Incorrect scaling on Steam Deck screen

[Jacalz]

Checklist

• I have searched the issue tracker for open issues that relate to the same problem, before opening a new one.
• This issue only relates to a single bug. I will open new issues for any other problems.

Describe the bug

Copying over from Jacalz/rymdport#159, Fyne applications are entirely unusable on Steam Deck (maybe even other small screens?). This is really problematic because anyone using a Steam Deck and then installing something like Rymdport or Supersonic on Flathub will be very annoyed because the apps have stopped working.

How to reproduce

1. Start any Fyne application on Steam Deck.
2. Notice that scaling makes it impossible to use the app.

Screenshots

Example code

Use Fyne demo or install Rymdport or Supersonic from Flathub.

Fyne version

v2.4.5

Go compiler version

1.22.3

Operating system and version

SteamOS

Additional Information

See Jacalz/rymdport#159 for more information.

[andydotxyz]

I don't think this can be universally true as I have seen many apps running on the steam deck. Is it related to user configuration or is this a recent problem?

[andydotxyz]

Any more information at all? Can the user run fyne_demo or otherwise collect scale data from the device?

[Jacalz]

I haven't quite had time to research this more. Maybe we can bring in @dalitz-bazalgette can chime in here?

[dalitz-bazalgette]

I did a bit more testing with a fresh install and this scaling issue seems to only happen on X11 (which is what SteamOS uses).

I installed Fedora 39 (because it uses KDE 5.X like SteamOS) on my Steam Deck and found that Rymdport and Supersonic scale correctly in wayland but in X11 they exhibit the issue as they do in SteamOS.

[andydotxyz]

There must be something more specific going on because X11 normally works really well.
Can you share what hardware / configuration you are testing the X11 with?

[dalitz-bazalgette]

I'm using the Valve Steam Deck. I did a fresh install of SteamOS and Fedora to make sure it wasn't my configuration that caused it.

Perhaps it's a combination of X11 and the 800x1280 display that causes it.

[Jacalz]

For what it is worth, I saw that I have an old but similar report from another user having bad scaling in Rymdport:

[Jacalz]

@dalitz-bazalgette Thanks for the testing. Does Fedora 40 (with what I presume is the latest KDE Plasma 6.1 desktop) get the same behaviour? I also find it strange that X11 shows issues but not Wayland. As the app is rendering through XWayland, it is usually as good or slightly worse than a pure X11 session.

[andydotxyz]

Perhaps it's a combination of X11 and the 800x1280 display that causes it.

The resolution should not matter - as long as the screen size is reported correctly... my guess is the RandR API has some incorrect data.

Is it possible to run the fyne_demo app on the device and choose "Advanced" so we can see what information is being detected?

[andydotxyz]

I have tracked down the source of the issue - the screen is reported (to GLFW at least) as 6x6cm. Instead of being 15.6cm wide. So the scaling is off - it thinks the UI should be 4.5x normal.
If I "fix" that with a small hack in our driver then the scale is determined as 1.7 which sounds about right and gives a good resolution of text:

I'm not sure how we can fix this at the GLFW layer though - if the XWayland wrapper is reporting it wrong...