CNA-GAP-030: FREEDIRECT keeps presenting at the old physical scale after a virtual-resolution change once the first Present has happened

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

FreeDirectRenderer::SetVirtualResolution recreates the surfaces and the display mode, but free-direct applies its SDL logical-presentation rectangle only once, so output after a change made following the first Present keeps the old logical size and scale. That FREEDIRECT always letterboxes whatever presentation mode is requested is published as CNA-GAP-017.

Identifier

CNA-GAP-030

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

GraphicsDevice presentation mode and virtual-resolution changes on FREEDIRECT

Expected behaviour

A virtual-resolution change applies to later frames.

Actual behaviour at TARGET

In FreeDirectRenderer.cpp, SetVirtualResolution calls Impl::CreateSurfaces, which creates a new shadow backbuffer and primary surface and calls IDirectDraw::SetDisplayMode. free-direct's PresentPrimary calls SDL_SetRenderLogicalPresentation (letterbox) once, guarded by a logicalPresentationSet_ flag that nothing resets, so a change after the first Present keeps the old physical scale. A code comment in SetVirtualResolution and freedirect-renderer.md record this as a known limitation that needs a change in free-direct itself. TransformWindowToLogical and TransformLogicalToWindow recompute the letterbox from the new logical size, so when the aspect ratio changes the pointer mapping is likely to disagree with the picture (inferred from the two code paths, not run).

Source locations

• modules/renderers/freedirect/src/FreeDirectRenderer.cpp — FreeDirectRenderer::SetPresentationMode and SetVirtualResolution
• docs/freedirect-renderer.md — SetPresentationMode / resize-after-first-Present row and known limitations

Evidence

Checked by reading at 009d40f5; not executed.

Independent re-verification: Checked by reading at 009d40f5 and the free-direct sibling checkout (unpinned, see CNA-VGAP-042); not executed. FreeDirect_ResizeTransaction covers the resize bookkeeping and surface transaction, not the physical output; the SetPresentationMode half of the original entry duplicates CNA-GAP-017 and was removed.

Focused reproduction

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

Current tests

FreeDirect_ResizeTransaction covers resize bookkeeping; no test compares physical output across presentation modes.

Regression test

After a free-direct change: a readback test per presentation mode and one for a resolution change after the first Present.

Blast radius

FREEDIRECT games that request a non-letterbox mode or change resolution at run time. Mouse transforms follow the letterbox actually used.

Workaround

Choose the virtual resolution before the first Present and accept letterboxing.