CNA-PLAT-013: Wayland gives no desktop pointer position, and browsers hide gamepads until a button press and gate pointer lock on a user gesture

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

Under SDL3's Wayland video driver the desktop pointer position reads (0, 0) and the cursor cannot be warped reliably; on the web a gamepad appears only after the player presses a button on it, and relative mouse mode engages only after a click.

Identifier

CNA-PLAT-013

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

Mouse::GetGlobalPositionEXT / WarpGlobalEXT on a Wayland session (SDL3's wayland video driver); GamePad connection and Mouse relative mode in Emscripten builds

Expected behaviour

Desktop-style pointer queries and immediate gamepad detection.

Actual behaviour at TARGET

platform-input-notes.md records, as verified in CNA's own input work (task 783), that under Wayland SDL_GetGlobalMouseState silently returns (0, 0) whatever the real cursor does, because the compositor does not give clients desktop coordinates, and that the operating-system cursor cannot be warped reliably. Sdl3Mouse passes those answers through: TryGetGlobalPosition reports success with SDL's values, and SetGlobalPosition returns SDL_WarpMouseGlobal's result. Window-local Mouse::SetPosition keeps XNA's contract through a virtual anchor. The same document records that the browser Gamepad API shows controllers only “until the user presses a button” and that pointer lock “requires a user gesture” and can be exited by the browser.

Source locations

• modules/platform/src/Sdl3/Sdl3InputServices.cpp — Sdl3Mouse::TryGetGlobalPosition and SetGlobalPosition pass SDL's answers through
• docs/platform-input-notes.md — Wayland: global position reads (0, 0), no reliable warp; web: pointer lock, gamepad privacy gate, reserved key combinations

Evidence

Checked by reading at c1c316b9; not executed. The Wayland behaviour is CNA's own recorded observation (task 783), not repeated here.

Focused reproduction

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

Current tests

None for the host behaviour itself.

Regression test

None; these are host policies.

Blast radius

Games on a Wayland session that read or warp the desktop pointer; games shipped to browsers.

Workaround

On Wayland, run the game under XWayland (SDL_VIDEODRIVER=x11) when global pointer access is required; on the web prompt for a click before enabling relative mode and before expecting gamepads.