CNA-BUG-263: TerminalMouse::SetPosition throws PlatformException although IPlatformMouse::SetPosition documents no exception, so XNA's Mouse.SetPosition throws on the terminal platform

CNA snapshot 009d40f5  ·  Known Issues › Current bugs  ·  source links pinned to 009d40f5

IPlatformMouse::SetPosition documents no exception, but TerminalMouse::SetPosition always throws PlatformException and Mouse::SetPosition calls it unguarded, so the XNA re-centre-the-cursor idiom throws once the terminal platform reports mouse input.

Identifier

CNA-BUG-263

Category

Bug

Subsystem

Input

Status

Open

Verified against

CNA 009d40f5 (009d40f5dd085c4e674d3479675fac84b12b3e0a)

Severity

Low (a triage suggestion, not a project priority)

Evidence basis

Source-verified: read at TARGET, not executed

Tests touching this area

Yes: see Current tests

Affected contract

Microsoft::Xna::Framework::Input::Mouse::SetPosition(int, int) on the terminal platform (TerminalMouse::SetPosition)

Expected behaviour

IPlatformMouse::SetPosition documents that it warps the pointer and that a zero window only records the position; it lists no exception, unlike SetRelativeMode, which documents PlatformNotSupportedException. XNA's Mouse.SetPosition has no failure mode for a platform that cannot warp, and CNA's own precedent for a platform without a pointer is a determinate no-op (plans/plan_platform.md PLAT-49 makes IsMouseVisible one).

Actual behaviour at TARGET

TerminalMouse::SetPosition always throws PlatformException (“SGR-1006 reports the pointer but cannot warp it”), and Mouse::SetPosition calls the platform mouse without a guard once the mouse service exists, that is, once the terminal reports mouse input. XNA code that re-centres the cursor every frame for camera control therefore throws on its first update. TerminalMouseTests.cpp pins the refusals of SetCursorVisible, SetCursor, SetRelativeMode and the global-pointer calls but has no case for SetPosition.

Source locations

• modules/platform/src/Terminal/TerminalMouse.cpp — SetPosition throws PlatformException
• modules/platform/include/CNA/Platform/Input/IPlatformMouse.hpp — SetPosition documents no exception; SetRelativeMode documents PlatformNotSupportedException
• modules/input/src/Xna/Mouse.cpp — Mouse::SetPosition forwards to the platform mouse unguarded
• modules/platform/tests/CNA/Platform/TerminalMouseTests.cpp — refusal cases; none for SetPosition

Evidence

Read at 009d40f5; nothing executed. Reported by the HM2 issue reviewer as a possible missing finding next to CNA-BUG-176 and re-verified by the orchestrator. Distinct from CNA-BUG-135 (the CNAEXT global-pointer trio, where the interface documents the throw) and CNA-BUG-176 (Game::IsMouseVisible).

Focused reproduction

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

Current tests

The terminal mouse tests pin the other refusals directly on TerminalMouse; none exercises SetPosition or the Mouse facade on the terminal platform.

Regression test

With the terminal platform current and mouse input reported, call Mouse::SetPosition(10, 10) and expect no exception; or document the throw on IPlatformMouse::SetPosition and catch it in the facade.

Blast radius

Terminal-platform sessions whose terminal reports mouse input and whose game calls Mouse::SetPosition; other platforms warp the pointer, and a platform without a mouse service does nothing.

Workaround

Do not call Mouse::SetPosition when the active platform is the terminal, or catch PlatformException around the call.