Win32: DPI Awareness is broken with OpenGL contexts

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:

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.

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.

@BillyDM

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?

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

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.

@BillyDM

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

No, that doesn't fix it.

@BillyDM

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

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

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

This also does not fix it.

#334 works for me too on AMD!

Can you guys try if #335 helps for the plugin (embedded window) case?

On nVidia #335 doesn't seem to work (testing thru bitwig).

Just tried #335 on AMD. render_femtovg works perfectly. clack_plugin works the first time the window is opened on FL Studio. But if I reopen the window, the GUI is missing.

After reopening:

@Soulusions

@Soulusions @danferns I have added some extra (temporary) logging on Windows in the clack_plugin example, and added a new clack_plugin_femtovg plugin to test the OpenGL behavior, can you guys give it a try and share the plugin's log outputs?

Both plugins look good on my system.

I've added logs from testing in Reaper (since FL Studio turns out to be at 100% scale for me).

Clack plugin:

// plugin opened on a 150% scale monitor
2026-09-10T08:21:15.908358Z DEBUG baseview::platform::win::dpi: Using DPI Awareness Context of type Some(PerMonitorDpiAware).
// moved to a 100% scale monitor, back and forth a couple of times
Resized: WindowSize { physical: PhysicalSize { width: 191, height: 96 }, logical: LogicalSize { width: 127.33333333333333, height: 64.0 }, scale_factor: 1.5 }
Resized: WindowSize { physical: PhysicalSize { width: 400, height: 201 }, logical: LogicalSize { width: 266.6666666666667, height: 134.0 }, scale_factor: 1.5 }
Resized: WindowSize { physical: PhysicalSize { width: 191, height: 96 }, logical: LogicalSize { width: 127.33333333333333, height: 64.0 }, scale_factor: 1.5 }
Resized: WindowSize { physical: PhysicalSize { width: 400, height: 201 }, logical: LogicalSize { width: 266.6666666666667, height: 134.0 }, scale_factor: 1.5 }
// clicked on gui which initiates a resize
Resized: WindowSize { physical: PhysicalSize { width: 450, height: 201 }, logical: LogicalSize { width: 300.0, height: 134.0 }, scale_factor: 1.5 }
Resized: WindowSize { physical: PhysicalSize { width: 500, height: 201 }, logical: LogicalSize { width: 333.3333333333333, height: 134.0 }, scale_factor: 1.5 }
// dragged corner a tiny bit
Resized: WindowSize { physical: PhysicalSize { width: 499, height: 201 }, logical: LogicalSize { width: 332.6666666666667, height: 134.0 }, scale_factor: 1.5 }

Clack plugin femtovg:

2026-09-10T08:22:57.559574Z DEBUG baseview::platform::win::dpi: OpenGL context requested: bypassing DPI awareness checking, using process DPI awareness instead.
2026-09-10T08:22:57.559659Z DEBUG baseview::platform::win::dpi: Using DPI Awareness Context of type Some(PerMonitorDpiAware).

(Moved other issue to #337)

@danferns

@danferns Thanks! The logs look like it's behaving correctly. For the other issues you raised, unless they're caused by #335, I think filing them as separate issues would be better, yes. 🙂

@Soulusions

I just got my hands on an NVIDIA Windows system, and while I could reproduce the original issue, it seems #335 fixes it (both standalone and in Bitwig).

@Soulusions do you still have issues with the latest commits on #335? If not then I think we'll be able to close this issue. 🙂

I can't get logs due to bitwig running plugins in a "server", but it looks like now the behavior in femtosvg with opengl is good.

I can't get logs due to bitwig running plugins in a "server", but it looks like now the behavior in femtosvg with opengl is good.

Plugin logs can be found in Bitwig's engine.log file.

I have just merged #335 and will publish it as part of the next release, since it seems to fix the issue for all of us I will close this issue, but feel free to comment here if the issue arises again. 🙂

Thank you Adrien, Billy, and @/Soulusions! Your work is really appreciated! This is not just great news for Rust plugin developers, but also of great benefit to users of said plugins! 😁

Win32: skip thread-scoped DPI awareness for OpenGL windows

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prokopyl commented on Aug 22, 2026

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