update api, add icons, fix picopass again

applications/services/gui/application.fam

@@ -13,6 +13,7 @@ App(
     sdk_headers=[
         "gui.h",
         "elements.h",
+        "canvas_i.h",
         "view_dispatcher.h",
         "view_stack.h",
         "modules/button_menu.h",

applications/services/gui/canvas_i.h

@@ -8,6 +8,10 @@
 #include "canvas.h"
 #include <u8g2.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /** Canvas structure
  */
 struct Canvas {
@@ -88,3 +92,7 @@ void canvas_set_orientation(Canvas* canvas, CanvasOrientation orientation);
  * @return     CanvasOrientation
  */
 CanvasOrientation canvas_get_orientation(const Canvas* canvas);
+
+#ifdef __cplusplus
+}
+#endif