Slow draw on loop handle drag with large samples

[prayerie]

loop handles seem to bug out the sample display when you drag them whilst on a large sample from redrawing the entire sample box every time

imo maybe a better option would be to save the previous state of the pixels before being drawn over and only redraw those before drawing the loop handles again at the next position, rather than redrawing the entire sample display. that worked for me for getting sample playback cursors to draw quickly without visual lag, although it was a lot easier as the buffer for the previously drawn pixels was just a single 1px wide straight line, whereas here there are the loop handles to consider, so it would probably be super complicated lol

[asiekierka]

Improved by 620c00c - the sample display is still redrawn in its entirety on every change, but the initial drawing of the sample waveform is done column by column, which reduces the annoying flicker.