Fix/workaround graphics issues breaking SteamVR use with Blender

Windows only workaround. I'll have to investigate Linux separately.

Steam's OpenGL compatibility is still new and doesn't work for us yet
(neither does it for standard OpenXR examples from what I've heard and
seen myself). We can work around that by falling back to our DirectX
compatibility layer.
Note that this DirectX compatibility still doesn't work for some
systems, see T76082.

Implementation note: Since the graphics binding extensions have to be
enabled before we can find out which runtime is in use (e.g. SteamVR vs.
Oculus, etc), we can now enable multiple graphics binding extensions but
settle for a single one to use later.

Once the SteamVR OpenGL backend works, we can remove this workaround
again.

Fixes T78267.

1 files changed, 52 insertions, 19 deletions

diff --git a/intern/ghost/intern/GHOST_XrContext.cpp b/intern/ghost/intern/GHOST_XrContext.cpp
index 16687c34679..6933103a2d6 100644
--- a/intern/ghost/intern/GHOST_XrContext.cpp
+++ b/intern/ghost/intern/GHOST_XrContext.cpp
@@ -88,18 +88,26 @@ void GHOST_XrContext::initialize(const GHOST_XrContextCreateInfo *create_info)
     printAvailableAPILayersAndExtensionsInfo();
   }
 
-  m_gpu_binding_type = determineGraphicsBindingTypeToEnable(create_info);
+  /* Multiple graphics binding extensions can be enabled, but only one will actually be used
+   * (determined later on). */
+  const std::vector<GHOST_TXrGraphicsBinding> graphics_binding_types =
+      determineGraphicsBindingTypesToEnable(create_info);
 
   assert(m_oxr->instance == XR_NULL_HANDLE);
-  createOpenXRInstance();
+  createOpenXRInstance(graphics_binding_types);
   storeInstanceProperties();
+
+  /* Multiple bindings may be enabled. Now that we know the runtime in use, settle for one. */
+  m_gpu_binding_type = determineGraphicsBindingTypeToUse(graphics_binding_types);
+
   printInstanceInfo();
   if (isDebugMode()) {
     initDebugMessenger();
   }
 }
 
-void GHOST_XrContext::createOpenXRInstance()
+void GHOST_XrContext::createOpenXRInstance(
+    const std::vector<GHOST_TXrGraphicsBinding> &graphics_binding_types)
 {
   XrInstanceCreateInfo create_info = {XR_TYPE_INSTANCE_CREATE_INFO};
 
@@ -108,7 +116,7 @@ void GHOST_XrContext::createOpenXRInstance()
   create_info.applicationInfo.apiVersion = XR_CURRENT_API_VERSION;
 
   getAPILayersToEnable(m_enabled_layers);
-  getExtensionsToEnable(m_enabled_extensions);
+  getExtensionsToEnable(graphics_binding_types, m_enabled_extensions);
   create_info.enabledApiLayerCount = m_enabled_layers.size();
   create_info.enabledApiLayerNames = m_enabled_layers.data();
   create_info.enabledExtensionCount = m_enabled_extensions.size();
@@ -393,14 +401,11 @@ static const char *openxr_ext_name_from_wm_gpu_binding(GHOST_TXrGraphicsBinding
 /**
  * Gather an array of names for the extensions to enable.
  */
-void GHOST_XrContext::getExtensionsToEnable(std::vector<const char *> &r_ext_names)
+void GHOST_XrContext::getExtensionsToEnable(
+    const std::vector<GHOST_TXrGraphicsBinding> &graphics_binding_types,
+    std::vector<const char *> &r_ext_names)
 {
-  assert(m_gpu_binding_type != GHOST_kXrGraphicsUnknown);
-
-  const char *gpu_binding = openxr_ext_name_from_wm_gpu_binding(m_gpu_binding_type);
-  static std::vector<std::string> try_ext;
-
-  try_ext.clear();
+  std::vector<std::string> try_ext;
 
   /* Try enabling debug extension. */
 #ifndef WIN32
@@ -409,12 +414,15 @@ void GHOST_XrContext::getExtensionsToEnable(std::vector<const char *> &r_ext_nam
   }
 #endif
 
-  r_ext_names.reserve(try_ext.size() + 1); /* + 1 for graphics binding extension. */
+  r_ext_names.reserve(try_ext.size() + graphics_binding_types.size());
 
-  /* Add graphics binding extension. */
-  assert(gpu_binding);
-  assert(openxr_extension_is_available(m_oxr->extensions, gpu_binding));
-  r_ext_names.push_back(gpu_binding);
+  /* Add graphics binding extensions (may be multiple ones, we'll settle for one to use later, once
+   * we have more info about the runtime). */
+  for (GHOST_TXrGraphicsBinding type : graphics_binding_types) {
+    const char *gpu_binding = openxr_ext_name_from_wm_gpu_binding(type);
+    assert(openxr_extension_is_available(m_oxr->extensions, gpu_binding));
+    r_ext_names.push_back(gpu_binding);
+  }
 
   for (const std::string &ext : try_ext) {
     if (openxr_extension_is_available(m_oxr->extensions, ext)) {
@@ -427,9 +435,10 @@ void GHOST_XrContext::getExtensionsToEnable(std::vector<const char *> &r_ext_nam
  * Decide which graphics binding extension to use based on
  * #GHOST_XrContextCreateInfo.gpu_binding_candidates and available extensions.
  */
-GHOST_TXrGraphicsBinding GHOST_XrContext::determineGraphicsBindingTypeToEnable(
+std::vector<GHOST_TXrGraphicsBinding> GHOST_XrContext::determineGraphicsBindingTypesToEnable(
     const GHOST_XrContextCreateInfo *create_info)
 {
+  std::vector<GHOST_TXrGraphicsBinding> result;
   assert(create_info->gpu_binding_candidates != NULL);
   assert(create_info->gpu_binding_candidates_count > 0);
 
@@ -438,11 +447,35 @@ GHOST_TXrGraphicsBinding GHOST_XrContext::determineGraphicsBindingTypeToEnable(
     const char *ext_name = openxr_ext_name_from_wm_gpu_binding(
         create_info->gpu_binding_candidates[i]);
     if (openxr_extension_is_available(m_oxr->extensions, ext_name)) {
-      return create_info->gpu_binding_candidates[i];
+      result.push_back(create_info->gpu_binding_candidates[i]);
     }
   }
 
-  return GHOST_kXrGraphicsUnknown;
+  if (result.empty()) {
+    throw GHOST_XrException("No supported graphics binding found.");
+  }
+
+  return result;
+}
+
+GHOST_TXrGraphicsBinding GHOST_XrContext::determineGraphicsBindingTypeToUse(
+    const std::vector<GHOST_TXrGraphicsBinding> &enabled_types)
+{
+  /* Return the first working type. */
+  for (GHOST_TXrGraphicsBinding type : enabled_types) {
+#if WIN32
+    /* The SteamVR OpenGL backend fails currently. Disable it and allow falling back to the DirectX
+     * one. */
+    if ((m_runtime_id == OPENXR_RUNTIME_STEAMVR) && (type == GHOST_kXrGraphicsOpenGL)) {
+      continue;
+    }
+#endif
+
+    assert(type != GHOST_kXrGraphicsUnknown);
+    return type;
+  }
+
+  throw GHOST_XrException("Failed to determine a graphics binding to use.");
 }
 
 /** \} */ /* OpenXR API-Layers and Extensions */