Most of our modern device drivers support semi-transparent colours so if Windows supports this, it should be straightforward to modify our wingcc device to do the same.
Alan W. Irwin
You expressed concern privately that the GDI graphics used by wingcc might not support semi-transparent colours. I have looked further into that.
Please take a look at http://msdn.microsoft.com/en-us/library/dd183458(v=vs.85).aspx. It appears to me they are essentially documenting colour transparency although they are referring to it as colour mixing.
Apparently GDI is quite old/deprecated. If the above idea does not work, another possibility is to move wingcc to GDI+ instead (assuming from the name that move would only be a small amount of work). For the GDI+ case, the colour transparency is documented at http://msdn.microsoft.com/en-us/library/ms533803(v=vs.85).aspx