Compositor: Implement support for the viewporter extension

[ChangeLog][Compositor] Added support for the viewporter Wayland extension.

Change-Id: I1d33652fab6ff18da4ae1ae3497f0ca43517420a
Reviewed-by: Pier Luigi Fiorini <pierluigi.fiorini@liri.io>

11 files changed, 661 insertions, 2 deletions

diff --git a/src/3rdparty/protocol/qt_attribution.json b/src/3rdparty/protocol/qt_attribution.json
index 3b286dbd4..477293118 100644
--- a/src/3rdparty/protocol/qt_attribution.json
+++ b/src/3rdparty/protocol/qt_attribution.json
@@ -56,6 +56,23 @@ Copyright (c) 2013 BMW Car IT GmbH"
     },
 
     {
+        "Id": "wayland-viewporter-protocol",
+        "Name": "Wayland Viewporter Protocol",
+        "QDocModule": "qtwaylandcompositor",
+        "QtUsage": "Used in the Qt Wayland Compositor API",
+        "Files": "viewporter.xml",
+
+        "Description": "The Wayland viewporter extension allows a client to scale or crop a surface without modifying the buffer",
+        "Homepage": "https://wayland.freedesktop.org",
+        "Version": "1",
+        "DownloadLocation": "https://cgit.freedesktop.org/wayland/wayland-protocols/plain/stable/viewporter/viewporter.xml",
+        "LicenseId": "MIT",
+        "License": "MIT License",
+        "LicenseFile": "MIT_LICENSE.txt",
+        "Copyright": "Copyright © 2013-2016 Collabora, Ltd."
+    },
+
+    {
         "Id": "wayland-xdg-decoration-protocol",
         "Name": "Wayland xdg-decoration Protocol",
         "QDocModule": "qtwaylandcompositor",
diff --git a/src/3rdparty/protocol/viewporter.xml b/src/3rdparty/protocol/viewporter.xml
new file mode 100644
index 000000000..c732d8c35
--- /dev/null
+++ b/src/3rdparty/protocol/viewporter.xml
@@ -0,0 +1,186 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<protocol name="viewporter">
+
+  <copyright>
+    Copyright © 2013-2016 Collabora, Ltd.
+
+    Permission is hereby granted, free of charge, to any person obtaining a
+    copy of this software and associated documentation files (the "Software"),
+    to deal in the Software without restriction, including without limitation
+    the rights to use, copy, modify, merge, publish, distribute, sublicense,
+    and/or sell copies of the Software, and to permit persons to whom the
+    Software is furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice (including the next
+    paragraph) shall be included in all copies or substantial portions of the
+    Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.
+  </copyright>
+
+  <interface name="wp_viewporter" version="1">
+    <description summary="surface cropping and scaling">
+      The global interface exposing surface cropping and scaling
+      capabilities is used to instantiate an interface extension for a
+      wl_surface object. This extended interface will then allow
+      cropping and scaling the surface contents, effectively
+      disconnecting the direct relationship between the buffer and the
+      surface size.
+    </description>
+
+    <request name="destroy" type="destructor">
+      <description summary="unbind from the cropping and scaling interface">
+	Informs the server that the client will not be using this
+	protocol object anymore. This does not affect any other objects,
+	wp_viewport objects included.
+      </description>
+    </request>
+
+    <enum name="error">
+      <entry name="viewport_exists" value="0"
+             summary="the surface already has a viewport object associated"/>
+    </enum>
+
+    <request name="get_viewport">
+      <description summary="extend surface interface for crop and scale">
+	Instantiate an interface extension for the given wl_surface to
+	crop and scale its content. If the given wl_surface already has
+	a wp_viewport object associated, the viewport_exists
+	protocol error is raised.
+      </description>
+      <arg name="id" type="new_id" interface="wp_viewport"
+           summary="the new viewport interface id"/>
+      <arg name="surface" type="object" interface="wl_surface"
+           summary="the surface"/>
+    </request>
+  </interface>
+
+  <interface name="wp_viewport" version="1">
+    <description summary="crop and scale interface to a wl_surface">
+      An additional interface to a wl_surface object, which allows the
+      client to specify the cropping and scaling of the surface
+      contents.
+
+      This interface works with two concepts: the source rectangle (src_x,
+      src_y, src_width, src_height), and the destination size (dst_width,
+      dst_height). The contents of the source rectangle are scaled to the
+      destination size, and content outside the source rectangle is ignored.
+      This state is double-buffered, and is applied on the next
+      wl_surface.commit.
+
+      The two parts of crop and scale state are independent: the source
+      rectangle, and the destination size. Initially both are unset, that
+      is, no scaling is applied. The whole of the current wl_buffer is
+      used as the source, and the surface size is as defined in
+      wl_surface.attach.
+
+      If the destination size is set, it causes the surface size to become
+      dst_width, dst_height. The source (rectangle) is scaled to exactly
+      this size. This overrides whatever the attached wl_buffer size is,
+      unless the wl_buffer is NULL. If the wl_buffer is NULL, the surface
+      has no content and therefore no size. Otherwise, the size is always
+      at least 1x1 in surface local coordinates.
+
+      If the source rectangle is set, it defines what area of the wl_buffer is
+      taken as the source. If the source rectangle is set and the destination
+      size is not set, then src_width and src_height must be integers, and the
+      surface size becomes the source rectangle size. This results in cropping
+      without scaling. If src_width or src_height are not integers and
+      destination size is not set, the bad_size protocol error is raised when
+      the surface state is applied.
+
+      The coordinate transformations from buffer pixel coordinates up to
+      the surface-local coordinates happen in the following order:
+        1. buffer_transform (wl_surface.set_buffer_transform)
+        2. buffer_scale (wl_surface.set_buffer_scale)
+        3. crop and scale (wp_viewport.set*)
+      This means, that the source rectangle coordinates of crop and scale
+      are given in the coordinates after the buffer transform and scale,
+      i.e. in the coordinates that would be the surface-local coordinates
+      if the crop and scale was not applied.
+
+      If src_x or src_y are negative, the bad_value protocol error is raised.
+      Otherwise, if the source rectangle is partially or completely outside of
+      the non-NULL wl_buffer, then the out_of_buffer protocol error is raised
+      when the surface state is applied. A NULL wl_buffer does not raise the
+      out_of_buffer error.
+
+      The x, y arguments of wl_surface.attach are applied as normal to
+      the surface. They indicate how many pixels to remove from the
+      surface size from the left and the top. In other words, they are
+      still in the surface-local coordinate system, just like dst_width
+      and dst_height are.
+
+      If the wl_surface associated with the wp_viewport is destroyed,
+      all wp_viewport requests except 'destroy' raise the protocol error
+      no_surface.
+
+      If the wp_viewport object is destroyed, the crop and scale
+      state is removed from the wl_surface. The change will be applied
+      on the next wl_surface.commit.
+    </description>
+
+    <request name="destroy" type="destructor">
+      <description summary="remove scaling and cropping from the surface">
+	The associated wl_surface's crop and scale state is removed.
+	The change is applied on the next wl_surface.commit.
+      </description>
+    </request>
+
+    <enum name="error">
+      <entry name="bad_value" value="0"
+	     summary="negative or zero values in width or height"/>
+      <entry name="bad_size" value="1"
+	     summary="destination size is not integer"/>
+      <entry name="out_of_buffer" value="2"
+	     summary="source rectangle extends outside of the content area"/>
+      <entry name="no_surface" value="3"
+	     summary="the wl_surface was destroyed"/>
+    </enum>
+
+    <request name="set_source">
+      <description summary="set the source rectangle for cropping">
+	Set the source rectangle of the associated wl_surface. See
+	wp_viewport for the description, and relation to the wl_buffer
+	size.
+
+	If all of x, y, width and height are -1.0, the source rectangle is
+	unset instead. Any other set of values where width or height are zero
+	or negative, or x or y are negative, raise the bad_value protocol
+	error.
+
+	The crop and scale state is double-buffered state, and will be
+	applied on the next wl_surface.commit.
+      </description>
+      <arg name="x" type="fixed" summary="source rectangle x"/>
+      <arg name="y" type="fixed" summary="source rectangle y"/>
+      <arg name="width" type="fixed" summary="source rectangle width"/>
+      <arg name="height" type="fixed" summary="source rectangle height"/>
+    </request>
+
+    <request name="set_destination">
+      <description summary="set the surface size for scaling">
+	Set the destination size of the associated wl_surface. See
+	wp_viewport for the description, and relation to the wl_buffer
+	size.
+
+	If width is -1 and height is -1, the destination size is unset
+	instead. Any other pair of values for width and height that
+	contains zero or negative values raises the bad_value protocol
+	error.
+
+	The crop and scale state is double-buffered state, and will be
+	applied on the next wl_surface.commit.
+      </description>
+      <arg name="width" type="int" summary="surface width"/>
+      <arg name="height" type="int" summary="surface height"/>
+    </request>
+  </interface>
+
+</protocol>
diff --git a/src/compositor/compositor_api/qwaylandquickcompositor.cpp b/src/compositor/compositor_api/qwaylandquickcompositor.cpp
index 8e8a903e3..426008a60 100644
--- a/src/compositor/compositor_api/qwaylandquickcompositor.cpp
+++ b/src/compositor/compositor_api/qwaylandquickcompositor.cpp
@@ -53,6 +53,7 @@
 #include "qwaylandquickitem.h"
 #include "qwaylandoutput.h"
 #include <QtWaylandCompositor/private/qwaylandcompositor_p.h>
+#include <QtWaylandCompositor/QWaylandViewporter>
 #include "qwaylandsurfacegrabber.h"
 
 QT_BEGIN_NAMESPACE
@@ -60,8 +61,9 @@ QT_BEGIN_NAMESPACE
 class QWaylandQuickCompositorPrivate : public QWaylandCompositorPrivate
 {
 public:
-    QWaylandQuickCompositorPrivate(QWaylandCompositor *compositor)
+    explicit QWaylandQuickCompositorPrivate(QWaylandCompositor *compositor)
         : QWaylandCompositorPrivate(compositor)
+        , m_viewporter(new QWaylandViewporter(compositor))
     {
     }
 protected:
@@ -69,6 +71,8 @@ protected:
     {
         return new QWaylandQuickSurface();
     }
+private:
+    QScopedPointer<QWaylandViewporter> m_viewporter;
 };
 
 QWaylandQuickCompositor::QWaylandQuickCompositor(QObject *parent)
diff --git a/src/compositor/compositor_api/qwaylandquickitem.cpp b/src/compositor/compositor_api/qwaylandquickitem.cpp
index bc8365982..f848a0169 100644
--- a/src/compositor/compositor_api/qwaylandquickitem.cpp
+++ b/src/compositor/compositor_api/qwaylandquickitem.cpp
@@ -1317,6 +1317,10 @@ QSGNode *QWaylandQuickItem::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeDat
         d->provider->setSmooth(smooth());
         node->setRect(rect);
 
+        qreal scale = surface()->bufferScale();
+        QRectF source = surface()->sourceGeometry();
+        node->setSourceRect(QRectF(source.topLeft() * scale, source.size() * scale));
+
         return node;
     } else {
         Q_ASSERT(!d->provider);
diff --git a/src/compositor/compositor_api/qwaylandsurface.cpp b/src/compositor/compositor_api/qwaylandsurface.cpp
index 8ad2389b6..eef51283c 100644
--- a/src/compositor/compositor_api/qwaylandsurface.cpp
+++ b/src/compositor/compositor_api/qwaylandsurface.cpp
@@ -235,6 +235,7 @@ void QWaylandSurfacePrivate::surface_commit(Resource *)
 
     // Needed in order to know whether we want to emit signals later
     QSize oldBufferSize = bufferSize;
+    QRectF oldSourceGeometry = sourceGeometry;
     QSize oldDestinationSize = destinationSize;
     bool oldHasContent = hasContent;
     int oldBufferScale = bufferScale;
@@ -244,7 +245,9 @@ void QWaylandSurfacePrivate::surface_commit(Resource *)
         bufferRef = pending.buffer;
     bufferScale = pending.bufferScale;
     bufferSize = bufferRef.size();
-    destinationSize = pending.destinationSize.isEmpty() ? bufferSize / bufferScale : pending.destinationSize;
+    QSize surfaceSize = bufferSize / bufferScale;
+    sourceGeometry = !pending.sourceGeometry.isValid() ? QRect(QPoint(), surfaceSize) : pending.sourceGeometry;
+    destinationSize = pending.destinationSize.isEmpty() ? sourceGeometry.size().toSize() : pending.destinationSize;
     damage = pending.damage.intersected(QRect(QPoint(), destinationSize));
     hasContent = bufferRef.hasContent();
     frameCallbacks << pendingFrameCallbacks;
@@ -252,6 +255,9 @@ void QWaylandSurfacePrivate::surface_commit(Resource *)
     opaqueRegion = pending.opaqueRegion.intersected(QRect(QPoint(), destinationSize));
     QPoint offsetForNextFrame = pending.offset;
 
+    if (viewport)
+        viewport->checkCommittedState();
+
     // Clear per-commit state
     pending.buffer = QWaylandBufferRef();
     pending.offset = QPoint();
@@ -284,6 +290,9 @@ void QWaylandSurfacePrivate::surface_commit(Resource *)
     if (oldDestinationSize != destinationSize)
         emit q->destinationSizeChanged();
 
+    if (oldSourceGeometry != sourceGeometry)
+        emit q->sourceGeometryChanged();
+
     if (oldHasContent != hasContent)
         emit q->hasContentChanged();
 
@@ -471,6 +480,35 @@ bool QWaylandSurface::hasContent() const
 }
 
 /*!
+ * \qmlproperty rect QtWaylandCompositor::WaylandSurface::sourceGeometry
+ *
+ * This property describes the portion of the attached Wayland buffer that should
+ * be drawn on the screen. The coordinates are from the corner of the buffer and are
+ * scaled by \l bufferScale.
+ *
+ * \sa bufferScale
+ * \sa bufferSize
+ * \sa destinationSize
+ */
+
+/*!
+ * \property QWaylandSurface::sourceGeometry
+ *
+ * This property describes the portion of the attached QWaylandBuffer that should
+ * be drawn on the screen. The coordinates are from the corner of the buffer and are
+ * scaled by \l bufferScale.
+ *
+ * \sa bufferScale
+ * \sa bufferSize
+ * \sa destinationSize
+ */
+QRectF QWaylandSurface::sourceGeometry() const
+{
+    Q_D(const QWaylandSurface);
+    return d->sourceGeometry;
+}
+
+/*!
  * \qmlproperty size QtWaylandCompositor::WaylandSurface::destinationSize
  *
  * This property holds the size of this WaylandSurface in surface coordinates.
diff --git a/src/compositor/compositor_api/qwaylandsurface.h b/src/compositor/compositor_api/qwaylandsurface.h
index 13f09f33c..9bf842900 100644
--- a/src/compositor/compositor_api/qwaylandsurface.h
+++ b/src/compositor/compositor_api/qwaylandsurface.h
@@ -81,6 +81,7 @@ class Q_WAYLAND_COMPOSITOR_EXPORT QWaylandSurface : public QWaylandObject
     Q_OBJECT
     Q_DECLARE_PRIVATE(QWaylandSurface)
     Q_PROPERTY(QWaylandClient *client READ client CONSTANT)
+    Q_PROPERTY(QRectF sourceGeometry READ sourceGeometry NOTIFY sourceGeometryChanged)
     Q_PROPERTY(QSize destinationSize READ destinationSize NOTIFY destinationSizeChanged)
 #if QT_DEPRECATED_SINCE(5, 13)
     Q_PROPERTY(QSize size READ size NOTIFY sizeChanged) // Qt 6: Remove
@@ -113,6 +114,7 @@ public:
 
     bool hasContent() const;
 
+    QRectF sourceGeometry() const;
     QSize destinationSize() const;
 #if QT_DEPRECATED_SINCE(5, 13)
     QT_DEPRECATED QSize size() const;
@@ -162,6 +164,7 @@ Q_SIGNALS:
     void damaged(const QRegion &rect);
     void parentChanged(QWaylandSurface *newParent, QWaylandSurface *oldParent);
     void childAdded(QWaylandSurface *child);
+    void sourceGeometryChanged();
     void destinationSizeChanged();
 #if QT_DEPRECATED_SINCE(5, 13)
     QT_DEPRECATED void sizeChanged();
diff --git a/src/compositor/compositor_api/qwaylandsurface_p.h b/src/compositor/compositor_api/qwaylandsurface_p.h
index b34367801..85643623d 100644
--- a/src/compositor/compositor_api/qwaylandsurface_p.h
+++ b/src/compositor/compositor_api/qwaylandsurface_p.h
@@ -73,6 +73,7 @@
 #include <wayland-util.h>
 
 #include <QtWaylandCompositor/private/qwayland-server-wayland.h>
+#include <QtWaylandCompositor/private/qwaylandviewporter_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -144,6 +145,7 @@ public: //member variables
     QRegion damage;
     QWaylandBufferRef bufferRef;
     QWaylandSurfaceRole *role = nullptr;
+    QWaylandViewporterPrivate::Viewport *viewport = nullptr;
 
     struct {
         QWaylandBufferRef buffer;
@@ -152,6 +154,7 @@ public: //member variables
         bool newlyAttached;
         QRegion inputRegion;
         int bufferScale;
+        QRectF sourceGeometry;
         QSize destinationSize;
         QRegion opaqueRegion;
     } pending;
@@ -167,6 +170,7 @@ public: //member variables
     QRegion inputRegion;
     QRegion opaqueRegion;
 
+    QRectF sourceGeometry;
     QSize destinationSize;
     QSize bufferSize;
     int bufferScale = 1;
diff --git a/src/compositor/extensions/extensions.pri b/src/compositor/extensions/extensions.pri
index 5c708f891..38fe79a2f 100644
--- a/src/compositor/extensions/extensions.pri
+++ b/src/compositor/extensions/extensions.pri
@@ -9,6 +9,7 @@ WAYLANDSERVERSOURCES += \
     ../extensions/qt-key-unstable-v1.xml \
     ../extensions/qt-windowmanager.xml \
     ../3rdparty/protocol/text-input-unstable-v2.xml \
+    ../3rdparty/protocol/viewporter.xml \
     ../3rdparty/protocol/xdg-shell-unstable-v6.xml \
     ../3rdparty/protocol/xdg-shell.xml \
     ../3rdparty/protocol/xdg-decoration-unstable-v1.xml \
@@ -27,6 +28,8 @@ HEADERS += \
     extensions/qwaylandtextinputmanager_p.h \
     extensions/qwaylandqtwindowmanager.h \
     extensions/qwaylandqtwindowmanager_p.h \
+    extensions/qwaylandviewporter.h \
+    extensions/qwaylandviewporter_p.h \
     extensions/qwaylandxdgshellv5.h \
     extensions/qwaylandxdgshellv5_p.h \
     extensions/qwaylandxdgshellv6.h \
@@ -49,6 +52,7 @@ SOURCES += \
     extensions/qwaylandtextinput.cpp \
     extensions/qwaylandtextinputmanager.cpp \
     extensions/qwaylandqtwindowmanager.cpp \
+    extensions/qwaylandviewporter.cpp \
     extensions/qwaylandxdgshellv5.cpp \
     extensions/qwaylandxdgshellv6.cpp \
     extensions/qwaylandxdgshell.cpp \
diff --git a/src/compositor/extensions/qwaylandviewporter.cpp b/src/compositor/extensions/qwaylandviewporter.cpp
new file mode 100644
index 000000000..3856c135d
--- /dev/null
+++ b/src/compositor/extensions/qwaylandviewporter.cpp
@@ -0,0 +1,243 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** 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 "qwaylandviewporter_p.h"
+
+#include <QtWaylandCompositor/QWaylandSurface>
+#include <QtWaylandCompositor/QWaylandCompositor>
+
+#include <QtWaylandCompositor/private/qwaylandsurface_p.h>
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \class QWaylandViewporter
+    \inmodule QtWaylandCompositor
+    \since 5.13
+    \brief Provides an extension for surface resizing and cropping.
+
+    The QWaylandViewporter extension provides a way for clients to resize and crop surface
+    contents.
+
+    QWaylandViewporter corresponds to the Wayland interface, \c wp_viewporter.
+*/
+
+/*!
+    Constructs a QWaylandViewporter object.
+*/
+QWaylandViewporter::QWaylandViewporter()
+    : QWaylandCompositorExtensionTemplate<QWaylandViewporter>(*new QWaylandViewporterPrivate)
+{
+}
+
+/*!
+ * Constructs a QWaylandViewporter object for the provided \a compositor.
+ */
+QWaylandViewporter::QWaylandViewporter(QWaylandCompositor *compositor)
+    : QWaylandCompositorExtensionTemplate<QWaylandViewporter>(compositor, *new QWaylandViewporterPrivate())
+{
+}
+
+/*!
+    Initializes the extension.
+*/
+void QWaylandViewporter::initialize()
+{
+    Q_D(QWaylandViewporter);
+
+    QWaylandCompositorExtensionTemplate::initialize();
+    auto *compositor = static_cast<QWaylandCompositor *>(extensionContainer());
+    if (!compositor) {
+        qWarning() << "Failed to find QWaylandCompositor when initializing QWaylandViewporter";
+        return;
+    }
+    d->init(compositor->display(), 1);
+}
+
+/*!
+    Returns the Wayland interface for the QWaylandViewporter.
+*/
+const wl_interface *QWaylandViewporter::interface()
+{
+    return QWaylandViewporterPrivate::interface();
+}
+
+void QWaylandViewporterPrivate::wp_viewporter_destroy(Resource *resource)
+{
+    // Viewport objects are allowed ot outlive the viewporter
+    wl_resource_destroy(resource->handle);
+}
+
+void QWaylandViewporterPrivate::wp_viewporter_get_viewport(Resource *resource, uint id, wl_resource *surfaceResource)
+{
+    auto *surface = QWaylandSurface::fromResource(surfaceResource);
+    if (!surface) {
+        qWarning() << "Couldn't find surface for viewporter";
+        return;
+    }
+
+    auto *surfacePrivate = QWaylandSurfacePrivate::get(surface);
+    if (surfacePrivate->viewport) {
+        wl_resource_post_error(resource->handle, WP_VIEWPORTER_ERROR_VIEWPORT_EXISTS,
+                               "viewport already exists for surface");
+        return;
+    }
+
+    surfacePrivate->viewport = new Viewport(surface, resource->client(), id);
+}
+
+QWaylandViewporterPrivate::Viewport::Viewport(QWaylandSurface *surface, wl_client *client, int id)
+    : QtWaylandServer::wp_viewport(client, id, /*version*/ 1)
+    , m_surface(surface)
+{
+    Q_ASSERT(surface);
+}
+
+QWaylandViewporterPrivate::Viewport::~Viewport()
+{
+    if (m_surface) {
+        auto *surfacePrivate = QWaylandSurfacePrivate::get(m_surface);
+        Q_ASSERT(surfacePrivate->viewport == this);
+        surfacePrivate->viewport = nullptr;
+    }
+}
+
+// This function has to be called immediately after a surface is committed, before no
+// other client events have been dispatched, or we may incorrectly error out on an
+// incomplete pending state. See comment below.
+void QWaylandViewporterPrivate::Viewport::checkCommittedState()
+{
+    auto *surfacePrivate = QWaylandSurfacePrivate::get(m_surface);
+
+    // We can't use the current state for destination/source when checking,
+    // as that has fallbacks to the buffer size so we can't distinguish
+    // between the set/unset case. We use the pending state because no other
+    // requests has modified it yet.
+    QSize destination = surfacePrivate->pending.destinationSize;
+    QRectF source = surfacePrivate->pending.sourceGeometry;
+
+    if (!destination.isValid() && source.size() != source.size().toSize()) {
+        wl_resource_post_error(resource()->handle, error_bad_size,
+                               "non-integer size (%fx%f) with unset destination",
+                               source.width(), source.height());
+        return;
+    }
+
+    QRectF max = QRectF(QPointF(), m_surface->bufferSize() / m_surface->bufferScale());
+    // We can't use QRectF.contains, because that would return false for values on the border
+    if (max.united(source) != max) {
+        wl_resource_post_error(resource()->handle, error_out_of_buffer,
+                               "source %f,%f, %fx%f extends outside attached buffer %fx%f",
+                               source.x(), source.y(), source.width(), source.height(),
+                               max.width(), max.height());
+        return;
+    }
+}
+
+
+void QWaylandViewporterPrivate::Viewport::wp_viewport_destroy_resource(Resource *resource)
+{
+    Q_UNUSED(resource);
+    delete this;
+}
+
+void QWaylandViewporterPrivate::Viewport::wp_viewport_destroy(Resource *resource)
+{
+    if (m_surface) {
+        auto *surfacePrivate = QWaylandSurfacePrivate::get(m_surface);
+        surfacePrivate->pending.destinationSize = QSize();
+        surfacePrivate->pending.sourceGeometry = QRectF();
+    }
+    wl_resource_destroy(resource->handle);
+}
+
+void QWaylandViewporterPrivate::Viewport::wp_viewport_set_source(QtWaylandServer::wp_viewport::Resource *resource, wl_fixed_t x, wl_fixed_t y, wl_fixed_t width, wl_fixed_t height)
+{
+    Q_UNUSED(resource);
+
+    if (!m_surface) {
+        wl_resource_post_error(resource->handle, error_no_surface,
+                               "set_source requested for destroyed surface");
+        return;
+    }
+
+    QPointF position(wl_fixed_to_double(x), wl_fixed_to_double(y));
+    QSizeF size(wl_fixed_to_double(width), wl_fixed_to_double(height));
+    QRectF sourceGeometry(position, size);
+
+    if (sourceGeometry == QRectF(-1, -1, -1, -1)) {
+        auto *surfacePrivate = QWaylandSurfacePrivate::get(m_surface);
+        surfacePrivate->pending.sourceGeometry = QRectF();
+        return;
+    }
+
+    if (position.x() < 0 || position.y() < 0) {
+        wl_resource_post_error(resource->handle, error_bad_value,
+                               "negative position in set_source");
+        return;
+    }
+
+    if (!size.isValid()) {
+        wl_resource_post_error(resource->handle, error_bad_value,
+                               "negative size in set_source");
+        return;
+    }
+
+    auto *surfacePrivate = QWaylandSurfacePrivate::get(m_surface);
+    surfacePrivate->pending.sourceGeometry = sourceGeometry;
+}
+
+void QWaylandViewporterPrivate::Viewport::wp_viewport_set_destination(QtWaylandServer::wp_viewport::Resource *resource, int32_t width, int32_t height)
+{
+    Q_UNUSED(resource);
+
+    if (!m_surface) {
+        wl_resource_post_error(resource->handle, error_no_surface,
+                               "set_destination requested for destroyed surface");
+        return;
+    }
+
+    QSize destinationSize(width, height);
+    if (!destinationSize.isValid() && destinationSize != QSize(-1, -1)) {
+        wl_resource_post_error(resource->handle, error_bad_value,
+                               "negative size in set_destination");
+        return;
+    }
+    auto *surfacePrivate = QWaylandSurfacePrivate::get(m_surface);
+    surfacePrivate->pending.destinationSize = destinationSize;
+}
+
+QT_END_NAMESPACE
diff --git a/src/compositor/extensions/qwaylandviewporter.h b/src/compositor/extensions/qwaylandviewporter.h
new file mode 100644
index 000000000..811c74145
--- /dev/null
+++ b/src/compositor/extensions/qwaylandviewporter.h
@@ -0,0 +1,63 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** 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 QWAYLANDVIEWPORTER_H
+#define QWAYLANDVIEWPORTER_H
+
+#include <QtWaylandCompositor/QWaylandCompositorExtension>
+
+QT_BEGIN_NAMESPACE
+
+class QWaylandViewporterPrivate;
+
+class Q_WAYLAND_COMPOSITOR_EXPORT QWaylandViewporter
+        : public QWaylandCompositorExtensionTemplate<QWaylandViewporter>
+{
+    Q_OBJECT
+    Q_DECLARE_PRIVATE(QWaylandViewporter)
+
+public:
+    explicit QWaylandViewporter();
+    explicit QWaylandViewporter(QWaylandCompositor *compositor);
+
+    void initialize() override;
+
+    static const struct wl_interface *interface();
+};
+
+QT_END_NAMESPACE
+
+#endif // QWAYLANDVIEWPORTER_H
diff --git a/src/compositor/extensions/qwaylandviewporter_p.h b/src/compositor/extensions/qwaylandviewporter_p.h
new file mode 100644
index 000000000..d22da6990
--- /dev/null
+++ b/src/compositor/extensions/qwaylandviewporter_p.h
@@ -0,0 +1,93 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** 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 QWAYLANDVIEWPORTER_P_H
+#define QWAYLANDVIEWPORTER_P_H
+
+#include "qwaylandviewporter.h"
+
+#include <QtWaylandCompositor/private/qwaylandcompositorextension_p.h>
+#include <QtWaylandCompositor/private/qwayland-server-viewporter.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.
+//
+
+QT_BEGIN_NAMESPACE
+
+class QWaylandSurface;
+
+class Q_WAYLAND_COMPOSITOR_EXPORT QWaylandViewporterPrivate
+        : public QWaylandCompositorExtensionPrivate
+        , public QtWaylandServer::wp_viewporter
+{
+    Q_DECLARE_PUBLIC(QWaylandViewporter)
+public:
+    explicit QWaylandViewporterPrivate() = default;
+
+    class Q_WAYLAND_COMPOSITOR_EXPORT Viewport
+            : public QtWaylandServer::wp_viewport
+    {
+    public:
+        explicit Viewport(QWaylandSurface *surface, wl_client *client, int id);
+        ~Viewport() override;
+        void checkCommittedState();
+
+    protected:
+        void wp_viewport_destroy_resource(Resource *resource) override;
+        void wp_viewport_destroy(Resource *resource) override;
+        void wp_viewport_set_source(Resource *resource, wl_fixed_t x, wl_fixed_t y, wl_fixed_t width, wl_fixed_t height) override;
+        void wp_viewport_set_destination(Resource *resource, int32_t width, int32_t height) override;
+
+    private:
+        QPointer<QWaylandSurface> m_surface = nullptr;
+    };
+
+protected:
+    void wp_viewporter_destroy(Resource *resource) override;
+    void wp_viewporter_get_viewport(Resource *resource, uint32_t id, wl_resource *surface) override;
+};
+
+QT_END_NAMESPACE
+
+#endif // QWAYLANDVIEWPORTER_P_H