RFR: 8280991: [XWayland] No displayChanged event after setDisplayMode call [v2]

[Phil Race]

On Tue, 25 Feb 2025 16:40:37 GMT, Alexander Zvegintsev <azvegint at openjdk.org> wrote:

>> Wayland clients are by design not allowed to change the resolution in Wayland.
>> XRandR in Xwayland is just an emulation, it doesn't actually change the desktop resolution. This emulation is per window/x11 client, so different clients can have different emulated resolutions at the same time.
>> 
>> Any request to get the current display mode from the system will always return the original screen resolution, even if we are in emulated resolution.
>> So with this fix, we store the last display mode set so that we can react correctly to the displayChanged event later.
>> 
>> ---
>> 
>> There are two system side fixes related to this issue, which causes missing ConfigureNotify events to be emitted when an emulated resolution change occurs:
>> 
>> 1. https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/731 - emits when the resolution changes to an emulated one 
>> 2. https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/890 - emits when the resolution changes to a native one 
>> 
>> The second one is only available in GnomeShell 43+ (e.g. Ubuntu 22.10+), so one of the tests is excluded for versions below that.
>> 
>> ---
>> 
>> Testing looks good (manual + automated).
>
> Alexander Zvegintsev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   NoResizeEventOnDMChangeTest update

What about, if we are on Wayland, behave the same in single-screen as you say happens any way with multi-screen - report only one resolution - the current / default one ?
I suggest this in part because I am not sure what the impact is of having the resolution be "emulated". If the app, and AWT think there's a different resolution than there really is, rendering quality could be affected.

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PR Comment: https://git.openjdk.org/jdk/pull/23774#issuecomment-2695568318