I can add shadow to widget:
QGraphicsDropShadowEffect *bodyShadow = new QGraphicsDropShadowEffect;
bodyShadow->setBlurRadius(9.0);
bodyShadow->setColor(QColor(0, 0, 0, 160));
bodyShadow->setOffset(4.0);
ui->widget->setGraphicsEffect(bodyShadow);
But this shadow will be only at left and down. I need shadow around widget. How to add this?
You can create your custom effect. I'll share an implementation that works.
customshadoweffect.h
#ifndef CUSTOMSHADOWEFFECT_H
#define CUSTOMSHADOWEFFECT_H
#include <QGraphicsDropShadowEffect>
#include <QGraphicsEffect>
class CustomShadowEffect : public QGraphicsEffect
{
Q_OBJECT
public:
explicit CustomShadowEffect(QObject *parent = 0);
void draw(QPainter* painter);
QRectF boundingRectFor(const QRectF& rect) const;
inline void setDistance(qreal distance) { _distance = distance; updateBoundingRect(); }
inline qreal distance() const { return _distance; }
inline void setBlurRadius(qreal blurRadius) { _blurRadius = blurRadius; updateBoundingRect(); }
inline qreal blurRadius() const { return _blurRadius; }
inline void setColor(const QColor& color) { _color = color; }
inline QColor color() const { return _color; }
private:
qreal _distance;
qreal _blurRadius;
QColor _color;
};
#endif // CUSTOMSHADOWEFFECT_H
customshadoweffect.cpp
#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));
}
Applying it (to a graphics item):
// ...
CustomShadowEffect *bodyShadow = new CustomShadowEffect();
bodyShadow->setBlurRadius(20.0);
bodyShadow->setDistance(6.0);
bodyShadow->setColor(QColor(0, 0, 0, 80));
item->setGraphicsEffect(bodyShadow);
// ...
Applying it (to a child widget):
//...
CustomShadowEffect *bodyShadow = new CustomShadowEffect();
bodyShadow->setBlurRadius(20.0);
bodyShadow->setDistance(6.0);
bodyShadow->setColor(QColor(0, 0, 0, 80));
ui->widget->setAutoFillBackground(true);
ui->widget->setGraphicsEffect(bodyShadow);
// ...
Result: