still I was unable to do a triplebuffer tecnique (til version 0.6 I was still unable to blit an offscreen on top of another offscreen with offset to do image compositions)
I have the same question. I ended up running Instruments on a Mac and saw that, sure enough, constant redraws showed up as substantial slices of the CPU.
But, it looks like with scaling and so forth, FramebufferWidget isnāt free (as far as I can tell it allocates 16x the size of the thing it buffers; doubled once for subsampling; doubled again because Iām running on a 4K display). I restructured my code to dirty FramebufferWidget when something needs to be redrawn, and nearly all overridden widgets are backed one.
I wish that there was a way to mark non-FramebufferWidget widgets as dirty, so that they would only get drawn as needed or when the area is invalidated.
If your screen DPI ratio is 2, its oversampling ratio is set to 1, so it should allocate 1x the size of the thing it buffers. No downscaling is needed after drawing.
If your DPI ratio is 1, then it would oversample by 2 and then downscale to pixel-perfect in world coordinates.
Then the widget would āflickerā as it would only be drawn every time it changes and would be invisible in all other frames.
The ādoubling twiceā was observed by stepping through VCV in the debugger. Both x and y used by FramebufferWidget are 4x the size of child. The zoom factor was set to 100%. I can provide more specifics if that is helpful.