Windows DPI scaling issue

[niminypiminy]

Linux typically runs at a 1.0 scale factor, so logical pixels map directly to physical pixels. On Windows, the OS default scaling is 125%. This means logical pixels map to 1.25 physical pixels, therefore UI elements like buttons and inputs appear larger on Windows unless the user manually reduces scaling to 100% in display settings. A flag to control scaling behavior, might help achieve cross-platform consistency.

[nicoburns]

If the system has a scale factor configured, do you not think we ought to respect that? How are we supposed to distinguish between the default scale factor and someone who wants the widgets to be larger and has configured the scale factor as such?

[niminypiminy]

Yes. What I had in mind was an app-level scaling override for parity, similar to what Qt exposes. Qt remains DPI-aware (so Windows doesn’t bitmap-scale it), but allows a developer-controlled factor such as:QT_SCALE_FACTOR=1.0
In this kind of model, the OS still reports the system scale factor, which on windows is default 125%, but the application chooses how to apply it. For example, the app could apply a factor of 0.9 × system_scale (or clamp to 1.0). I can actually achieve this with rust boilerplate, but would be simpler with out-of-box-option.

[nicoburns]

Hmm.. QT seems to document the QT_SCALE_FACTOR enviroment variable as being "for debugging and testing purposes" (https://doc.qt.io/qt-6/highdpi.html#environment-variable-reference).

Would simply giving you a simple way to access the system scale factor work for you? (i.e. use_scale_factor hook, use_winit_window hook, or similar?)

Blitz does have an additional "zoom" factor on top of the system scale factor. Currently the end-user can control this with Ctrl-+ and Ctrl-- (Cmd on macos) similar to browsers.

[niminypiminy]

Yes, that would be much better solution. So in this way if the system default is 1.25, I can set the root zoom to 1.0 / 1.25 (0.8) to achieve parity with say default linux environment.