Drawing ideas

[JeremyLeland]

FillRect seems much faster than equivalent Path2D. A few ideas to try:

• Can we fake a circle with a radial gradient to transparency? Can we fake a stroke this way?
• Can we draw triangles with skewed rectangles? Try this: https://stackoverflow.com/questions/18124127/skew-size-and-rotate-a-rectangle-to-fit-triangle-perfectly

Make it easier to compare drawing methods in demo. Specifically:

• combined paths versus individual paths.
• slider to control number of shapes (to see where it gets bad)
• doing all path work directly in canvas context vs making a new Path2D each from (how is heap/GC affected? Does new Path2D cause more hiccups, or does it do basically the same thing as direct to canvas?)

also try rasterizing vector once and drawing that image a bunch of times. See how that looks, and if it’s meaningfully faster.

[JeremyLeland]

Rasterizing seems to be the way to go. Buttery smooth, get to keep all the effects and gradients I was using before.

It's a bit of a pain to get the sizes lined up and to know when to update, but this seems to be the best option across browsers and my test devices.