Merge pull request #22238 from hrydgard/sdl-prefer-wayland

SDL: Prefer Wayland when we're in a Wayland session

SDL/SDLMain.cpp

@@ -1793,6 +1793,17 @@ int main(int argc, char *argv[]) {
 	SDL_SetHint(SDL_HINT_TOUCH_MOUSE_EVENTS, "0");
 #endif
 
+	// SDL's automatic pick between Wayland and X11 doesn't always land on Wayland even in a
+	// Wayland session, and going through XWayland instead costs us scaling and input quality.
+	// So ask for it explicitly when the session looks like Wayland - unless the user has set
+	// SDL_VIDEO_DRIVER, in which case they've already told us what they want.
+	// WAYLAND_DISPLAY is only set on Wayland sessions, so this is a no-op elsewhere.
+	bool preferWayland = false;
+	if (getenv("WAYLAND_DISPLAY") && !getenv("SDL_VIDEO_DRIVER")) {
+		SDL_SetHint(SDL_HINT_VIDEO_DRIVER, "wayland");
+		preferWayland = true;
+	}
+
 	bool vulkanMayBeAvailable = false;
 	if (VulkanMayBeAvailable()) {
 		fprintf(stderr, "DEBUG: Vulkan might be available.\n");
@@ -1821,11 +1832,30 @@ int main(int argc, char *argv[]) {
 		fprintf(stderr, "Failed to initialize SDL with joystick support. Retrying without.\n");
 		joystick_enabled = false;
 		if (!SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO)) {
-			fprintf(stderr, "Unable to initialize SDL: %s\n", SDL_GetError());
-			return 1;
+			bool initialized = false;
+			if (preferWayland) {
+				// Asking for Wayland may be exactly what failed, so let SDL pick instead.
+				fprintf(stderr, "Unable to initialize SDL with the Wayland video driver (%s). Letting SDL choose.\n", SDL_GetError());
+				SDL_SetHint(SDL_HINT_VIDEO_DRIVER, nullptr);
+				preferWayland = false;
+				// Retry with joystick support - it was the video driver that failed, not the joysticks.
+				if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_JOYSTICK | SDL_INIT_GAMEPAD | SDL_INIT_AUDIO)) {
+					joystick_enabled = true;
+					initialized = true;
+				} else {
+					initialized = SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO);
+				}
+			}
+			if (!initialized) {
+				fprintf(stderr, "Unable to initialize SDL: %s\n", SDL_GetError());
+				return 1;
+			}
 		}
 	}
 
+	const char *videoDriver = SDL_GetCurrentVideoDriver();
+	fprintf(stderr, "Info: SDL video driver: %s\n", videoDriver ? videoDriver : "(none)");
+
 	fprintf(stderr, "Info: We compiled against SDL version %d.%d.%d", SDL_VERSIONNUM_MAJOR(compiled), SDL_VERSIONNUM_MINOR(compiled), SDL_VERSIONNUM_MICRO(compiled));
 	if (compiled != linked) {
 		fprintf(stderr, ", but we are linking against SDL version %d.%d.%d., be aware that this can lead to unexpected behaviors\n", SDL_VERSIONNUM_MAJOR(linked), SDL_VERSIONNUM_MINOR(linked), SDL_VERSIONNUM_MICRO(linked));