CNA-PLAT-001: CANVAS, FREEDIRECT, SDL_RENDERER, HTML_DOM and SVG_DOM throw for any Texture2D mip level above 0, so mipmapped textures (including XNB textures with mip chains) cannot be uploaded there

CNA snapshot 009d40f5  ·  Known Issues › Platform limitations  ·  source links pinned to 009d40f5

The texture renderers of CANVAS, FREEDIRECT, SDL_RENDERER, HTML_DOM and SVG_DOM throw std::runtime_error from UpdatePixelsLevel for level > 0 because Canvas 2D, DirectDraw, SDL_Renderer and DOM surfaces 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 009d40f5 (009d40f5dd085c4e674d3479675fac84b12b3e0a)

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 CANVAS and FREEDIRECT

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

CanvasTextureRenderer::UpdatePixelsLevel (CanvasTextureRenderer.cpp), the FreeDirect texture and render-target renderers (ThrowMipLevelUnsupported in FreeDirectRenderer.cpp), SdlTextureRenderer::UpdatePixelsLevel (SdlRenderer.cpp), HtmlDomTextureRenderer::UpdatePixelsLevel and SvgDomTextureRenderer::UpdatePixelsLevel throw std::runtime_error for level != 0 ("does not support mip-level texture uploads ... Use Texture2D::SetData(level=0, ...) only"), and each renderer's doc marks this throws-by-design. 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 these renderers with a std::runtime_error rather than a NotSupportedException.

Source locations

• modules/renderers/canvas/src/CanvasTextureRenderer.cpp — CanvasTextureRenderer::UpdatePixelsLevel
• modules/renderers/freedirect/src/FreeDirectRenderer.cpp — ThrowMipLevelUnsupported and the texture renderers' level uploads
• modules/content/src/Xnb/Texture2DContentTypeReader.cpp — per-level SetData loop

Evidence

Checked by reading the named sources at 009d40f5; nothing was built or executed for this entry. The XNB consequence is inferred from the reader's upload loop; no mipmapped asset was loaded on either renderer.

Independent re-verification: Checked by reading the named sources at 009d40f5; nothing was built or executed for this entry. The XNB consequence is traced through Texture2DReader, Texture2D::SetData and the renderers' level uploads; no mipmapped asset was loaded on any renderer. Tests: Check C of freedirect_texture_rendertarget_test.cpp pins the FreeDirect throw; no CANVAS test exists and no test loads a mipmapped XNB texture on these renderers.

Focused reproduction

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

Current tests

No CANVAS or FREEDIRECT test loads a mipmapped texture.

Regression test

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

Blast radius

Games whose content was built with mipmaps and that target CANVAS or FREEDIRECT.

Workaround

Rebuild textures without mipmaps for these targets.