bug#14744: 24.3.50; Flickering mouse-face on process output

[Eli Zaretskii <eliz@gnu.org>]

> From: Christopher Schmidt <christopher@ch.ristopher.com>
> Date: Sat, 29 Jun 2013 10:47:15 +0100 (BST)
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> > Redisplay of a window always includes redisplay of the tool bar.  The
> > latter involves drawing the buttons, and then applying the depressed
> > faced to the button that the mouse pointer hovers above.  That is what
> > you see, I believe.  So why do you consider that a bug?
> 
> I was not talking about the tool bar.  I was talking about the buttons
> in the other window of Emacs, such as
> 
>     Emacs Tutorial	Learn basic keystroke commands
>     ^^^^^^^^^^^^^^
>     Emacs Guided Tour	Overview of Emacs features at gnu.org
>     ^^^^^^^^^^^^^^^^^
>     View Emacs Manual	View the Emacs manual using Info
>     ^^^^^^^^^^^^^^^^^

That doesn't matter.  In the situation you described, Emacs redisplays
all the windows, which involves redrawing the mouse highlight of these
buttons.

> I see actual flickering.  That is, I move my mouse cursor over the text
> and expect the text face to be highlight as long as the cursor is
> somewhere in between the continuous fragment of text.  It is not.  The
> actual face is switching between two faces, one of them being highlight.

Because we redraw the window.

Redisplay optimization that refrains from redrawing windows other than
the one whose buffer and mode line get updated was never implemented.

For the record, what is the real-life use case where this matters?