No canvas stall on Windows, patterns and every blend mode on the graphics card
A fix first: on Windows, the first time a page drew shapes, clips or blend modes on a graphics card canvas, 0.1.410 could freeze for 6 to 10 seconds while Windows' shader compiler built the drawing programs. They are now built once, in the background, as soon as the browser starts, and a canvas draws on the processor (the same pixels) until they are ready. Canvas pattern fills and all 26 blend modes now draw on the graphics card too; the seven blend modes that need exact decimal maths match the software to the last bit on Mac, and stay on the processor on Windows, whose shader compiler cannot build them.
No freeze on Windows
Windows' graphics compiler takes several seconds over the canvas drawing programs. 0.1.410 built them on the page's own thread the first time a page needed one, so the page stopped while it waited. Now one set is built for the whole browser on a thread of its own when it starts; until it is ready a canvas simply stays on the processor, drawing the same pixels.
Patterns on the graphics card
A pattern fill (createPattern) now samples its tile in whole numbers from the corner of the shape it fills, as drawImage does, so the graphics card can draw it and gets the same bytes. Repeat in x, in y, both or neither all work, under any turn or scale.
Every blend mode, exact
Colour-dodge, colour-burn, soft-light, hue, saturation, color and luminosity are computed in decimal numbers, and the graphics card's own decimal maths is not exact. On Mac the graphics card canvas now computes them the processor's way, step by step: products in whole numbers, divisions as long division, square roots corrected to the exactly rounded value. Every blend mode matches the software canvas byte for byte on every test.