CNA-PLAT-001: SDL_RENDERER throws for any Texture2D mip level above 0, so mipmapped textures (including XNB textures with mip chains) cannot be uploaded there

CNA snapshot c1c316b9  ·  Known Issues › Platform limitations  ·  source links pinned to c1c316b9

SDL_RENDERER's texture renderer throws std::runtime_error from UpdatePixelsLevel for level > 0 because SDL_Renderer textures have no mip chain; the XNB Texture2D reader uploads every level it reads.

Identifier

CNA-PLAT-001

Category

Platform limitation

Subsystem

Graphics & renderers

Status

Open

Verified against

CNA c1c316b9 (c1c316b9c7a846ce8002809c151fcd1af14942c9)

Evidence basis

Source-verified: read at TARGET, not executed

Tests touching this area

Yes: see Current tests

Affected contract

Texture2D::SetData(level > 0, ...) and ContentManager::Load<Texture2D> of mipmapped assets on SDL_RENDERER

Expected behaviour

On renderers without mip sampling a mip chain can only be ignored; XNA content commonly ships textures with generated mip levels.

Actual behaviour at TARGET

SdlTextureRenderer::UpdatePixelsLevel (SdlRenderer.cpp) throws std::runtime_error for level != 0 (“does not support mip-level texture uploads ... Use Texture2D::SetData(level=0, ...) only”), by design: SDL_Renderer textures have no mip chain. The XNB reader (Texture2DContentTypeReader.cpp) creates the texture with mipMap = levelCount > 1 and calls SetData(level, ...) for every level; Texture2D::SetData forwards level > 0 to the renderer, so a mipmapped XNB texture fails to load on SDL_RENDERER with a std::runtime_error rather than a NotSupportedException.

Source locations

• modules/renderers/sdl-renderer/src/SdlRenderer.cpp — SdlTextureRenderer::UpdatePixelsLevel
• modules/content/src/Xnb/Texture2DContentTypeReader.cpp — per-level SetData loop

Evidence

Checked by reading the named sources at c1c316b9; nothing was built or executed for this entry. The XNB consequence is traced through Texture2DReader, Texture2D::SetData and the renderer's level upload; no mipmapped asset was loaded. SDL_Renderer_Texture2D_MipLevelThrows (sdlrenderer_texture2d_miplevel_throws_test.cpp) pins the throw.

Focused reproduction

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

Current tests

SDL_Renderer_Texture2D_MipLevelThrows pins the throw; no SDL_RENDERER test loads a mipmapped XNB texture.

Regression test

A test that loads a mipmapped XNB texture on SDL_RENDERER and expects either success (levels ignored) or a documented NotSupportedException.

Blast radius

Games whose content was built with mipmaps and that target SDL_RENDERER.

Workaround

Rebuild textures without mipmaps for this target.