feat: improve scroll at bottom to support scrolling without focus (#104)

Author: guillaumeboehm

lua/opencode/config.lua

@@ -102,6 +102,7 @@ M.defaults = {
       tools = {
         show_output = true,
       },
+      always_scroll_to_bottom = false,
     },
     input = {
       text = {

lua/opencode/types.lua

@@ -114,6 +114,7 @@
 ---@class OpencodeUIOutputConfig
 ---@field tools { show_output: boolean }
 ---@field rendering OpencodeUIOutputRenderingConfig
+---@field always_scroll_to_bottom boolean
 
 ---@class OpencodeContextConfig
 ---@field enabled boolean

lua/opencode/ui/output_window.lua

@@ -3,6 +3,7 @@ local config = require('opencode.config')
 
 local M = {}
 M.namespace = vim.api.nvim_create_namespace('opencode_output')
+M.viewport_at_bottom = true
 
 function M.create_buf()
   local output_buf = vim.api.nvim_create_buf(false, true)
@@ -27,6 +28,36 @@ 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)
+  if config.ui.output.always_scroll_to_bottom then
+    return true
+  end
+
+  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
+  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
+  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 })
@@ -177,13 +208,23 @@ 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()
+      M.viewport_at_bottom = M.is_at_bottom(windows.output_win)
+    end,
+  })
 end
 
 function M.clear()
   M.set_lines({})
   -- clear extmarks in all namespaces as I've seen RenderMarkdown leave some
   -- extmarks behind
   M.clear_extmarks(0, -1, true)
+  M.viewport_at_bottom = true
 end
 
 return M

lua/opencode/ui/renderer.lua

@@ -50,6 +50,7 @@ function M.reset()
     require('opencode.api').respond_to_permission('reject')
   end
   state.current_permission = nil
+
   trigger_on_data_rendered()
 end
 
@@ -224,26 +225,30 @@ 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 output_window.viewport_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 })
+    output_window.viewport_at_bottom = true
+  else
+    -- User has scrolled up, don't scroll
+    output_window.viewport_at_bottom = false
   end
 end