QML UIs don’t respect the scale factor for HiDPI display

[Shih-Yuan Lee]

Ubuntu 14.04.2

Reproducible Steps:

1. Login Unity desktop environment.
2. Change the scale factor to 2 in Displays of System Settings.
3. Open Amazon webapp.

Expected Result:

* We can see the scaled Amazon website.

Actual Result:

* Amazon website is still very small.

[Olivier Tilloy (osomon)]

Not sure what you are expecting here. Should the webview increase its scale factor automatically to account for the setting change?
How do firefox and chromium behave in that regard, on the same configuration?

[Launchpad Janitor (janitor)]

[Expired for webbrowser-app (Ubuntu) because there has been no activity for 60 days.]

[Olivier Tilloy (osomon)]

fourdollars: can you please answer my question in comment #3, so that we can confirm the bug?

[Shih-Yuan Lee (fourdollars)]

Yes, the webapp should increase its scale factor automatically to account for the setting change.
Although Google Chrome or Mozilla Firefox don't support this behavior, but they do scale up after restarting the applications.
In my point of view, the webapp should support the scaling up at least after restarting the webapp.

[Olivier Tilloy (osomon)]

It’s not just the webview that doesn’t scale up, it’s the entire browser UI. And any UI written in QML, for that matter (UIs using traditional QWidgets scale up correctly). This setting should probably be propagated by Qt to the QML scene graph, and the oxide WebView (being a QQuickItem) would pick it up automatically.

[Shih-Yuan Lee (fourdollars)]

Hi, I found there is a environment variable from http://doc.qt.io/qt-5/highdpi.html.
If we set QT_DEVICE_PIXEL_RATIO=auto in the system with HiDPI, it does work but doesn't work very well.

[Shih-Yuan Lee (fourdollars)]

Comment #8 is tested by Ubuntu 16.04.

[Timo Jyrinki (timo-jyrinki)]

Ubuntu 16.04 ships with Qt 5.5, which doesn't have the Qt's new HiDPI work. If you want to try out Qt 5.6, there's a PPA that can be installed (and uninstalled) with instructions from https://wiki.ubuntu.com/Touch/QtTesting

It will only land in Ubuntu 16.10.