The Upload method shouldn't blend. Only those methods which take a draw.Op arg (Fill, Draw, Copy Scale) should blend. (Upload could possibly also take a draw.Op arg, and then blend, but I think that that is a separate issue).

I think the top image is actually working as intended, although IIRC the windriver doesn't do textures yet. In particular, the top image matches what I see on x11driver and gldriver/linux.

https://go.googlesource.com/exp/+/master/shiny/screen/screen.go#202 says that "The destination's contents are overwritten; the draw operator is implicitly draw.Src."

CL https://golang.org/cl/19213 mentions this issue.

what I see on x11driver and gldriver/linux

Please post picture of your x/exp/shiny/example/basic window on linux, so I can see what else needs to be done for windows. Thank you.

Alex

Screenshot of the top-left corner of my window: