Add QOffScreenSurface platform API abstraction

This follows the work done in 6ff79478a44fce12ca18832a56db4a370a9ff417.

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

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

    QAndroidPlatformOffscreenSurface::fromNative(ANativeWindow);

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

    surface->platformInterface<QAndroidPlatformOffscreenSurface>()
                ->nativeSurface()

Fixes: QTBUG-85874
Change-Id: I29c459866e0355a52320d5d473e8b147e050acb3
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

6 files changed, 206 insertions, 72 deletions

diff --git a/src/gui/kernel/kernel.pri b/src/gui/kernel/kernel.pri
index 011e0ce00d..48fd18f8d2 100644
--- a/src/gui/kernel/kernel.pri
+++ b/src/gui/kernel/kernel.pri
@@ -6,6 +6,8 @@ PRECOMPILED_HEADER = kernel/qt_gui_pch.h
 
 KERNEL_P= kernel
 HEADERS += \
+        kernel/qoffscreensurface_p.h \
+        kernel/qoffscreensurface_platform.h \
         kernel/qtguiglobal.h \
         kernel/qtguiglobal_p.h \
         kernel/qgenericpluginfactory.h \
diff --git a/src/gui/kernel/qoffscreensurface.cpp b/src/gui/kernel/qoffscreensurface.cpp
index fbd5c6a079..9875911d30 100644
--- a/src/gui/kernel/qoffscreensurface.cpp
+++ b/src/gui/kernel/qoffscreensurface.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2020 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtGui module of the Qt Toolkit.
@@ -42,7 +42,7 @@
 #include "qguiapplication_p.h"
 #include "qscreen.h"
 #include "qplatformintegration.h"
-#include "qplatformoffscreensurface.h"
+#include "qoffscreensurface_p.h"
 #include "qwindow.h"
 #include "qplatformwindow.h"
 
@@ -50,6 +50,18 @@
 
 QT_BEGIN_NAMESPACE
 
+
+/*!
+    \fn T QOffScreenSurface::platformInterface<T>()
+
+    Returns a platform interface of type T for the surface.
+
+    This function provides access to platform specific functionality
+    of QOffScreenSurface, as defined in the QPlatformInterface namespace.
+
+    If the requested interface is not available a \nullptr is returned.
+*/
+
 /*!
     \class QOffscreenSurface
     \inmodule QtGui
@@ -91,36 +103,6 @@ QT_BEGIN_NAMESPACE
     native surface. For the use cases of QOffscreenSurface (rendering to FBOs, texture
     upload) this is not a problem.
 */
-class Q_GUI_EXPORT QOffscreenSurfacePrivate : public QObjectPrivate
-{
-    Q_DECLARE_PUBLIC(QOffscreenSurface)
-
-public:
-    QOffscreenSurfacePrivate()
-        : QObjectPrivate()
-        , surfaceType(QSurface::OpenGLSurface)
-        , platformOffscreenSurface(nullptr)
-        , offscreenWindow(nullptr)
-        , requestedFormat(QSurfaceFormat::defaultFormat())
-        , screen(nullptr)
-        , size(1, 1)
-        , nativeHandle(nullptr)
-    {
-    }
-
-    ~QOffscreenSurfacePrivate()
-    {
-    }
-
-    QSurface::SurfaceType surfaceType;
-    QPlatformOffscreenSurface *platformOffscreenSurface;
-    QWindow *offscreenWindow;
-    QSurfaceFormat requestedFormat;
-    QScreen *screen;
-    QSize size;
-    void *nativeHandle;
-};
-
 
 /*!
     \since 5.10
@@ -228,8 +210,6 @@ void QOffscreenSurface::destroy()
         delete d->offscreenWindow;
         d->offscreenWindow = nullptr;
     }
-
-    d->nativeHandle = nullptr;
 }
 
 /*!
@@ -344,26 +324,6 @@ void QOffscreenSurface::setScreen(QScreen *newScreen)
 }
 
 /*!
-    Sets the native handle to which the offscreen surface is connected to \a handle.
-
-    The native handle will be resolved in the create() function. Calling
-    this function after create() will not re-create a native surface.
-
-    \note The interpretation of the native handle is platform specific.  Only
-    some platforms will support adopting native handles of offscreen surfaces
-    and platforms that do not implement this support will ignore the handle.
-
-    \since 5.9
-    \sa nativeHandle()
-*/
-
-void QOffscreenSurface::setNativeHandle(void *handle)
-{
-    Q_D(QOffscreenSurface);
-    d->nativeHandle = handle;
-}
-
-/*!
     Called when the offscreen surface's screen is destroyed.
 
     \internal
@@ -395,19 +355,6 @@ QPlatformOffscreenSurface *QOffscreenSurface::handle() const
 }
 
 /*!
-    Returns an optional native handle to which the offscreen surface is connected.
-
-    \since 5.9
-    \sa setNativeHandle()
-*/
-
-void *QOffscreenSurface::nativeHandle() const
-{
-    Q_D(const QOffscreenSurface);
-    return d->nativeHandle;
-}
-
-/*!
     Returns the platform surface corresponding to the offscreen surface.
 
     \internal
diff --git a/src/gui/kernel/qoffscreensurface.h b/src/gui/kernel/qoffscreensurface.h
index 1a3c476244..fe8db44633 100644
--- a/src/gui/kernel/qoffscreensurface.h
+++ b/src/gui/kernel/qoffscreensurface.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2020 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtGui module of the Qt Toolkit.
@@ -79,8 +79,8 @@ public:
 
     QPlatformOffscreenSurface *handle() const;
 
-    void *nativeHandle() const;
-    void setNativeHandle(void *handle);
+    template <typename T>
+    T *platformInterface() const;
 
 Q_SIGNALS:
     void screenChanged(QScreen *screen);
@@ -97,4 +97,6 @@ private:
 
 QT_END_NAMESPACE
 
+#include <QtGui/qoffscreensurface_platform.h>
+
 #endif // QOFFSCREENSURFACE_H
diff --git a/src/gui/kernel/qoffscreensurface_p.h b/src/gui/kernel/qoffscreensurface_p.h
new file mode 100644
index 0000000000..5b41e71c29
--- /dev/null
+++ b/src/gui/kernel/qoffscreensurface_p.h
@@ -0,0 +1,95 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtGui module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QOFFSCREENSURFACE_P_H
+#define QOFFSCREENSURFACE_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include "qplatformoffscreensurface.h"
+
+#include <private/qwindow_p.h>
+
+QT_BEGIN_NAMESPACE
+
+class Q_GUI_EXPORT QOffscreenSurfacePrivate : public QObjectPrivate
+{
+    Q_DECLARE_PUBLIC(QOffscreenSurface)
+
+public:
+    QOffscreenSurfacePrivate()
+        : QObjectPrivate()
+          , surfaceType(QSurface::OpenGLSurface)
+          , platformOffscreenSurface(nullptr)
+          , offscreenWindow(nullptr)
+          , requestedFormat(QSurfaceFormat::defaultFormat())
+          , screen(nullptr)
+          , size(1, 1)
+    {
+    }
+
+    ~QOffscreenSurfacePrivate()
+    {
+    }
+
+    static QOffscreenSurfacePrivate *get(QOffscreenSurface *surface)
+    {
+        return surface ? surface->d_func() : nullptr;
+    }
+
+    QSurface::SurfaceType surfaceType;
+    QPlatformOffscreenSurface *platformOffscreenSurface;
+    QWindow *offscreenWindow;
+    QSurfaceFormat requestedFormat;
+    QScreen *screen;
+    QSize size;
+};
+
+QT_END_NAMESPACE
+
+#endif // QOFFSCREENSURFACE_P_H
diff --git a/src/gui/kernel/qoffscreensurface_platform.h b/src/gui/kernel/qoffscreensurface_platform.h
new file mode 100644
index 0000000000..87e6b453a7
--- /dev/null
+++ b/src/gui/kernel/qoffscreensurface_platform.h
@@ -0,0 +1,67 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtGui module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QOFFSCREENSURFACE_PLATFORM_H
+#define QOFFSCREENSURFACE_PLATFORM_H
+
+#include <QtGui/qtguiglobal.h>
+#include <QtGui/qoffscreensurface.h>
+
+#if defined(Q_OS_ANDROID)
+QT_FORWARD_DECLARE_CLASS(ANativeWindow);
+#endif
+
+QT_BEGIN_NAMESPACE
+
+namespace QPlatformInterface {
+
+#if defined(Q_OS_ANDROID)
+struct Q_GUI_EXPORT QAndroidPlatformOffscreenSurface
+{
+    QT_DECLARE_PLATFORM_INTERFACE(QAndroidPlatformOffscreenSurface)
+    static QOffscreenSurface *fromNative(ANativeWindow *nativeSurface);
+    virtual ANativeWindow *nativeSurface() const = 0;
+};
+#endif
+
+} // QPlatformInterface
+
+QT_END_NAMESPACE
+
+#endif // QOFFSCREENSURFACE_PLATFORM_H
diff --git a/src/gui/kernel/qplatformoffscreensurface.h b/src/gui/kernel/qplatformoffscreensurface.h
index cef0fab7e1..1d06336956 100644
--- a/src/gui/kernel/qplatformoffscreensurface.h
+++ b/src/gui/kernel/qplatformoffscreensurface.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2020 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtGui module of the Qt Toolkit.
@@ -49,8 +49,9 @@
 // source and binary incompatible with future versions of Qt.
 //
 
-#include <QtGui/qtguiglobal.h>
 #include "qplatformsurface.h"
+
+#include <QtGui/qoffscreensurface.h>
 #include <QtCore/qscopedpointer.h>
 
 QT_BEGIN_NAMESPACE
@@ -75,10 +76,30 @@ public:
 
 protected:
     QScopedPointer<QPlatformOffscreenSurfacePrivate> d_ptr;
+    friend class QOffscreenSurfacePrivate;
 private:
     Q_DISABLE_COPY(QPlatformOffscreenSurface)
 };
 
+template <typename T>
+T *QOffscreenSurface::platformInterface() const
+{
+    return dynamic_cast<T*>(surfaceHandle());
+}
+
+namespace QPlatformInterface::Private {
+
+#if defined(Q_OS_ANDROID)
+struct Q_GUI_EXPORT QAndroidOffScreenIntegration
+{
+    QT_DECLARE_PLATFORM_INTERFACE(QAndroidOffScreenIntegration)
+    virtual QOffscreenSurface *createOffscreenSurface(ANativeWindow *nativeSurface) const = 0;
+};
+#endif
+
+} // QPlatformInterface::Private
+
+
 QT_END_NAMESPACE
 
 #endif // QPLATFORMOFFSCREENSURFACE_H