Re: auto-insert help-buffer

[Chong Yidong <cyd@stupidchicken.com>]

> emacs -q
> M-x auto-insert
> Prompt for keyword
> C-h
>
> opens a help-buffer with descriptions, but without the
> corresponding keywords visible.
>
> This buffer vanishes, when clicked by mouse.
>
> =>
>
> scroll-bar-toolkit-scroll: Wrong type argument

An easier way is to evaluate

  (let ((minibuffer-help-form "You are inserting a skeleton."))
    (read-string "Foo: " "Bar"))

type C-h, click on the help window, and observe the error.

This seems to be the result of the following code in keyboard.c:3316.

Basically, we record-unwind-protect the current window configuration
before launching the help form, which creates a new window.
Therefore, when the mouse click on the temporary window comes through,
the unbind_to first removes the window, then runs the mouse bindings,
which fail because the window is no longer live.

One possibility is to remove the unwind protect; the other is to check
in the mouse-click functions whether the desired window is live or
not.  Which solution is preferable?

  /* Process the help character specially if enabled */
  if (!NILP (Vhelp_form) && help_char_p (c))
    {
      Lisp_Object tem0;
      count = SPECPDL_INDEX ();

      record_unwind_protect (Fset_window_configuration,
			     Fcurrent_window_configuration (Qnil));

      tem0 = Feval (Vhelp_form);
      if (STRINGP (tem0))
	internal_with_output_to_temp_buffer ("*Help*", print_help, tem0);

      cancel_echoing ();
      do
	c = read_char (0, 0, 0, Qnil, 0, NULL);
      while (BUFFERP (c));
      /* Remove the help from the frame */
      unbind_to (count, Qnil);