Represents the type of mouse event collision detection.
You can also set the value.
If htProvince is specified, mouse events will be received only in non-zero areas in the area image.
If you specify htMask, you will only receive mouse events if the mask (opacity) image value is greater than or equal to the value specified by the Layer.hitThreshold property.
Mouse events that are not received are processed in a deeper layer.
The initial state is htMask.