From a52404f25829ecf410eab39a6dcfdd69086de2b7 Mon Sep 17 00:00:00 2001
From: laserpants <johannes@isomorphic.co>
Date: Tue, 22 Mar 2016 08:23:04 +0300
Subject: [PATCH] add custom drop shadow class

---
 customshadoweffect.cpp  | 76 +++++++++++++++++++++++++++++++++++++++++
 customshadoweffect.h    | 33 ++++++++++++++++++
 qt-material-widgets.pro |  6 ++--
 3 files changed, 113 insertions(+), 2 deletions(-)
 create mode 100644 customshadoweffect.cpp
 create mode 100644 customshadoweffect.h

diff --git a/customshadoweffect.cpp b/customshadoweffect.cpp
new file mode 100644
index 0000000..d2994e1
--- /dev/null
+++ b/customshadoweffect.cpp
@@ -0,0 +1,76 @@
+#include "customshadoweffect.h"
+#include <QPainter>
+
+CustomShadowEffect::CustomShadowEffect(QObject *parent)
+    : QGraphicsEffect(parent),
+      _distance(4.0),
+      _blurRadius(10.0),
+      _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
+{
+    const qreal delta = blurRadius() + distance();
+    return rect.united(rect.adjusted(-delta, -delta, delta, delta));
+}
diff --git a/customshadoweffect.h b/customshadoweffect.h
new file mode 100644
index 0000000..7a8825c
--- /dev/null
+++ b/customshadoweffect.h
@@ -0,0 +1,33 @@
+/*
+ * http://stackoverflow.com/questions/23718827/qt-shadow-around-window
+ */
+#ifndef CUSTOMSHADOWEFFECT_H
+#define CUSTOMSHADOWEFFECT_H
+
+#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
diff --git a/qt-material-widgets.pro b/qt-material-widgets.pro
index 9cb4fa3..749a782 100644
--- a/qt-material-widgets.pro
+++ b/qt-material-widgets.pro
@@ -31,7 +31,8 @@ SOURCES += main.cpp\
     examples/appbarexamples.cpp \
     examples/iconbuttonexamples.cpp \
     examples/tabsexamples.cpp \
-    examples/tableexamples.cpp
+    examples/tableexamples.cpp \
+    customshadoweffect.cpp
 
 HEADERS  += mainwindow.h \
     style.h \
@@ -58,4 +59,5 @@ HEADERS  += mainwindow.h \
     examples/appbarexamples.h \
     examples/iconbuttonexamples.h \
     examples/tabsexamples.h \
-    examples/tableexamples.h
+    examples/tableexamples.h \
+    customshadoweffect.h