h = luaL_checknumber(L, 4);
+  SDL_SetTextInputRect(&rect);
+  return 0;
+}
+
+static int f_clear_ime(lua_State *L) {
+#if SDL_VERSION_ATLEAST(2, 0, 22)
+  SDL_ClearComposition();
+#endif
+  return 0;
+}
+
 
 static int f_raise_window(lua_State *L) {
   /*
@@ -986,6 +1020,8 @@ static const luaL_Reg lib[] = {
   { "set_window_hit_test", f_set_window_hit_test },
   { "get_window_size",     f_get_window_size     },
   { "set_window_size",     f_set_window_size     },
+  { "set_text_input_rect", f_set_text_input_rect },
+  { "clear_ime",           f_clear_ime           },
   { "window_has_focus",    f_window_has_focus    },
   { "raise_window",        f_raise_window        },
   { "show_fatal_error",    f_show_fatal_error    },

src/main.c

@@ -133,6 +133,12 @@ int main(int argc, char **argv) {
 #if SDL_VERSION_ATLEAST(2, 0, 5)
   SDL_SetHint(SDL_HINT_MOUSE_FOCUS_CLICKTHROUGH, "1");
 #endif
+#if SDL_VERSION_ATLEAST(2, 0, 18)
+  SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");
+#endif
+#if SDL_VERSION_ATLEAST(2, 0, 22)
+  SDL_SetHint(SDL_HINT_IME_SUPPORT_EXTENDED_TEXT, "1");
+#endif
 
 #if SDL_VERSION_ATLEAST(2, 0, 8)
   /* This hint tells SDL to respect borderless window as a normal window.