add headless graphics api

openxr/src/graphics/headless.rs

@@ -0,0 +1,68 @@
+use crate::*;
+
+/// Used to create a session without graphics.
+///
+/// See [`XR_MND_headless`] for details.
+///
+/// [`XR_MND_headless`]: https://www.khronos.org/registry/OpenXR/specs/1.1/html/xrspec.html#XR_MND_headless
+pub enum Headless {}
+
+impl Graphics for Headless {
+ type Requirements = Requirements;
+ type SessionCreateInfo = SessionCreateInfo;
+ type SwapchainImage = HeadlessSwapchainImage;
+ type Format = HeadlessFormat;
+
+ fn raise_format(_: i64) -> Self::Format {
+ // used by enumerate_swapchain_formats, which returns empty
+ unreachable!()
+ }
+ fn lower_format(f: Self::Format) -> i64 {
+ // used by create_swapchain, which is not available in headless
+ match f {}
+ }
+
+ fn requirements(_instance: &Instance, _system: SystemId) -> Result<Requirements> {
+ Ok(Requirements {})
+ }
+
+ unsafe fn create_session(
+ instance: &Instance,
+ system: SystemId,
+ _info: &SessionCreateInfo,
+ ) -> Result<sys::Session> {
+ let info = sys::SessionCreateInfo {
+ ty: sys::SessionCreateInfo::TYPE,
+ next: std::ptr::null(),
+ create_flags: Default::default(),
+ system_id: system,
+ };
+ let mut out = sys::Session::NULL;
+ cvt((instance.fp().create_session)(
+ instance.as_raw(),
+ &info,
+ &mut out,
+ ))?;
+ Ok(out)
+ }
+
+ fn enumerate_swapchain_images(
+ _swapchain: &Swapchain<Self>,
+ ) -> Result<Vec<Self::SwapchainImage>> {
+ // in a MND_headless session, xrEnumerateSwapchainFormats will always
+ // enumerate 0 formats, and so it's not possible to create a swapchain
+ unreachable!();
+ }
+}
+
+#[derive(Clone, Copy)]
+pub struct Requirements {}
+
+#[derive(Clone, Copy)]
+pub struct SessionCreateInfo {}
+
+#[derive(Clone, Copy)]
+pub enum HeadlessSwapchainImage {}
+
+#[derive(Clone, Copy)]
+pub enum HeadlessFormat {}

openxr/src/graphics/mod.rs

@@ -49,3 +49,6 @@ pub use opengl::OpenGL;
 
 pub mod opengles;
 pub use opengles::OpenGlEs;
+
+pub mod headless;
+pub use headless::Headless;