Use drawing_cache without disable mechanism

Also moved cache to `DocView`

data/core/docview.lua

@@ -56,6 +56,7 @@ function DocView:new(doc)
   self.doc = assert(doc)
   self.font = "code_font"
   self.last_x_offset = {}
+  self.drawing_cache = {}
 end
 
 
@@ -97,37 +98,51 @@ function DocView:get_filename()
 end
 
 
-function DocView:get_scrollable_size()
+function DocView:compute_scrollable_size()
   return self:get_line_height() * (#self.doc.lines - 1) + self.size.y
 end
 
-function DocView:get_h_scrollable_size()
-  local doc_change_id = self.doc:get_change_id()
-  if self.last_doc_change_id ~= doc_change_id then
-    self.last_doc_change_id = doc_change_id
-    local xmargin = 3 * self:get_font():get_width(' ') -- from DocView:scroll_to_make_visible
-    -- TODO: make Doc calculate the real longest line in pixels, not in characters,
-    -- as the current implementation only works for monospace fonts
-    local long_line = next(self.doc.long_lines.line_numbers) or 1
-    self.h_scrollable_size = self:get_col_x_offset(long_line, self.doc.long_lines.length)
-                             + self:get_gutter_width() + xmargin
-  end
-  return self.h_scrollable_size
+
+function DocView:get_scrollable_size()
+  return self.drawing_cache.scrollable_size
 end
 
+
+function DocView:compute_h_scrollable_size()
+  local xmargin = 3 * self:get_font():get_width(' ') -- from DocView:scroll_to_make_visible
+  local long_line = next(self.doc.long_lines.line_numbers) or 1
+  return self:get_col_x_offset(long_line, self.doc.long_lines.length) + self:get_gutter_width() + xmargin
+end
+
+
+function DocView:get_h_scrollable_size()
+  return self.drawing_cache.h_scrollable_size
+end
+
+
 function DocView:get_font()
   return style[self.font]
 end
 
 
-function DocView:get_line_height()
+function DocView:compute_line_height()
   return math.floor(self:get_font():get_height() * config.line_height)
 end
 
 
+function DocView:get_line_height()
+  return self.drawing_cache.line_height
+end
+
+
+function DocView:compute_gutter_width()
+  return self:get_font():get_width(#self.doc.lines)
+end
+
+
 function DocView:get_gutter_width()
   local padding = style.padding.x * 2
-  return self:get_font():get_width(#self.doc.lines) + padding, padding
+  return self.drawing_cache.gutter_width + padding, padding
 end
 
 
@@ -321,6 +336,7 @@ end
 
 
 function DocView:update()
+  self:update_drawing_cache()
   -- scroll to make caret visible and reset blink timer if it moved
   local line, col = self.doc:get_selection()
   if (line ~= self.last_line or col ~= self.last_col) and self.size.x > 0 then
@@ -461,4 +477,13 @@ function DocView:draw()
 end
 
 
+function DocView:update_drawing_cache()
+  local cache = self.drawing_cache
+  cache.gutter_width      = self:compute_gutter_width()
+  cache.line_height       = self:compute_line_height()
+  cache.scrollable_size   = self:compute_scrollable_size()
+  cache.h_scrollable_size = self:compute_h_scrollable_size()
+end
+
+
 return DocView

data/core/rootview.lua

@@ -754,6 +754,7 @@ function RootView:open_doc(doc)
   local view = DocView(doc)
   node:add_view(view)
   self.root_node:update_layout()
+  view:update_drawing_cache()
   view:scroll_to_line(view.doc:get_selection(), true, true)
   return view
 end

data/core/view.lua

@@ -21,6 +21,7 @@ function View:new()
   self.scrollable = false
 end
 
+
 function View:move_towards(t, k, dest, rate)
   if type(t) ~= "table" then
     return self:move_towards(self, t, k, dest, rate)

data/plugins/scale.lua

@@ -56,6 +56,8 @@ local function set_scale(scale)
     renderer.font.set_size(style.code_font, s * style.code_font:get_size())
   end
 
+  view:update_drawing_cache()
+
   -- restore scroll positions
   for view, n in pairs(scrolls) do
     view.scroll.y = n * (view:get_scrollable_size() - view.size.y)