CNA-BUG-194: The SDL2-only configuration guard recommends VULKAN, which the SDL2 platform cannot run

CNA snapshot 009d40f5  ·  Known Issues › Current bugs  ·  source links pinned to 009d40f5

Sdl2OnlyConfiguration.cmake's error text lists VULKAN among the SDL-independent renderers to choose, but Sdl2Platform::GetVulkanSurface returns null, so a VULKAN build on SDL2 can only fail later at GraphicsDevice construction.

Identifier

CNA-BUG-194

Category

Bug

Subsystem

Build & CI

Status

Open

Verified against

CNA 009d40f5 (009d40f5dd085c4e674d3479675fac84b12b3e0a)

Severity

Low (a triage suggestion, not a project priority)

Evidence basis

Source-verified: read at TARGET, not executed

Tests touching this area

Yes: see Current tests

Affected contract

cmake/Sdl2OnlyConfiguration.cmake's diagnostic recommending SDL-independent renderers

Expected behaviour

When an SDL2 platform and SDL2 audio are selected with a renderer that links SDL3, the guard refuses and names renderers the configuration can actually use. A renderer it recommends should reach a working device.

Actual behaviour at TARGET

The message reads “Choose OPENGLES2/OPENGLES3/OPENGL33, VULKAN, SOFTWARE, HEADLESS or another SDL-independent renderer.” But Sdl2Platform::GetVulkanSurface returns nullptr and vulkanSurface stays false, so a VULKAN build on the SDL2 platform reaches RequirePlatformVulkanSurface, which throws PlatformNotSupportedException(VulkanSurface) at device construction. VULKAN is SDL-independent, so the guard does not reject it, but recommending it sends the user to a configuration that cannot start a device.

Source locations

• cmake/Sdl2OnlyConfiguration.cmake — the error text recommending VULKAN
• modules/platform/src/Sdl2/Sdl2Platform.cpp — GetVulkanSurface returns nullptr; GetCapabilities leaves vulkanSurface false
• modules/graphics/include/CNA/Internal/Renderers/Common/PlatformVulkanRendererState.hpp — RequirePlatformVulkanSurface throws on a null service

Evidence

Checked by reading the guard's message, Sdl2Platform's Vulkan accessor and capability set, and the Vulkan renderer's RequirePlatformVulkanSurface at 009d40f5. Not executed. The SDL2 platform's own guide already lists VULKAN as “not yet -- needs IPlatformVulkanSurface”, so the guard's recommendation contradicts CNA's own renderer-compatibility table.

Focused reproduction

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

Current tests

Sdl2OnlyRendererGate.cmake checks that SDL3-linked renderers are rejected and that OPENGLES3 is accepted; it does not check the text of the recommendation.

Regression test

Drop VULKAN from the message (or add an SDL2 Vulkan surface service). A test could assert the recommended set contains no renderer whose SDL2 capability is false.

Blast radius

Users configuring an SDL2-only build who follow the guard's advice and pick VULKAN; every other recommended renderer (the GL profiles, SOFTWARE, HEADLESS) works on SDL2.

Workaround

On the SDL2 platform choose OPENGLES2/OPENGLES3/OPENGL33, SOFTWARE or HEADLESS, not VULKAN.