render/pixman: implement preferred_read_format

include/render/pixman.h

@@ -46,6 +46,7 @@ struct wlr_pixman_texture {
 };
 
 pixman_format_code_t get_pixman_format_from_drm(uint32_t fmt);
+uint32_t get_drm_format_from_pixman(pixman_format_code_t fmt);
 const uint32_t *get_pixman_drm_formats(size_t *len);
 
 #endif

render/pixman/pixel_format.c

@@ -49,6 +49,17 @@ pixman_format_code_t get_pixman_format_from_drm(uint32_t fmt) {
 	return 0;
 }
 
+uint32_t get_drm_format_from_pixman(pixman_format_code_t fmt) {
+	for (size_t i = 0; i < sizeof(formats) / sizeof(*formats); ++i) {
+		if (formats[i].pixman_format == fmt) {
+			return formats[i].drm_format;
+		}
+	}
+
+	wlr_log(WLR_ERROR, "pixman format 0x%"PRIX32" has no drm equivalent", fmt);
+	return DRM_FORMAT_INVALID;
+}
+
 const uint32_t *get_pixman_drm_formats(size_t *len) {
 	static uint32_t drm_formats[sizeof(formats) / sizeof(formats[0])];
 	*len = sizeof(formats) / sizeof(formats[0]);

render/pixman/renderer.c

@@ -369,6 +369,17 @@ static void pixman_destroy(struct wlr_renderer *wlr_renderer) {
 	free(renderer);
 }
 
+static uint32_t pixman_preferred_read_format(
+		struct wlr_renderer *wlr_renderer) {
+	struct wlr_pixman_renderer *renderer = get_renderer(wlr_renderer);
+	struct wlr_pixman_buffer *buffer = renderer->current_buffer;
+
+	pixman_format_code_t pixman_format = pixman_image_get_format(
+			buffer->image);
+
+	return get_drm_format_from_pixman(pixman_format);
+}
+
 static const struct wlr_renderer_impl renderer_impl = {
 	.begin = pixman_begin,
 	.clear = pixman_clear,
@@ -380,6 +391,7 @@ static const struct wlr_renderer_impl renderer_impl = {
 	.texture_from_pixels = pixman_texture_from_pixels,
 	.bind_buffer = pixman_bind_buffer,
 	.destroy = pixman_destroy,
+	.preferred_read_format = pixman_preferred_read_format,
 };
 
 struct wlr_renderer *wlr_pixman_renderer_create(void) {