CNA-GAP-016: Several live GraphicsDevices share process-wide window and input slots with last-writer semantics

CNA snapshot 009d40f5  ·  Known Issues › Functional gaps  ·  source links pinned to 009d40f5

The window-to-renderer registry is a static, unsynchronised map with no ownership check, and TextInputEXT and Mouse keep one process-wide window slot, so two devices overwrite each other's registry entries and input target.

Identifier

CNA-GAP-016

Category

Functional gap

Subsystem

Graphics & renderers

Status

Open

Verified against

CNA 009d40f5 (009d40f5dd085c4e674d3479675fac84b12b3e0a)

Evidence basis

Source-verified: read at TARGET, not executed

Tests touching this area

Yes: see Current tests

Affected contract

IGraphicsRenderer::RegisterForWindow/UnregisterForWindow/GetForWindow; TextInputEXT and Mouse window binding with more than one GraphicsDevice

Expected behaviour

CNA allows several devices and caller-provided (borrowed) windows; each device's input routing and window lookup should stay correct while the others live.

Actual behaviour at TARGET

RegisterForWindow in IGraphicsRenderer.hpp does windowRegistry()[window] = renderer and UnregisterForWindow erases by window id, with no owner check and no lock; two devices attached to one borrowed window overwrite each other, and destroying either removes the survivor's entry (used by Mouse and the input bridge). GraphicsDevice.cpp's createOrAttachWindow sets the process-wide TextInputEXT and Mouse window slots to its window, and destroyNativeResources clears them only if they still point at it, so the last device created owns input. XNA's own Mouse.WindowHandle is also a single static slot.

Source locations

• modules/graphics/include/CNA/Internal/Renderers/Common/IGraphicsRenderer.hpp — RegisterForWindow, UnregisterForWindow, GetForWindow, windowRegistry
• modules/graphics/src/Xna/GraphicsDevice.cpp — createOrAttachWindow and destroyNativeResources input-slot handling
• modules/graphics/tests/CNA/Internal/Renderers/Common/IGraphicsRendererWindowRegistryTests.cpp — distinct-window and replace-on-register tests

Evidence

Checked by reading the named sources at 009d40f5; nothing was built or executed for this entry.

Focused reproduction

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

Current tests

IGraphicsRendererWindowRegistryTests.cpp pins distinct windows and replacement; SDL_GPU's constructor-exception test covers unregistration after a failed construction. Nothing covers two devices on one window, concurrent lookup, or two devices' input slots.

Regression test

A test with two devices on one borrowed window (destroy one, the other stays registered) and a test of input routing with two live devices.

Blast radius

Tools and editors that host several devices or share one window between devices; single-device games are unaffected.

Workaround

Use one GraphicsDevice per window and create input-owning devices last.