[wayland] Add a virtual framebuffer backend

A new backend which doesn't present the rendered output. It uses a
QPainter scene, renders to a QImage but doesn't present it anywhere.
Thus a real virtual backend.

By exporting the environment variable KWIN_WAYLAND_VIRTUAL_SCREENSHOTS
the backend creates a temporary dir, prints the path to std-out and
saves each rendered frame into that directory. Of course with exit it
will be deleted again.

backends/CMakeLists.txt

@@ -5,6 +5,7 @@ add_subdirectory(fbdev)
 if(HAVE_LIBHYBRIS)
     add_subdirectory(hwcomposer)
 endif()
+add_subdirectory(virtual)
 add_subdirectory(wayland)
 if(X11_XCB_FOUND)
     add_subdirectory(x11)

backends/virtual/CMakeLists.txt

@@ -0,0 +1,15 @@
+set(VIRTUAL_SOURCES
+    virtual_backend.cpp
+    scene_qpainter_virtual_backend.cpp
+    screens_virtual.cpp
+)
+
+add_library(KWinWaylandVirtualBackend MODULE ${VIRTUAL_SOURCES})
+target_link_libraries(KWinWaylandVirtualBackend kwin)
+
+install(
+    TARGETS
+        KWinWaylandVirtualBackend
+    DESTINATION
+        ${PLUGIN_INSTALL_DIR}/org.kde.kwin.waylandbackends/
+)

backends/virtual/scene_qpainter_virtual_backend.cpp

@@ -0,0 +1,99 @@
+/********************************************************************
+ KWin - the KDE window manager
+ This file is part of the KDE project.
+
+Copyright (C) 2015 Martin Gräßlin <mgraesslin@kde.org>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*********************************************************************/
+#include "scene_qpainter_virtual_backend.h"
+#include "virtual_backend.h"
+#include "cursor.h"
+
+#include <QDebug>
+#include <QPainter>
+#include <QTemporaryDir>
+
+namespace KWin
+{
+VirtualQPainterBackend::VirtualQPainterBackend(VirtualBackend *backend)
+    : QPainterBackend()
+    , m_backBuffer(backend->size(), QImage::Format_RGB32)
+    , m_backend(backend)
+{
+    if (qEnvironmentVariableIsSet("KWIN_WAYLAND_VIRTUAL_SCREENSHOTS")) {
+        m_screenshotDir.reset(new QTemporaryDir);
+        if (!m_screenshotDir->isValid()) {
+            m_screenshotDir.reset();
+        }
+        if (!m_screenshotDir.isNull()) {
+            qDebug() << "Screenshots saved to: " << m_screenshotDir->path();
+        }
+    }
+}
+
+VirtualQPainterBackend::~VirtualQPainterBackend() = default;
+
+QImage *VirtualQPainterBackend::buffer()
+{
+    return &m_backBuffer;
+}
+
+bool VirtualQPainterBackend::needsFullRepaint() const
+{
+    return true;
+}
+
+void VirtualQPainterBackend::prepareRenderingFrame()
+{
+}
+
+void VirtualQPainterBackend::screenGeometryChanged(const QSize &size)
+{
+    if (m_backBuffer.size() != size) {
+        m_backBuffer = QImage(size, QImage::Format_RGB32);
+        m_backBuffer.fill(Qt::black);
+    }
+}
+
+void VirtualQPainterBackend::present(int mask, const QRegion &damage)
+{
+    Q_UNUSED(mask)
+    Q_UNUSED(damage)
+    if (!m_screenshotDir.isNull()) {
+        m_backBuffer.save(QStringLiteral("%1/%2.png").arg(m_screenshotDir->path()).arg(QString::number(m_frameCounter++)));
+    }
+}
+
+bool VirtualQPainterBackend::usesOverlayWindow() const
+{
+    return false;
+}
+
+void VirtualQPainterBackend::renderCursor(QPainter *painter)
+{
+    if (!m_backend->usesSoftwareCursor()) {
+        return;
+    }
+    const QImage img = m_backend->softwareCursor();
+    if (img.isNull()) {
+        return;
+    }
+    const QPoint cursorPos = Cursor::pos();
+    const QPoint hotspot = m_backend->softwareCursorHotspot();
+    painter->drawImage(cursorPos - hotspot, img);
+    m_backend->markCursorAsRendered();
+}
+
+}

backends/virtual/scene_qpainter_virtual_backend.h

@@ -0,0 +1,58 @@
+/********************************************************************
+ KWin - the KDE window manager
+ This file is part of the KDE project.
+
+Copyright (C) 2015 Martin Gräßlin <mgraesslin@kde.org>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*********************************************************************/
+#ifndef KWIN_SCENE_QPAINTER_X11_BACKEND_H
+#define KWIN_SCENE_QPAINTER_X11_BACKEND_H
+
+#include "scene_qpainter.h"
+
+#include <QObject>
+
+class QTemporaryDir;
+
+namespace KWin
+{
+
+class VirtualBackend;
+
+class VirtualQPainterBackend : public QObject, public QPainterBackend
+{
+    Q_OBJECT
+public:
+    VirtualQPainterBackend(VirtualBackend *backend);
+    virtual ~VirtualQPainterBackend();
+
+    QImage *buffer() override;
+    bool needsFullRepaint() const override;
+    bool usesOverlayWindow() const override;
+    void prepareRenderingFrame() override;
+    void present(int mask, const QRegion &damage) override;
+    void screenGeometryChanged(const QSize &size) override;
+    void renderCursor(QPainter *painter) override;
+
+private:
+    QImage m_backBuffer;
+    VirtualBackend *m_backend;
+    QScopedPointer<QTemporaryDir> m_screenshotDir;
+    int m_frameCounter = 0;
+};
+
+}
+
+#endif

backends/virtual/screens_virtual.cpp

@@ -0,0 +1,70 @@
+/********************************************************************
+ KWin - the KDE window manager
+ This file is part of the KDE project.
+
+Copyright (C) 2015 Martin Gräßlin <mgraesslin@kde.org>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*********************************************************************/
+#include "screens_virtual.h"
+#include "virtual_backend.h"
+
+namespace KWin
+{
+
+VirtualScreens::VirtualScreens(VirtualBackend *backend, QObject *parent)
+    : Screens(parent)
+    , m_backend(backend)
+{
+}
+
+VirtualScreens::~VirtualScreens() = default;
+
+void VirtualScreens::init()
+{
+    KWin::Screens::init();
+    connect(m_backend, &VirtualBackend::sizeChanged,
+            this, &VirtualScreens::startChangedTimer);
+    updateCount();
+    emit changed();
+}
+
+QRect VirtualScreens::geometry(int screen) const
+{
+    if (screen == 0) {
+        return QRect(QPoint(0, 0), size(screen));
+    }
+    return QRect();
+}
+
+QSize VirtualScreens::size(int screen) const
+{
+    if (screen == 0) {
+        return m_backend->size();
+    }
+    return QSize();
+}
+
+void VirtualScreens::updateCount()
+{
+    setCount(1);
+}
+
+int VirtualScreens::number(const QPoint &pos) const
+{
+    Q_UNUSED(pos)
+    return 0;
+}
+
+}

backends/virtual/screens_virtual.h

@@ -0,0 +1,47 @@
+/********************************************************************
+ KWin - the KDE window manager
+ This file is part of the KDE project.
+
+Copyright (C) 2015 Martin Gräßlin <mgraesslin@kde.org>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*********************************************************************/
+#ifndef KWIN_SCREENS_VIRTUAL_H
+#define KWIN_SCREENS_VIRTUAL_H
+#include "screens.h"
+
+namespace KWin
+{
+class VirtualBackend;
+
+class VirtualScreens : public Screens
+{
+    Q_OBJECT
+public:
+    VirtualScreens(VirtualBackend *backend, QObject *parent = nullptr);
+    virtual ~VirtualScreens();
+    void init() override;
+    QRect geometry(int screen) const override;
+    int number(const QPoint &pos) const override;
+    QSize size(int screen) const override;
+    void updateCount() override;
+
+private:
+    VirtualBackend *m_backend;
+};
+
+}
+
+#endif
+

backends/virtual/virtual.json

@@ -0,0 +1,8 @@
+{
+    "KPlugin": {
+        "Id": "KWinWaylandVirtualBackend",
+        "Name": "virtual",
+        "Description": "Render to a virtual framebuffer."
+    },
+    "input": true
+}

backends/virtual/virtual_backend.cpp

@@ -0,0 +1,61 @@
+/********************************************************************
+ KWin - the KDE window manager
+ This file is part of the KDE project.
+
+Copyright (C) 2015 Martin Gräßlin <mgraesslin@kde.org>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*********************************************************************/
+#include "virtual_backend.h"
+#include "scene_qpainter_virtual_backend.h"
+#include "screens_virtual.h"
+#include "wayland_server.h"
+// KWayland
+#include <KWayland/Server/seat_interface.h>
+
+namespace KWin
+{
+
+VirtualBackend::VirtualBackend(QObject *parent)
+    : AbstractBackend(parent)
+{
+    setSoftWareCursor(true);
+    setSupportsPointerWarping(true);
+    // currently only QPainter - enforce it
+    qputenv("KWIN_COMPOSE", QByteArrayLiteral("Q"));
+}
+
+VirtualBackend::~VirtualBackend() = default;
+
+void VirtualBackend::init()
+{
+    m_size = initialWindowSize();
+    setReady(true);
+    waylandServer()->seat()->setHasPointer(true);
+    waylandServer()->seat()->setHasKeyboard(true);
+    waylandServer()->seat()->setHasTouch(true);
+    emit screensQueried();
+}
+
+Screens *VirtualBackend::createScreens(QObject *parent)
+{
+    return new VirtualScreens(this, parent);
+}
+
+QPainterBackend *VirtualBackend::createQPainterBackend()
+{
+    return new VirtualQPainterBackend(this);
+}
+
+}

backends/virtual/virtual_backend.h

@@ -0,0 +1,59 @@
+/********************************************************************
+ KWin - the KDE window manager
+ This file is part of the KDE project.
+
+Copyright (C) 2015 Martin Gräßlin <mgraesslin@kde.org>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*********************************************************************/
+#ifndef KWIN_X11WINDOWED_BACKEND_H
+#define KWIN_X11WINDOWED_BACKEND_H
+#include "abstract_backend.h"
+
+#include <kwin_export.h>
+
+#include <QObject>
+#include <QSize>
+
+namespace KWin
+{
+
+class KWIN_EXPORT VirtualBackend : public AbstractBackend
+{
+    Q_OBJECT
+    Q_INTERFACES(KWin::AbstractBackend)
+    Q_PLUGIN_METADATA(IID "org.kde.kwin.AbstractBackend" FILE "virtual.json")
+    Q_PROPERTY(QSize size READ size NOTIFY sizeChanged)
+public:
+    VirtualBackend(QObject *parent = nullptr);
+    virtual ~VirtualBackend();
+    void init() override;
+
+    QSize size() const {
+        return m_size;
+    }
+
+    Screens *createScreens(QObject *parent = nullptr) override;
+    QPainterBackend* createQPainterBackend() override;
+
+Q_SIGNALS:
+    void sizeChanged();
+
+private:
+    QSize m_size;
+};
+
+}
+
+#endif

main_wayland.cpp

@@ -326,6 +326,7 @@ static const QString s_drmPlugin = QStringLiteral("KWinWaylandDrmBackend");
 #if HAVE_LIBHYBRIS
 static const QString s_hwcomposerPlugin = QStringLiteral("KWinWaylandHwcomposerBackend");
 #endif
+static const QString s_virtualPlugin = QStringLiteral("KWinWaylandVirtualBackend");
 
 static QString automaticBackendSelection()
 {
@@ -411,6 +412,7 @@ int main(int argc, char * argv[])
     QCommandLineOption waylandDisplayOption(QStringLiteral("wayland-display"),
                                             i18n("The Wayland Display to use in windowed mode on platform Wayland."),
                                             QStringLiteral("display"));
+    QCommandLineOption virtualFbOption(QStringLiteral("virtual"), i18n("Render to a virtual framebuffer."));
     QCommandLineOption widthOption(QStringLiteral("width"),
                                    i18n("The width for windowed mode. Default width is 1024."),
                                    QStringLiteral("width"));
@@ -437,7 +439,10 @@ int main(int argc, char * argv[])
         parser.addOption(framebufferOption);
         parser.addOption(framebufferDeviceOption);
     }
-    if (hasPlugin(KWin::s_x11Plugin)) {
+    if (hasPlugin(KWin::s_virtualPlugin)) {
+        parser.addOption(virtualFbOption);
+    }
+    if (hasPlugin(KWin::s_x11Plugin) || hasPlugin(KWin::s_virtualPlugin)) {
         parser.addOption(widthOption);
         parser.addOption(heightOption);
     }
@@ -545,6 +550,9 @@ int main(int argc, char * argv[])
         pluginName = KWin::s_hwcomposerPlugin;
     }
 #endif
+    if (parser.isSet(virtualFbOption)) {
+        pluginName = KWin::s_virtualPlugin;
+    }
 
     if (pluginName.isEmpty()) {
         std::cerr << "No backend specified through command line argument, trying auto resolution" << std::endl;