wayland: add support for single-pixel-buffer-v1 protocol

[Sunderland93]

Description

Add support for single-pixel-buffer-v1 protocol for optimizing the use of the wl_shm 1x1 pixel case. I'm not sure I implemented the creation of a single-pixel buffer correctly in its current form, so a review is required. Also note that support for this protocol is currently available in GNOME and wlroots.

See https://gitlab.freedesktop.org/wayland/wayland-protocols/-/blob/main/staging/single-pixel-buffer/single-pixel-buffer-v1.xml

Related Issues

No

Related Pull Requests

No

Reviewers

@ColinKinloch

[ColinKinloch]

I think single pixel buffers are only really useful in special cases.
For example the black borders around a video in a video player can be achieved by creating a subsurface attaching a single pixel buffer and using a viewport to scale it to the window size and layering a subsurface with the video attached above it e.g. waylandsink.

It could be used instead of the splash screen to display black at the window scale.
That could be done by changing the following line to use the output of wp_single_pixel_buffer_manager_v1_create_u32_rgba_buffer

RetroArch/gfx/common/wayland_common.c

Line 643 in 8864062

wl_surface_attach(wl->surface, buffer->wl_buffer, 0, 0);

However this would still need a fallback for compositors that don't support single pixel buffers and I'm not sure would have much of a benefit.

[Sunderland93]

However this would still need a fallback for compositors that don't support single pixel buffers and I'm not sure would have much of a benefit.

Do you have any suggestions?

[ColinKinloch]

In the wl_draw_splash_screen function check for the single pixel buffer manager. If it exists create a black single pixel buffer, otherwise do the shm checkerboard stuff.
Then attach which ever wl_buffer was created to the surface.

Also to test it you need two monitors attached or make this line always true:

RetroArch/gfx/common/wayland_common.c

Line 847 in 8864062

if (video_monitor_index == 0 && wl_list_length (&wl->all_outputs) > 1)

[Sunderland93]

@ColinKinloch latest commit works as you suggests

[ColinKinloch]

This line from #17309 should allow the single pixel buffer to be scaled at a sensible size. otherwise it will be a single pixel window:

RetroArch/gfx/common/wayland_common.c

Lines 638 to 639 in f276757

	if (wl->viewport)
	wp_viewport_set_destination(wl->viewport, wl->width, wl->height);

Also if you change these to DEFAULT_WINDOWED_WIDTH and DEFAULT_WINDOWED_HEIGHT etc. the window will not be arbitrarily the size of the splash screen image:

RetroArch/gfx/common/wayland_common.c

Lines 682 to 683 in f276757

	wl->floating_width = SPLASH_WINDOW_WIDTH;
	wl->floating_height = SPLASH_WINDOW_HEIGHT;

edit: It won't produce a single pixel window. The viewport is correctly sized by a previous configure event..

[ColinKinloch]

Apart from the nitpick. This seems fine to merge as is.
I'll update #17309 after.

[Sunderland93]

Thank you!

[LibretroAdmin]

Hopefully I merged these two PRs in the right order.