chore(refactor): pass callback when computing extmarks to make move to async parsing easier

## Details

In order to take advantage of async treesitter parsing we'll need to use
a callback pattern to compute and add `extmarks` after parsing finishes.

Currently (from some local testing) I'm not seeing improvements to
responsiveness from this so am not making the full change to actually do
this for now.

However to make adopting it easier in the future I'm updating the
structure of how `parse` is called to use a callback, even if it's not
necessary for the time being.

In order to do this the logic of displaying `extmarks` needed to be
separated into its own method from the logic that sets `extmarks`.

This is because in the event that we need to `parse` we need to both set
and display the `extmarks` as part of the callback, and in the event we
don't we just want to display the `extmarks` immediately. Since one
happens in a callback and the other directly the logic can't be shared
as part of the same method and needed to be moved to its own.

There are technically some small changes to behavior but they should not
cause any problems:

- Previously we only called `on.clear` when removing marks due to a mode
  change. However when we `parse` and get new marks we also need to
  clear the buffer to remove any not needed for the current render
  cycle. The `on.clear` callback is now called in both of these cases.
- The time between clearing old marks and showing new marks is
  "massively" reduced. Before we would clear, then parse, then display.
  Now the behavior is parse, then clear, then display. Since the parse
  step is the most expensive the gap is much lower, from local testing
  goes from 10s of milliseconds to less than 1. Neither of these is
  really something people can notice so no visible change.

Author: MeanderingProgrammer

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 ## Pre-release
 
+### Features
+
+- change code.border to thin instead of hide if version < 0.11.0 [a706be7](https://github.com/MeanderingProgrammer/render-markdown.nvim/commit/a706be739257a6203524741da2da540bc190bbe2)
+- allow image links to use custom icons based on destination [ac3e74f](https://github.com/MeanderingProgrammer/render-markdown.nvim/commit/ac3e74ffdb0bcf7282445ac12083fb6bd44858a1)
+
 ## 8.5.0 (2025-06-10)
 
 ### Features

lua/render-markdown/core/ui.lua

@@ -122,10 +122,8 @@ function Updater:run()
     end
     if not render then
         self:clear()
-        M.config.on.clear({ buf = self.buf, win = self.win })
     else
         self:render()
-        M.config.on.render({ buf = self.buf, win = self.win })
     end
 end
 
@@ -135,20 +133,49 @@ function Updater:clear()
     for _, extmark in ipairs(extmarks) do
         extmark:hide(M.ns, self.buf)
     end
+    M.config.on.clear({ buf = self.buf, win = self.win })
 end
 
 ---@private
 function Updater:render()
     if self:changed() then
-        local initial = self.decorator:initial()
-        self:clear()
-        local extmarks = self:get_extmarks()
-        self.decorator:set(extmarks)
-        if initial then
-            compat.fix_lsp_window(self.buf, self.win, extmarks)
-            M.config.on.initial({ buf = self.buf, win = self.win })
-        end
+        self:parse(function(extmarks)
+            if not extmarks then
+                return
+            end
+            local initial = self.decorator:initial()
+            self:clear()
+            self.decorator:set(extmarks)
+            if initial then
+                compat.fix_lsp_window(self.buf, self.win, extmarks)
+                M.config.on.initial({ buf = self.buf, win = self.win })
+            end
+            self:display()
+        end)
+    else
+        self:display()
+    end
+end
+
+---@private
+---@param callback fun(extmarks: render.md.Extmark[]|nil)
+function Updater:parse(callback)
+    local ok, parser = pcall(vim.treesitter.get_parser, self.buf)
+    if ok and parser then
+        -- reset buffer context
+        local context = Context.new(self.buf, self.win, self.config, self.mode)
+        -- make sure injections are processed
+        context.view:parse(parser)
+        local marks = handlers.run(context, parser)
+        callback(iter.list.map(marks, Extmark.new))
+    else
+        log.buf('error', 'Fail', self.buf, 'no treesitter parser found')
+        callback(nil)
     end
+end
+
+---@private
+function Updater:display()
     local range = self:hidden()
     local extmarks = self.decorator:get()
     for _, extmark in ipairs(extmarks) do
@@ -158,22 +185,7 @@ function Updater:render()
             extmark:show(M.ns, self.buf)
         end
     end
-end
-
----@private
----@return render.md.Extmark[]
-function Updater:get_extmarks()
-    local ok, parser = pcall(vim.treesitter.get_parser, self.buf)
-    if not ok or not parser then
-        log.buf('error', 'Fail', self.buf, 'no treesitter parser found')
-        return {}
-    end
-    -- reset buffer context
-    local context = Context.new(self.buf, self.win, self.config, self.mode)
-    -- make sure injections are processed
-    context.view:parse(parser)
-    local marks = handlers.run(context, parser)
-    return iter.list.map(marks, Extmark.new)
+    M.config.on.render({ buf = self.buf, win = self.win })
 end
 
 ---@private

lua/render-markdown/health.lua

@@ -5,7 +5,7 @@ local state = require('render-markdown.state')
 local M = {}
 
 ---@private
-M.version = '8.5.4'
+M.version = '8.5.5'
 
 function M.check()
     M.start('version')