#include "customshadoweffect.h"

#include <QPainter>

// #include <QGraphicsEffect>



CustomShadowEffect::CustomShadowEffect ( QObject* parent ) :

    QGraphicsEffect ( parent ),

    _distance ( 4.0f ),

    _blurRadius ( 10.0f ),

    _color ( 0, 0, 0, 80 )

{

}



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



void CustomShadowEffect::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 CustomShadowEffect::boundingRectFor ( const QRectF& rect ) const

{

    qreal delta = blurRadius() + distance();

    return rect.united ( rect.adjusted ( -delta, -delta, delta, delta ) );

}