perf(stack-view): render only changed lines

Author: mhiro2

lua/peekstack/types.lua

@@ -151,6 +151,7 @@
 ---@field winid integer?
 ---@field root_winid integer?
 ---@field line_to_id table<integer, integer>
+---@field render_keys string[]
 ---@field filter string?
 ---@field header_lines integer
 ---@field help_bufnr integer?

lua/peekstack/ui/stack_view/init.lua

@@ -61,6 +61,7 @@ local function get_state()
       winid = nil,
       root_winid = nil,
       line_to_id = {},
+      render_keys = {},
       filter = nil,
       header_lines = 0,
       help_bufnr = nil,
@@ -150,6 +151,7 @@ local function reset_open_state(s)
   s.winid = nil
   s.bufnr = nil
   s.root_winid = nil
+  s.render_keys = {}
   s.autoclose_suspended = 0
   s.help_augroup = nil
 end
@@ -231,6 +233,7 @@ function M.open()
   s.root_winid = find_root_winid()
   s.bufnr = vim.api.nvim_create_buf(false, true)
   s.winid = vim.api.nvim_open_win(s.bufnr, true, stack_view_win_config())
+  s.render_keys = {}
 
   vim.wo[s.winid].cursorline = true
   vim.wo[s.winid].winhighlight = "CursorLine:PeekstackStackViewCursorLine"

lua/peekstack/ui/stack_view/render.lua

@@ -315,6 +315,110 @@ local function get_preview_line(source_bufnr, line, max_width, preview_prefix)
   }
 end
 
+---@param line string
+---@param line_hls PeekstackStackViewHighlight[]
+---@param preview PeekstackStackViewPreviewLine?
+---@return string
+local function line_render_key(line, line_hls, preview)
+  local parts = { line }
+  for _, hl in ipairs(line_hls) do
+    parts[#parts + 1] = string.format("%d:%d:%s", hl.col_start, hl.col_end, hl.hl_group)
+  end
+  if preview then
+    parts[#parts + 1] = string.format(
+      "preview:%d:%d:%d:%d:%d",
+      preview.source_bufnr,
+      preview.source_line,
+      preview.source_col_start,
+      preview.source_col_end,
+      preview.preview_col_start
+    )
+  end
+  return table.concat(parts, "|")
+end
+
+---@param items string[]
+---@param start_idx integer
+---@param end_idx integer
+---@return string[]
+local function slice_lines(items, start_idx, end_idx)
+  if end_idx < start_idx then
+    return {}
+  end
+
+  ---@type string[]
+  local slice = {}
+  for idx = start_idx, end_idx do
+    slice[#slice + 1] = items[idx]
+  end
+  return slice
+end
+
+---@param old_keys string[]
+---@param new_keys string[]
+---@return integer?, integer?, integer?
+local function diff_range(old_keys, new_keys)
+  local old_count = #old_keys
+  local new_count = #new_keys
+  local start_idx = 1
+
+  while start_idx <= old_count and start_idx <= new_count and old_keys[start_idx] == new_keys[start_idx] do
+    start_idx = start_idx + 1
+  end
+
+  if start_idx > old_count and start_idx > new_count then
+    return nil, nil, nil
+  end
+
+  local old_end = old_count
+  local new_end = new_count
+  while old_end >= start_idx and new_end >= start_idx and old_keys[old_end] == new_keys[new_end] do
+    old_end = old_end - 1
+    new_end = new_end - 1
+  end
+
+  return start_idx, old_end, new_end
+end
+
+---@param bufnr integer
+---@param highlights PeekstackStackViewHighlight[][]
+---@param preview_lines table<integer, PeekstackStackViewPreviewLine>
+---@param start_idx integer
+---@param end_idx integer
+local function apply_highlights_in_range(bufnr, highlights, preview_lines, start_idx, end_idx)
+  if end_idx < start_idx then
+    return
+  end
+
+  for line_idx = start_idx, end_idx do
+    for _, hl in ipairs(highlights[line_idx] or {}) do
+      local opts = {
+        end_col = hl.col_end,
+        hl_group = hl.hl_group,
+      }
+      if hl.hl_group == "PeekstackStackViewPreview" then
+        opts.priority = PREVIEW_BASE_HL_PRIORITY
+      end
+      vim.api.nvim_buf_set_extmark(bufnr, NS, line_idx - 1, hl.col_start, {
+        end_col = opts.end_col,
+        hl_group = opts.hl_group,
+        priority = opts.priority,
+      })
+    end
+  end
+
+  ---@type table<integer, PeekstackStackViewPreviewLine>
+  local changed_previews = {}
+  for line_idx = start_idx, end_idx do
+    if preview_lines[line_idx] then
+      changed_previews[line_idx] = preview_lines[line_idx]
+    end
+  end
+  if next(changed_previews) then
+    apply_preview_treesitter_highlights(bufnr, changed_previews)
+  end
+end
+
 ---@param s PeekstackStackViewState
 ---@param is_ready fun(s: PeekstackStackViewState): boolean
 function M.render(s, is_ready)
@@ -478,29 +582,25 @@ function M.render(s, is_ready)
     end
   end
 
-  vim.bo[s.bufnr].modifiable = true
-  vim.api.nvim_buf_set_lines(s.bufnr, 0, -1, false, lines)
-  vim.bo[s.bufnr].modifiable = false
-
-  vim.api.nvim_buf_clear_namespace(s.bufnr, NS, 0, -1)
-  for line_idx, line_hls in ipairs(highlights) do
-    for _, hl in ipairs(line_hls) do
-      local opts = {
-        end_col = hl.col_end,
-        hl_group = hl.hl_group,
-      }
-      if hl.hl_group == "PeekstackStackViewPreview" then
-        opts.priority = PREVIEW_BASE_HL_PRIORITY
-      end
-      vim.api.nvim_buf_set_extmark(s.bufnr, NS, line_idx - 1, hl.col_start, {
-        end_col = opts.end_col,
-        hl_group = opts.hl_group,
-        priority = opts.priority,
-      })
-    end
+  ---@type string[]
+  local line_keys = {}
+  for line_idx, line in ipairs(lines) do
+    line_keys[line_idx] = line_render_key(line, highlights[line_idx] or {}, preview_lines[line_idx])
   end
 
-  apply_preview_treesitter_highlights(s.bufnr, preview_lines)
+  local old_keys = s.render_keys or {}
+  local start_idx, old_end, new_end = diff_range(old_keys, line_keys)
+  if start_idx then
+    local replace = slice_lines(lines, start_idx, new_end)
+
+    vim.bo[s.bufnr].modifiable = true
+    vim.api.nvim_buf_set_lines(s.bufnr, start_idx - 1, old_end, false, replace)
+    vim.bo[s.bufnr].modifiable = false
+
+    vim.api.nvim_buf_clear_namespace(s.bufnr, NS, start_idx - 1, old_end)
+    apply_highlights_in_range(s.bufnr, highlights, preview_lines, start_idx, new_end)
+  end
+  s.render_keys = line_keys
 
   if s.winid and vim.api.nvim_win_is_valid(s.winid) and s.bufnr and vim.api.nvim_buf_is_valid(s.bufnr) then
     local line_count = vim.api.nvim_buf_line_count(s.bufnr)

tests/stack_view_spec.lua

@@ -84,6 +84,73 @@ describe("peekstack.ui.stack_view", function()
     assert.is_true(lines[1]:find("Stack: 2", 1, true) ~= nil)
   end)
 
+  it("skips line updates when rendered content is unchanged", function()
+    local root_winid = vim.api.nvim_get_current_win()
+    local s = stack.current_stack(root_winid)
+    s.popups = {
+      { id = 1, title = "Alpha", location = location_for("/tmp/alpha.lua"), pinned = false },
+      { id = 2, title = "Beta", location = location_for("/tmp/beta.lua"), pinned = false },
+    }
+
+    stack_view.open()
+    local state = stack_view._get_state()
+    stack_view._render(state)
+
+    local original_set_lines = vim.api.nvim_buf_set_lines
+    local calls = 0
+    local ok, err = pcall(function()
+      vim.api.nvim_buf_set_lines = function(...)
+        calls = calls + 1
+        return original_set_lines(...)
+      end
+
+      stack_view._render(state)
+      assert.equals(0, calls)
+    end)
+    vim.api.nvim_buf_set_lines = original_set_lines
+    if not ok then
+      error(err)
+    end
+  end)
+
+  it("updates only changed line range when one entry changes", function()
+    local root_winid = vim.api.nvim_get_current_win()
+    local s = stack.current_stack(root_winid)
+    s.popups = {
+      { id = 1, title = "Alpha", location = location_for("/tmp/alpha.lua"), pinned = false },
+      { id = 2, title = "Beta", location = location_for("/tmp/beta.lua"), pinned = false },
+    }
+
+    stack_view.open()
+    local state = stack_view._get_state()
+    stack_view._render(state)
+
+    local original_set_lines = vim.api.nvim_buf_set_lines
+    local calls = {}
+    local ok, err = pcall(function()
+      vim.api.nvim_buf_set_lines = function(bufnr, start, finish, strict_indexing, replacement)
+        table.insert(calls, {
+          start = start,
+          finish = finish,
+          count = #replacement,
+        })
+        return original_set_lines(bufnr, start, finish, strict_indexing, replacement)
+      end
+
+      s.popups[2].title = "Beta updated"
+      stack_view._render(state)
+
+      assert.equals(1, #calls)
+      assert.equals(2, calls[1].start)
+      assert.equals(3, calls[1].finish)
+      assert.equals(1, calls[1].count)
+    end)
+    vim.api.nvim_buf_set_lines = original_set_lines
+    if not ok then
+      error(err)
+    end
+  end)
+
   it("renders empty state with header", function()
     stack_view.open()
     local state = stack_view._get_state()