Waveform: avoid QPainter glitch with ranges < 1 px

[ronso0]

Noticed when setting loop_in and loop_out at the same position (it's not, seems they are correct to be 1+ samples apart):
If the range is < 1 xp, as long as the range start marker is visible in the waveform, the range would be rendered to span until the end of the view.

Can't tell what the actual issue is, QPainter with QRectF // rendering engine?
It's strange though: the glitch does not occur at zoom levels 16.7%, 50% and 100% (on FullHD screen, LateNight @ min width) where the range rectangle width is 0.25 * [odd int].
Anyway, rounding up the width to 1 px solves the issue on all zoom levels.

zoom	rect.width()	okay?
10%	0.15	❌
11%	0.166	❌
12.5	0.1875	❌
14.3%	0.214	❌
16.7%	0.25	✔️
20%	0.3	❌
25%	0.375	❌
33.3%	0.5	❌
50%	0.75	✔️
100%	1.5	✔️

I don't mind if this goes into 2.3.3 or the next release

[Swiftb0y]

Thanks. Lets wait for the 2.3.3 release first since this is low priority.

[ronso0]

Sure.
Maybe someone can figure out was actually causes issue when using those width/height values

mixxx/src/waveform/renderers/waveformrendermarkrange.cpp

Line 85 in 9cbd4cd

painter->drawImage(rect, *selectedImage, rect);

[ronso0]

FWIW
using

painter->drawImage(rect.topLeft(), *selectedImage, rect);

doesn't prevent the glitch.

[Swiftb0y]

2.3.3 was released. Merge?

[ronso0]

Sure.