Win32: DPI Awareness is broken with OpenGL contexts

[BillyDM]

Fractional scaling does not appear to be working on Windows. This is the output I get when running the render_femtovg example with the display set to 125% scale.

The mouse cursor is also not in the correct place.

Egui-baseview also looks pixelated and has an incorrect window size when ran in standalone mode on Windows with fractional scaling:

When ran as a plugin, the window has an incorrect size:

[prokopyl]

Notes from further testing from Discord:

• This only affects OpenGL, not Wgpu/DirectX, nor softbuffer-based examples.
• From added logging, baseview does indeed receive the updated DPI information, so this seems to be purely a rendering issue.
• This has been only reproduced on AMD GPUs, but not tested on others. VMWare virtual GPUs are not affected by this issue somehow.

[BillyDM]

I know baseview manages its own OpenGL context. Is there maybe something special you need to do with the context on Windows? We could look into how glutin/glow does this.

[prokopyl]

Looking into this again, I just realized that the OpenGL view seems to be actually scaled twice for some reason?

@BillyDM I'm not sure if this is a regression, have you had this problem with Baseview on windows before? Do you think you could bisect the issue?

[BillyDM]

Ok, I'll see if I can recreate the issue on an older version of baseview tomorrow.

[BillyDM]

Ok, found that the issue happens from 468c21b onwards (Win32: Migrate to Per-Monitor V2 Thread-based DPI awareness (#266)).

The commits before that one start off at with the rendered image not filling the whole window, but after resizing the window once, everything works correctly.

[prokopyl]

@BillyDM Can you try the fix in this branch to see if it helps? https://github.com/RustAudio/baseview/tree/win32-opengl-fix

[BillyDM]

No, that doesn't fix it.

[prokopyl]

@BillyDM can you try the latest one on that branch?

Sorry to use you as a ping-pong like that 😅

[danferns]

If you guys can use another hand I'm here :)

[danferns]

This also does not fix it.