Added a ScrollingLabel that scrolls on hover when the text doesn't fit.

src/libtomahawk/CMakeLists.txt

@@ -159,6 +159,7 @@ set( libGuiSources
     widgets/RecentPlaylistsModel.cpp
     widgets/RecentlyPlayedPlaylistsModel.cpp
     widgets/ScriptCollectionHeader.cpp
+    widgets/ScrollingLabel.cpp
     widgets/SearchWidget.cpp
     widgets/SeekSlider.cpp
     widgets/SourceTreePopupDialog.cpp

src/libtomahawk/playlist/ColumnViewPreviewWidget.cpp

@@ -21,6 +21,7 @@
 #include "ColumnView.h"
 #include "widgets/PlayableCover.h"
 #include "widgets/QueryLabel.h"
+#include "widgets/ScrollingLabel.h"
 #include "utils/Logger.h"
 #include "Source.h"
 #include "utils/TomahawkUtilsGui.h"
@@ -66,12 +67,13 @@ ColumnViewPreviewWidget::ColumnViewPreviewWidget( ColumnView* parent )
     mainLayout->addSpacing( 16 );
 #endif
 
-    m_trackLabel = new QLabel( this );
-    m_trackLabel->setAlignment( Qt::AlignCenter );
+    m_trackLabel = new ScrollingLabel( this );
+    //m_trackLabel->setAlignment( Qt::AlignCenter );
     QFont font;
     font.setPointSize( TomahawkUtils::defaultFontSize() + 9 );
     font.setBold( true );
     m_trackLabel->setFont( font );
+    m_trackLabel->setFixedHeight( QFontMetrics( font ).height() + 6 );
     mainLayout->addWidget( m_trackLabel );
 
     m_artistLabel = new QueryLabel( this );

src/libtomahawk/playlist/ColumnViewPreviewWidget.h

@@ -28,6 +28,7 @@ class ColumnView;
 class QueryLabel;
 class PlayableCover;
 class QLabel;
+class ScrollingLabel;
 
 class DLLEXPORT ColumnViewPreviewWidget : public QWidget
 {
@@ -66,7 +67,7 @@ private:
     QLabel* m_yearLabel;
     QLabel* m_yearValue;
 
-    QLabel* m_trackLabel;
+    ScrollingLabel* m_trackLabel;
 
     QueryLabel* m_artistLabel;
 };

src/libtomahawk/widgets/ScrollingLabel.cpp

@@ -0,0 +1,191 @@
+/* === This file is part of Tomahawk Player - <http://tomahawk-player.org> ===
+ *
+ *   Copyright 2014, Teo Mrnjavac <teo@kde.org>
+ *
+ *   Tomahawk 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 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   Tomahawk 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 Tomahawk. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "ScrollingLabel.h"
+
+#include "utils/DpiScaler.h"
+
+#include <QPainter>
+
+
+ScrollingLabel::ScrollingLabel( QWidget* parent)
+    : QWidget( parent )
+    , m_scrollPos( 0 )
+    , m_isMouseOver( false )
+{
+    m_staticText.setTextFormat( Qt::PlainText );
+
+    setFixedHeight( fontMetrics().height() );
+    m_leftMargin = height() / 3;
+
+    m_separator = QString::fromUtf8( "    \u26AB    " );
+
+    connect( &m_timer, SIGNAL( timeout() ), this, SLOT( onTimerTimeout() ) );
+    m_timer.setInterval( 10 );
+}
+
+
+QString
+ScrollingLabel::text() const
+{
+    return m_text;
+}
+
+
+void
+ScrollingLabel::setText( QString text )
+{
+    m_text = text;
+    updateText();
+    update();
+}
+
+
+void
+ScrollingLabel::updateText()
+{
+    m_timer.stop();
+
+    m_singleTextWidth = fontMetrics().width( m_text );
+    m_scrollEnabled = ( m_singleTextWidth > width() - m_leftMargin );
+
+    m_scrollPos = -64;
+
+    if ( m_scrollEnabled && m_isMouseOver )
+    {
+        m_staticText.setText( m_text + m_separator );
+        m_timer.start();
+    }
+    else
+        m_staticText.setText( m_text );
+
+    m_staticText.prepare( QTransform(), font() );
+    m_wholeTextSize = QSize( fontMetrics().width( m_staticText.text() ),
+                             fontMetrics().height() );
+}
+
+
+void
+ScrollingLabel::paintEvent( QPaintEvent* )
+{
+    QPainter p( this );
+
+    if ( m_scrollEnabled )
+    {
+        m_buffer.fill( qRgba(0, 0, 0, 0) );
+        QPainter pb( &m_buffer );
+        pb.setPen( p.pen() );
+        pb.setFont( p.font() );
+
+        int x = qMin( -m_scrollPos, 0 ) + m_leftMargin;
+        while ( x < width() )
+        {
+            pb.drawStaticText( QPointF( x, ( height() - m_wholeTextSize.height() ) / 2 ) + QPoint( 2, 2 ), m_staticText );
+            x += m_wholeTextSize.width();
+        }
+
+        TomahawkUtils::DpiScaler s( this );
+        //Apply Alpha Channel
+        pb.setCompositionMode( QPainter::CompositionMode_DestinationIn );
+        pb.setClipRect( width() - s.scaledX( 15 ),
+                        0,
+                        s.scaledX( 15 ),
+                        height() );
+        pb.drawImage( 0, 0, m_alphaChannel );
+        pb.setClipRect( 0, 0, s.scaledX( 15 ), height() );
+        //initial situation: don't apply alpha channel in the left half of the image at all; apply it more and more until scrollPos gets positive
+        if ( m_scrollPos < 0 )
+            pb.setOpacity( (qreal)( qMax( -s.scaledX( 8 ), m_scrollPos ) + s.scaledX( 8 ) ) / s.scaledX( 8 ) );
+        pb.drawImage( 0, 0, m_alphaChannel );
+
+        //pb.end();
+        p.drawImage( 0, 0, m_buffer );
+    }
+    else
+    {
+        if ( m_wholeTextSize.width() > width() - 2*m_leftMargin )
+        {
+            p.drawStaticText( QPointF( m_leftMargin, ( height() - m_wholeTextSize.height() ) / 2 ),
+                              m_staticText );
+        }
+        else
+        {
+            p.drawStaticText( QPointF( ( width() - m_wholeTextSize.width() ) / 2.,
+                                       ( height() - m_wholeTextSize.height() ) / 2. ),
+                              m_staticText );
+        }
+    }
+}
+
+
+void
+ScrollingLabel::resizeEvent( QResizeEvent* )
+{
+    //From limmes@StackOverflow
+    //When the widget is resized, we need to update the alpha channel.
+    m_alphaChannel = QImage( size(), QImage::Format_ARGB32_Premultiplied );
+    m_buffer = QImage( size(), QImage::Format_ARGB32_Premultiplied );
+
+    //Create Alpha Channel:
+    if ( width() >  64 )
+    {
+        //create first scanline
+        QRgb* scanline1 = (QRgb*)m_alphaChannel.scanLine( 0 );
+        for ( int x = 1; x < 16; ++x )
+            scanline1[ x - 1 ] = scanline1[ width() - x ] = qRgba( 0, 0, 0, x << 4 );
+        for ( int x = 15; x < width() - 15; ++x )
+            scanline1[ x ] = qRgb( 0, 0, 0 );
+        //copy scanline to the other ones
+        for ( int y = 1; y < height(); ++y )
+            memcpy( m_alphaChannel.scanLine( y ), (uchar*)scanline1, width() * 4 );
+    }
+    else
+        m_alphaChannel.fill( qRgb( 0, 0, 0 ) );
+
+
+    //Update scrolling state
+    bool newScrollEnabled = ( m_singleTextWidth > width() - m_leftMargin );
+    if( newScrollEnabled != m_scrollEnabled )
+        updateText();
+}
+
+
+void
+ScrollingLabel::enterEvent( QEvent* )
+{
+    m_isMouseOver = true;
+    updateText();
+    update();
+}
+
+
+void
+ScrollingLabel::leaveEvent( QEvent* )
+{
+    m_isMouseOver = false;
+    updateText();
+    update();
+}
+
+
+void
+ScrollingLabel::onTimerTimeout()
+{
+    m_scrollPos = ( m_scrollPos + 1 ) % m_wholeTextSize.width();
+    update();
+}

src/libtomahawk/widgets/ScrollingLabel.h

@@ -0,0 +1,64 @@
+/* === This file is part of Tomahawk Player - <http://tomahawk-player.org> ===
+ *
+ *   Copyright 2014, Teo Mrnjavac <teo@kde.org>
+ *
+ *   Tomahawk 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 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   Tomahawk 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 Tomahawk. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef SCROLLINGLABEL_H
+#define SCROLLINGLABEL_H
+
+#include <QWidget>
+#include <QStaticText>
+#include <QTimer>
+
+
+class ScrollingLabel : public QWidget
+{
+    Q_OBJECT
+    Q_PROPERTY( QString text READ text WRITE setText )
+
+public:
+    explicit ScrollingLabel( QWidget* parent = 0 );
+
+public slots:
+    QString text() const;
+    void setText( QString text );
+
+protected:
+    virtual void paintEvent( QPaintEvent* );
+    virtual void resizeEvent( QResizeEvent* );
+    virtual void enterEvent( QEvent* );
+    virtual void leaveEvent( QEvent* );
+
+private:
+    bool m_isMouseOver;
+    void updateText();
+    QString m_text;
+    QString m_separator;
+    QStaticText m_staticText;
+    int m_singleTextWidth;
+    QSize m_wholeTextSize;
+    int m_leftMargin;
+    bool m_scrollEnabled;
+    int m_scrollPos;
+    QImage m_alphaChannel;
+    QImage m_buffer;
+    QTimer m_timer;
+
+private slots:
+    virtual void onTimerTimeout();
+};
+
+#endif // SCROLLINGLABEL_H