Add QGraphicsOpacityEffect.

This is a common effect that many many customers have asked for.

Reviewed-by: Samuel

3 files changed, 92 insertions, 0 deletions

diff --git a/src/gui/effects/qgraphicseffect.cpp b/src/gui/effects/qgraphicseffect.cpp
index 949922a..0653204 100644
--- a/src/gui/effects/qgraphicseffect.cpp
+++ b/src/gui/effects/qgraphicseffect.cpp
@@ -64,6 +64,7 @@
     \o QGraphicsPixelizeEffect - pixelizes the item with any pixel size
     \o QGraphicsBlurEffect - blurs the item by a given radius
     \o QGraphicsDropShadowEffect - renders a dropshadow behind the item
+    \o QGraphicsBlurEffect - renders the item with an opacity
     \endlist
 
     If all you want is to add an effect to an item, you should visit the
@@ -568,5 +569,61 @@ void QGraphicsDropShadowEffect::draw(QPainter *painter, QGraphicsEffectSource *s
     painter->setWorldTransform(restoreTransform);
 }
 
+QGraphicsOpacityEffect::QGraphicsOpacityEffect(QObject *parent)
+    : QGraphicsEffect(*new QGraphicsOpacityEffectPrivate, parent)
+{
+}
+
+QGraphicsOpacityEffect::~QGraphicsOpacityEffect()
+{
+}
+
+qreal QGraphicsOpacityEffect::opacity() const
+{
+    Q_D(const QGraphicsOpacityEffect);
+    return d->opacity;
+}
+
+void QGraphicsOpacityEffect::setOpacity(qreal opacity)
+{
+    Q_D(QGraphicsOpacityEffect);
+    if (qFuzzyCompare(d->opacity, opacity))
+        return;
+    d->opacity = opacity;
+    emit opacityChanged(opacity);
+}
+
+void QGraphicsOpacityEffect::draw(QPainter *painter, QGraphicsEffectSource *source)
+{
+    Q_D(QGraphicsOpacityEffect);
+
+    // Transparent; nothing to draw.
+    if (qFuzzyIsNull(d->opacity))
+        return;
+
+    // Opaque; draw directly without going through a pixmap.
+    if (qFuzzyIsNull(d->opacity - 1)) {
+        source->draw(painter);
+        return;
+    }
+
+    painter->save();
+    painter->setOpacity(d->opacity);
+
+    QPoint offset;
+    if (source->isPixmap()) {
+        // No point in drawing in device coordinates (pixmap will be scaled anyways).
+        const QPixmap pixmap = source->pixmap(Qt::LogicalCoordinates, &offset);
+        painter->drawPixmap(offset, pixmap);
+    } else {
+        // Draw pixmap in device coordinates to avoid pixmap scaling;
+        const QPixmap pixmap = source->pixmap(Qt::DeviceCoordinates, &offset);
+        painter->setWorldTransform(QTransform());
+        painter->drawPixmap(offset, pixmap);
+    }
+
+    painter->restore();
+}
+
 QT_END_NAMESPACE
 
diff --git a/src/gui/effects/qgraphicseffect.h b/src/gui/effects/qgraphicseffect.h
index 99d8548..18ae3cf 100644
--- a/src/gui/effects/qgraphicseffect.h
+++ b/src/gui/effects/qgraphicseffect.h
@@ -269,6 +269,31 @@ private:
     Q_DISABLE_COPY(QGraphicsDropShadowEffect)
 };
 
+class QGraphicsOpacityEffectPrivate;
+class Q_GUI_EXPORT QGraphicsOpacityEffect: public QGraphicsEffect
+{
+    Q_OBJECT
+    Q_PROPERTY(int opacity READ opacity WRITE setOpacity NOTIFY opacityChanged)
+public:
+    QGraphicsOpacityEffect(QObject *parent = 0);
+    ~QGraphicsOpacityEffect();
+
+    qreal opacity() const;
+
+public Q_SLOTS:
+    void setOpacity(qreal opacity);
+
+Q_SIGNALS:
+    void opacityChanged(qreal opacity);
+
+protected:
+    void draw(QPainter *painter, QGraphicsEffectSource *source);
+
+private:
+    Q_DECLARE_PRIVATE(QGraphicsOpacityEffect)
+    Q_DISABLE_COPY(QGraphicsOpacityEffect)
+};
+
 QT_END_NAMESPACE
 
 QT_END_HEADER
diff --git a/src/gui/effects/qgraphicseffect_p.h b/src/gui/effects/qgraphicseffect_p.h
index 35f2d40..f5d0e80 100644
--- a/src/gui/effects/qgraphicseffect_p.h
+++ b/src/gui/effects/qgraphicseffect_p.h
@@ -160,6 +160,16 @@ public:
     QPixmapDropShadowFilter *filter;
 };
 
+class QGraphicsOpacityEffectPrivate : public QGraphicsEffectPrivate
+{
+    Q_DECLARE_PUBLIC(QGraphicsOpacityEffect)
+public:
+    QGraphicsOpacityEffectPrivate() : opacity(0.7) {}
+    ~QGraphicsOpacityEffectPrivate() {}
+
+    qreal opacity;
+};
+
 QT_END_NAMESPACE
 
 #endif // QGRAPHICSEFFECT_P_H