Improve `smoothcaret` plugin (#46)

- Add support for multiple carets
- Avoid making the caret "jump" around on blink
- Don't animate the caret during scroll
- Consistently animate the caret on click

1 files changed, 67 insertions, 10 deletions

diff --git a/plugins/smoothcaret.lua b/plugins/smoothcaret.lua
index 26f7d98..40d852e 100644
--- a/plugins/smoothcaret.lua
+++ b/plugins/smoothcaret.lua
@@ -1,4 +1,5 @@
 -- mod-version:2 -- lite-xl 2.0
+local core = require "core"
 local config = require "core.config"
 local style = require "core.style"
 local DocView = require "core.docview"
@@ -9,18 +10,74 @@ local docview_update = DocView.update
 function DocView:update()
   docview_update(self)
 
-  if not self.caret then
-    self.caret = { current = { x = 0, y = 0 }, target = { x = 0, y = 0 } }
-  end  
-  local c = self.caret
-  self:move_towards(c.current, "x", c.target.x, config.plugins.smoothcaret.rate)
-  self:move_towards(c.current, "y", c.target.y, config.plugins.smoothcaret.rate)
+  local minline, maxline = self:get_visible_line_range()
+
+  -- We need to keep track of all the carets
+  if not self.carets then
+    self.carets = { }
+  end
+  -- and we need the list of visible ones that `DocView:draw_caret` will use in succession
+  self.visible_carets = { }
+
+  local idx, v_idx = 1, 1
+  for _, line, col in self.doc:get_selections() do
+    local x, y = self:get_line_screen_position(line)
+    -- Keep the position relative to the whole View
+    -- This way scrolling won't animate the caret
+    x = x + self:get_col_x_offset(line, col) + self.scroll.x
+    y = y + self.scroll.y
+
+    if not self.carets[idx] then
+      self.carets[idx] = { current = { x = x, y = y }, target = { x = x, y = y } }
+    end
+
+    local c = self.carets[idx]
+    c.target.x = x
+    c.target.y = y
+
+    -- Chech if the number of carets changed
+    if self.last_n_selections ~= #self.doc.selections then
+      -- Don't animate when there are new carets
+      c.current.x = x
+      c.current.y = y
+    else
+      self:move_towards(c.current, "x", c.target.x, config.plugins.smoothcaret.rate)
+      self:move_towards(c.current, "y", c.target.y, config.plugins.smoothcaret.rate)
+    end
+
+    -- Keep track of visible carets
+    if line >= minline and line <= maxline then
+      self.visible_carets[v_idx] = self.carets[idx]
+      v_idx = v_idx + 1
+    end
+    idx = idx + 1
+  end
+  self.last_n_selections = #self.doc.selections
+
+  -- Remove unused carets to avoid animating new ones when they are added
+  for i = idx, #self.carets do
+    self.carets[idx] = nil
+  end
+
+  if self.mouse_selecting ~= self.last_mouse_selecting then
+    self.last_mouse_selecting = self.mouse_selecting
+    -- Show the caret on click, so that it can be seen moving towards the new position
+    if self.mouse_selecting then
+      core.blink_timer = core.blink_timer + config.blink_period / 2
+      core.redraw = true
+    end
+  end
+
+  -- This is used by `DocView:draw_caret` to keep track of the current caret
+  self.caret_idx = 1
 end
 
 function DocView:draw_caret(x, y)
-  local c = self.caret
+  local c = self.visible_carets[self.caret_idx] or { current = { x = x, y = y } }
   local lh = self:get_line_height()
-  c.target.x = x
-  c.target.y = y
-  renderer.draw_rect(c.current.x, c.current.y, style.caret_width, lh, style.caret)
+
+  -- We use the scroll position to move back to the position relative to the window
+  renderer.draw_rect(c.current.x - self.scroll.x, c.current.y - self.scroll.y, style.caret_width, lh, style.caret)
+
+  self.caret_idx = self.caret_idx + 1
 end