Blur the song/artist info panes while waiting for info to load

src/songinfo/songinfobase.cpp

@@ -61,7 +61,7 @@ SongInfoBase::SongInfoBase(NetworkAccessManager* network, QWidget* parent)
 }
 
 void SongInfoBase::Clear() {
-  fader_->Start();
+  fader_->StartFade();
 
   qDeleteAll(widgets_);
   widgets_.clear();
@@ -128,6 +128,7 @@ void SongInfoBase::MaybeUpdate(const Song& metadata) {
 }
 
 void SongInfoBase::Update(const Song& metadata) {
+  fader_->StartBlur();
   current_request_id_ = fetcher_->FetchInfo(metadata);
 }
 

src/widgets/widgetfadehelper.cpp

@@ -20,22 +20,38 @@
 #include <QTimeLine>
 #include <QtDebug>
 
+// Exported by QtGui
+void qt_blurImage(QPainter *p, QImage &blurImage, qreal radius, bool quality, bool alphaOnly, int transposed = 0);
+
 WidgetFadeHelper::WidgetFadeHelper(QWidget* parent, int msec)
   : QWidget(parent),
     parent_(parent),
-    timeline_(new QTimeLine(msec, this))
+    blur_timeline_(new QTimeLine(msec, this)),
+    fade_timeline_(new QTimeLine(msec, this))
 {
   setAttribute(Qt::WA_TransparentForMouseEvents);
 
-  connect(timeline_, SIGNAL(valueChanged(qreal)), SLOT(update()));
-  connect(timeline_, SIGNAL(finished()), SLOT(hide()));
+  connect(blur_timeline_, SIGNAL(valueChanged(qreal)), SLOT(update()));
+  connect(fade_timeline_, SIGNAL(valueChanged(qreal)), SLOT(update()));
+  connect(fade_timeline_, SIGNAL(finished()), SLOT(FadeFinished()));
 
   hide();
 }
 
-void WidgetFadeHelper::Start() {
+void WidgetFadeHelper::StartBlur() {
   // Take a "screenshot" of the window
-  pixmap_ = QPixmap::grabWidget(parent_);
+  original_pixmap_ = QPixmap::grabWidget(parent_);
+  QImage original_image = original_pixmap_.toImage();
+
+  // Blur it
+  QImage blurred(original_image.size(), QImage::Format_ARGB32_Premultiplied);
+  blurred.fill(Qt::transparent);
+
+  QPainter blur_painter(&blurred);
+  qt_blurImage(&blur_painter, original_image, 10.0, true, false);
+  blur_painter.end();
+
+  blurred_pixmap_ = QPixmap::fromImage(blurred);
 
   // Cover the parent
   resize(parent_->size());
@@ -43,12 +59,45 @@ void WidgetFadeHelper::Start() {
   show();
 
   // Start the timeline
-  timeline_->start();
+  blur_timeline_->stop();
+  blur_timeline_->start();
+}
+
+void WidgetFadeHelper::StartFade() {
+  if (blur_timeline_->state() == QTimeLine::Running) {
+    // Blur timeline is still running, so we need render the current state
+    // into a new pixmap.
+    QPixmap pixmap(original_pixmap_);
+    QPainter painter(&pixmap);
+    painter.setOpacity(blur_timeline_->currentValue());
+    painter.drawPixmap(0, 0, blurred_pixmap_);
+    painter.end();
+    blurred_pixmap_ = pixmap;
+  }
+  blur_timeline_->stop();
+  original_pixmap_ = QPixmap();
+
+  // Start the timeline
+  fade_timeline_->stop();
+  fade_timeline_->start();
 }
 
 void WidgetFadeHelper::paintEvent(QPaintEvent* ) {
   QPainter p(this);
 
-  p.setOpacity(1.0 - timeline_->currentValue());
-  p.drawPixmap(0, 0, pixmap_);
+  if (fade_timeline_->state() != QTimeLine::Running) {
+    // We're fading in the blur
+    p.setOpacity(blur_timeline_->currentValue());
+  } else {
+    // Fading out the blur into the new image
+    p.setOpacity(1.0 - fade_timeline_->currentValue());
+  }
+
+  p.drawPixmap(0, 0, blurred_pixmap_);
+}
+
+void WidgetFadeHelper::FadeFinished() {
+  hide();
+  original_pixmap_ = QPixmap();
+  blurred_pixmap_ = QPixmap();
 }

src/widgets/widgetfadehelper.h

@@ -28,16 +28,22 @@ public:
   WidgetFadeHelper(QWidget* parent, int msec = 500);
 
 public slots:
-  void Start();
+  void StartBlur();
+  void StartFade();
 
 protected:
   void paintEvent(QPaintEvent*);
 
+private slots:
+  void FadeFinished();
+
 private:
   QWidget* parent_;
-  QTimeLine* timeline_;
+  QTimeLine* blur_timeline_;
+  QTimeLine* fade_timeline_;
 
-  QPixmap pixmap_;
+  QPixmap original_pixmap_;
+  QPixmap blurred_pixmap_;
 };
 
 #endif // WIDGETFADEHELPER_H