shadow_effect.cpp

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#include "gui/graphics_effects/shadow_effect.h"
 
#include <QPainter>
 
QT_BEGIN_NAMESPACE
extern Q_WIDGETS_EXPORT void qt_blurImage(QPainter* p, QImage& blurImage, qreal radius, bool quality, bool alphaOnly, int transposed = 0);
QT_END_NAMESPACE
 
namespace hal
{
    ShadowEffect::ShadowEffect(QObject* parent) : QGraphicsEffect(parent), mDistance(4.0f), mBlurRadius(10.0f), mColor(0, 0, 0, 80)
    {
    }
 
    void ShadowEffect::draw(QPainter* painter)
    {
        // if nothing to show outside the item, just draw source
        if ((blurRadius() + distance()) <= 0)
        {
            drawSource(painter);
            return;
        }
 
        PixmapPadMode mode = QGraphicsEffect::PadToEffectiveBoundingRect;
        QPoint offset;
        const QPixmap px = sourcePixmap(Qt::DeviceCoordinates, &offset, mode);
 
        // return if no source
        if (px.isNull())
            return;
 
        // save world transform
        QTransform restoreTransform = painter->worldTransform();
        painter->setWorldTransform(QTransform());
 
        // Calculate size for the background image
        QSize szi(px.size().width() + 2 * distance(), px.size().height() + 2 * distance());
 
        QImage tmp(szi, QImage::Format_ARGB32_Premultiplied);
        QPixmap scaled = px.scaled(szi);
        tmp.fill(0);
        QPainter tmpPainter(&tmp);
        tmpPainter.setCompositionMode(QPainter::CompositionMode_Source);
        tmpPainter.drawPixmap(QPointF(-distance(), -distance()), scaled);
        tmpPainter.end();
 
        // blur the alpha channel
        QImage blurred(tmp.size(), QImage::Format_ARGB32_Premultiplied);
        blurred.fill(0);
        QPainter blurPainter(&blurred);
        qt_blurImage(&blurPainter, tmp, blurRadius(), false, true);
        blurPainter.end();
 
        tmp = blurred;
 
        // blacken the image...
        tmpPainter.begin(&tmp);
        tmpPainter.setCompositionMode(QPainter::CompositionMode_SourceIn);
        tmpPainter.fillRect(tmp.rect(), color());
        tmpPainter.end();
 
        // draw the blurred shadow...
        painter->drawImage(offset, tmp);
 
        // draw the actual pixmap...
        painter->drawPixmap(offset, px, QRectF());
 
        // restore world transform
        painter->setWorldTransform(restoreTransform);
    }
 
    QRectF ShadowEffect::boundingRectFor(const QRectF& rect) const
    {
        qreal delta = blurRadius() + distance();
        return rect.united(rect.adjusted(-delta, -delta, delta, delta));
    }
}