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

[Victor Dyakov]

On Tue, 25 Feb 2025 12:07:11 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).

@honkar-jdk @prrace please review

-------------

PR Comment: https://git.openjdk.org/jdk/pull/23774#issuecomment-2682468250