lv_draw_task_t struct

The ID of the draw_unit which should take this task.

Set to which extent `preferred_draw_unit_id` is good at this task. 80: means 20% better (faster) than software rendering 100: the default value 110: means 10% worse (slower) than software rendering.

The area where to draw.

The real draw area. E.g. for shadow, outline, or transformed images it's different from `area`.

The original area which is updated.

The clip area of the layer is saved here when the draw task is created. As the clip area of the layer can be changed as new draw tasks are added its current value needs to be saved. Therefore during drawing the layer's clip area shouldn't be used as it might be already changed for other draw tasks.

int instead of lv_draw_task_state_t to be sure its atomic.