The product preview asked the viewport executor for the full physical
viewport, so a maximised 4K window (~8 MP) was refused against the 4 MP
limit on every frame. The preview now draws at the largest size of the
same aspect the executor admits (RenderLimits::fit, scratch included)
and filters it up into the viewport through the existing offscreen
blit. Viewports within the limits still draw at full size.
PNG setups past the image limits now say what the limits are and the
largest size at that aspect, and the image panel offers to use it.
Co-authored-by: Claude Opus 5.5 <[email protected]>
