bug#3347: 23.0.93; unnecessary display updates with mouse-drag-region

[YAMAMOTO Mitsuharu]

On Mon, 14 Sep 2020 23:44:39 +0900,
Lars Ingebrigtsen wrote:
> 
> YAMAMOTO Mitsuharu <mituharu@math.s.chiba-u.ac.jp> writes:
> 
> > Mouse dragging over a text in the default face causes unnecessary
> > updates in other windows displaying the same buffer.
> >
> > Steps to reproduce:
> >
> >   1. Invoke "Quartz Debug.app" on Mac OS X and check the "Flash screen
> >      updates" button.
> >   2. $ emacs -Q -D
> >   3. C-x 2
> >   4. Drag the mouse over the *scratch* buffer text in the first
> >      window.
> 
> (This was 11 years ago.)
> 
> The Quartz Debug app doesn't seem to exist on Macos any more, so I'm
> unable to try the recipe.

It is now included in "Additional Tools for Xcode", which can be
downloaded from https://developer.apple.com/download/more/ (You might
need to sign in with your Apple ID.)


> Do you still see this problem in more recent versions of Emacs?

Yes, but you need to disable double-buffering with
(set-frame-paremter nil 'inhibit-double-buffering t) .
Otherwise, Quartz Debug thinks the whole frame is updated.

                                     YAMAMOTO Mitsuharu
                                mituharu@math.s.chiba-u.ac.jp