Window Thumbnail support for QML

A new QML item "ThumbnailItem" is registered to the TabBox. The
C++ implementation finds the EffectWindow of the TabBox and adds
itself to the EffectWindow.

While rendering the EffectWindow the information for all registered
ThumbnailItems are extracted and the thumbnail is rendered on top
of the EffectWindow.

This has obvious limitations like you cannot put other QML items
on top of the thumbnail. Nevertheless it works well enough to
be a possible replacement for e.g. BoxSwitch effect.

When compositing is disabled an icon is rendered instead of the
Thumbnail.

One TabBox Layout inspired by BoxSwitch Effect is added. For the
KCM small pre-rendered items are used.

REVIEW: 103039

CMakeLists.txt

@@ -109,6 +109,7 @@ set(kwin_KDEINIT_SRCS
    scene_basic.cpp
    scene_xrender.cpp
    scene_opengl.cpp
+   thumbnailitem.cpp
    lanczosfilter.cpp
    deleted.cpp
    effects.cpp
@@ -254,6 +255,7 @@ install( FILES
     tabbox/qml/small_icons.qml
     tabbox/qml/tabbox.qml
     tabbox/qml/text.qml
+    tabbox/qml/thumbnails.qml
     tabbox/qml/IconTabBox.qml
     DESTINATION ${DATA_INSTALL_DIR}/kwin/tabbox )
 

effects.cpp

@@ -30,6 +30,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #ifdef KWIN_BUILD_TABBOX
 #include "tabbox.h"
 #endif
+#include "thumbnailitem.h"
 #include "workspace.h"
 #include "kwinglutils.h"
 
@@ -1278,7 +1279,9 @@ void EffectsHandlerImpl::slotHideOutline()
 // EffectWindowImpl
 //****************************************
 
-EffectWindowImpl::EffectWindowImpl() : EffectWindow()
+EffectWindowImpl::EffectWindowImpl()
+    : QObject(NULL)
+    , EffectWindow()
     , toplevel(NULL)
     , sw(NULL)
 {
@@ -1743,6 +1746,36 @@ EffectWindow* effectWindow(Scene::Window* w)
     return ret;
 }
 
+void EffectWindowImpl::registerThumbnail(ThumbnailItem *item)
+{
+    insertThumbnail(item);
+    connect(item, SIGNAL(destroyed(QObject*)), SLOT(thumbnailDestroyed(QObject*)));
+    connect(item, SIGNAL(wIdChanged(qulonglong)), SLOT(thumbnailTargetChanged()));
+}
+
+void EffectWindowImpl::thumbnailDestroyed(QObject *object)
+{
+    // we know it is a ThumbnailItem
+    m_thumbnails.remove(static_cast<ThumbnailItem*>(object));
+}
+
+void EffectWindowImpl::thumbnailTargetChanged()
+{
+    if (ThumbnailItem *item = qobject_cast<ThumbnailItem*>(sender())) {
+        insertThumbnail(item);
+    }
+}
+
+void EffectWindowImpl::insertThumbnail(ThumbnailItem *item)
+{
+    EffectWindow *w = effects->findWindow(item->wId());
+    if (w) {
+        m_thumbnails.insert(item, QWeakPointer<EffectWindowImpl>(static_cast<EffectWindowImpl*>(w)));
+    } else {
+        m_thumbnails.insert(item, QWeakPointer<EffectWindowImpl>());
+    }
+}
+
 //****************************************
 // EffectWindowGroupImpl
 //****************************************

effects.h

@@ -37,6 +37,8 @@ class KService;
 namespace KWin
 {
 
+class ThumbnailItem;
+
 class Client;
 class Deleted;
 class Unmanaged;
@@ -218,8 +220,9 @@ private:
     QList< Effect* >::iterator m_currentBuildQuadsIterator;
 };
 
-class EffectWindowImpl : public EffectWindow
+class EffectWindowImpl : public QObject, public EffectWindow
 {
+    Q_OBJECT
 public:
     EffectWindowImpl();
     virtual ~EffectWindowImpl();
@@ -315,10 +318,20 @@ public:
 
     void setData(int role, const QVariant &data);
     QVariant data(int role) const;
+
+    void registerThumbnail(ThumbnailItem *item);
+    QHash<ThumbnailItem*, QWeakPointer<EffectWindowImpl> > const &thumbnails() const {
+        return m_thumbnails;
+    }
+private Q_SLOTS:
+    void thumbnailDestroyed(QObject *object);
+    void thumbnailTargetChanged();
 private:
+    void insertThumbnail(ThumbnailItem *item);
     Toplevel* toplevel;
     Scene::Window* sw; // This one is used only during paint pass.
     QHash<int, QVariant> dataMap;
+    QHash<ThumbnailItem*, QWeakPointer<EffectWindowImpl> > m_thumbnails;
 };
 
 class EffectWindowGroupImpl

kcmkwin/kwintabbox/CMakeLists.txt

@@ -5,6 +5,7 @@ include_directories( ${KDEBASE_WORKSPACE_SOURCE_DIR}/kwin/tabbox )
 set(kcm_kwintabbox_PART_SRCS
     main.cpp
     layoutconfig.cpp
+    thumbnailitem.cpp
     ${KDEBASE_WORKSPACE_SOURCE_DIR}/kwin/tabbox/clientitemdelegate.cpp
     ${KDEBASE_WORKSPACE_SOURCE_DIR}/kwin/tabbox/clientmodel.cpp
     ${KDEBASE_WORKSPACE_SOURCE_DIR}/kwin/tabbox/declarative.cpp
@@ -27,3 +28,4 @@ install(TARGETS kcm_kwintabbox  DESTINATION ${PLUGIN_INSTALL_DIR} )
 ########### install files ###############
 install( FILES kwintabbox.desktop DESTINATION  ${SERVICES_INSTALL_DIR} )
 install( FILES qml/main.qml DESTINATION ${DATA_INSTALL_DIR}/kwin/kcm_kwintabbox)
+install( FILES thumbnails/konqueror.png thumbnails/kmail.png thumbnails/systemsettings.png thumbnails/dolphin.png DESTINATION ${DATA_INSTALL_DIR}/kwin/kcm_kwintabbox)

kcmkwin/kwintabbox/layoutconfig.cpp

@@ -19,6 +19,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *********************************************************************/
 // own
 #include "layoutconfig.h"
+#include "thumbnailitem.h"
 #include <QtDeclarative/qdeclarative.h>
 #include <QtDeclarative/QDeclarativeContext>
 #include <QtDeclarative/QDeclarativeEngine>
@@ -60,6 +61,7 @@ LayoutConfig::LayoutConfig(QWidget* parent)
     kdeclarative.setDeclarativeEngine(engine());
     kdeclarative.initialize();
     kdeclarative.setupBindings();
+    qmlRegisterType<ThumbnailItem>("org.kde.kwin", 0, 1, "ThumbnailItem");
     rootContext()->setContextProperty("clientModel", model);
     rootContext()->setContextProperty("layoutModel", m_layoutsModels);
     setSource(KStandardDirs::locate("data", "kwin/kcm_kwintabbox/main.qml"));
@@ -131,6 +133,7 @@ ExampleClientModel::ExampleClientModel (QObject* parent)
     roles[Qt::UserRole] = "caption";
     roles[Qt::UserRole+1] = "minimized";
     roles[Qt::UserRole+2] = "desktopName";
+    roles[Qt::UserRole+4] = "windowId";
     setRoleNames(roles);
     init();
 }
@@ -167,6 +170,18 @@ QVariant ExampleClientModel::data(const QModelIndex &index, int role) const
         return i18nc("An example Desktop Name", "Desktop 1");
     case Qt::UserRole+3:
         return KDesktopFile(m_nameList.at(index.row())).readIcon();
+    case Qt::UserRole+4:
+        const QString desktopFile = KDesktopFile(m_nameList.at(index.row())).fileName().split('/').last();
+        if (desktopFile == "konqbrowser.desktop") {
+            return ThumbnailItem::Konqueror;
+        } else if (desktopFile == "KMail2.desktop") {
+            return ThumbnailItem::KMail;
+        } else if (desktopFile == "systemsettings.desktop") {
+            return ThumbnailItem::Systemsettings;
+        } else if (desktopFile == "dolphin.desktop") {
+            return ThumbnailItem::Dolphin;
+        }
+        return 0;
     }
     return QVariant();
 }
@@ -194,8 +209,9 @@ LayoutModel::~LayoutModel()
 void LayoutModel::init()
 {
     QStringList layouts;
-    layouts << "informative" << "compact" << "text" << "big_icons" << "small_icons";
+    layouts << "thumbnails" << "informative" << "compact" << "text" << "big_icons" << "small_icons";
     QStringList descriptions;
+    descriptions << i18nc("Name for a window switcher layout showing live window thumbnails", "Thumbnails");
     descriptions << i18nc("Name for a window switcher layout showing icon, name and desktop", "Informative");
     descriptions << i18nc("Name for a window switcher layout showing only icon and name", "Compact");
     descriptions << i18nc("Name for a window switcher layout showing only the name", "Text");

kcmkwin/kwintabbox/thumbnailitem.cpp

@@ -0,0 +1,89 @@
+/********************************************************************
+ KWin - the KDE window manager
+ This file is part of the KDE project.
+
+Copyright (C) 2011 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 "thumbnailitem.h"
+// Qt
+#include <QtDeclarative/QDeclarativeContext>
+#include <QtDeclarative/QDeclarativeEngine>
+#include <QtDeclarative/QDeclarativeView>
+// KDE
+#include <KDE/KDebug>
+#include <KDE/KStandardDirs>
+
+namespace KWin
+{
+ThumbnailItem::ThumbnailItem(QDeclarativeItem* parent)
+    : QDeclarativeItem(parent)
+    , m_wId(0)
+    , m_image()
+{
+    setFlags(flags() & ~QGraphicsItem::ItemHasNoContents);
+}
+
+ThumbnailItem::~ThumbnailItem()
+{
+}
+
+void ThumbnailItem::setWId(qulonglong wId)
+{
+    m_wId = wId;
+    emit wIdChanged(wId);
+    findImage();
+}
+
+void ThumbnailItem::findImage()
+{
+    QString imagePath;
+    switch (m_wId) {
+    case Konqueror:
+        imagePath = KStandardDirs::locate("data", "kwin/kcm_kwintabbox/konqueror.png");
+        break;
+    case Systemsettings:
+        imagePath = KStandardDirs::locate("data", "kwin/kcm_kwintabbox/systemsettings.png");
+        break;
+    case KMail:
+        imagePath = KStandardDirs::locate("data", "kwin/kcm_kwintabbox/kmail.png");
+        break;
+    case Dolphin:
+        imagePath = KStandardDirs::locate("data", "kwin/kcm_kwintabbox/dolphin.png");
+        break;
+    default:
+        // ignore
+        break;
+    }
+    if (imagePath.isNull()) {
+        m_image = QImage();
+    } else {
+        m_image = QImage(imagePath);
+    }
+}
+
+void ThumbnailItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
+{
+    if (m_image.isNull()) {
+        // no image: default behavior
+        QDeclarativeItem::paint(painter, option, widget);
+    }
+    QSizeF difference(boundingRect().width() - m_image.width(), boundingRect().height() - m_image.height());
+    const QRectF drawRect(boundingRect().x() + difference.width()/2.0, boundingRect().y(), m_image.width(), m_image.height());
+    painter->drawImage(drawRect, m_image);
+}
+
+} // namespace KWin

kcmkwin/kwintabbox/thumbnailitem.h

@@ -0,0 +1,59 @@
+/********************************************************************
+ KWin - the KDE window manager
+ This file is part of the KDE project.
+
+Copyright (C) 2011 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_THUMBNAILITEM_H
+#define KWIN_THUMBNAILITEM_H
+
+#include <QtDeclarative/QDeclarativeItem>
+
+namespace KWin
+{
+
+class ThumbnailItem : public QDeclarativeItem
+{
+    Q_OBJECT
+    Q_PROPERTY(qulonglong wId READ wId WRITE setWId NOTIFY wIdChanged SCRIPTABLE true)
+public:
+    ThumbnailItem(QDeclarativeItem *parent = 0);
+    virtual ~ThumbnailItem();
+
+    qulonglong wId() const {
+        return m_wId;
+    }
+    void setWId(qulonglong wId);
+    virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
+
+    enum Thumbnail {
+        Konqueror = 1,
+        KMail,
+        Systemsettings,
+        Dolphin
+    };
+Q_SIGNALS:
+    void wIdChanged(qulonglong wid);
+private:
+    void findImage();
+    qulonglong m_wId;
+    QImage m_image;
+};
+
+} // KWin
+
+#endif // KWIN_THUMBNAILITEM_H

scene.cpp

@@ -81,6 +81,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "shadow.h"
 
 #include <kephal/screens.h>
+#include "thumbnailitem.h"
 
 namespace KWin
 {
@@ -388,6 +389,44 @@ void Scene::paintWindow(Window* w, int mask, QRegion region, WindowQuadList quad
     WindowPaintData data(w->window()->effectWindow());
     data.quads = quads;
     effects->paintWindow(effectWindow(w), mask, region, data);
+    // paint thumbnails on top of window
+    EffectWindowImpl *wImpl = static_cast<EffectWindowImpl*>(effectWindow(w));
+    for (QHash<ThumbnailItem*, QWeakPointer<EffectWindowImpl> >::const_iterator it = wImpl->thumbnails().constBegin();
+            it != wImpl->thumbnails().constEnd();
+            ++it) {
+        if (it.value().isNull()) {
+            continue;
+        }
+        ThumbnailItem *item = it.key();
+        if (!item->isVisible()) {
+            continue;
+        }
+        EffectWindowImpl *thumb = it.value().data();
+        WindowPaintData thumbData(thumb);
+        thumbData.opacity = data.opacity;
+
+        QSizeF size = QSizeF(thumb->size());
+        size.scale(QSizeF(item->sceneBoundingRect().width(), item->sceneBoundingRect().height()), Qt::KeepAspectRatio);
+        thumbData.xScale = size.width() / static_cast<qreal>(thumb->width());
+        thumbData.yScale = size.height() / static_cast<qreal>(thumb->height());
+        const int x = item->scenePos().x() + w->x() + (item->width() - size.width()) / 2;
+        const int y = item->scenePos().y() + w->y() + (item->height() - size.height()) / 2;
+        thumbData.xTranslate = x - thumb->x();
+        thumbData.yTranslate = y - thumb->y();
+        int thumbMask = PAINT_WINDOW_TRANSFORMED | PAINT_WINDOW_LANCZOS;
+        if (thumbData.opacity == 1.0) {
+            thumbMask |= PAINT_WINDOW_OPAQUE;
+        } else {
+            thumbMask |= PAINT_WINDOW_TRANSLUCENT;
+        }
+        if (x < wImpl->x() || x + size.width() > wImpl->x() + wImpl->width() ||
+            y < wImpl->y() || y + size.height() > wImpl->y() + wImpl->height()) {
+            // don't render windows outside the containing window.
+            // TODO: improve by spliting out the window quads which do not fit
+            continue;
+        }
+        effects->drawWindow(thumb, thumbMask, QRegion(x, y, size.width(), size.height()), thumbData);
+    }
 }
 
 // the function that'll be eventually called by paintWindow() above

tabbox/clientmodel.cpp

@@ -42,6 +42,7 @@ ClientModel::ClientModel(QObject* parent)
     roles[CaptionRole] = "caption";
     roles[DesktopNameRole] = "desktopName";
     roles[MinimizedRole] = "minimized";
+    roles[WIdRole] = "windowId";
     setRoleNames(roles);
 }
 

tabbox/declarative.cpp

@@ -37,6 +37,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <KDE/Plasma/WindowEffects>
 #include <kdeclarative.h>
 #include <kephal/screens.h>
+// KWin
+#include "thumbnailitem.h"
 
 namespace KWin
 {
@@ -103,6 +105,8 @@ DeclarativeView::DeclarativeView(QAbstractItemModel *model, QWidget *parent)
     kdeclarative.setDeclarativeEngine(engine());
     kdeclarative.initialize();
     kdeclarative.setupBindings();
+    qmlRegisterType<ThumbnailItem>("org.kde.kwin", 0, 1, "ThumbnailItem");
+    rootContext()->setContextProperty("viewId", static_cast<qulonglong>(winId()));
     rootContext()->setContextProperty("clientModel", model);
     setSource(QUrl(KStandardDirs::locate("data", "kwin/tabbox/tabbox.qml")));
 

tabbox/qml/thumbnails.qml

@@ -0,0 +1,167 @@
+/********************************************************************
+ KWin - the KDE window manager
+ This file is part of the KDE project.
+
+Copyright (C) 2011 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/>.
+*********************************************************************/
+import QtQuick 1.0
+import org.kde.plasma.core 0.1 as PlasmaCore
+import org.kde.qtextracomponents 0.1
+import org.kde.kwin 0.1 as KWin
+
+Item {
+    id: thumbnailTabBox
+    property int screenWidth : 1
+    property int screenHeight : 1
+    property real screenFactor: screenWidth/screenHeight
+    property int imagePathPrefix: (new Date()).getTime()
+    property int optimalWidth: (thumbnailListView.thumbnailWidth + hoverItem.margins.left + hoverItem.margins.right) * thumbnailListView.count + background.margins.left + background.margins.bottom
+    property int optimalHeight: thumbnailListView.thumbnailWidth*(1.0/screenFactor) + hoverItem.margins.top + hoverItem.margins.bottom + background.margins.top + background.margins.bottom + 40
+    property bool canStretchX: false
+    property bool canStretchY: false
+    width: Math.min(Math.max(screenWidth * 0.3, optimalWidth), screenWidth * 0.9)
+    height: Math.min(Math.max(screenHeight * 0.15, optimalHeight), screenHeight * 0.7)
+    clip: true
+
+
+    function setModel(model) {
+        thumbnailListView.model = model;
+        thumbnailListView.imageId++;
+    }
+
+    function modelChanged() {
+        thumbnailListView.imageId++;
+    }
+
+    PlasmaCore.FrameSvgItem {
+        id: background
+        anchors.fill: parent
+        imagePath: "dialogs/background"
+    }
+    // just to get the margin sizes
+    PlasmaCore.FrameSvgItem {
+        id: hoverItem
+        imagePath: "widgets/viewitem"
+        prefix: "hover"
+        visible: false
+    }
+
+    PlasmaCore.Theme {
+        id: theme
+    }
+
+    ListView {
+        /**
+         * Called from C++ to get the index at a mouse pos.
+         **/
+        function indexAtMousePos(pos) {
+            return thumbnailListView.indexAt(pos.x, pos.y);
+        }
+        signal currentIndexChanged(int index)
+        id: thumbnailListView
+        objectName: "listView"
+        orientation: ListView.Horizontal
+        // used for image provider URL to trick Qt into reloading icons when the model changes
+        property int imageId: 0
+        property int thumbnailWidth: 300
+        height: thumbnailWidth * (1.0/screenFactor) + hoverItem.margins.bottom + hoverItem.margins.top
+        spacing: 5
+        anchors {
+            top: parent.top
+            left: parent.left
+            right: parent.right
+            topMargin: background.margins.top
+            leftMargin: background.margins.left
+            rightMargin: background.margins.right
+            bottomMargin: background.margins.bottom
+        }
+        clip: true
+        delegate: Item {
+            property alias data: thumbnailItem.data
+            id: delegateItem
+            width: thumbnailListView.thumbnailWidth
+            height: thumbnailListView.thumbnailWidth*(1.0/screenFactor)
+            KWin.ThumbnailItem {
+                property variant data: model
+                id: thumbnailItem
+                wId: windowId
+                anchors {
+                    fill: parent
+                    leftMargin: hoverItem.margins.left
+                    rightMargin: hoverItem.margins.right
+                    topMargin: hoverItem.margins.top
+                    bottomMargin: hoverItem.margins.bottom
+                }
+            }
+        }
+        highlight: PlasmaCore.FrameSvgItem {
+            id: highlightItem
+            imagePath: "widgets/viewitem"
+            prefix: "hover"
+            width: thumbnailListView.thumbnailWidth
+            height: thumbnailListView.thumbnailWidth*(1.0/screenFactor)
+        }
+        MouseArea {
+            anchors.fill: parent
+            onClicked: {
+                thumbnailListView.currentIndex = thumbnailListView.indexAt(mouse.x, mouse.y);
+                thumbnailListView.currentIndexChanged(thumbnailListView.currentIndex);
+            }
+        }
+    }
+    Item {
+        height: 40
+        anchors {
+            top: thumbnailListView.bottom
+            left: parent.left
+            right: parent.right
+            bottom: parent.bottom
+            topMargin: hoverItem.margins.bottom
+            leftMargin: background.margins.left
+            rightMargin: background.margins.right
+            bottomMargin: background.margins.bottom
+        }
+        Image {
+            id: iconItem
+            source: "image://client/" + thumbnailListView.currentIndex + "/" + thumbnailTabBox.imagePathPrefix + "-" + thumbnailListView.imageId
+            width: 32
+            height: 32
+            sourceSize {
+                width: 32
+                height: 32
+            }
+            anchors {
+                verticalCenter: parent.verticalCenter
+                right: textItem.left
+                rightMargin: 4
+            }
+        }
+        Text {
+            id: textItem
+            text: thumbnailListView.currentItem ? thumbnailListView.currentItem.data.caption : ""
+            horizontalAlignment: Text.AlignHCenter
+            verticalAlignment: Text.AlignVCenter
+            color: theme.textColor
+            font {
+                bold: true
+            }
+            anchors {
+                verticalCenter: parent.verticalCenter
+                horizontalCenter: parent.horizontalCenter
+            }
+        }
+    }
+}

thumbnailitem.cpp

@@ -0,0 +1,113 @@
+/********************************************************************
+ KWin - the KDE window manager
+ This file is part of the KDE project.
+
+Copyright (C) 2011 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 "thumbnailitem.h"
+// KWin
+#include "client.h"
+#include "effects.h"
+#include "workspace.h"
+// Qt
+#include <QtDeclarative/QDeclarativeContext>
+#include <QtDeclarative/QDeclarativeEngine>
+#include <QtDeclarative/QDeclarativeView>
+// KDE
+#include <KDE/KDebug>
+
+namespace KWin
+{
+ThumbnailItem::ThumbnailItem(QDeclarativeItem* parent)
+    : QDeclarativeItem(parent)
+    , m_wId(0)
+    , m_parent(QWeakPointer<EffectWindowImpl>())
+{
+    setFlags(flags() & ~QGraphicsItem::ItemHasNoContents);
+    if (effects) {
+        connect(effects, SIGNAL(windowAdded(EffectWindow*)), SLOT(effectWindowAdded()));
+    }
+    QTimer::singleShot(0, this, SLOT(init()));
+}
+
+ThumbnailItem::~ThumbnailItem()
+{
+}
+
+void ThumbnailItem::init()
+{
+    findParentEffectWindow();
+    if (!m_parent.isNull()) {
+        m_parent.data()->registerThumbnail(this);
+    }
+}
+
+void ThumbnailItem::findParentEffectWindow()
+{
+    if (effects) {
+        QDeclarativeContext *ctx = QDeclarativeEngine::contextForObject(this);
+        if (!ctx) {
+            kDebug(1212) << "No Context";
+            return;
+        }
+        const QVariant variant = ctx->engine()->rootContext()->contextProperty("viewId");
+        if (!variant.isValid()) {
+            kDebug(1212) << "Required context property 'viewId' not found";
+            return;
+        }
+        if (EffectWindowImpl *w = static_cast<EffectWindowImpl*>(effects->findWindow(variant.value<qulonglong>()))) {
+            m_parent = QWeakPointer<EffectWindowImpl>(w);
+        }
+    }
+}
+
+void ThumbnailItem::setWId(qulonglong wId)
+{
+    m_wId = wId;
+    emit wIdChanged(wId);
+}
+
+void ThumbnailItem::effectWindowAdded()
+{
+    // the window might be added before the EffectWindow is created
+    // by using this slot we can register the thumbnail when it is finally created
+    if (m_parent.isNull()) {
+        findParentEffectWindow();
+        if (!m_parent.isNull()) {
+            m_parent.data()->registerThumbnail(this);
+        }
+    }
+}
+
+void ThumbnailItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
+{
+    if (effects) {
+        QDeclarativeItem::paint(painter, option, widget);
+        return;
+    }
+    Client *client = Workspace::self()->findClient(WindowMatchPredicate(m_wId));
+    if (!client) {
+        QDeclarativeItem::paint(painter, option, widget);
+        return;
+    }
+    QPixmap pixmap = client->icon(boundingRect().size().toSize());
+    const QSize size(boundingRect().size().toSize() - pixmap.size());
+    painter->drawPixmap(boundingRect().adjusted(size.width()/2.0, size.height()/2.0, -size.width()/2.0, -size.height()/2.0).toRect(),
+                        pixmap);
+}
+
+} // namespace KWin

thumbnailitem.h

@@ -0,0 +1,59 @@
+/********************************************************************
+ KWin - the KDE window manager
+ This file is part of the KDE project.
+
+Copyright (C) 2011 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_THUMBNAILITEM_H
+#define KWIN_THUMBNAILITEM_H
+
+#include <QtCore/QWeakPointer>
+#include <QtDeclarative/QDeclarativeItem>
+
+namespace KWin
+{
+
+class EffectWindow;
+class EffectWindowImpl;
+
+class ThumbnailItem : public QDeclarativeItem
+{
+    Q_OBJECT
+    Q_PROPERTY(qulonglong wId READ wId WRITE setWId NOTIFY wIdChanged SCRIPTABLE true)
+public:
+    ThumbnailItem(QDeclarativeItem *parent = 0);
+    virtual ~ThumbnailItem();
+
+    qulonglong wId() const {
+        return m_wId;
+    }
+    void setWId(qulonglong wId);
+    virtual void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
+Q_SIGNALS:
+    void wIdChanged(qulonglong wid);
+private Q_SLOTS:
+    void init();
+    void effectWindowAdded();
+private:
+    void findParentEffectWindow();
+    qulonglong m_wId;
+    QWeakPointer<EffectWindowImpl> m_parent;
+};
+
+} // KWin
+
+#endif // KWIN_THUMBNAILITEM_H