Replace the QRhi rendering in OverlayController (private Qt API) with the
render backends of the vrdashboard template (src/render/), which use public
Qt API only (QQuickRenderTarget::fromOpenGLTexture / fromVulkanImage). The
binary then runs on another Qt 6 patch release, e.g. the Steam Frame's system
Qt.
The Vulkan backend also does what SteamVR requires and the QRhi path lacked:
the required instance/device extensions and the HMD's GPU (via
openvr_init::renderInterop()), VK_FORMAT_R8G8B8A8_UNORM, and the transition to
TRANSFER_SRC_OPTIMAL after each frame.
- New option --graphics-api opengl|vulkan (default opengl, no fallback).
- Shutdown() calls VR_Shutdown before the render target and Qt's device go
(crash on the Steam Frame with Vulkan otherwise); it runs only once.
- Mouse y is flipped on every platform: SteamVR reports it in GL convention.
- Render delay 5 -> 16 ms (about 60 fps).
- GuiPrivate is no longer needed.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>