Add API to grab a surface's content

This patch adds a new QWaylandSurfaceGrabber class. The user can use it
to grab a surface's content, and get a QImage with the data.

Change-Id: I25dd72a8ba39201cd91addbfc976b93ca1e05112
Reviewed-by: Pier Luigi Fiorini <pierluigi.fiorini@gmail.com>

8 files changed, 316 insertions, 1 deletions

diff --git a/src/compositor/compositor_api/compositor_api.pri b/src/compositor/compositor_api/compositor_api.pri
index d5ea9a9a4..1140efe34 100644
--- a/src/compositor/compositor_api/compositor_api.pri
+++ b/src/compositor/compositor_api/compositor_api.pri
@@ -23,6 +23,7 @@ HEADERS += \
     compositor_api/qwaylandview.h \
     compositor_api/qwaylandview_p.h \
     compositor_api/qwaylandresource.h \
+    compositor_api/qwaylandsurfacegrabber.h \
 
 SOURCES += \
     compositor_api/qwaylandcompositor.cpp \
@@ -39,6 +40,7 @@ SOURCES += \
     compositor_api/qwaylanddestroylistener.cpp \
     compositor_api/qwaylandview.cpp \
     compositor_api/qwaylandresource.cpp \
+    compositor_api/qwaylandsurfacegrabber.cpp \
 
 QT += core-private
 
diff --git a/src/compositor/compositor_api/qwaylandcompositor.cpp b/src/compositor/compositor_api/qwaylandcompositor.cpp
index 57e8397b9..17b089dcf 100644
--- a/src/compositor/compositor_api/qwaylandcompositor.cpp
+++ b/src/compositor/compositor_api/qwaylandcompositor.cpp
@@ -46,6 +46,7 @@
 #include <QtWaylandCompositor/qwaylandkeyboard.h>
 #include <QtWaylandCompositor/qwaylandpointer.h>
 #include <QtWaylandCompositor/qwaylandtouch.h>
+#include <QtWaylandCompositor/qwaylandsurfacegrabber.h>
 
 #include <QtWaylandCompositor/private/qwaylandkeyboard_p.h>
 #include <QtWaylandCompositor/private/qwaylandsurface_p.h>
@@ -75,6 +76,13 @@
 #include <QtGui/qpa/qplatformnativeinterface.h>
 #include <QtGui/private/qguiapplication_p.h>
 
+#ifdef QT_COMPOSITOR_WAYLAND_GL
+#   include <QtGui/private/qopengltextureblitter_p.h>
+#   include <QOpenGLContext>
+#   include <QOpenGLFramebufferObject>
+#   include <QMatrix4x4>
+#endif
+
 QT_BEGIN_NAMESPACE
 
 namespace QtWayland {
@@ -819,4 +827,50 @@ void QWaylandCompositor::setUseHardwareIntegrationExtension(bool use)
     useHardwareIntegrationExtensionChanged();
 }
 
+/*!
+ * Grab the surface content from the given \a buffer.
+ * The default implementation requires a OpenGL context to be bound to the current thread
+ * to work. If this is not possible reimplement this function in your compositor subclass
+ * to implement custom logic.
+ * The default implementation only grabs SHM and OpenGL buffers, reimplement this in your
+ * compositor subclass to handle more buffer types.
+ * You should not call this manually, but rather use \a QWaylandSurfaceGrabber.
+ */
+void QWaylandCompositor::grabSurface(QWaylandSurfaceGrabber *grabber, const QWaylandBufferRef &buffer)
+{
+    if (buffer.isShm()) {
+        emit grabber->success(buffer.image());
+    } else {
+#ifdef QT_COMPOSITOR_WAYLAND_GL
+        if (QOpenGLContext::currentContext()) {
+            QOpenGLFramebufferObject fbo(buffer.size());
+            fbo.bind();
+            QOpenGLTextureBlitter blitter;
+            blitter.create();
+            blitter.bind();
+
+            glViewport(0, 0, buffer.size().width(), buffer.size().height());
+
+            QOpenGLTextureBlitter::Origin surfaceOrigin =
+                buffer.origin() == QWaylandSurface::OriginTopLeft
+                ? QOpenGLTextureBlitter::OriginTopLeft
+                : QOpenGLTextureBlitter::OriginBottomLeft;
+
+            GLuint texture;
+            glGenTextures(1, &texture);
+            glBindTexture(GL_TEXTURE_2D, texture);
+            glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+            buffer.bindToTexture();
+            blitter.blit(texture, QMatrix4x4(), surfaceOrigin);
+
+            blitter.release();
+            glDeleteTextures(1, &texture);
+
+            emit grabber->success(fbo.toImage());
+        } else
+#endif
+        emit grabber->failed(QWaylandSurfaceGrabber::UnknownBufferType);
+    }
+}
+
 QT_END_NAMESPACE
diff --git a/src/compositor/compositor_api/qwaylandcompositor.h b/src/compositor/compositor_api/qwaylandcompositor.h
index ab90e12f9..a30786eb2 100644
--- a/src/compositor/compositor_api/qwaylandcompositor.h
+++ b/src/compositor/compositor_api/qwaylandcompositor.h
@@ -63,6 +63,8 @@ class QWaylandView;
 class QWaylandPointer;
 class QWaylandKeyboard;
 class QWaylandTouch;
+class QWaylandSurfaceGrabber;
+class QWaylandBufferRef;
 
 class Q_WAYLAND_COMPOSITOR_EXPORT QWaylandCompositor : public QWaylandObject
 {
@@ -115,6 +117,8 @@ public:
     bool useHardwareIntegrationExtension() const;
     void setUseHardwareIntegrationExtension(bool use);
 
+    virtual void grabSurface(QWaylandSurfaceGrabber *grabber, const QWaylandBufferRef &buffer);
+
 public Q_SLOTS:
     void processWaylandEvents();
 
diff --git a/src/compositor/compositor_api/qwaylandquickcompositor.cpp b/src/compositor/compositor_api/qwaylandquickcompositor.cpp
index a30ea05b3..dc13368f2 100644
--- a/src/compositor/compositor_api/qwaylandquickcompositor.cpp
+++ b/src/compositor/compositor_api/qwaylandquickcompositor.cpp
@@ -36,6 +36,11 @@
 ****************************************************************************/
 
 #include <QtQml/QQmlEngine>
+#include <QQuickWindow>
+#include <QtGui/private/qopengltextureblitter_p.h>
+#include <QOpenGLFramebufferObject>
+#include <QMatrix4x4>
+#include <QRunnable>
 
 #include "qwaylandclient.h"
 #include "qwaylandquickcompositor.h"
@@ -44,6 +49,7 @@
 #include "qwaylandquickitem.h"
 #include "qwaylandoutput.h"
 #include <QtWaylandCompositor/private/qwaylandcompositor_p.h>
+#include "qwaylandsurfacegrabber.h"
 
 QT_BEGIN_NAMESPACE
 
@@ -102,4 +108,64 @@ void QWaylandQuickCompositor::componentComplete()
     create();
 }
 
+/*!
+ * Grab the surface content from the given \a buffer.
+ * Reimplemented from QWaylandCompositor::grabSurface.
+ */
+void QWaylandQuickCompositor::grabSurface(QWaylandSurfaceGrabber *grabber, const QWaylandBufferRef &buffer)
+{
+    if (buffer.isShm()) {
+        QWaylandCompositor::grabSurface(grabber, buffer);
+        return;
+    }
+
+    QWaylandQuickOutput *output = static_cast<QWaylandQuickOutput *>(defaultOutput());
+    if (!output) {
+        emit grabber->failed(QWaylandSurfaceGrabber::RendererNotReady);
+        return;
+    }
+
+    // We cannot grab the surface now, we need to have a current opengl context, so we
+    // need to be in the render thread
+    class GrabState : public QRunnable
+    {
+    public:
+        QWaylandSurfaceGrabber *grabber;
+        QWaylandBufferRef buffer;
+
+        void run() Q_DECL_OVERRIDE
+        {
+            QOpenGLFramebufferObject fbo(buffer.size());
+            fbo.bind();
+            QOpenGLTextureBlitter blitter;
+            blitter.create();
+            blitter.bind();
+
+            glViewport(0, 0, buffer.size().width(), buffer.size().height());
+
+            QOpenGLTextureBlitter::Origin surfaceOrigin =
+                buffer.origin() == QWaylandSurface::OriginTopLeft
+                ? QOpenGLTextureBlitter::OriginTopLeft
+                : QOpenGLTextureBlitter::OriginBottomLeft;
+
+            GLuint texture;
+            glGenTextures(1, &texture);
+            glBindTexture(GL_TEXTURE_2D, texture);
+            glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+            buffer.bindToTexture();
+            blitter.blit(texture, QMatrix4x4(), surfaceOrigin);
+
+            blitter.release();
+            glDeleteTextures(1, &texture);
+
+            emit grabber->success(fbo.toImage());
+        }
+    };
+
+    GrabState *state = new GrabState;
+    state->grabber = grabber;
+    state->buffer = buffer;
+    static_cast<QQuickWindow *>(output->window())->scheduleRenderJob(state, QQuickWindow::NoStage);
+}
+
 QT_END_NAMESPACE
diff --git a/src/compositor/compositor_api/qwaylandquickcompositor.h b/src/compositor/compositor_api/qwaylandquickcompositor.h
index bf25adfbb..6e0c5d315 100644
--- a/src/compositor/compositor_api/qwaylandquickcompositor.h
+++ b/src/compositor/compositor_api/qwaylandquickcompositor.h
@@ -54,6 +54,8 @@ public:
     QWaylandQuickCompositor(QObject *parent = 0);
     void create() Q_DECL_OVERRIDE;
 
+    void grabSurface(QWaylandSurfaceGrabber *grabber, const QWaylandBufferRef &buffer) Q_DECL_OVERRIDE;
+
 protected:
     void classBegin() Q_DECL_OVERRIDE;
     void componentComplete() Q_DECL_OVERRIDE;
diff --git a/src/compositor/compositor_api/qwaylandsurface_p.h b/src/compositor/compositor_api/qwaylandsurface_p.h
index 73057c54e..635820931 100644
--- a/src/compositor/compositor_api/qwaylandsurface_p.h
+++ b/src/compositor/compositor_api/qwaylandsurface_p.h
@@ -137,7 +137,7 @@ protected:
     void setBackBuffer(QtWayland::SurfaceBuffer *buffer, const QRegion &damage);
     QtWayland::SurfaceBuffer *createSurfaceBuffer(struct ::wl_resource *buffer);
 
-protected: //member variables
+public: //member variables
     QWaylandCompositor *compositor;
     int refCount;
     QWaylandClient *client;
diff --git a/src/compositor/compositor_api/qwaylandsurfacegrabber.cpp b/src/compositor/compositor_api/qwaylandsurfacegrabber.cpp
new file mode 100644
index 000000000..ab3342269
--- /dev/null
+++ b/src/compositor/compositor_api/qwaylandsurfacegrabber.cpp
@@ -0,0 +1,115 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 Klarälvdalens Datakonsult AB (KDAB).
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtWaylandCompositor module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL3$
+** 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 http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://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.LGPLv3 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.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 later as published by the Free
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qwaylandsurfacegrabber.h"
+
+#include <QtCore/private/qobject_p.h>
+#include <QtWaylandCompositor/qwaylandsurface.h>
+#include <QtWaylandCompositor/qwaylandcompositor.h>
+#include <QtWaylandCompositor/private/qwaylandsurface_p.h>
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \class QWaylandSurfaceGrabber
+    \inmodule QtWaylandCompositor
+    \since 5.7
+    \brief The QWaylandSurfaceGrabber class allows to read the content of a QWaylandSurface
+
+    Sometimes it is needed to get the contents of a surface, for example to provide a screenshot
+    to the user. The QWaylandSurfaceGrabber class provides a simple method to do so, without
+    having to care what type of buffer backs the surface, be it SHM, OpenGL or something else.
+*/
+
+/*!
+    \enum QWaylandSurfaceGrabber::Error
+
+    The Error enum describes the reason for a grab failure.
+
+    \value InvalidSurface The surface is null or otherwise not valid.
+    \value NoBufferAttached The client has not attached a buffer on the surface yet.
+    \value UnknownBufferType The buffer attached on the surface is of an unknown type.
+    \value RendererNotReady The compositor renderer is not ready to grab the surface content.
+ */
+
+class QWaylandSurfaceGrabberPrivate : public QObjectPrivate
+{
+    Q_DECLARE_PUBLIC(QWaylandSurfaceGrabber)
+
+    QWaylandSurface *surface;
+};
+
+/*!
+ * Create a QWaylandSurfaceGrabber object with the given \a surface and \a parent
+ */
+QWaylandSurfaceGrabber::QWaylandSurfaceGrabber(QWaylandSurface *surface, QObject *parent)
+                      : QObject(*(new QWaylandSurfaceGrabberPrivate), parent)
+{
+    Q_D(QWaylandSurfaceGrabber);
+    d->surface = surface;
+}
+
+/*!
+ * Returns the surface set on this object
+ */
+QWaylandSurface *QWaylandSurfaceGrabber::surface() const
+{
+    Q_D(const QWaylandSurfaceGrabber);
+    return d->surface;
+}
+
+/*!
+ * Grab the content of the surface set on this object.
+ * It may not be possible to do that immediately so the \a success and \a failed signals
+ * should be used to be notified of when the grab is completed.
+ */
+void QWaylandSurfaceGrabber::grab()
+{
+    Q_D(QWaylandSurfaceGrabber);
+    if (!d->surface) {
+        emit failed(InvalidSurface);
+        return;
+    }
+
+    QWaylandSurfacePrivate *surf = QWaylandSurfacePrivate::get(d->surface);
+    QWaylandBufferRef buf = surf->bufferRef;
+    if (!buf.hasBuffer()) {
+        emit failed(NoBufferAttached);
+        return;
+    }
+
+    d->surface->compositor()->grabSurface(this, buf);
+}
diff --git a/src/compositor/compositor_api/qwaylandsurfacegrabber.h b/src/compositor/compositor_api/qwaylandsurfacegrabber.h
new file mode 100644
index 000000000..28f984102
--- /dev/null
+++ b/src/compositor/compositor_api/qwaylandsurfacegrabber.h
@@ -0,0 +1,72 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 Klarälvdalens Datakonsult AB (KDAB).
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtWaylandCompositor module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL3$
+** 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 http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://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.LGPLv3 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.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 later as published by the Free
+** Software Foundation and appearing in the file LICENSE.GPL included in
+** the packaging of this file. Please review the following information to
+** ensure the GNU General Public License version 2.0 requirements will be
+** met: http://www.gnu.org/licenses/gpl-2.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QWAYLANDSURFACEGRABBER_H
+#define QWAYLANDSURFACEGRABBER_H
+
+#include <QtWaylandCompositor/qwaylandexport.h>
+#include <QtCore/QObject>
+
+QT_BEGIN_NAMESPACE
+
+class QWaylandSurface;
+class QWaylandSurfaceGrabberPrivate;
+
+class Q_WAYLAND_COMPOSITOR_EXPORT QWaylandSurfaceGrabber : public QObject
+{
+    Q_OBJECT
+    Q_DECLARE_PRIVATE(QWaylandSurfaceGrabber)
+public:
+    enum Error {
+        InvalidSurface,
+        NoBufferAttached,
+        UnknownBufferType,
+        RendererNotReady,
+    };
+    Q_ENUM(Error)
+    explicit QWaylandSurfaceGrabber(QWaylandSurface *surface, QObject *parent = Q_NULLPTR);
+
+    QWaylandSurface *surface() const;
+    void grab();
+
+Q_SIGNALS:
+    void success(const QImage &image);
+    void failed(Error error);
+};
+
+QT_END_NAMESPACE
+
+#endif // QWAYLANDSURFACEGRABBER_H