Labels are rendered too small on high DPI devices

[boardend]

I have observed that labels get rendered in different sizes depending on the browser used (Chromium 118.0.5993.88 / Firefox 119.0b9) on my system (Ubuntu 22.04, Wayland, Scale 150%).

Also @andreasneumann reported that this test project is rendered with smaller labels than on QGIS Desktop.

Probably we have to set qtFontDpi depending on the devicePixelRatio property.

See also https://doc.qt.io/qt-6/highdpi.html

[wonder-sk]

It is also worth checking whether size of map symbols (point size, line width) is correct - e.g. when you set 1cm point size symbol on desktop QGIS, whether it will be 1cm on screen also in the browser.

Some things I would try to fix DPI issues:

• QgsMapSettings::setDevicePixelRatio()
• QgsMapSettings::setOutputDpi()

[andreasneumann]

It is a bit hard to tell - but Martin could be right. It could be that the whole symbology and not just the labels are affected.

Here is a screenshot showing the symbology in wasm (left) and QGIS Desktop (right).

I have the impression that in QGIS Desktop point symbol sizes and stroke-widths are also a bit larger - but it is a bit hard to tell.

[boardend]

This is fixed and ready to be tested on https://qgis.github.io/qgis-js

I did some tests with Ubuntu 22.04 on Wayland (150% and 200% scale) and X11 (200% scale) in latest Firefox and Chromium.

@andreasneumann could you do a test on Windows?

Maybe this fixes also #9, otherwise I would have a look at this next.

[andreasneumann]

The current version looks fine to me. I think we can close this issue.