-\func{bool}{Union}{\param{const wxBitmap&}{ bmp},
- \param{const wxColour&}{ transColour = wxNullColour},
+\func{bool}{Union}{\param{const wxBitmap\&}{ bmp}}
+
+Finds the union of this region and the the non-transparent pixels of a
+bitmap. Bitmap's mask is used to determine transparency. If the bitmap doesn't
+have a mask, solid rectangle of bitmap's dimensions is used.
+
+\func{bool}{Union}{\param{const wxBitmap\&}{ bmp},
+ \param{const wxColour\&}{ transColour},