feat(renderer): incremental rendering, markdown-on-idle, and changed-line highlights

Author: sudo-tee

lua/opencode/config.lua

@@ -142,6 +142,11 @@ M.defaults = {
       rendering = {
         markdown_debounce_ms = 250,
         on_data_rendered = nil,
+        markdown_on_idle = false,
+        -- If set to a number, markdown rendering will be deferred while
+        -- `state.user_message_count[session_id]` is greater than this value.
+        -- If `nil`, the existing behavior is used (defer while > 0).
+        markdown_on_idle_threshold = nil,
         event_throttle_ms = 40,
         event_collapsing = true,
       },
@@ -255,6 +260,8 @@ M.defaults = {
     enabled = false,
     capture_streamed_events = false,
     show_ids = true,
+    highlight_changed_lines = true,
+    highlight_changed_lines_timeout_ms = 120,
     quick_chat = {
       keep_session = false,
       set_active_session = false,

lua/opencode/core.lua

@@ -537,6 +537,8 @@ M.initialize_current_model = Promise.async(function()
 end)
 
 M._on_user_message_count_change = Promise.async(function(_, new, old)
+  require('opencode.ui.renderer.flush').flush_pending_on_data_rendered()
+
   if config.hooks and config.hooks.on_done_thinking then
     local all_sessions = session.get_all_workspace_sessions():await()
     local done_sessions = vim.tbl_filter(function(s)

lua/opencode/types.lua

@@ -172,6 +172,7 @@
 ---@class OpencodeUIOutputRenderingConfig
 ---@field markdown_debounce_ms number
 ---@field on_data_rendered (fun(buf: integer, win: integer)|boolean)|nil
+---@field markdown_on_idle boolean
 ---@field event_throttle_ms number
 ---@field event_collapsing boolean
 
@@ -207,6 +208,8 @@
 ---@field enabled boolean
 ---@field capture_streamed_events boolean
 ---@field show_ids boolean
+---@field highlight_changed_lines boolean
+---@field highlight_changed_lines_timeout_ms number
 ---@field quick_chat {keep_session: boolean, set_active_session: boolean}
 
 ---@class OpencodeHooks

lua/opencode/ui/highlight.lua

@@ -47,6 +47,7 @@ function M.setup()
     vim.api.nvim_set_hl(0, 'OpencodeQuestionOption', { link = 'Normal', default = true })
     vim.api.nvim_set_hl(0, 'OpencodeQuestionBorder', { fg = '#E3F2FD', default = true })
     vim.api.nvim_set_hl(0, 'OpencodeQuestionTitle', { link = '@label', bold = true, default = true })
+    vim.api.nvim_set_hl(0, 'OpencodeChangedLines', { bg = '#FFF3BF', default = true })
   else
     vim.api.nvim_set_hl(0, 'OpencodeBorder', { fg = '#616161', default = true })
     vim.api.nvim_set_hl(0, 'OpencodeBackground', { link = 'Normal', default = true })
@@ -90,6 +91,7 @@ function M.setup()
     vim.api.nvim_set_hl(0, 'OpencodeQuestionOption', { link = 'Normal', default = true })
     vim.api.nvim_set_hl(0, 'OpencodeQuestionBorder', { fg = '#2B3A5A', default = true })
     vim.api.nvim_set_hl(0, 'OpencodeQuestionTitle', { link = '@label', bold = true, default = true })
+    vim.api.nvim_set_hl(0, 'OpencodeChangedLines', { bg = '#3D3520', default = true })
   end
 end
 

lua/opencode/ui/output_window.lua

@@ -4,6 +4,8 @@ local window_options = require('opencode.ui.window_options')
 
 local M = {}
 M.namespace = vim.api.nvim_create_namespace('opencode_output')
+M.debug_namespace = vim.api.nvim_create_namespace('opencode_output_debug')
+M.markdown_namespace = vim.api.nvim_create_namespace('opencode_output_markdown')
 
 local _update_depth = 0
 local _update_buf = nil
@@ -107,7 +109,12 @@ function M.is_at_bottom(win)
 end
 
 function M.setup(windows)
-  window_options.set_window_option('winhighlight', config.ui.window_highlight, windows.output_win, { save_original = true })
+  window_options.set_window_option(
+    'winhighlight',
+    config.ui.window_highlight,
+    windows.output_win,
+    { save_original = true }
+  )
   window_options.set_window_option('wrap', true, windows.output_win, { save_original = true })
   window_options.set_window_option('linebreak', true, windows.output_win, { save_original = true })
   window_options.set_window_option('number', false, windows.output_win, { save_original = true })
@@ -117,6 +124,8 @@ function M.setup(windows)
   window_options.set_buffer_option('bufhidden', 'hide', windows.output_buf)
   window_options.set_buffer_option('buflisted', false, windows.output_buf)
   window_options.set_buffer_option('swapfile', false, windows.output_buf)
+  window_options.set_buffer_option('undofile', false, windows.output_buf)
+  window_options.set_buffer_option('undolevels', -1, windows.output_buf)
 
   if config.ui.position ~= 'current' then
     window_options.set_window_option('winfixbuf', true, windows.output_win, { save_original = true })
@@ -188,6 +197,28 @@ function M.set_lines(lines, start_line, end_line)
   start_line = start_line or 0
   end_line = end_line or -1
 
+  -- Avoid rewriting unchanged lines to prevent flashing/flicker when
+  -- re-rendering formatted parts (e.g. markdown). Compare the target range
+  -- with the existing buffer lines and skip the write when identical.
+  local ok, existing = pcall(vim.api.nvim_buf_get_lines, buf, start_line, end_line, false)
+  if ok and existing then
+    local same = true
+    if #existing ~= #lines then
+      same = false
+    else
+      for i = 1, #lines do
+        if existing[i] ~= lines[i] then
+          same = false
+          break
+        end
+      end
+    end
+
+    if same then
+      return
+    end
+  end
+
   if _update_depth == 0 then
     vim.api.nvim_set_option_value('modifiable', true, { buf = buf })
     vim.api.nvim_buf_set_lines(buf, start_line, end_line, false, lines)
@@ -246,6 +277,40 @@ function M.set_extmarks(extmarks, line_offset)
   end
 end
 
+---@param start_line integer
+---@param end_line integer
+function M.highlight_changed_lines(start_line, end_line)
+  local windows = state.windows
+  if not windows or not windows.output_buf or not vim.api.nvim_buf_is_valid(windows.output_buf) then
+    return
+  end
+  if not config.debug.highlight_changed_lines then
+    return
+  end
+
+  local buf = windows.output_buf
+  local first = math.max(0, start_line)
+  if end_line < start_line then
+    return
+  end
+  local last = math.max(first, end_line)
+
+  vim.api.nvim_buf_clear_namespace(buf, M.debug_namespace, first, last + 1)
+  for line = first, last do
+    vim.api.nvim_buf_set_extmark(buf, M.debug_namespace, line, 0, {
+      line_hl_group = 'OpencodeChangedLines',
+      hl_eol = true,
+      priority = 250,
+    })
+  end
+
+  vim.defer_fn(function()
+    if vim.api.nvim_buf_is_valid(buf) then
+      vim.api.nvim_buf_clear_namespace(buf, M.debug_namespace, first, last + 1)
+    end
+  end, config.debug.highlight_changed_lines_timeout_ms or 120)
+end
+
 function M.focus_output(should_stop_insert)
   if not M.mounted() then
     return

lua/opencode/ui/renderer/buffer.lua

@@ -12,6 +12,59 @@ local function has_actions(actions)
   return type(actions) == 'table' and #actions > 0
 end
 
+local function unchanged_prefix_len(previous_formatted, formatted_data)
+  local previous_lines = previous_formatted and previous_formatted.lines or {}
+  local next_lines = formatted_data and formatted_data.lines or {}
+  local prefix_len = 0
+
+  for i = 1, math.min(#previous_lines, #next_lines) do
+    if previous_lines[i] ~= next_lines[i] then
+      break
+    end
+    prefix_len = i
+  end
+
+  return prefix_len
+end
+
+local function slice_lines(lines, start_idx)
+  local slice = {}
+  for i = start_idx, #(lines or {}) do
+    slice[#slice + 1] = lines[i]
+  end
+  return slice
+end
+
+local function slice_extmarks(extmarks, start_line)
+  local slice = {}
+  for line_idx, marks in pairs(extmarks or {}) do
+    if line_idx >= start_line + 1 then
+      slice[line_idx - start_line] = vim.deepcopy(marks)
+    end
+  end
+  return slice
+end
+
+local function highlight_written_lines(start_line, lines)
+  if #lines == 0 then
+    return
+  end
+  output_window.highlight_changed_lines(start_line, start_line + #lines - 1)
+end
+
+local function apply_extmarks(previous_formatted, formatted_data, line_start, old_line_end, new_line_end)
+  local prefix_len = unchanged_prefix_len(previous_formatted, formatted_data)
+  local clear_start = line_start + prefix_len
+  local clear_end = math.max(old_line_end, new_line_end) + 1
+
+  output_window.clear_extmarks(clear_start, clear_end)
+
+  local extmarks = slice_extmarks(formatted_data.extmarks, prefix_len)
+  if has_extmarks(extmarks) then
+    output_window.set_extmarks(extmarks, clear_start)
+  end
+end
+
 local function get_message_insert_line(message_id)
   local rendered_message = ctx.render_state:get_message(message_id)
   if rendered_message and rendered_message.line_start then
@@ -80,6 +133,7 @@ end
 
 local function write_at(lines, start_line, end_line)
   output_window.set_lines(lines, start_line, end_line)
+  highlight_written_lines(start_line, lines)
   return {
     line_start = start_line,
     line_end = start_line + #lines - 1,
@@ -100,13 +154,7 @@ local function apply_part_actions(part_id, formatted_data, line_start)
   end
 end
 
-local function apply_part_extmarks(part_id, formatted_data, line_start, line_end)
-  output_window.clear_extmarks(line_start - 1, line_end + 1)
-
-  if has_extmarks(formatted_data.extmarks) then
-    output_window.set_extmarks(formatted_data.extmarks, line_start)
-  end
-
+local function set_part_extmark_state(part_id, formatted_data)
   local part_data = ctx.render_state:get_part(part_id)
   if part_data then
     part_data.has_extmarks = has_extmarks(formatted_data.extmarks)
@@ -142,17 +190,19 @@ function M.find_part_by_call_id(call_id, message_id)
   return ctx.render_state:get_part_by_call_id(call_id, message_id)
 end
 
-function M.upsert_message_now(message_id, formatted_data)
+function M.upsert_message_now(message_id, formatted_data, previous_formatted)
   local cached = ctx.render_state:get_message(message_id)
   if cached and cached.line_start and cached.line_end then
-    output_window.clear_extmarks(cached.line_start, cached.line_end + 1)
-    output_window.set_lines(formatted_data.lines, cached.line_start, cached.line_end + 1)
-    if has_extmarks(formatted_data.extmarks) then
-      output_window.set_extmarks(formatted_data.extmarks, cached.line_start)
-    end
-
     local old_line_end = cached.line_end
+    local prefix_len = unchanged_prefix_len(previous_formatted, formatted_data)
+    local write_start = cached.line_start + prefix_len
+    local lines_to_write = slice_lines(formatted_data.lines, prefix_len + 1)
+
+    output_window.set_lines(lines_to_write, write_start, cached.line_end + 1)
+    highlight_written_lines(write_start, lines_to_write)
+
     local new_line_end = cached.line_start + #formatted_data.lines - 1
+    apply_extmarks(previous_formatted, formatted_data, cached.line_start, old_line_end, new_line_end)
     ctx.render_state:set_message(cached.message, cached.line_start, new_line_end)
 
     local delta = new_line_end - old_line_end
@@ -178,18 +228,25 @@ function M.upsert_message_now(message_id, formatted_data)
   return false
 end
 
-function M.upsert_part_now(part_id, message_id, formatted_data)
+function M.upsert_part_now(part_id, message_id, formatted_data, previous_formatted)
   local cached = ctx.render_state:get_part(part_id)
   if cached and cached.line_start and cached.line_end then
-    output_window.set_lines(formatted_data.lines, cached.line_start, cached.line_end + 1)
+    local old_line_end = cached.line_end
+    local prefix_len = unchanged_prefix_len(previous_formatted, formatted_data)
+    local write_start = cached.line_start + prefix_len
+    local lines_to_write = slice_lines(formatted_data.lines, prefix_len + 1)
+
+    output_window.set_lines(lines_to_write, write_start, cached.line_end + 1)
+    highlight_written_lines(write_start, lines_to_write)
 
     local new_line_end = cached.line_start + #formatted_data.lines - 1
     apply_part_actions(part_id, formatted_data, cached.line_start)
 
     if new_line_end ~= cached.line_end then
       ctx.render_state:update_part_lines(part_id, cached.line_start, new_line_end)
     end
-    apply_part_extmarks(part_id, formatted_data, cached.line_start, new_line_end)
+    apply_extmarks(previous_formatted, formatted_data, cached.line_start, old_line_end, new_line_end)
+    set_part_extmark_state(part_id, formatted_data)
     return true
   end
 
@@ -204,29 +261,35 @@ function M.upsert_part_now(part_id, message_id, formatted_data)
     ctx.render_state:shift_all(insert_at, #formatted_data.lines)
     ctx.render_state:set_part(part_data.part, range.line_start, range.line_end)
     apply_part_actions(part_id, formatted_data, range.line_start)
-    apply_part_extmarks(part_id, formatted_data, range.line_start, range.line_end)
+    if has_extmarks(formatted_data.extmarks) then
+      output_window.set_extmarks(formatted_data.extmarks, range.line_start)
+    end
+    set_part_extmark_state(part_id, formatted_data)
     return true
   end
 
   return false
 end
 
-function M.append_part_now(part_id, extra_lines, extra_extmarks)
+function M.append_part_now(part_id, extra_lines, extra_extmarks, previous_formatted)
   local cached = ctx.render_state:get_part(part_id)
   if not cached or not cached.line_start or not cached.line_end or #extra_lines == 0 then
     return false
   end
 
   local insert_at = cached.line_end + 1
+  local old_line_end = cached.line_end
   output_window.set_lines(extra_lines, insert_at, insert_at)
+  highlight_written_lines(insert_at, extra_lines)
 
   local new_line_end = cached.line_end + #extra_lines
   ctx.render_state:update_part_lines(part_id, cached.line_start, new_line_end)
 
   local formatted_data = ctx.formatted_parts[part_id]
   if formatted_data then
     apply_part_actions(part_id, formatted_data, cached.line_start)
-    apply_part_extmarks(part_id, formatted_data, cached.line_start, new_line_end)
+    apply_extmarks(previous_formatted, formatted_data, cached.line_start, old_line_end, new_line_end)
+    set_part_extmark_state(part_id, formatted_data)
   elseif has_extmarks(extra_extmarks) then
     output_window.set_extmarks(extra_extmarks, insert_at)
   end

lua/opencode/ui/renderer/ctx.lua

@@ -26,6 +26,7 @@ local ctx = {
     removed_messages = {},
   },
   flush_scheduled = false,
+  markdown_render_scheduled = false,
 }
 
 function ctx:reset()
@@ -46,6 +47,7 @@ function ctx:reset()
     removed_messages = {},
   }
   self.flush_scheduled = false
+  self.markdown_render_scheduled = false
 end
 
 return ctx