bug#13623: 24.3.50; Redisplay issue with transient-mark-mode

[Dmitry Antipov <dmantipov@yandex.ru>]

On 02/06/2013 06:31 PM, Stefan Monnier wrote:

> For my use case, the optimisations that matter are the ones that avoid
> looking at the unmodified (and mostly all iconified) frames when I work
> within a frame or switch between two frames (or maybe 3 at most: the
> origin, the destination and the minibuffer-only frame).

This is a question of splitting global state between frames because current
tricks like ++windows_or_buffers_changed effectively prevents single-frame
redisplay optimizations.  I have a few experimental patches with per-frame
fonts_changed_p and cursor_type_changed flags. Since font/cursor changes
are rare, the effect is negligible, but this opens the way towards more
interesting things. On the other side, I suspect that the most of users
are either 1) uses single-frame configuration or 2) uses reasonably modern
hardware where the complete redisplay (all frames) is faster than the period
between two keystrokes and so doesn't affect an editing experience.

Dmitry