CNA-GAP-026: SDL_RENDERER cannot honour TextureAddressMode.Wrap or Mirror for SpriteBatch; a Wrap draw silently shows clamped pixels

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

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Evidence basis: source-verified at the pinned commit; recorded by CNA's own run (not repeated here); tests exist (not executed for this page). Claims on this page were checked by reading the CNA source at commit 009d40f5; unless a sentence says otherwise, nothing here was built or executed. Nothing on this page was executed unless the Evidence section says so.

SDL_RenderTexture's source-rectangle sampling has one fixed edge-clamping behaviour, SetSamplerAddressMode is not overridden, and CNA records the Wrap/Mirror decision (Tasks 686/687) as blocked.

Identifier: CNA-GAP-026
Category: Functional gap
Subsystem: Graphics & renderers
Status: Open
Verified against: CNA 009d40f5 (009d40f5dd085c4e674d3479675fac84b12b3e0a)
Evidence basis: Recorded by CNA: CNA's own recorded run, not repeated here
Tests touching this area: Yes: see Current tests
Affected contract: SamplerState.AddressU/AddressV = Wrap or Mirror with SpriteBatch source rectangles beyond the texture on SDL_RENDERER

Expected behaviour

XNA SpriteBatch with SamplerState.LinearWrap/PointWrap tiles a texture when the source rectangle exceeds its bounds (a common tiling trick).

Actual behaviour at TARGET

The header of sdlrenderer_texture_address_mode_clamp_test.cpp records that SetSamplerAddressMode is a no-op for this renderer, that SDL's texture address mode applies only to SDL_RenderGeometry, and that the fixed behaviour matches Clamp by accident. sdl-renderer-2d-completeness.md marks Wrap/Mirror as BLOCKED (Tasks 686/687). No error is raised.

Source locations

modules/renderers/sdl-renderer/examples/sdlrenderer_texture_address_mode_clamp_test.cpp — header analysis of address modes
docs/sdl-renderer-2d-completeness.md — TextureAddressMode Wrap/Mirror BLOCKED entry
modules/renderers/sdl-renderer/include/CNA/Internal/Renderers/SdlRenderer/SdlRenderer.hpp — no SetSamplerAddressMode override

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

The clamp test pins Clamp; nothing asserts Wrap or Mirror.

Regression test

Either render wrapped sprites through SDL_RenderGeometry with the texture address mode, or refuse Wrap/Mirror explicitly and test the refusal.

Blast radius

Tiled backgrounds and scrolling textures drawn with a Wrap sampler on SDL_RENDERER.

Workaround

Tile with several Draw calls.

The same subject is explained at several altitudes. These are the neighbouring pages at each one.

Deep dives: SDL_RENDERER: address modes
Known issues: Functional gap index