The input passthrough setting is used to prohibit or allow input events to pass through a layer. If a layer is opaque or semi-opaque input events should probably not be allowed to pass through. If the layer is completely transparent then input events may be allowed to pass through to interact with widgets on layers further back in the hierarchy. 

An application that disables this is responsible for ensuring that it is modified when the dimensions of the layer change.

LIB_EXPORT laBool laLayer_GetAllowInputPassThrough(
    const laLayer* layer
);

laBool - the state of the layer's passthrough flag