Use viewports for non-fullscreen windows when the desktop uses fractional scaling and the window is flagged as DPI-aware to provide a backbuffer mapped as close to 1:1 output as possible. In the cases of odd window sizes the backbuffer may be a pixel off of scaling perfectly into the window size due to its scaled size being rounded off, but a minute amount of scaling during output is likely preferable to the large amounts of overdraw needed with integer scaled buffers.
Expose as many emulated display modes as possible. They will currently display stretched to the display's native desktop aspect, but if an application requires a hardcoded resolution, it will work at minimum.
Aside from the change in the emulated display mode list, the Wayland event handling code had to be updated to support separate scaling for the x and y axes, as square pixels are no longer guaranteed.
Wayland doesn't support mode switching, however Wayland compositors can support the wp_viewporter protocol, which allows for the mapping of arbitrarily sized buffer regions to output surfaces. Use this functionality, when available, for fullscreen output when using non-native display modes and/or when dealing with scaled desktops, which can incur significant overdraw without this extension.
This also allows for the exposure of arbitrarily sized, emulated display modes, which can be useful for legacy compatability.
1. Mod index values are (mostly) constant, so can be done with xkb_state_new
2. Mods can change without the group changing, avoid remap events if possible
Lastly, as a bonus, I added braces to the locale check, because I was nearby.
When using shared linking (linking in the normal way with
-lwayland-client) rather than loading Wayland libraries dynamically at
runtime, listing symbols that don't exist in the current version results
in a build failure. We don't actually call wl_proxy_marshal_flags() or
wl_proxy_marshal_array_flags() directly; the reason we need them is
that they're called by the code generated by wayland-scanner >= 1.20.
If we're building against an older Wayland library, then we'll have its
corresponding version of wayland-scanner (mismatched versions are not
supported), so we won't need those two symbols, and can avoid generating
a dependency on them.
Conversely, if we're building against a newer Wayland library, the
generated code will call them unconditionally, so we cannot treat them as
optional and gracefully fall back: that would result in a crash. Instead,
treat them as a mandatory part of the Wayland library, so that if they
are not found at runtime, we can fall back to X11 without crashing.
libwayland 1.18 is in several LTS distributions (Ubuntu 20.04,
Debian 11, RHEL 8) so avoiding a hard dependency on 1.20 is quite
useful.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Resolves: https://github.com/libsdl-org/SDL/issues/5376
Using wl-output to get the desktop display dimensions and dividing by the integer scale factor will not return the correct result when using a desktop with fractional scaling (e.g. a 3840x2160 display at 150% will incorrectly report the scaled desktop area as 1920x1080 instead of 2560x1440). Use the xdg-output protocol, if available, to retrieve the correct desktop dimensions and offset.
Versions 1 through 3 of the protocol are supported.
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