CNA-BUG-135: Mouse::SetCaptureEXT, GetGlobalPositionEXT and WarpGlobalEXT let PlatformNotSupportedException escape on the terminal platform

CNA snapshot c1c316b9  ·  Known Issues › Current bugs  ·  source links pinned to c1c316b9

The terminal mouse service throws PlatformNotSupportedException from SetCapture, TryGetGlobalPosition and SetGlobalPosition, and the Mouse wrappers do not catch it, although they document false (or (0, 0)) for an unsupported platform.

Identifier

CNA-BUG-135

Category

Bug

Subsystem

Input

Status

Open

Verified against

CNA c1c316b9 (c1c316b9c7a846ce8002809c151fcd1af14942c9)

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

Mouse::SetCaptureEXT(bool), Mouse::GetGlobalPositionEXT(int&, int&), Mouse::WarpGlobalEXT(int, int)

Expected behaviour

Mouse.hpp documents SetCaptureEXT and WarpGlobalEXT as returning false “if the platform does not support” the operation, and GetGlobalPositionEXT in Mouse.cpp zeroes its outputs first “so a platform with no desktop pointer answers (0, 0)”.

Actual behaviour at TARGET

The wrappers call the platform mouse directly. TerminalMouse (TerminalMouse.cpp) throws PlatformNotSupportedException from all three methods, as IPlatformMouse.hpp allows (“@throws PlatformNotSupportedException If the platform reports no GlobalPointer capability”). The exception reaches the game. The SDL3 platform answers through SDL on every video driver, and the headless platform has no mouse service, so the wrappers return their documented defaults there.

Source locations

• modules/input/src/Xna/Mouse.cpp — Mouse::SetCaptureEXT, GetGlobalPositionEXT, WarpGlobalEXT: no capability check, no catch
• modules/input/include/Microsoft/Xna/Framework/Input/Mouse.hpp — documented false return for unsupported platforms
• modules/platform/src/Terminal/TerminalMouse.cpp — SetCapture, TryGetGlobalPosition, SetGlobalPosition throw
• modules/platform/include/CNA/Platform/Input/IPlatformMouse.hpp — @throws PlatformNotSupportedException contract

Evidence

Checked by reading at c1c316b9; not executed on a terminal.

Focused reproduction

// Illustrative; not compiled or run. CNA_PLATFORM=TERMINAL.
int x = 0, y = 0;
Mouse::GetGlobalPositionEXT(x, y);  // expected (0, 0); actual: PlatformNotSupportedException

Current tests

TheRealPlatformIsSafeForAllThree in MouseGlobalTests.cpp asserts no throw on the test platform only; the throwing backends are not driven through the wrappers.

Regression test

The same test against a canned mouse whose three methods throw PlatformNotSupportedException; the fix is a GlobalPointer capability check (or a catch) in the three wrappers.

Blast radius

Games calling the three CNAEXT mouse functions on the terminal platform. SDL3 (on every video driver) and headless answer normally.

Workaround

Catch PlatformNotSupportedException around the calls, or check the platform's GlobalPointer capability first.