many images not rendered at retina resolution on macOS

[m0dB]

Bug Description

On macOS retina, many images are not rendered at HDPI. I always noticed this with the rec button, the on air icon, the settings button, and the MIXXX logo, but on closer inspection, it affects many more icons.

This can be clearly observed in this zoomed screenshot composition: the pixels of the images are double the size of the pixels of the text, which is rendered correctly. Note that the images are all svgs.

Version

2.4.0

OS

macOS

[JoergAtGithub]

I set the HIDPI /Retina scaling to 400% on Windows and everything looks fine:

Are you sure that HIDPI is the reason and not macOS?

[m0dB]

Yeah that looks nice...

I think this scaling is done differently on macOS than on windows, and it looks like a Qt bug to me.

If you log the devicePixelRatio() in a widget, what value does that give you? 1? or 4?

I have tried to find a solution programmatically, but even if I render the style into a pixmap with a devicePixelRatio of 2, the svg is rendered at low res.

I think this is related:

"This pixmap generation happens in a QIconEngine. The default engine scales pixmaps down if required, but never up"

And indeed, if I change the document size of for example the settings icon from
<svg width="76" height="16" version="1.1" xmlns="http://www.w3.org/2000/svg">
to
<svg width="152" height="32" version="1.1" xmlns="http://www.w3.org/2000/svg">

and scale the contents, it looks good.

[m0dB]

@JoergAtGithub I created a PR with upscaled svgs. Could you check if this has any drawbacks on windows?

[ronso0]

Fixed in LateNight by #12407

[ronso0]

@m0dB This was only fixed for LateNight, what about the other skins?