Gui: Direct Draw API (#2215)

* Furi: allow on-fly thread priority change. Gui: Direct Draw API. DirectDraw debug app.
* Gui: drop input in direct draw
* Furi: handle priority change for starting threads
* DirectDraw: rollback to FreeRTOS primitives for priority change

applications/services/gui/canvas.h

@@ -67,6 +67,18 @@ typedef struct {
 /** Canvas anonymous structure */
 typedef struct Canvas Canvas;
 
+/** Reset canvas drawing tools configuration
+ *
+ * @param      canvas  Canvas instance
+ */
+void canvas_reset(Canvas* canvas);
+
+/** Commit canvas. Send buffer to display
+ *
+ * @param      canvas  Canvas instance
+ */
+void canvas_commit(Canvas* canvas);
+
 /** Get Canvas width
  *
  * @param      canvas  Canvas instance