[PATCH 5/5] xwayland: Pixmap flips of child windows on sub-surfaces

Michel Dänzer michel at daenzer.net
Thu Aug 31 02:01:44 UTC 2017

On 30/08/17 06:11 PM, Roman Gilg wrote:
> Sorry, apparently I didn't understand your explanation the last time.
> Can you explain why non-Present requests need to see the sub-surface
> contents?

Because the semantics of PresentPixmap are that the contents of the
source pixmap become part of the destination window. E.g. a later X11
request reading from the window must return the same contents that were
in the pixmap when PresentPixmap was executed.

> And how they see the contents of normal Wayland surfaces?

This is why flips set the presented pixmap as the window pixmap. Any X11
request using a window eventually uses its window pixmap to access the
window contents.

> On Wed, Aug 30, 2017 at 4:10 AM, Michel Dänzer <michel at daenzer.net
> <mailto:michel at daenzer.net>> wrote:
>     On 30/08/17 12:24 AM, Roman Gilg wrote:
>     > This patch enables Pixmap flips for child windows via Wayland
>     > sub-surfaces.
>     That can't be done so easily for the reasons I've explained before
>     (basically, non-Present requests would need to "see" the subsurface
>     contents as well), so I'm afraid I have to NAK this patch in this form.

Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer

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