Using PolyLine and drawing less points.

[clrnd]

WaveEdit used 50% of my MacBook Pro 2015 CPU when completely idle.

The culprit was renderBankGrid which needs to draw so many lines (just commenting it dropped usage to 13%).

Drawing only a fourth of the points and using AddPolyLine (which draws them all together), I managed to get the CPU usage down to 20%.

(I know "CPU usage" is a weak measure, I did check v-sync-less framerate too)

This of course means the preview waves lose some resolution, so no hard feelings if you don't wanna merge this 😁

(I guess the "correct" way to do this is some kind of interpolation)