buffer: add single-pixel-buffer-v1 special case in buffer_is_opaque()

types/buffer/buffer.c

@@ -1,4 +1,5 @@
 #include <assert.h>
+#include <drm_fourcc.h>
 #include <string.h>
 #include <wlr/interfaces/wlr_buffer.h>
 #include "render/pixel_format.h"
@@ -111,7 +112,16 @@ bool buffer_is_opaque(struct wlr_buffer *buffer) {
 		format = shm.format;
 	} else if (wlr_buffer_begin_data_ptr_access(buffer,
 			WLR_BUFFER_DATA_PTR_ACCESS_READ, &data, &format, &stride)) {
+		bool opaque = false;
+		if (buffer->width == 1 && buffer->height == 1 && format == DRM_FORMAT_ARGB8888) {
+			// Special case for single-pixel-buffer-v1
+			const uint8_t *argb8888 = data; // little-endian byte order
+			opaque = argb8888[3] == 0xFF;
+		}
 		wlr_buffer_end_data_ptr_access(buffer);
+		if (opaque) {
+			return true;
+		}
 	} else {
 		return false;
 	}