feat(ui): Improve scroll at bottom to support scrolling without focus

Author: guillaumeboehm

lua/opencode/state.lua

@@ -14,6 +14,7 @@
 ---@field last_input_window_position integer[]|nil
 ---@field last_output_window_position integer[]|nil
 ---@field last_code_win_before_opencode integer|nil
+---@field output_window_at_bottom boolean
 ---@field current_code_buf number|nil
 ---@field display_route any|nil
 ---@field current_mode string
@@ -55,6 +56,7 @@ local _state = {
   last_focused_opencode_window = nil,
   last_input_window_position = nil,
   last_output_window_position = nil,
+  output_window_at_bottom = true,
   last_code_win_before_opencode = nil,
   current_code_buf = nil,
   display_route = nil,

lua/opencode/ui/output_window.lua

@@ -27,6 +27,32 @@ function M.mounted(windows)
   return windows and windows.output_buf and windows.output_win and vim.api.nvim_win_is_valid(windows.output_win)
 end
 
+---Check if the output window is currently at the bottom
+---@param win? integer Window ID, defaults to state.windows.output_win
+---@return boolean true if at bottom, false otherwise
+function M.is_at_bottom(win)
+  win = win or (state.windows and state.windows.output_win)
+
+  if not win or not vim.api.nvim_win_is_valid(win) then
+    return true  -- Assume at bottom if window invalid
+  end
+
+  if not state.windows or not state.windows.output_buf then
+    return true
+  end
+
+  local ok, line_count = pcall(vim.api.nvim_buf_line_count, state.windows.output_buf)
+  if not ok or not line_count or line_count == 0 then
+    return true  -- Empty buffer, consider at bottom
+  end
+
+  local botline = vim.fn.line('w$', win)
+
+  -- Consider at bottom if bottom visible line is at or near the end
+  -- Use -1 tolerance for wrapped lines
+  return botline >= line_count - 1
+end
+
 function M.setup(windows)
   vim.api.nvim_set_option_value('winhighlight', config.ui.window_highlight, { win = windows.output_win })
   vim.api.nvim_set_option_value('wrap', true, { win = windows.output_win })
@@ -177,6 +203,16 @@ function M.setup_autocmds(windows, group)
   state.subscribe('current_permission', function()
     require('opencode.keymap').toggle_permission_keymap(windows.output_buf)
   end)
+
+  -- Track scroll position when window is scrolled
+  vim.api.nvim_create_autocmd('WinScrolled', {
+    group = group,
+    buffer = windows.output_buf,
+    callback = function()
+      -- Update state to track if user is at bottom
+      state.output_window_at_bottom = M.is_at_bottom(windows.output_win)
+    end,
+  })
 end
 
 function M.clear()

lua/opencode/ui/renderer.lua

@@ -46,6 +46,10 @@ function M.reset()
   state.messages = {}
   state.last_user_message = nil
   state.current_permission = nil
+
+  -- Reset scroll state when session changes
+  state.output_window_at_bottom = true
+
   trigger_on_data_rendered()
 end
 
@@ -220,26 +224,30 @@ function M.scroll_to_bottom()
     return
   end
 
-  local botline = vim.fn.line('w$', state.windows.output_win)
-  local cursor = vim.api.nvim_win_get_cursor(state.windows.output_win)
-  local cursor_row = cursor[1] or 0
-  local is_focused = vim.api.nvim_get_current_win() == state.windows.output_win
-
   local prev_line_count = M._prev_line_count or 0
 
   ---@cast line_count integer
   M._prev_line_count = line_count
 
-  local was_at_bottom = (botline >= prev_line_count) or prev_line_count == 0
-
   trigger_on_data_rendered()
 
-  if is_focused and cursor_row < prev_line_count - 1 then
-    return
+  -- Determine if we should scroll to bottom
+  local should_scroll = false
+
+  -- Always scroll on initial render
+  if prev_line_count == 0 then
+    should_scroll = true
+  -- Scroll if user is at bottom (respects manual scroll position)
+  elseif state.output_window_at_bottom then
+    should_scroll = true
   end
 
-  if was_at_bottom or not is_focused then
+  if should_scroll then
     vim.api.nvim_win_set_cursor(state.windows.output_win, { line_count, 0 })
+    state.output_window_at_bottom = true
+  else
+    -- User has scrolled up, don't scroll
+    state.output_window_at_bottom = false
   end
 end