compositor: Create the inverse of the output matrix

Signed-off-by: Derek Foreman <derekf@osg.samsung.com>
Reviewed-by: Bryce Harrington <b.harrington@samsung.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

src/compositor.c

@@ -4003,6 +4003,8 @@ weston_output_update_matrix(struct weston_output *output)
 				    output->current_scale, 1);
 
 	output->dirty = 0;
+
+	weston_matrix_invert(&output->inverse_matrix, &output->matrix);
 }
 
 static void

src/compositor.h

@@ -185,6 +185,8 @@ struct weston_output {
 
 	/** From global to output buffer coordinates. */
 	struct weston_matrix matrix;
+	/** From output buffer to global coordinates. */
+	struct weston_matrix inverse_matrix;
 
 	struct wl_list animation_list;
 	int32_t x, y, width, height;