Previews displayed in the launcher.

CMakeLists.txt

@@ -305,7 +305,7 @@ endif (USE_DBUS)
 ## Qt5 setup setup
 if (ENABLE_QT)
 	message(STATUS "Qt launcher enabled, checking for Qt 5.1 / qmake")
-	find_package(Qt5 5.1 COMPONENTS Widgets)
+        find_package(Qt5 5.1 COMPONENTS Widgets Network)
 	if (Qt5Widgets_FOUND)
 		message(STATUS "Will enable Qt launcher GUI")
 		message(STATUS "  Qt5Widgets version: ${Qt5Widgets_VERSION_STRING}")

src/GUI/AircraftItemDelegate.cxx

@@ -46,6 +46,8 @@ AircraftItemDelegate::AircraftItemDelegate(QListView* view) :
 
     m_leftArrowIcon.load(":/left-arrow-icon");
     m_rightArrowIcon.load(":/right-arrow-icon");
+    m_openPreviewsIcon.load(":/preview-icon");
+    m_openPreviewsIcon = m_openPreviewsIcon.scaled(32, 32, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
 }
 
 void AircraftItemDelegate::paint(QPainter * painter, const QStyleOptionViewItem & option,
@@ -79,15 +81,22 @@ void AircraftItemDelegate::paint(QPainter * painter, const QStyleOptionViewItem
         painter->drawLine(option.rect.topLeft(), option.rect.topRight());
     }
 
-
+    // thumbnail
     QPixmap thumbnail = index.data(Qt::DecorationRole).value<QPixmap>();
     quint32 yPos = contentRect.center().y() - (thumbnail.height() / 2);
     painter->drawPixmap(contentRect.left(), yPos, thumbnail);
 
     // draw 1px frame
+    QRect thumbFrame(contentRect.left(), yPos, thumbnail.width(), thumbnail.height());
     painter->setPen(QColor(0x7f, 0x7f, 0x7f));
     painter->setBrush(Qt::NoBrush);
-    painter->drawRect(contentRect.left(), yPos, thumbnail.width(), thumbnail.height());
+    painter->drawRect(thumbFrame);
+
+    if (!index.data(AircraftPreviewsRole).toList().empty()) {
+        QRect previewIconRect = m_openPreviewsIcon.rect();
+        previewIconRect.moveBottomLeft(thumbFrame.bottomLeft());
+        painter->drawPixmap(previewIconRect, m_openPreviewsIcon);
+    }
 
     // draw bottom dividing line
     painter->drawLine(contentRect.left(), contentRect.bottom() + MARGIN,
@@ -337,6 +346,13 @@ bool AircraftItemDelegate::eventFilter( QObject*, QEvent* event )
             
             return true;
         }
+
+        if ((event->type() == QEvent::MouseButtonRelease) &&
+            !index.data(AircraftPreviewsRole).toList().empty() &&
+            showPreviewsRect(vr, index).contains(me->pos()))
+        {
+            emit showPreviews(index);
+        }
     } else if ( event->type() == QEvent::MouseMove ) {
 
     }
@@ -381,6 +397,18 @@ QRect AircraftItemDelegate::packageButtonRect(const QRect& visualRect, const QMo
                  BUTTON_WIDTH, BUTTON_HEIGHT);
 }
 
+QRect AircraftItemDelegate::showPreviewsRect(const QRect& visualRect, const QModelIndex& index) const
+{
+    QRect contentRect = visualRect.adjusted(MARGIN, MARGIN, -MARGIN, -MARGIN);
+    QPixmap thumbnail = index.data(Qt::DecorationRole).value<QPixmap>();
+    const quint32 yPos = contentRect.center().y() - (thumbnail.height() / 2);
+    QRect thumbFrame(contentRect.left(), yPos, thumbnail.width(), thumbnail.height());
+
+    QRect previewIconRect = m_openPreviewsIcon.rect();
+    previewIconRect.moveBottomLeft(thumbFrame.bottomLeft());
+    return previewIconRect;
+}
+
 void AircraftItemDelegate::drawRating(QPainter* painter, QString label, const QRect& box, int value) const
 {
     QRect dotBox = box;

src/GUI/AircraftItemDelegate.hxx

@@ -50,17 +50,23 @@ Q_SIGNALS:
     void requestUninstall(const QModelIndex& index);
 
     void cancelDownload(const QModelIndex& index);
+
+    void showPreviews(const QModelIndex& index);
+
 private:
     QRect leftCycleArrowRect(const QRect& visualRect, const QModelIndex& index) const;
     QRect rightCycleArrowRect(const QRect& visualRect, const QModelIndex& index) const;
 
     QRect packageButtonRect(const QRect& visualRect, const QModelIndex& index) const;
 
+    QRect showPreviewsRect(const QRect& visualRect, const QModelIndex& index) const;
+
     void drawRating(QPainter* painter, QString label, const QRect& box, int value) const;
 
     QListView* m_view;
     QPixmap m_leftArrowIcon,
-        m_rightArrowIcon;
+        m_rightArrowIcon,
+        m_openPreviewsIcon;
 };
 
 #endif

src/GUI/AircraftModel.cxx

@@ -40,28 +40,18 @@
 // FlightGear
 #include <Main/globals.hxx>
 
-
 const int STANDARD_THUMBNAIL_HEIGHT = 128;
 const int STANDARD_THUMBNAIL_WIDTH = 172;
+static quint32 CACHE_VERSION = 6;
 
 using namespace simgear::pkg;
 
-AircraftItem::AircraftItem() :
+AircraftItem::AircraftItem()
-    excluded(false),
-    usesHeliports(false),
-    usesSeaports(false)
 {
-    // oh for C++11 initialisers
-    for (int i=0; i<4; ++i) ratings[i] = 0;
 }
 
-AircraftItem::AircraftItem(QDir dir, QString filePath) :
+AircraftItem::AircraftItem(QDir dir, QString filePath)
-    excluded(false),
-    usesHeliports(false),
-    usesSeaports(false)
 {
-    for (int i=0; i<4; ++i) ratings[i] = 0;
-
     SGPropertyNode root;
     readProperties(filePath.toStdString(), &root);
 
@@ -113,6 +103,16 @@ AircraftItem::AircraftItem(QDir dir, QString filePath) :
             }
         } // of tags iteration
     } // of set-xml has tags
+
+    if (sim->hasChild("previews")) {
+        SGPropertyNode_ptr previewsNode = sim->getChild("previews");
+        for (auto previewNode : previewsNode->getChildren("preview")) {
+            // add file path as url
+            QString pathInXml = QString::fromStdString(previewNode->getStringValue("path"));
+            QString previewPath = dir.absoluteFilePath(pathInXml);
+            previews.append(QUrl::fromLocalFile(previewPath));
+        }
+    }
 }
 
 QString AircraftItem::baseName() const
@@ -131,6 +131,7 @@ void AircraftItem::fromDataStream(QDataStream& ds)
 
     ds >> description >> longDescription >> authors >> variantOf;
     for (int i=0; i<4; ++i) ds >> ratings[i];
+    ds >> previews;
 }
 
 void AircraftItem::toDataStream(QDataStream& ds) const
@@ -142,6 +143,7 @@ void AircraftItem::toDataStream(QDataStream& ds) const
 
     ds << description << longDescription << authors << variantOf;
     for (int i=0; i<4; ++i) ds << ratings[i];
+    ds << previews;
 }
 
 QPixmap AircraftItem::thumbnail(bool loadIfRequired) const
@@ -161,9 +163,6 @@ QPixmap AircraftItem::thumbnail(bool loadIfRequired) const
     return m_thumbnail;
 }
 
-
-static quint32 CACHE_VERSION = 5;
-
 class AircraftScanThread : public QThread
 {
     Q_OBJECT
@@ -402,14 +401,22 @@ protected:
         if (pix.height() > STANDARD_THUMBNAIL_HEIGHT) {
             pix = pix.scaledToHeight(STANDARD_THUMBNAIL_HEIGHT, Qt::SmoothTransformation);
         }
-        m_model->m_thumbnailPixmapCache.insert(QString::fromStdString(aThumbnailUrl), pix);
 
-        // notify any affected items. Linear scan here avoids another map/dict
+        m_model->m_downloadedPixmapCache.insert(QString::fromStdString(aThumbnailUrl), pix);
-        // structure.
+
+        // notify any affected items. Linear scan here avoids another map/dict structure.
         for (auto pkg : m_model->m_packages) {
-            const string_list& urls(pkg->thumbnailUrls());
+            const int variantCount = pkg->variants().size();
-            auto cit = std::find(urls.begin(), urls.end(), aThumbnailUrl);
+            bool notifyChanged = false;
-            if (cit != urls.end()) {
+
+            for (int v=0; v < variantCount; ++v) {
+                const Package::Thumbnail& thumb(pkg->thumbnailForVariant(v));
+                if (thumb.url == aThumbnailUrl) {
+                    notifyChanged = true;
+                }
+            }
+
+            if (notifyChanged) {
                 QModelIndex mi = indexForPackage(pkg);
                 m_model->dataChanged(mi, mi);
             }
@@ -593,10 +600,6 @@ QVariant AircraftItemModel::data(const QModelIndex& index, int role) const
         return m_delegateStates.at(row).variant;
     }
 
-    if (role == AircraftCurrentThumbnailRole) {
-        return m_delegateStates.at(row).thumbnail;
-    }
-
     if (row >= m_items.size()) {
         quint32 packageIndex = row - m_items.size();
         const PackageRef& pkg(m_packages[packageIndex]);
@@ -623,20 +626,7 @@ QVariant AircraftItemModel::dataFromItem(AircraftItemPtr item, const DelegateSta
         return item->variants.count();
     }
 
-    if (role == AircraftThumbnailCountRole) {
+    if (role >= AircraftVariantDescriptionRole) {
-        QPixmap p = item->thumbnail();
-        return p.isNull() ? 0 : 1;
-    }
-
-    if (role == AircraftThumbnailSizeRole) {
-        QPixmap pm = item->thumbnail(false);
-        if (pm.isNull()) {
-            return QSize(STANDARD_THUMBNAIL_WIDTH, STANDARD_THUMBNAIL_HEIGHT);
-        }
-        return pm.size();
-    }
-
-    if ((role >= AircraftVariantDescriptionRole) && (role < AircraftThumbnailRole)) {
         int variantIndex = role - AircraftVariantDescriptionRole;
         return item->variants.at(variantIndex)->description;
     }
@@ -648,6 +638,14 @@ QVariant AircraftItemModel::dataFromItem(AircraftItemPtr item, const DelegateSta
         }
     }
 
+    if (role == AircraftThumbnailSizeRole) {
+        QPixmap pm = item->thumbnail(false);
+        if (pm.isNull()) {
+            return QSize(STANDARD_THUMBNAIL_WIDTH, STANDARD_THUMBNAIL_HEIGHT);
+        }
+        return pm.size();
+    }
+
     if (role == Qt::DisplayRole) {
         if (item->description.isEmpty()) {
             return tr("Missing description for: %1").arg(item->baseName());
@@ -662,7 +660,13 @@ QVariant AircraftItemModel::dataFromItem(AircraftItemPtr item, const DelegateSta
         return item->authors;
     } else if ((role >= AircraftRatingRole) && (role < AircraftVariantDescriptionRole)) {
         return item->ratings[role - AircraftRatingRole];
-    } else if (role >= AircraftThumbnailRole) {
+    } else if (role == AircraftPreviewsRole) {
+        QVariantList result;
+        Q_FOREACH(QUrl u, item->previews) {
+            result.append(u);
+        }
+        return result;
+    } else if (role == AircraftThumbnailRole) {
         return item->thumbnail();
     } else if (role == AircraftPackageIdRole) {
         // can we fake an ID? otherwise fall through to a null variant
@@ -692,10 +696,10 @@ QVariant AircraftItemModel::dataFromItem(AircraftItemPtr item, const DelegateSta
 QVariant AircraftItemModel::dataFromPackage(const PackageRef& item, const DelegateState& state, int role) const
 {
     if (role == Qt::DecorationRole) {
-        role = AircraftThumbnailRole; // use first thumbnail
+        role = AircraftThumbnailRole;
     }
 
-    if ((role >= AircraftVariantDescriptionRole) && (role < AircraftThumbnailRole)) {
+    if (role >= AircraftVariantDescriptionRole) {
         int variantIndex = role - AircraftVariantDescriptionRole;
         QString desc = QString::fromStdString(item->nameForVariant(variantIndex));
         if (desc.isEmpty()) {
@@ -743,11 +747,10 @@ QVariant AircraftItemModel::dataFromPackage(const PackageRef& item, const Delega
         if (pm.isNull())
             return QSize(STANDARD_THUMBNAIL_WIDTH, STANDARD_THUMBNAIL_HEIGHT);
         return pm.size();
-    } else if (role >= AircraftThumbnailRole) {
+    } else if (role == AircraftThumbnailRole) {
-        DelegateState changedState(state);
+        return packageThumbnail(item, state);
-        // override the current thumbnail as required
+    } else if (role == AircraftPreviewsRole) {
-        changedState.thumbnail = (role - AircraftThumbnailRole);
+        return packagePreviews(item, state);
-        return packageThumbnail(item, changedState);
     } else if (role == AircraftAuthorsRole) {
         std::string authors = item->getLocalisedProp("author", state.variant);
         if (!authors.empty()) {
@@ -776,46 +779,69 @@ QVariant AircraftItemModel::dataFromPackage(const PackageRef& item, const Delega
 
 QVariant AircraftItemModel::packageThumbnail(PackageRef p, const DelegateState& ds, bool download) const
 {
-    const string_list& thumbnails(p->thumbnailUrls());
+    const Package::Thumbnail& thumb(p->thumbnailForVariant(ds.variant));
-    if (ds.thumbnail >= static_cast<int>(thumbnails.size())) {
+    if (thumb.url.empty()) {
         return QVariant();
     }
 
-    std::string thumbnailUrl = thumbnails.at(ds.thumbnail);
+    QString urlQString(QString::fromStdString(thumb.url));
-    QString urlQString(QString::fromStdString(thumbnailUrl));
+    if (m_downloadedPixmapCache.contains(urlQString)) {
-    if (m_thumbnailPixmapCache.contains(urlQString)) {
         // cache hit, easy
-        return m_thumbnailPixmapCache.value(urlQString);
+        return m_downloadedPixmapCache.value(urlQString);
     }
 
-// check the on-disk store. This relies on the order of thumbnails in the
+// check the on-disk store.
-// results of thumbnailUrls and thumbnails corresponding
     InstallRef ex = p->existingInstall();
     if (ex.valid()) {
-        const string_list& thumbNames(p->thumbnails());
+        SGPath thumbPath = ex->path() / thumb.path;
-        if (!thumbNames.empty()) {
+        if (thumbPath.exists()) {
-            SGPath path(ex->path());
-            path.append(p->thumbnails()[ds.thumbnail]);
-            if (path.exists()) {
             QPixmap pix;
-                pix.load(QString::fromStdString(path.utf8Str()));
+            pix.load(QString::fromStdString(thumbPath.utf8Str()));
             // resize to the standard size
             if (pix.height() > STANDARD_THUMBNAIL_HEIGHT) {
                 pix = pix.scaledToHeight(STANDARD_THUMBNAIL_HEIGHT);
             }
-                m_thumbnailPixmapCache[urlQString] = pix;
+            m_downloadedPixmapCache[urlQString] = pix;
             return pix;
         }
-        } // of have thumbnail file names
     } // of have existing install
 
     if (download) {
-        m_packageRoot->requestThumbnailData(thumbnailUrl);
+        m_packageRoot->requestThumbnailData(thumb.url);
     }
 
     return QVariant();
 }
 
+QVariant AircraftItemModel::packagePreviews(PackageRef p, const DelegateState& ds) const
+{
+    const Package::PreviewVec& previews = p->previewsForVariant(ds.variant);
+    if (previews.empty()) {
+        return QVariant();
+    }
+
+    QVariantList result;
+    // if we have an install, return file URLs, not remote (http) ones
+    InstallRef ex = p->existingInstall();
+    if (ex.valid()) {
+        for (auto p : previews) {
+            SGPath localPreviewPath = ex->path() / p.path;
+            if (!localPreviewPath.exists()) {
+                qWarning() << "missing local preview" << QString::fromStdString(localPreviewPath.utf8Str());
+                continue;
+            }
+            result.append(QUrl::fromLocalFile(QString::fromStdString(localPreviewPath.utf8Str())));
+        }
+    }
+
+    // return remote urls
+    for (auto p : previews) {
+        result.append(QUrl(QString::fromStdString(p.url)));
+    }
+
+    return result;
+}
+
 bool AircraftItemModel::setData(const QModelIndex &index, const QVariant &value, int role)
   {
       int row = index.row();
@@ -831,16 +857,6 @@ bool AircraftItemModel::setData(const QModelIndex &index, const QVariant &value,
           return true;
       }
 
-      if (role == AircraftCurrentThumbnailRole) {
-          if (m_delegateStates[row].thumbnail == newValue) {
-              return true;
-          }
-
-          m_delegateStates[row].thumbnail = newValue;
-          emit dataChanged(index, index);
-          return true;
-      }
-
       return false;
   }
 

src/GUI/AircraftModel.hxx

@@ -38,7 +38,6 @@ const int AircraftPathRole = Qt::UserRole + 1;
 const int AircraftAuthorsRole = Qt::UserRole + 2;
 const int AircraftVariantRole = Qt::UserRole + 3;
 const int AircraftVariantCountRole = Qt::UserRole + 4;
-const int AircraftThumbnailCountRole = Qt::UserRole + 5;
 const int AircraftPackageIdRole = Qt::UserRole + 6;
 const int AircraftPackageStatusRole = Qt::UserRole + 7;
 const int AircraftPackageProgressRole = Qt::UserRole + 8;
@@ -51,12 +50,12 @@ const int AircraftURIRole = Qt::UserRole + 14;
 const int AircraftThumbnailSizeRole = Qt::UserRole + 15;
 const int AircraftIsHelicopterRole = Qt::UserRole + 16;
 const int AircraftIsSeaplaneRole = Qt::UserRole + 17;
-const int AircraftCurrentThumbnailRole = Qt::UserRole + 18;
 const int AircraftPackageRefRole = Qt::UserRole + 19;
+const int AircraftThumbnailRole = Qt::UserRole + 20;
+const int AircraftPreviewsRole = Qt::UserRole + 21;
 
 const int AircraftRatingRole = Qt::UserRole + 100;
 const int AircraftVariantDescriptionRole = Qt::UserRole + 200;
-const int AircraftThumbnailRole = Qt::UserRole + 300;
 
 class AircraftScanThread;
 class QDataStream;
@@ -81,17 +80,18 @@ struct AircraftItem
 
     QPixmap thumbnail(bool loadIfRequired = true) const;
 
-    bool excluded;
+    bool excluded = false;
     QString path;
     QString description;
     QString longDescription;
     QString authors;
-    int ratings[4];
+    int ratings[4] = {0, 0, 0, 0};
     QString variantOf;
     QDateTime pathModTime;
     QList<AircraftItemPtr> variants;
-    bool usesHeliports;
+    bool usesHeliports = false;
-    bool usesSeaports;
+    bool usesSeaports = false;
+    QList<QUrl> previews;
 private:
     mutable QPixmap m_thumbnail;
 };
@@ -199,6 +199,8 @@ private:
     QVariant packageThumbnail(simgear::pkg::PackageRef p,
                               const DelegateState& state, bool download = true) const;
 
+    QVariant packagePreviews(simgear::pkg::PackageRef p, const DelegateState &ds) const;
+
     void abandonCurrentScan();
     void refreshPackages();
     
@@ -217,7 +219,7 @@ private:
     simgear::pkg::RootRef m_packageRoot;
     simgear::pkg::PackageList m_packages;
         
-    mutable QHash<QString, QPixmap> m_thumbnailPixmapCache;
+    mutable QHash<QString, QPixmap> m_downloadedPixmapCache;
 };
 
 #endif // of FG_GUI_AIRCRAFT_MODEL

src/GUI/CMakeLists.txt

@@ -117,11 +117,13 @@ if (HAVE_QT)
                             InstallSceneryDialog.cxx
                             EditCustomMPServerDialog.cxx
                             EditCustomMPServerDialog.hxx
+                            PreviewWindow.cpp
+                            PreviewWindow.h
                             ${uic_sources}
                             ${qrc_sources})
 
     set_property(TARGET fglauncher PROPERTY AUTOMOC ON)
-    target_link_libraries(fglauncher Qt5::Core Qt5::Widgets SimGearCore)
+    target_link_libraries(fglauncher Qt5::Core Qt5::Widgets Qt5::Network SimGearCore)
     target_include_directories(fglauncher PRIVATE ${PROJECT_BINARY_DIR}/src/GUI)
 
 

src/GUI/Launcher.ui

@@ -34,7 +34,7 @@
     <item row="0" column="0">
      <widget class="QTabWidget" name="tabWidget">
       <property name="currentIndex">
-                <number>0</number>
+       <number>1</number>
       </property>
       <widget class="QWidget" name="summaryTab">
        <attribute name="title">

src/GUI/QtLauncher.cxx

@@ -69,6 +69,7 @@
 #include "AircraftModel.hxx"
 #include "PathsDialog.hxx"
 #include "EditCustomMPServerDialog.hxx"
+#include "previewwindow.h"
 
 #include <Main/globals.hxx>
 #include <Main/fg_props.hxx>
@@ -854,6 +855,8 @@ QtLauncher::QtLauncher() :
             this, &QtLauncher::onRequestPackageUninstall);
     connect(delegate, &AircraftItemDelegate::cancelDownload,
             this, &QtLauncher::onCancelDownload);
+    connect(delegate, &AircraftItemDelegate::showPreviews,
+            this, &QtLauncher::onShowPreviews);
 
     connect(m_aircraftModel, &AircraftItemModel::aircraftInstallCompleted,
             this, &QtLauncher::onAircraftInstalledCompleted);
@@ -1401,6 +1404,14 @@ void QtLauncher::onRequestPackageUninstall(const QModelIndex& index)
     }
 }
 
+void QtLauncher::onShowPreviews(const QModelIndex &index)
+{
+    QVariant urls = index.data(AircraftPreviewsRole);
+
+    PreviewWindow* previewWindow = new PreviewWindow;
+    previewWindow->setUrls(urls.toList());
+}
+
 void QtLauncher::onCancelDownload(const QModelIndex& index)
 {
     QString pkg = index.data(AircraftPackageIdRole).toString();

src/GUI/QtLauncher_private.hxx

@@ -75,7 +75,7 @@ private slots:
     void onAircraftSelected(const QModelIndex& index);
     void onRequestPackageInstall(const QModelIndex& index);
     void onRequestPackageUninstall(const QModelIndex& index);
-
+    void onShowPreviews(const QModelIndex& index);
     void onCancelDownload(const QModelIndex& index);
 
     void onPopupAircraftHistory();

src/GUI/previewwindow.cpp

@@ -0,0 +1,108 @@
+#include "previewwindow.h"
+
+#include <QPainter>
+#include <QMouseEvent>
+#include <QNetworkReply>
+
+const int BORDER_SIZE = 16;
+
+PreviewWindow::PreviewWindow(QWidget *parent)
+    : QDialog(parent)
+    , m_netAccess(new QNetworkAccessManager(this))
+{
+    setWindowFlags(Qt::Popup);
+    setModal(true);
+
+    m_closeIcon.load(":/preview/close-icon");
+    m_leftIcon.load(":/preview/left-arrow-icon");
+    m_rightIcon.load(":/preview/right-arrow-icon");
+}
+
+void PreviewWindow::setUrls(QVariantList urls)
+{
+    m_cache.clear();
+
+    Q_FOREACH (QVariant v, urls) {
+        QUrl url = v.toUrl();
+        qWarning() << v;
+        m_urls.append(url);
+        QNetworkReply* reply = m_netAccess->get(QNetworkRequest(url));
+        connect(reply, &QNetworkReply::finished, this, &PreviewWindow::onDownloadFinished);
+    }
+}
+
+void PreviewWindow::paintEvent(QPaintEvent *pe)
+{
+    QUrl key = m_urls.at(m_currentPreview);
+    QPixmap pm = m_cache.value(key.toString());
+    if (pm.isNull()) {
+        qWarning() << "null pixmap";
+    }
+
+    QPainter painter(this);
+    painter.fillRect(rect(), Qt::black);
+
+    QRect imgRect = rect().adjusted(BORDER_SIZE, BORDER_SIZE, -BORDER_SIZE, -BORDER_SIZE);
+    painter.drawPixmap(imgRect, pm);
+
+    QRect closeIconRect = m_closeIcon.rect();
+    closeIconRect.moveTopRight(rect().topRight());
+    painter.drawPixmap(closeIconRect, m_closeIcon);
+
+    QRect leftArrowRect = m_leftIcon.rect();
+    unsigned int iconTop = rect().center().y() - (m_leftIcon.size().height() / 2);
+    leftArrowRect.moveTopLeft(QPoint(0, iconTop));
+    painter.drawPixmap(leftArrowRect, m_leftIcon);
+
+    QRect rightArrowRect = m_rightIcon.rect();
+    rightArrowRect.moveTopRight(QPoint(width(), iconTop));
+    painter.drawPixmap(rightArrowRect, m_rightIcon);
+}
+
+void PreviewWindow::mouseReleaseEvent(QMouseEvent *event)
+{
+    QRect closeIconRect = m_closeIcon.rect();
+    closeIconRect.moveTopRight(rect().topRight());
+
+    QRect leftArrowRect = m_leftIcon.rect();
+    unsigned int iconTop = rect().center().y() - (m_leftIcon.size().height() / 2);
+    leftArrowRect.moveTopLeft(QPoint(0, iconTop));
+
+    QRect rightArrowRect = m_rightIcon.rect();
+    rightArrowRect.moveTopRight(QPoint(width(), iconTop));
+
+    if (closeIconRect.contains(event->pos())) {
+        close();
+        deleteLater();
+    }
+
+    if (leftArrowRect.contains(event->pos())) {
+        m_currentPreview = (m_currentPreview - 1) % m_urls.size();
+        update();
+    }
+
+    if (rightArrowRect.contains(event->pos())) {
+        m_currentPreview = (m_currentPreview + 1) % m_urls.size();
+        update();
+    }
+}
+
+void PreviewWindow::onDownloadFinished()
+{
+    QNetworkReply* reply = qobject_cast<QNetworkReply*>(sender());
+
+    QImage img;
+    if (!img.load(reply, nullptr)) {
+        qWarning() << "failed to read image data from" << reply->url();
+        return;
+    }
+
+    m_cache.insert(reply->url().toString(), QPixmap::fromImage(img));
+
+    if (!isVisible()) {
+        QSize winSize(img.width() + BORDER_SIZE * 2, img.height() + BORDER_SIZE * 2);
+        resize(winSize);
+
+        show();
+    }
+}

src/GUI/previewwindow.h

@@ -0,0 +1,39 @@
+#ifndef PREVIEWWINDOW_H
+#define PREVIEWWINDOW_H
+
+#include <QDialog>
+
+#include <QVariant>
+#include <QNetworkAccessManager>
+#include <QMap>
+
+class PreviewWindow : public QDialog
+{
+    Q_OBJECT
+public:
+    explicit PreviewWindow(QWidget *parent = 0);
+
+    void setUrls(QVariantList urls);
+
+signals:
+
+public slots:
+
+protected:
+    virtual void paintEvent(QPaintEvent *pe) override;
+
+    virtual void mouseReleaseEvent(QMouseEvent *event) override;
+
+private:
+    void onDownloadFinished();
+
+
+    unsigned int m_currentPreview = 0;
+    QNetworkAccessManager* m_netAccess;
+    QList<QUrl> m_urls;
+    QMap<QUrl, QPixmap> m_cache;
+
+    QPixmap m_leftIcon, m_rightIcon, m_closeIcon;
+};
+
+#endif // PREVIEWWINDOW_H

src/GUI/resources.qrc

@@ -19,5 +19,11 @@
         <file alias="ndb-large-icon">ndb-large-icon.png</file>
         <file alias="airplane-icon">airplane-icon.png</file>
         <file alias="airport-closed-icon">airport-closed-icon.png</file>
+        <file alias="preview-icon">preview-icon.png</file>
+    </qresource>
+    <qresource prefix="/preview">
+        <file alias="close-icon">preview-close.png</file>
+        <file alias="left-arrow-icon">preview-left-arrow.png</file>
+        <file alias="right-arrow-icon">preview-right-arrow.png</file>
     </qresource>
 </RCC>