A transparency group whose members blend with the art below it, and a
masked object with a blend mode, are drawn over a copy of that art. For
each such group in each frame, the renderer rendered everything drawn
so far into a new pixmap the size of its context (on the canvas, the
whole view), started that context again and drew that pixmap back into
it as an image, which the next copy and the frame rendered again. At
2880x1800, a document with 50 translucent groups, each holding a
Multiply rectangle, took 299 ms a frame on 8 threads.
Every render that composites in 8 bits, the canvas included, now keeps
that picture and renders what the context draws next over it. The
backdrop is still cut from the picture. The 50 groups take 65 ms a
frame, and the frames have the same pixels. Renders that composite in
floating point (raster exports, Save for Web, Object › Rasterize and
Crop Image) still draw the picture back.
Docs: docs/target-app-parity.md.
78980c8190