Re: Window configurations

[martin rudalics <rudalics@gmx.at>]

 > Thinking more about this, I believe now this function should be
 > like `view-mode-exit':

I had something like this in mind.  BTW, I have rewritten this code in
the meantime using a window parameter called `quit-restore'.  From a
preliminary description ...

    The `quit-restore' parameter tells how to proceed with a window when
the user "quits" it by invoking `quit-restore-window', see *Note
Displaying Buffers::.  The following non-`nil' values of this parameter
have a special meaning.

`t'
      This means to delete the associated window.  By default, `t' is
      used for a "temporary" window that was obtained by splitting an
      existing window.

`frame'
      This means to delete the associated window's frame.  This value
      indicates that the associated windows was obtained by popping up a
      new frame showing just this window.  If the window is no more
      needed, it should be deleted together with the containing frame.

A list
      This option is useful when the associated window was borrowed to
      temporarily display some buffer and quitting shall "restore" the
      previous contents of the window.  The first three elements of the
      list must specify a buffer, a window start position, and a window
      point.  Quitting the window will then try to display the indicated
      buffer with the given start position and point in that window.

      The fourth element, if non-`nil', must denote a live buffer.  If
      specified, quitting will restore the previous window contents if
      and only if the buffer shown in the window is the buffer named by
      this element.

      The fifth element, if non-`nil', should specify the desired height
      of the window when its buffer is restored.  This value is applied
      if the buffer temporarily shown in the window was in
      `temp-buffer-resize-mode' to restore the original height of the
      window.

... and the description of `quit-restore-window' goes like ...

    The command described next allows to quit the window chosen by
`display-buffer' and restore the previous state without undoing changes
to the window configuration that happend _after_ `display-buffer' was
called.  A more drastic solution is to save the window configuration
before calling `display-buffer' and eventually restoring the saved
configuration, *Note Window Configurations::.  That solution sometimes
has the undesirable side-effect that all changes that happened after
the configuration was saved are undone too.

  -- Command: quit-restore-window &optional window kill
      This command "quits" WINDOW restoring its previous contents if
      possible.  The argument WINDOW must be a live window and defaults
      to the selected one.  This function always returns `nil'.

      According to information stored in WINDOW's `quit-restore' window
      parameter (*note Window Parameters::) this function performs one
      of the following actions.

         * Delete WINDOW and its frame.  This action is useful when
           WINDOW was created on a standalone frame and there are other
           frames left.

         * Delete WINDOW.  This action is usually taken when WINDOW was
           obtained by splitting some existing window.

         * Restore the buffer previously displayed in WINDOW.  This
           action is taken when WINDOW was temporarily reused for
           displaying some other buffer.

         * Make WINDOW display some other buffer.  This action is usually
           taken when the three preceding ones are not applicable.

      If its value was non-`nil', this function resets WINDOW's
      `quit-restore' parameter to `nil'.

      If the optional argument KILL is non-`nil', this means in addition
      kill WINDOW's buffer.  If KILL is `nil', this simply puts WINDOW's
      buffer at the end of the buffer list.  Interactively, KILL is the
      prefix argument.

... where `quit-restore-window' here replaces `quit-window' which has
too obscure semantics for my taste.  And obviously, exiting `view-mode'
calls `quit-restore-window' here too.

However, restoring a window configuration is a more primitive operation
than exiting `view-mode'.  One of the most hairy situation occurs when
you kill a buffer: There's a window of vulnerability when the
`kill-buffer' routine calls `replace_buffer_in_all_windows' and the
latter, for some reason, doesn't do what it has been told, for example,
because a `window-configuration-change-hook' shows the buffer to be
killed in some other window.  Obviously, doing things like that in a
configuration change hook is foolish as in

(get-buffer-create "*foo*")

(defun foo-lish ()
   (let (window-configuration-change-hook)
     (set-window-buffer (frame-first-window) "*foo*")))

(add-hook 'window-configuration-change-hook 'foo-lish)

and now doing (kill-buffer "*foo*").  But I'm not sure whether there are
useful things a `window-configuration-change-hook' could do along these
lines.

martin