[7.4.x-7.5] QT.AA_EnableHighDpiScaling results in wrong DPI on some screens

[ichorid]

A user on the forum reported detected a QT bug with auto-scaling.

This happens for all the 7.4.x series along with the experimental build or 7.5.

[ichorid]

The user tried a custom Tribler build that does not include

tribler/src/tribler-gui/tribler_gui/tribler_app.py

Line 13 in 3afa97f

QCoreApplication.setAttribute(Qt.AA_EnableHighDpiScaling)

lines. It solved his problem.

Apparently, QT DPI scaling detects DPI wrongly on some Windows machines.

[Rik44444]

same problem here, i am not using a custom build, i'm using the most recent stable build from tribler.org 7.4.4. . i'm on Windows 10, HP laptop, display res 1920/1080, scaling at 150%.

[ichorid]

@Rik44444 , thanks for reporting! We're probably going to include some kind of option to turn the scaling off in the upcoming 7.5 release.

[ichorid]

For 7.5 we're not going to provide the settings option as it will require some pretty invasive changes in how our GUI settings are processed. To solve this properly we should do as the QT manual states:

Always use the qreal versions of the QPainter drawing API.
Size windows and dialogs in relation to the corresponding screen size.
Replace hard-coded sizes in layouts and drawing code with values calculated from font metrics or screen size.

and change the GUI settings loading order so the GUI will first load its settings, and only then will create the window. This will enable us to create a "scaling factor" option in the GUI that will be available for tuning by the user.

For people who are affected by this problem:
you can try adding QT_SCALE_FACTOR=1 environment variable, and/or play with the value to adjust it to DPI.

[ichorid]

Another report on the forum.

[drew2a]

This could be fixed by

• Rewrite the GUI to use a Qt webview (HTML+Javascript) #7736