pixman-renderer: share region_global_to_output()

Converting a region from global coordinates to output pixel coordinates
will become useful in GL-renderer soon, so move this function to be
shared. It is tricky to reinvent.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

libweston/backend.h

@@ -170,6 +170,10 @@ weston_output_transform_coordinate(struct weston_output *output,
 				   double device_x, double device_y,
 				   double *x, double *y);
 
+void
+weston_output_region_from_global(struct weston_output *output,
+				 pixman_region32_t *region);
+
 /* weston_seat */
 
 void

libweston/compositor.c

@@ -5844,6 +5844,36 @@ weston_compositor_reflow_outputs(struct weston_compositor *compositor,
 	}
 }
 
+/** Transform a region in-place from global to output coordinates
+ *
+ * \param output The output that defines the transformation.
+ * \param region The region to be transformed in-place.
+ *
+ * This takes a region in the global coordinate system, and takes into account
+ * output position, transform and scale, and the zoom, and converts the region
+ * into output pixel coordinates in the framebuffer.
+ *
+ * Uses floating-point operations if zoom is active, which may round to expand
+ * the region.
+ *
+ * \internal
+ * \ingroup output
+ */
+WL_EXPORT void
+weston_output_region_from_global(struct weston_output *output,
+				 pixman_region32_t *region)
+{
+	if (output->zoom.active) {
+		weston_matrix_transform_region(region, &output->matrix, region);
+	} else {
+		pixman_region32_translate(region, -output->x, -output->y);
+		weston_transformed_region(output->width, output->height,
+					  output->transform,
+					  output->current_scale,
+					  region, region);
+	}
+}
+
 static void
 weston_output_update_matrix(struct weston_output *output)
 {

libweston/pixman-renderer.c

@@ -125,20 +125,6 @@ pixman_renderer_read_pixels(struct weston_output *output,
 	return 0;
 }
 
-static void
-region_global_to_output(struct weston_output *output, pixman_region32_t *region)
-{
-	if (output->zoom.active) {
-		weston_matrix_transform_region(region, &output->matrix, region);
-	} else {
-		pixman_region32_translate(region, -output->x, -output->y);
-		weston_transformed_region(output->width, output->height,
-					  output->transform,
-					  output->current_scale,
-					  region, region);
-	}
-}
-
 #define D2F(v) pixman_double_to_fixed((double)v)
 
 static void
@@ -426,7 +412,8 @@ draw_view_translated(struct weston_view *view, struct weston_output *output,
 							  repaint_global,
 							  &surface->opaque,
 							  view);
-			region_global_to_output(output, &repaint_output);
+			weston_output_region_from_global(output,
+							 &repaint_output);
 
 			repaint_region(view, output, &repaint_output, NULL,
 				       PIXMAN_OP_SRC);
@@ -437,7 +424,7 @@ draw_view_translated(struct weston_view *view, struct weston_output *output,
 		region_intersect_only_translation(&repaint_output,
 						  repaint_global,
 						  &surface_blend, view);
-		region_global_to_output(output, &repaint_output);
+		weston_output_region_from_global(output, &repaint_output);
 
 		repaint_region(view, output, &repaint_output, NULL,
 			       PIXMAN_OP_OVER);
@@ -473,7 +460,7 @@ draw_view_source_clipped(struct weston_view *view,
 
 	pixman_region32_init(&repaint_output);
 	pixman_region32_copy(&repaint_output, repaint_global);
-	region_global_to_output(output, &repaint_output);
+	weston_output_region_from_global(output, &repaint_output);
 
 	repaint_region(view, output, &repaint_output, &buffer_region,
 		       PIXMAN_OP_OVER);
@@ -546,7 +533,7 @@ copy_to_hw_buffer(struct weston_output *output, pixman_region32_t *region)
 	pixman_region32_init(&output_region);
 	pixman_region32_copy(&output_region, region);
 
-	region_global_to_output(output, &output_region);
+	weston_output_region_from_global(output, &output_region);
 
 	pixman_image_set_clip_region32 (po->hw_buffer, &output_region);
 	pixman_region32_fini(&output_region);