Re: [PATCH xserver 1/3] present: Only update screen pixmap from flip pixmap once per unflip

[Keith Packard]

Michel Dänzer  writes:

> From: Michel Dänzer 
>
> present_unflip may be called several times from present_check_flip_window
> during the same unflip. We can only copy to the screen pixmap the first
> time, otherwise we may scribble over other windows. The flip pixmap
> contents don't get updated after the first time anyway.
>
> Fixes at least the following problems, which were introduced by commit
> 806470b9 ("present: Copy unflip contents back to the Screen Pixmap"):
>
> On xfwm4 without compositing, run glxgears and put its window into
> fullscreen mode to start flipping. While in fullscreen, open the xfwm4
> window menu by pressing Alt-Space. The window menu was invisible most
> of the time because it was getting scribbled over by a repeated unflip
> copy.
>
> When switching a flipping window out of fullscreen, a repeated unflip
> copy could leave artifacts of the flip pixmap on the desktop.
>
> Signed-off-by: Michel Dänzer 

Reviewed-by: Keith Packard 

> +/* Update the screen pixmap with the current flip pixmap contents
> + * Only do this the first time for a particular unflip operation, or
> + * we'll probably scribble over other windows
> + */
> +if (screen->GetWindowPixmap(screen->root) == screen_priv->flip_pixmap) {
> +present_copy_region(>drawable, screen_priv->flip_pixmap,
> +NULL, 0, 0);
> +}
> +

This removes the check for flip_pixmap && flip_window, but the
flip_pixmap check is not needed as you're checking it against the root
pixmap which is never NULL, and the check for flip_window was redundant
before as it was always set when flip_pixmap was set.

-- 
-keith


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Re: [PATCH xserver 1/3] present: Only update screen pixmap from flip pixmap once per unflip

[Chris Wilson]

On Fri, Feb 19, 2016 at 11:39:10AM +0900, Michel Dänzer wrote:
> From: Michel Dänzer 
> 
> present_unflip may be called several times from present_check_flip_window
> during the same unflip. We can only copy to the screen pixmap the first
> time, otherwise we may scribble over other windows. The flip pixmap
> contents don't get updated after the first time anyway.
> 
> Fixes at least the following problems, which were introduced by commit
> 806470b9 ("present: Copy unflip contents back to the Screen Pixmap"):
> 
> On xfwm4 without compositing, run glxgears and put its window into
> fullscreen mode to start flipping. While in fullscreen, open the xfwm4
> window menu by pressing Alt-Space. The window menu was invisible most
> of the time because it was getting scribbled over by a repeated unflip
> copy.
> 
> When switching a flipping window out of fullscreen, a repeated unflip
> copy could leave artifacts of the flip pixmap on the desktop.
> 
> Signed-off-by: Michel Dänzer 

And the ordering is better: we should do the restoration of the contents
before we restore the window->pixmap linkage.

Reviewed-by: Chris Wilson 
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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