Make `indentguide` highlight the current block

1 files changed, 81 insertions, 13 deletions

diff --git a/plugins/indentguide.lua b/plugins/indentguide.lua
index 0513be4..1c4f8ae 100644
--- a/plugins/indentguide.lua
+++ b/plugins/indentguide.lua
@@ -4,18 +4,28 @@ local config = require "core.config"
 local DocView = require "core.docview"
 
 
+-- TODO: replace with `doc:get_indent_info()` when 2.1 releases
+local function get_indent_info(doc)
+  if doc.get_indent_info then
+    return doc:get_indent_info()
+  end
+  return config.tab_type, config.indent_size
+end
+
+
 local function get_line_spaces(doc, idx, dir)
+  local _, indent_size = get_indent_info(doc)
   local text = doc.lines[idx]
-  if not text then
-    return 0
+  if not text or #text == 1 then
+    return -1
   end
   local s, e = text:find("^%s*")
   if e == #text then
     return get_line_spaces(doc, idx + dir, dir)
   end
   local n = 0
-  for i = s, e do
-    n = n + (text:byte(i) == 9 and config.indent_size or 1)
+  for _,b in pairs({text:byte(s, e)}) do
+    n = n + (b == 9 and indent_size or 1)
   end
   return n
 end
@@ -30,21 +40,79 @@ local function get_line_indent_guide_spaces(doc, idx)
   return get_line_spaces(doc, idx)
 end
 
+local docview_update = DocView.update
+function DocView:update()
+  docview_update(self)
 
-local draw_line_text = DocView.draw_line_text
+  local function get_indent(idx)
+    if idx < 1 or idx > #self.doc.lines then return -1 end
+    if not self.lineguide_indents[idx] then
+      self.lineguide_indents[idx] = get_line_indent_guide_spaces(self.doc, idx)
+    end
+    return self.lineguide_indents[idx]
+  end
+
+  self.lineguide_indents = {}
+  self.lineguide_indent_active = {}
+
+  local minline, maxline = self:get_visible_line_range()
+  for i = minline, maxline do
+    self.lineguide_indents[i] = get_line_indent_guide_spaces(self.doc, i)
+  end
+
+  local line = self.doc:get_selection()
+  local lvl = get_indent(line)
+  local top, bottom
+  local _, indent_size = get_indent_info(self.doc)
 
+  -- check if we're the header or the footer of a block
+  if get_indent(line + 1) > lvl and get_indent(line + 1) <= lvl + indent_size then
+    top = true
+    lvl = get_indent(line + 1)
+  elseif get_indent(line - 1) > lvl and get_indent(line - 1) <= lvl + indent_size then
+    bottom = true
+    lvl = get_indent(line - 1)
+  end
+
+  self.lineguide_indent_active[line] = lvl
+
+  -- check if the lines before the current are part of the block
+  local i = line - 1
+  if i > 0 and not top then
+    repeat
+      if get_indent(i) <= lvl - indent_size then break end
+      self.lineguide_indent_active[i] = lvl
+      i = i - 1
+    until i < minline
+  end
+  -- check if the lines after the current are part of the block
+  i = line + 1
+  if i <= #self.doc.lines and not bottom then
+    repeat
+      if get_indent(i) <= lvl - indent_size then break end
+      self.lineguide_indent_active[i] = lvl
+      i = i + 1
+    until i > maxline
+  end
+end
+
+
+local draw_line_text = DocView.draw_line_text
 function DocView:draw_line_text(idx, x, y)
-  local spaces = get_line_indent_guide_spaces(self.doc, idx)
-  local w = math.ceil(1 * SCALE)
+  local spaces = self.lineguide_indents[idx] or -1
+  local _, indent_size = get_indent_info(self.doc)
+  local w = math.max(1, SCALE)
   local h = self:get_line_height()
-  local sspaces = ""
   local font = self:get_font()
-  local ss = font:subpixel_scale()
-  for _ = 0, spaces - 1, config.indent_size do
+  local space_sz = font:get_width(" ")
+  for i = 0, spaces - 1, indent_size do
     local color = style.guide or style.selection
-    local sw = font:get_width_subpixel(sspaces) / ss
-    renderer.draw_rect(x + sw, y, w, h, color)
-    sspaces = sspaces .. (' '):rep(config.indent_size)
+    local active_lvl = self.lineguide_indent_active[idx] or -1
+    if i < active_lvl and i + indent_size >= active_lvl then
+      color = style.accent
+    end
+    local sw = space_sz * i
+    renderer.draw_rect(math.ceil(x + sw), y, w, h, color)
   end
   draw_line_text(self, idx, x, y)
 end