Introduce platform API abstraction for QOpenGLContext

The API is available by including qopenglcontext.h as usual,
but scoped in the QPlatformInterface namespace. The namespace
exposes platform specific type-safe interfaces that provide:

 a) Factory functions for adopting native contexts, e.g.

    QCocoaGLContext::fromNative(nsContext, shareContext);

 b) Access to underlying native handles, e.g.

    openGLContext->platformInterface<QCocoaGLContext>->nativeContext()

 c) Platform specific functionality, e.g.

    static QWGLContext::openGLModuleHandle()

    openGLContext->platformInterface<QEGLContext>->doSomething();

The platform interfaces live close to the classes they extend,
removing the need for complex indirection and plumbing, and
avoids kitchen-sink modules and APIs such as the extras modules,
QPlatformFunctions, or QPlatformNativeInterface.

In the case of QOpenGLContext these platform APIs are backed
by the platform plugin, so dynamic_cast is used to ensure the
platform plugin supports the requested interface, but this is
and implementation detail. The interface APIs are agnostic
to where the implementation lives, while still being available
to the user as part of the APIs they extend/augment.

The documentation will be restored when the dust settles.

Task-number: QTBUG-80233
Change-Id: Iac612403383991c4b24064332542a6e4bcbb3293
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

5 files changed, 75 insertions, 54 deletions

diff --git a/src/plugins/platforms/windows/qwindowsglcontext.cpp b/src/plugins/platforms/windows/qwindowsglcontext.cpp
index c1921810e7..aa93b85289 100644
--- a/src/plugins/platforms/windows/qwindowsglcontext.cpp
+++ b/src/plugins/platforms/windows/qwindowsglcontext.cpp
@@ -46,7 +46,6 @@
 #include <QtCore/qsysinfo.h>
 #include <QtGui/qguiapplication.h>
 #include <qpa/qplatformnativeinterface.h>
-#include <QtPlatformHeaders/qwglnativecontext.h>
 
 #include <algorithm>
 
@@ -225,6 +224,11 @@ QWindowsOpenGLContext *QOpenGLStaticContext::createContext(QOpenGLContext *conte
     return new QWindowsGLContext(this, context);
 }
 
+QWindowsOpenGLContext *QOpenGLStaticContext::createContext(HGLRC context, HWND window)
+{
+    return new QWindowsGLContext(this, context, window);
+}
+
 template <class MaskType, class FlagType> inline bool testFlag(MaskType mask, FlagType flag)
 {
     return (mask & MaskType(flag)) != 0;
@@ -1056,48 +1060,6 @@ QWindowsGLContext::QWindowsGLContext(QOpenGLStaticContext *staticContext,
     if (!m_staticContext) // Something went very wrong. Stop here, isValid() will return false.
         return;
 
-    QVariant nativeHandle = context->nativeHandle();
-    if (!nativeHandle.isNull()) {
-        // Adopt and existing context.
-        if (!nativeHandle.canConvert<QWGLNativeContext>()) {
-            qWarning("QWindowsGLContext: Requires a QWGLNativeContext");
-            return;
-        }
-        auto handle = nativeHandle.value<QWGLNativeContext>();
-        HGLRC wglcontext = handle.context();
-        HWND wnd = handle.window();
-        if (!wglcontext || !wnd) {
-            qWarning("QWindowsGLContext: No context and window given");
-            return;
-        }
-
-        HDC dc = GetDC(wnd);
-        // A window with an associated pixel format is mandatory.
-        // When no SetPixelFormat() call has been made, the following will fail.
-        m_pixelFormat = GetPixelFormat(dc);
-        bool ok = m_pixelFormat != 0;
-        if (!ok)
-            qWarning("QWindowsGLContext: Failed to get pixel format");
-        ok = DescribePixelFormat(dc, m_pixelFormat, sizeof(PIXELFORMATDESCRIPTOR), &m_obtainedPixelFormatDescriptor);
-        if (!ok) {
-            qWarning("QWindowsGLContext: Failed to describe pixel format");
-        } else {
-            QWindowsOpenGLAdditionalFormat obtainedAdditional;
-            m_obtainedFormat = GDI::qSurfaceFormatFromPixelFormat(m_obtainedPixelFormatDescriptor, &obtainedAdditional);
-            m_renderingContext = wglcontext;
-            ok = updateObtainedParams(dc);
-        }
-
-        ReleaseDC(wnd, dc);
-
-        if (ok)
-            m_ownsContext = false;
-        else
-            m_renderingContext = nullptr;
-
-        return;
-    }
-
     QSurfaceFormat format = context->format();
     if (format.renderableType() == QSurfaceFormat::DefaultRenderableType)
         format.setRenderableType(QSurfaceFormat::OpenGL);
@@ -1199,11 +1161,6 @@ QWindowsGLContext::QWindowsGLContext(QOpenGLStaticContext *staticContext,
 
     } while (false);
 
-    // Make the HGLRC retrievable via QOpenGLContext::nativeHandle().
-    // Do not provide the window since it is the dummy one and it is about to disappear.
-    if (m_renderingContext)
-        context->setNativeHandle(QVariant::fromValue<QWGLNativeContext>(QWGLNativeContext(m_renderingContext, nullptr)));
-
     if (hdc)
         ReleaseDC(dummyWindow, hdc);
     if (dummyWindow)
@@ -1217,6 +1174,37 @@ QWindowsGLContext::QWindowsGLContext(QOpenGLStaticContext *staticContext,
         << "\n    HGLRC=" << m_renderingContext;
 }
 
+QWindowsGLContext::QWindowsGLContext(QOpenGLStaticContext *staticContext, HGLRC wglcontext, HWND wnd)
+    : m_staticContext(staticContext)
+{
+    if (!m_staticContext) // Something went very wrong. Stop here, isValid() will return false.
+        return;
+
+    HDC dc = GetDC(wnd);
+    // A window with an associated pixel format is mandatory.
+    // When no SetPixelFormat() call has been made, the following will fail.
+    m_pixelFormat = GetPixelFormat(dc);
+    bool ok = m_pixelFormat != 0;
+    if (!ok)
+        qWarning("QWindowsGLContext: Failed to get pixel format");
+    ok = DescribePixelFormat(dc, m_pixelFormat, sizeof(PIXELFORMATDESCRIPTOR), &m_obtainedPixelFormatDescriptor);
+    if (!ok) {
+        qWarning("QWindowsGLContext: Failed to describe pixel format");
+    } else {
+        QWindowsOpenGLAdditionalFormat obtainedAdditional;
+        m_obtainedFormat = GDI::qSurfaceFormatFromPixelFormat(m_obtainedPixelFormatDescriptor, &obtainedAdditional);
+        m_renderingContext = wglcontext;
+        ok = updateObtainedParams(dc);
+    }
+
+    ReleaseDC(wnd, dc);
+
+    if (ok)
+        m_ownsContext = false;
+    else
+        m_renderingContext = nullptr;
+}
+
 QWindowsGLContext::~QWindowsGLContext()
 {
     if (m_renderingContext && m_ownsContext)
diff --git a/src/plugins/platforms/windows/qwindowsglcontext.h b/src/plugins/platforms/windows/qwindowsglcontext.h
index 608cc9cfea..2970f3d333 100644
--- a/src/plugins/platforms/windows/qwindowsglcontext.h
+++ b/src/plugins/platforms/windows/qwindowsglcontext.h
@@ -174,6 +174,7 @@ public:
     static QByteArray getGlString(unsigned int which);
 
     QWindowsOpenGLContext *createContext(QOpenGLContext *context) override;
+    QWindowsOpenGLContext *createContext(HGLRC context, HWND window) override;
     void *moduleHandle() const override { return opengl32.moduleHandle(); }
     QOpenGLContext::OpenGLModuleType moduleType() const override
     { return QOpenGLContext::LibGL; }
@@ -199,10 +200,12 @@ public:
     static QWindowsOpengl32DLL opengl32;
 };
 
-class QWindowsGLContext : public QWindowsOpenGLContext
+class QWindowsGLContext : public QWindowsOpenGLContext, public QPlatformInterface::QWGLContext
 {
 public:
     explicit QWindowsGLContext(QOpenGLStaticContext *staticContext, QOpenGLContext *context);
+    explicit QWindowsGLContext(QOpenGLStaticContext *staticContext, HGLRC context, HWND window);
+
     ~QWindowsGLContext() override;
     bool isSharing() const override { return context()->shareHandle(); }
     bool isValid() const override { return m_renderingContext && !m_lost; }
@@ -219,7 +222,7 @@ public:
 
     HGLRC renderingContext() const { return m_renderingContext; }
 
-    void *nativeContext() const override { return m_renderingContext; }
+    HGLRC nativeContext() const override { return m_renderingContext; }
 
 private:
     typedef GLenum (APIENTRY *GlGetGraphicsResetStatusArbType)();
diff --git a/src/plugins/platforms/windows/qwindowsintegration.cpp b/src/plugins/platforms/windows/qwindowsintegration.cpp
index 96abfe5b01..ea077bc695 100644
--- a/src/plugins/platforms/windows/qwindowsintegration.cpp
+++ b/src/plugins/platforms/windows/qwindowsintegration.cpp
@@ -475,6 +475,33 @@ QOpenGLContext::OpenGLModuleType QWindowsIntegration::openGLModuleType()
 #endif
 }
 
+HMODULE QWindowsIntegration::openGLModuleHandle() const
+{
+    if (QWindowsStaticOpenGLContext *staticOpenGLContext = QWindowsIntegration::staticOpenGLContext())
+        return static_cast<HMODULE>(staticOpenGLContext->moduleHandle());
+
+    return nullptr;
+}
+
+QOpenGLContext *QWindowsIntegration::createOpenGLContext(HGLRC ctx, HWND window, QOpenGLContext *shareContext) const
+{
+    if (!ctx || !window)
+        return nullptr;
+
+    if (QWindowsStaticOpenGLContext *staticOpenGLContext = QWindowsIntegration::staticOpenGLContext()) {
+        QScopedPointer<QWindowsOpenGLContext> result(staticOpenGLContext->createContext(ctx, window));
+        if (result->isValid()) {
+            auto *context = new QOpenGLContext;
+            context->setShareContext(shareContext);
+            auto *contextPrivate = QOpenGLContextPrivate::get(context);
+            contextPrivate->adopt(result.take());
+            return context;
+        }
+    }
+
+    return nullptr;
+}
+
 QWindowsStaticOpenGLContext *QWindowsIntegration::staticOpenGLContext()
 {
     QWindowsIntegration *integration = QWindowsIntegration::instance();
diff --git a/src/plugins/platforms/windows/qwindowsintegration.h b/src/plugins/platforms/windows/qwindowsintegration.h
index 3c3763745c..348da5c58c 100644
--- a/src/plugins/platforms/windows/qwindowsintegration.h
+++ b/src/plugins/platforms/windows/qwindowsintegration.h
@@ -44,6 +44,8 @@
 #include <qpa/qplatformintegration.h>
 #include <QtCore/qscopedpointer.h>
 #include <QtGui/private/qwindowsfontdatabase_p.h>
+#include <QtGui/private/qopenglcontext_p.h>
+#include <qpa/qplatformopenglcontext.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -52,7 +54,7 @@ struct QWindowsWindowData;
 class QWindowsWindow;
 class QWindowsStaticOpenGLContext;
 
-class QWindowsIntegration : public QPlatformIntegration
+class QWindowsIntegration : public QPlatformIntegration, public QPlatformInterface::Private::QWindowsGLIntegration
 {
     Q_DISABLE_COPY_MOVE(QWindowsIntegration)
 public:
@@ -87,6 +89,9 @@ public:
     QPlatformOpenGLContext *createPlatformOpenGLContext(QOpenGLContext *context) const override;
     QOpenGLContext::OpenGLModuleType openGLModuleType() override;
     static QWindowsStaticOpenGLContext *staticOpenGLContext();
+
+    HMODULE openGLModuleHandle() const override;
+    QOpenGLContext *createOpenGLContext(HGLRC context, HWND window, QOpenGLContext *shareContext) const;
 #endif
     QAbstractEventDispatcher *createEventDispatcher() const override;
     void initialize() override;
diff --git a/src/plugins/platforms/windows/qwindowsopenglcontext.h b/src/plugins/platforms/windows/qwindowsopenglcontext.h
index 6d9c85f738..78ff23669c 100644
--- a/src/plugins/platforms/windows/qwindowsopenglcontext.h
+++ b/src/plugins/platforms/windows/qwindowsopenglcontext.h
@@ -57,6 +57,7 @@ public:
     virtual ~QWindowsStaticOpenGLContext() = default;
 
     virtual QWindowsOpenGLContext *createContext(QOpenGLContext *context) = 0;
+    virtual QWindowsOpenGLContext *createContext(HGLRC context, HWND window) = 0;
     virtual void *moduleHandle() const = 0;
     virtual QOpenGLContext::OpenGLModuleType moduleType() const = 0;
     virtual bool supportsThreadedOpenGL() const { return false; }
@@ -77,9 +78,6 @@ class QWindowsOpenGLContext : public QPlatformOpenGLContext
 {
     Q_DISABLE_COPY_MOVE(QWindowsOpenGLContext)
 public:
-    // Returns the native context handle (e.g. HGLRC for WGL).
-    virtual void *nativeContext() const = 0;
-
     // These should be implemented only for some winsys interfaces, for example EGL.
     // For others, like WGL, they are not relevant.
     virtual void *nativeDisplay() const { return nullptr; }