Alpha blending amounts are cumulative from parent to child. If a parent is blended at 50% then logically a child should also implicitely be blended at 50%. If a child further explictely enables blending at 50% then the cumulative amount is 25%.

LIB_EXPORT uint32_t laWidget_GetCumulativeAlphaAmount(
    laWidget* wgt
);

uint32_t - the cumulative blending amount