Integrate `libmonado` and use it to pass battery status by jvyden · Pull Request #229 · Supreeeme/xrizer

jvyden · 2025-11-13T00:20:33Z

Closes #26.

Summary

This PR integrates the libmonado library through the libmonado-rs crate, the same crate wlx-overlay-s and others use. I've integrated it as an optional (but enabled by default) feature, with the ability for it to be either entirely compiled out or be silently unavailable on startup if we can't find Monado.

As a demonstration of usage of the new library, I've also integrated the DeviceIsCharging_Bool, DeviceProvidesBatteryStatus_Bool, and DeviceBatteryPercentage_Float tracked properties to allow games to observe device battery status.

Testing

I've tested this on WiVRn and it seems to work well for headset battery. I do not have a headset that reports controller battery through OpenXR, so I had a friend test it on their Index and it also worked.

In both cases, I've tested in Resonite using the game's built-in scripting language to observe the values reported directly.

Additionally, on WiVRn you need to specify LIBMONADO_PATH before xrizer can connect to Monado from within Proton's container. This seems to work fine on Monado for a reason I'm not sure why, but I've made an issue to track a workaround in libmonado-rs: technobaboo/libmonado-rs#24

Notes

This is my first time integrating a feature like this into a Rust project, and I'm not sure if I'm initializing libmonado in the correct place. Guidance here and with code quality would be appreciated as I'm not familiar with Rust.
I'm not entirely certain that libmonado is thread-safe, but over the past 3-4 days I've had no issues in release builds with wrapping the library context in a Send/Sync.
Unsure how to integrate unit tests into this. Should I not care about this since the bulk of these features are in other projects?

src/monado.rs

src/system.rs

ImSapphire · 2025-11-14T22:56:03Z

src/system.rs

+                    if let Some(err) = unsafe { err.as_mut() } {
+                        *err = vr::ETrackedPropertyError::UnknownProperty;
+                    }


Suggested change

if let Some(err) = unsafe { err.as_mut() } {

*err = vr::ETrackedPropertyError::UnknownProperty;

}

i think what we actually want here is ValueNotProvidedByDevice?

did so in 820fc0e but lmk if you want still want UnknownProperty by default

it probably doesn't matter in practice, but I don't think returning an error when the battery isn't available makes sense for this property, unsure what SteamVR does

Supreeeme · 2025-11-15T22:43:44Z

src/system.rs

+                let Some(d) = self.mnd_get_device_battery(device_index) else {
+                    if let Some(err) = unsafe { err.as_mut() } {
+                        *err = vr::ETrackedPropertyError::ValueNotProvidedByDevice;
+                    }
+                    return 0.0;
+                };
+
+                if !d.present {
+                    if let Some(err) = unsafe { err.as_mut() } {
+                        *err = vr::ETrackedPropertyError::ValueNotProvidedByDevice;
+                    }
+                    return 0.0;
+                }
+
+                return d.charge;


Suggested change

let Some(d) = self.mnd_get_device_battery(device_index) else {

if let Some(err) = unsafe { err.as_mut() } {

*err = vr::ETrackedPropertyError::ValueNotProvidedByDevice;

}

return 0.0;

};

if !d.present {

if let Some(err) = unsafe { err.as_mut() } {

*err = vr::ETrackedPropertyError::ValueNotProvidedByDevice;

}

return 0.0;

}

return d.charge;

let battery = self.mnd_get_device_battery(device_index);

if let Some(charge) = battery.and_then(|b| b.present.then_some(b.charge)) {

return charge;

} else {

if let Some(err) = unsafe { err.as_mut() } {

*err = vr::ETrackedPropertyError::ValueNotProvidedByDevice;

}

return 0.0;

}

Supreeeme · 2025-11-15T22:45:00Z

src/system.rs

+                let Some(d) = self.mnd_get_device_battery(device_index) else {
+                    if let Some(err) = unsafe { err.as_mut() } {
+                        *err = vr::ETrackedPropertyError::ValueNotProvidedByDevice;
+                    }
+                    return false;
+                };
+
+                return d.present;


Suggested change

let Some(d) = self.mnd_get_device_battery(device_index) else {

if let Some(err) = unsafe { err.as_mut() } {

*err = vr::ETrackedPropertyError::ValueNotProvidedByDevice;

}

return false;

};

return d.present;

if let Some(d) = self.mnd_get_device_battery(device_index) {

return d.present;

} else {

if let Some(err) = unsafe { err.as_mut() } {

*err = vr::ETrackedPropertyError::ValueNotProvidedByDevice;

}

return false;

};

Supreeeme · 2025-11-15T22:47:05Z

src/system.rs

+                let Some(d) = self.mnd_get_device_battery(device_index) else {
+                    if let Some(err) = unsafe { err.as_mut() } {
+                        *err = vr::ETrackedPropertyError::ValueNotProvidedByDevice;
+                    }
+                    return false;
+                };
+
+                if !d.present {
+                    if let Some(err) = unsafe { err.as_mut() } {
+                        *err = vr::ETrackedPropertyError::ValueNotProvidedByDevice;
+                    }
+                    return false;
+                }
+
+                return d.charging;


Suggested change

let Some(d) = self.mnd_get_device_battery(device_index) else {

if let Some(err) = unsafe { err.as_mut() } {

*err = vr::ETrackedPropertyError::ValueNotProvidedByDevice;

}

return false;

};

if !d.present {

if let Some(err) = unsafe { err.as_mut() } {

*err = vr::ETrackedPropertyError::ValueNotProvidedByDevice;

}

return false;

}

return d.charging;

let battery = self.mnd_get_device_battery(device_index);

if let Some(charging) = battery.and_then(|b| b.present.then_some(b.charging)) {

return charging;

} else {

if let Some(err) = unsafe { err.as_mut() } {

*err = vr::ETrackedPropertyError::ValueNotProvidedByDevice;

}

return false;

}

Supreeeme · 2025-11-15T22:49:16Z

src/system.rs

    }
+
+    #[cfg(feature = "monado")]
+    pub fn mnd_get_device_battery(&self, device_index: u32) -> Option<BatteryStatus> {


Suggested change

pub fn mnd_get_device_battery(&self, device_index: u32) -> Option<BatteryStatus> {

fn mnd_get_device_battery(&self, device_index: u32) -> Option<BatteryStatus> {

Supreeeme · 2025-11-15T22:49:55Z

src/monado.rs

+unsafe impl Send for SafeMonado {}
+unsafe impl Sync for SafeMonado {}


This needs a comment explaining why it's done

galister · 2025-11-20T13:46:32Z

It's important to know that libmonado uses a separate IPC session to communicate with Monado, essentially the same as what libopenxr_monado does.

There are 2 major issues with this:

Monado has a low-low IPC client limit of 8. Once the limit is hit, it's not possible to launch more XR client applications. I have already ran into issues with just tools like Motoc and Wlx, and have ended up bumping the limit on my local build to 16.
While libmonado's IPC session counts as a headless session, there's a shortcoming in Monado that makes it create a full compositor object even for headless sessions. Due to this, these IPC sessions may not be so lightweight as they seem. Edit: this only happens with MND_HEADLESS, not with libmonado.

There is an unpublished extension EXT_battery_state_display, currently offered only by SteamVR. I would personally consider waiting for that to be finalized, as that would allow us to have a less intrusive solution.

ImSapphire · 2025-11-22T04:38:07Z

Monado has a low-low IPC client limit of 8. Once the limit is hit, it's not possible to launch more XR client applications. I have already ran into issues with just tools like Motoc and Wlx, and have ended up bumping the limit on my local build to 16.

Maybe we should have this bumped upstream?

While libmonado's IPC session counts as a headless session, there's a shortcoming in Monado that makes it create a full compositor object even for headless sessions. Due to this, these IPC sessions may not be so lightweight as they seem. Edit: this only happens with MND_HEADLESS, not with libmonado.

This should be fixed in https://gitlab.freedesktop.org/monado/monado/-/merge_requests/2606

galister · 2025-11-27T01:21:14Z

Monado IPC client increase: https://gitlab.freedesktop.org/monado/monado/-/merge_requests/2644

SpookySkeletons · 2025-12-01T17:59:59Z

Monado IPC client increase: https://gitlab.freedesktop.org/monado/monado/-/merge_requests/2644

Now merged.

SpookySkeletons · 2026-01-15T06:24:23Z

Mind giving this a rebase?

jvyden · 2026-01-15T06:27:10Z

Sure, sorry, forgot about this branch. I should have this up to date tomorrow.

jvyden added 5 commits November 7, 2025 16:26

Basic libmonado hello world

ac1c5c7

libmonado integration into openxr_data

d6a10f9

Report battery status via device properties

a45172d

Merge branch 'main' into libmonado

640ec8a

cargo fmt

22d4b28

ImSapphire reviewed Nov 14, 2025

View reviewed changes

Apply suggestions from code review

0a1908d

jvyden force-pushed the libmonado branch from 820fc0e to 0a1908d Compare November 15, 2025 21:53

jvyden requested a review from ImSapphire November 15, 2025 21:54

Supreeeme reviewed Nov 15, 2025

View reviewed changes

ImSapphire mentioned this pull request Dec 14, 2025

[Feature Request]: Headset battery reporting in game WiVRn/WiVRn#672

Closed

	if let Some(err) = unsafe { err.as_mut() } {
	*err = vr::ETrackedPropertyError::UnknownProperty;
	}

	pub fn mnd_get_device_battery(&self, device_index: u32) -> Option<BatteryStatus> {
	fn mnd_get_device_battery(&self, device_index: u32) -> Option<BatteryStatus> {

		unsafe impl Send for SafeMonado {}
		unsafe impl Sync for SafeMonado {}

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Summary

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ImSapphire Nov 16, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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galister commented Nov 20, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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ImSapphire commented Nov 22, 2025

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SpookySkeletons commented Dec 1, 2025

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SpookySkeletons commented Jan 15, 2026

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jvyden commented Jan 15, 2026

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jvyden commented Nov 13, 2025 •

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