Hi David! Sorry for answering late, but I'm buried under a huge pile of work...
The relevant lines of code in the GTK plug-in are here:
Basically one gets the icc transform from sRGB to the display profile via
and then apples the transform to a buffer of floating-point data:
Is this what you need? Could you point me to the lines of code in the QT plug-in where you would like to introduce the color transform?