OpenGL: Create ContextExternal for use without EGL

Allows passing in appropriate callbacks for managing
the OpenGL context, as opposed to relying on Dawn+EGL
for OpenGL context management.

include/dawn/native/OpenGLBackend.h

@@ -26,6 +26,10 @@ struct DAWN_NATIVE_EXPORT AdapterDiscoveryOptions : public AdapterDiscoveryOptio
     explicit AdapterDiscoveryOptions(WGPUBackendType type);
 
     void* (*getProc)(const char*);
+    // Context
+    void (*makeCurrent)(void*);
+    void (*destroy)(void*);
+    void* userData;
 };
 
 // TODO(crbug.com/dawn/810): This struct can be removed once Chrome is no longer using it.

src/dawn/native/CMakeLists.txt

@@ -444,6 +444,8 @@ if (DAWN_ENABLE_OPENGL)
         "opengl/ComputePipelineGL.h"
         "opengl/ContextEGL.cpp"
         "opengl/ContextEGL.h"
+        "opengl/ContextExternal.cpp"
+        "opengl/ContextExternal.h"
         "opengl/DeviceGL.cpp"
         "opengl/DeviceGL.h"
         "opengl/EGLFunctions.cpp"

src/dawn/native/opengl/AdapterGL.cpp

@@ -21,6 +21,7 @@
 #include "dawn/common/GPUInfo.h"
 #include "dawn/native/Instance.h"
 #include "dawn/native/opengl/ContextEGL.h"
+#include "dawn/native/opengl/ContextExternal.h"
 #include "dawn/native/opengl/DeviceGL.h"
 
 namespace dawn::native::opengl {
@@ -53,12 +54,21 @@ uint32_t GetVendorIdFromVendors(const char* vendor) {
 
 }  // anonymous namespace
 
-Adapter::Adapter(InstanceBase* instance, wgpu::BackendType backendType)
-    : AdapterBase(instance, backendType) {}
+Adapter::Adapter(InstanceBase* instance,
+                 wgpu::BackendType backendType,
+                 void (*makeCurrent)(void*),
+                 void (*destroy)(void*),
+                 void* userData)
+    : AdapterBase(instance, backendType),
+      mMakeCurrent(makeCurrent),
+      mDestroy(destroy),
+      mUserData(userData) {}
 
 MaybeError Adapter::InitializeGLFunctions(void* (*getProc)(const char*)) {
-    // Use getProc to populate the dispatch table
-    mEGLFunctions.Init(getProc);
+    if (mMakeCurrent == nullptr) {
+        // Use getProc to populate the dispatch table
+        mEGLFunctions.Init(getProc);
+    }
     return mFunctions.Initialize(getProc);
 }
 
@@ -153,7 +163,11 @@ ResultOrError<Ref<DeviceBase>> Adapter::CreateDeviceImpl(const DeviceDescriptor*
     EGLenum api =
         GetBackendType() == wgpu::BackendType::OpenGL ? EGL_OPENGL_API : EGL_OPENGL_ES_API;
     std::unique_ptr<Device::Context> context;
-    DAWN_TRY_ASSIGN(context, ContextEGL::Create(mEGLFunctions, api));
+    if (mMakeCurrent != nullptr) {
+        DAWN_TRY_ASSIGN(context, ContextExternal::Create(mMakeCurrent, mDestroy, mUserData));
+    } else {
+        DAWN_TRY_ASSIGN(context, ContextEGL::Create(mEGLFunctions, api));
+    }
     return Device::Create(this, descriptor, mFunctions, std::move(context));
 }
 

src/dawn/native/opengl/AdapterGL.h

@@ -23,7 +23,11 @@ namespace dawn::native::opengl {
 
 class Adapter : public AdapterBase {
   public:
-    Adapter(InstanceBase* instance, wgpu::BackendType backendType);
+    Adapter(InstanceBase* instance,
+            wgpu::BackendType backendType,
+            void (*makeCurrent)(void*),
+            void (*destroy)(void*),
+            void* userData);
 
     MaybeError InitializeGLFunctions(void* (*getProc)(const char*));
 
@@ -40,6 +44,9 @@ class Adapter : public AdapterBase {
 
     OpenGLFunctions mFunctions;
     EGLFunctions mEGLFunctions;
+    void (*mMakeCurrent)(void*);
+    void (*mDestroy)(void*);
+    void* mUserData;
 };
 
 }  // namespace dawn::native::opengl

src/dawn/native/opengl/BackendGL.cpp

@@ -96,7 +96,8 @@ ResultOrError<std::vector<Ref<AdapterBase>>> Backend::DiscoverAdapters(
     DAWN_INVALID_IF(options->getProc == nullptr, "AdapterDiscoveryOptions::getProc must be set");
 
     Ref<Adapter> adapter = AcquireRef(
-        new Adapter(GetInstance(), static_cast<wgpu::BackendType>(optionsBase->backendType)));
+        new Adapter(GetInstance(), static_cast<wgpu::BackendType>(optionsBase->backendType),
+                    options->makeCurrent, options->destroy, options->userData));
     DAWN_TRY(adapter->InitializeGLFunctions(options->getProc));
     DAWN_TRY(adapter->Initialize());
 

src/dawn/native/opengl/ContextExternal.cpp

@@ -0,0 +1,39 @@
+// Copyright 2022 The Dawn Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "dawn/native/opengl/ContextExternal.h"
+
+#include <memory>
+
+namespace dawn::native::opengl {
+
+ResultOrError<std::unique_ptr<ContextExternal>> ContextExternal::Create(void (*makeCurrent)(void*),
+                                                                        void (*destroy)(void*),
+                                                                        void* userData) {
+    return std::unique_ptr<ContextExternal>(new ContextExternal(makeCurrent, destroy, userData));
+}
+
+void ContextExternal::MakeCurrent() {
+    if (mMakeCurrent) {
+        mMakeCurrent(mUserData);
+    }
+}
+
+ContextExternal::~ContextExternal() {
+    if (mDestroy) {
+        mDestroy(mUserData);
+    }
+}
+
+}  // namespace dawn::native::opengl

src/dawn/native/opengl/ContextExternal.h

@@ -0,0 +1,43 @@
+// Copyright 2022 The Dawn Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef SRC_DAWN_NATIVE_OPENGL_CONTEXTEXTERNAL_H_
+#define SRC_DAWN_NATIVE_OPENGL_CONTEXTEXTERNAL_H_
+
+#include <memory>
+
+#include "dawn/native/opengl/DeviceGL.h"
+
+namespace dawn::native::opengl {
+
+class ContextExternal : public Device::Context {
+  public:
+    static ResultOrError<std::unique_ptr<ContextExternal>> Create(void (*makeCurrent)(void*),
+                                                                  void (*destroy)(void*),
+                                                                  void* userData);
+    void MakeCurrent() override;
+    ~ContextExternal() override;
+
+  private:
+    ContextExternal(void (*makeCurrent)(void*), void (*destroy)(void*), void* userData)
+        : mMakeCurrent(makeCurrent), mDestroy(destroy), mUserData(userData) {}
+
+    void (*mMakeCurrent)(void*);
+    void (*mDestroy)(void*);
+    void* mUserData;
+};
+
+}  // namespace dawn::native::opengl
+
+#endif  // SRC_DAWN_NATIVE_OPENGL_CONTEXTEXTERNAL_H_

src/dawn/native/opengl/OpenGLVersion.cpp

@@ -25,8 +25,16 @@ MaybeError OpenGLVersion::Initialize(GetProcAddress getProc) {
     if (getString == nullptr) {
         return DAWN_INTERNAL_ERROR("Couldn't load glGetString");
     }
+    PFNGLGETERRORPROC getError = reinterpret_cast<PFNGLGETERRORPROC>(getProc("glGetError"));
+    if (getError == nullptr) {
+        return DAWN_INTERNAL_ERROR("Couldn't load glGetError");
+    }
 
     const char* version = reinterpret_cast<const char*>(getString(GL_VERSION));
+    if (version == nullptr) {
+        GLenum error = getError();
+        return DAWN_INTERNAL_ERROR("glGetString failed: {}");
+    }
 
     if (strstr(version, "OpenGL ES") != nullptr) {
         // ES spec states that the GL_VERSION string will be in the following format: