[SailfishDevel] Drawing ShaderEffect to Canvas

[Kimmo Lindholm]

> Yeah grabToImage() is pretty costly due to the pixel readback. What you want
> is to draw your ShaderEffect into a texture and then draw that texture directly
> onto the canvas without going through the pixel readback / CPU memory code
> path that  grabToImage would imply. Not sure how exactly we would swing that
> with the current Canvas design (at least if we take threaded/non-threaded and
> Image codepaths into account), but feel free to open a suggestion for that on
> bugreports.qt.io. Something might happen :)

Will do. Thanks.

-kimmo