Structure: laDrawSurfaceWidget_t 

A draw surface widget is a special widget that allows an application to perform custom HAL draw calls during Aria's paint loop. To use, create and add a draw surface widget to the desired place in the widget tree. Then register for the callback through the API 'laDrawSurfaceWidget_SetDrawCallback'. This callback occurs during the paint loop. The application should then be free to adjust the HAL draw state and issue draw calls as desired. The HAL layer, buffer, or context state must not be adjusted in any way. 

It is also important to not stall for too long during the draw callback.

typedef struct laDrawSurfaceWidget_t {
  laWidget widget;
  laDrawSurfaceWidget_DrawCallback cb;
} laDrawSurfaceWidget;

None.