CNA-PLAT-014: Compass and Motion work only on Android; desktop sensors come only through the SDL3 platform, and web targets are refused

CNA snapshot c1c316b9 · Known Issues › Platform limitations · source links pinned to c1c316b9

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Evidence basis: source-verified at the pinned commit; tests exist (not executed for this page). Claims on this page were checked by reading the CNA source at commit c1c316b9; unless a sentence says otherwise, nothing here was built or executed. Nothing on this page was executed unless the Evidence section says so.

Compass::IsSupported and Motion::IsSupported are false everywhere except Android, as SDL3 exposes no magnetometer or fused-orientation API; Accelerometer and Gyroscope read real sensors on Android, iOS and desktop, never in a browser.

Identifier: CNA-PLAT-014
Category: Platform limitation
Subsystem: Platforms
Status: Open
Verified against: CNA c1c316b9 (c1c316b9c7a846ce8002809c151fcd1af14942c9)
Evidence basis: Source-verified: read at TARGET, not executed
Tests touching this area: Yes: see Current tests
Affected contract: Compass, Motion, Accelerometer and Gyroscope IsSupported per target

Expected behaviour

WP7's four sensor classes on every CNA target.

Actual behaviour at TARGET

Compass.cpp returns the Android backend's answer under __ANDROID__ and false otherwise (“SDL3 exposes no magnetometer/compass API on any supported platform”); Motion.cpp has the same shape. Accelerometer.cpp accepts Android, iOS and Desktop targets and excludes the browser “by the established target policy”.

Since INPUT-EMU-001 (31a560af9) Accelerometer has an opt-in keyboard emulation (setKeyboardEmulationEnabledEXT): while it is on, IsSupported is true on every target, browser included, but readings come from the keyboard, not a sensor.

Source locations

modules/devices/src/Sensors/Compass.cpp — Compass::getIsSupportedProperty
modules/devices/src/Sensors/Motion.cpp — Motion::getIsSupportedProperty
modules/devices/src/Sensors/Accelerometer.cpp — Accelerometer::getIsSupportedProperty target policy

Evidence

Checked by reading at c1c316b9; not executed.

Focused reproduction

No focused reproduction is known. Nothing has been invented here; the evidence above is what exists.

Current tests

The not-supported paths are unit tested on the host.

Regression test

None; a new backend would bring its own tests.

Blast radius

Games using Compass or Motion outside Android, or any sensor in a browser build.

Workaround

Check IsSupported and fall back to other input.

The same subject is explained at several altitudes. These are the neighbouring pages at each one.

User guide: Sensors guide
Deep dives: Sensors and vibration: compass · Sensors and vibration: motion
Known issues: Platform limitation index