Wayland protocol clarification questions

Pekka Paalanen ppaalanen at gmail.com
Tue May 2 08:50:55 UTC 2023

On Sun, 30 Apr 2023 10:29:31 +0200
Tarek Sander <tsanderdev at gmail.com> wrote:

> Hello,
> I want to write a Wayland compositor and while reading the protocol 
> specification, I noticed some things that aren't clear to me:


> - How does the input and opaque region of a surface behave on a resize? 
> Do the additional pixels get automatically added for the input region?

Resize works by the client sending requests to change the wl_surface
size. If it also wants to change input or opaque regions, it must do so
explicitly. Automatic changes to these regions do not exist, both
requests have the wording:

	Otherwise, the pending and current regions are never changed...

> - Is it valid for the wp_presentation_feedback::kind bitfield to contain 
> no flag at all?


> - What exactly is the anchor rectangle of an xdg_positioner?

The compositor decides the positioning of popups in order to keep them
from going e.g. off-screen, and the positioner gives the rules how such
surface can be positioned without breaking the UI look. Personally I've
never looked at the details, so maybe someone else will answer this.

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