fix(scroll): handle NUL bytes in wrapped output lines

Author: sudo-tee

lua/opencode/ui/output_window.lua

@@ -215,6 +215,8 @@ function M.on_user_navigation(win)
   local previous_cursor = M._last_cursor_by_win[win]
   M._last_cursor_by_win[win] = cursor
   local bottom_text = vim.api.nvim_buf_get_lines(windows.output_buf, effective_bottom - 1, effective_bottom, false)[1] --[[@as string]]
+  -- Avoid Blob conversion at the Vimscript boundary without shifting byte offsets.
+  bottom_text = bottom_text:gsub('%z', '\n')
   local cursor_at_end = cursor_line >= effective_bottom and cursor[2] >= math.max(0, vim.fn.match(bottom_text, '.$'))
   local moved_toward_end = (previous_cursor and (cursor_line > previous_cursor[1] or cursor[2] > previous_cursor[2]))
     or (top and previous_top and top > previous_top)

lua/opencode/ui/renderer/scroll.lua

@@ -3,6 +3,15 @@ local output_window = require('opencode.ui.output_window')
 
 local M = {}
 
+---@param text string
+---@return integer
+local function line_display_width(text)
+  -- Vimscript receives NUL-containing Lua strings as Blobs. Its string
+  -- representation of a buffer NUL is a newline, with the same display width.
+  local display_text = text:gsub('%z', '\n')
+  return math.max(1, vim.fn.strdisplaywidth(display_text))
+end
+
 ---@param win integer
 ---@return boolean
 local function window_wraps(win)
@@ -38,7 +47,7 @@ local function get_bottom_aligned_topline(buf, win, target_line)
         line = fold_start - 1
       else
         local text = vim.api.nvim_buf_get_lines(buf, line - 1, line, false)[1] or ''
-        local display_width = math.max(1, vim.fn.strdisplaywidth(text))
+        local display_width = line_display_width(text)
         rows = rows + math.max(1, math.ceil(display_width / text_width))
         line = line - 1
       end
@@ -87,10 +96,7 @@ local function end_of_target_line_fits_view(buf, win, target_line)
       end)
     else
       local text = vim.api.nvim_buf_get_lines(buf, line - 1, line, false)[1] or ''
-      if type(text) ~= 'string' then
-        text = tostring(text)
-      end
-      local display_width = math.max(1, vim.fn.strdisplaywidth(text))
+      local display_width = line_display_width(text)
       rows = rows + math.max(1, math.ceil(display_width / text_width))
       line = line + 1
     end
@@ -128,9 +134,6 @@ function M.scroll_win_to_bottom(win, buf)
   end
 
   local target_text = vim.api.nvim_buf_get_lines(buf, target_line - 1, target_line, false)[1] or ''
-  if type(target_text) ~= 'string' then
-    target_text = tostring(target_text)
-  end
   local visible_bottom = output_window.get_visible_bottom_line(win)
   vim.api.nvim_win_set_cursor(win, { target_line, #target_text })
   state.ui.set_cursor_position('output', { target_line, #target_text })

tests/unit/cursor_tracking_spec.lua

@@ -579,6 +579,51 @@ describe('renderer.scroll_to_bottom', function()
     config.values.ui.output.always_scroll_to_bottom = false
   end)
 
+  it('follows visible binary output without converting NUL-containing strings to Blobs', function()
+    local scroll = require('opencode.ui.renderer.scroll')
+    local text = string.rep('x\0', 15)
+    vim.api.nvim_win_set_width(win, 20)
+    vim.api.nvim_win_set_height(win, 5)
+    vim.api.nvim_set_option_value('wrap', true, { win = win })
+    vim.api.nvim_buf_set_lines(buf, 0, -1, false, { 'header', text })
+    vim.api.nvim_win_set_cursor(win, { 1, 0 })
+
+    assert.equals(2, output_window.get_visible_bottom_line(win))
+    scroll.scroll_win_to_bottom(win, buf)
+    assert.same({ 2, #text - 1 }, vim.api.nvim_win_get_cursor(win))
+
+    local snapshot = scroll.pre_flush(buf)
+    assert.is_true(snapshot.follow)
+    text = text .. string.rep('y\0', 10)
+    vim.api.nvim_buf_set_lines(buf, 1, 2, false, { text })
+    scroll.post_flush(snapshot, buf)
+
+    assert.same({ 2, #text - 1 }, vim.api.nvim_win_get_cursor(win))
+    assert.equals(text, vim.api.nvim_buf_get_lines(buf, 1, 2, false)[1])
+  end)
+
+  it('bottom-aligns binary output using the display width of NUL bytes', function()
+    local scroll = require('opencode.ui.renderer.scroll')
+    local lines = {}
+    for i = 1, 20 do
+      lines[i] = 'line ' .. i
+    end
+    lines[19] = string.rep('x\0', 10)
+    vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
+    vim.api.nvim_win_set_width(win, 20)
+    vim.api.nvim_win_set_height(win, 5)
+    vim.api.nvim_set_option_value('wrap', true, { win = win })
+    vim.api.nvim_win_set_cursor(win, { 1, 0 })
+
+    assert.is_true(output_window.get_visible_bottom_line(win) < 20)
+    scroll.scroll_win_to_bottom(win, buf)
+
+    assert.equals(17, output_window.get_visible_top_line(win))
+    assert.equals(20, output_window.get_visible_bottom_line(win))
+    assert.equals(20, vim.api.nvim_win_get_cursor(win)[1])
+    assert.equals(lines[19], vim.api.nvim_buf_get_lines(buf, 18, 19, false)[1])
+  end)
+
   it('moves to the visual end when the last wrapped line grows', function()
     local long_line = string.rep('x', 120)
     local longer_line = string.rep('x', 180)