optimize a bit rootston renderer if there's no surface transform

rootston/output.c

@@ -63,6 +63,12 @@ static void render_surface(struct wlr_surface *surface,
 			float scale[16];
 			wlr_matrix_scale(&scale, render_width, render_height, 1);
 
+			float transform[16];
+			wlr_matrix_mul(&translate_center, &rotate, &transform);
+			wlr_matrix_mul(&transform, &translate_origin, &transform);
+			wlr_matrix_mul(&transform, &scale, &transform);
+
+			if (surface->current->transform != WL_OUTPUT_TRANSFORM_NORMAL) {
 				float surface_translate_center[16];
 				wlr_matrix_translate(&surface_translate_center, 0.5, 0.5, 0);
 
@@ -73,14 +79,12 @@ static void render_surface(struct wlr_surface *surface,
 				float surface_translate_origin[16];
 				wlr_matrix_translate(&surface_translate_origin, -0.5, -0.5, 0);
 
-			float transform[16];
+				wlr_matrix_mul(&transform, &surface_translate_center,
-			wlr_matrix_mul(&translate_center, &rotate, &transform);
+					&transform);
-			wlr_matrix_mul(&transform, &translate_origin, &transform);
-			wlr_matrix_mul(&transform, &scale, &transform);
-
-			wlr_matrix_mul(&transform, &surface_translate_center, &transform);
 				wlr_matrix_mul(&transform, &surface_transform, &transform);
-			wlr_matrix_mul(&transform, &surface_translate_origin, &transform);
+				wlr_matrix_mul(&transform, &surface_translate_origin,
+					&transform);
+			}
 
 			wlr_matrix_mul(&wlr_output->transform_matrix, &transform, &matrix);