xdg_shell: handle_commit() could receive new geometry of size outside of the toplevel set boundaries (#9130)

[dawsers]

I don't know if this PR can have unintended consequences, but it fixes #9130

I think this is a bug in Qt, because they set the minimum size and then commit a surface with smaller geometry than the minimum size, but using this workaround that I think should be valid in general, we can "fix" it.

The client was setting a minimum size for the toplevel, and then committing a geometry with a smaller size. handle_commit() was seeing the new size and calling wlr_xdg_toplevel_set_size() that was sending a new configure with the smaller size. This was creating a loop where the client would alternate sending commits with the smaller and the bigger size, resulting in flickering of the window.

[dawsers]

Another option would be to add the check to wlroots, in uint32_t wlr_xdg_toplevel_set_size(struct wlr_xdg_toplevel *toplevel, int32_t width, int32_t height), something like:

uint32_t wlr_xdg_toplevel_set_size(struct wlr_xdg_toplevel *toplevel,
		int32_t width, int32_t height) {
	assert(width >= 0 && height >= 0);
	if ((toplevel->pending.min_width > 0 && width < toplevel->pending.min_width) ||
		(toplevel->pending.min_height > 0 && height < toplevel->pending.min_height) ||
		(toplevel->pending.max_width > 0 && width > toplevel->pending.max_width) ||
		(toplevel->pending.max_height > 0 && height > toplevel->pending.max_height)) {
		return 0;
	}
	toplevel->scheduled.width = width;
	toplevel->scheduled.height = height;
	return wlr_xdg_surface_schedule_configure(toplevel->base);
}

[emersion]

new_geo comes from the client, so it sounds surprising to have it send a size which doesn't comply with its own constraints…

[dawsers]

I agree it's definitely a bug in the client, but the Qt Print dialog is used extensively, and the flicker happens every time, even with a simple application like I wrote for the bug report (#9130). So I thought the check wouldn't hurt while at the same time it would fix that annoyance.