qt: allow dragging, copying and saving QR code

Add context menu and drag handling to QR code widget.

src/qt/forms/receiverequestdialog.ui

@@ -15,7 +15,7 @@
   </property>
   <layout class="QVBoxLayout" name="verticalLayout_3">
    <item>
-    <widget class="QLabel" name="lblQRCode">
+    <widget class="QRImageWidget" name="lblQRCode">
      <property name="sizePolicy">
       <sizepolicy hsizetype="Expanding" vsizetype="Expanding">
        <horstretch>0</horstretch>
@@ -233,6 +233,11 @@
    <extends>QWidget</extends>
    <header>bitcoinamountfield.h</header>
   </customwidget>
+  <customwidget>
+   <class>QRImageWidget</class>
+   <extends>QLabel</extends>
+   <header>receiverequestdialog.h</header>
+  </customwidget>
  </customwidgets>
  <resources/>
  <connections/>

src/qt/receiverequestdialog.cpp

@@ -7,6 +7,7 @@
 #include "optionsmodel.h"
 
 #include <QPixmap>
+#include <QClipboard>
 #if QT_VERSION < 0x050000
 #include <QUrl>
 #endif
@@ -17,6 +18,51 @@
 #include <qrencode.h>
 #endif
 
+QRImageWidget::QRImageWidget(QWidget *parent):
+    QLabel(parent)
+{
+    setContextMenuPolicy(Qt::ActionsContextMenu);
+
+    QAction *saveImageAction = new QAction(tr("&Save Image..."), this);
+    connect(saveImageAction, SIGNAL(triggered()), this, SLOT(saveImage()));
+    addAction(saveImageAction);
+    QAction *copyImageAction = new QAction(tr("&Copy Image"), this);
+    connect(copyImageAction, SIGNAL(triggered()), this, SLOT(copyImage()));
+    addAction(copyImageAction);
+}
+
+QImage QRImageWidget::exportImage()
+{
+    return pixmap()->toImage().scaled(EXPORT_IMAGE_SIZE, EXPORT_IMAGE_SIZE);
+}
+
+void QRImageWidget::mousePressEvent(QMouseEvent *event)
+{
+    if(event->button() == Qt::LeftButton)
+    {
+        QMimeData *mimeData = new QMimeData;
+        mimeData->setImageData(exportImage());
+
+        QDrag *drag = new QDrag(this);
+        drag->setMimeData(mimeData);
+        drag->exec();
+    }
+}
+
+void QRImageWidget::saveImage()
+{
+    QString fn = GUIUtil::getSaveFileName(this, tr("Save QR Code"), QString(), tr("PNG Images (*.png)"));
+    if (!fn.isEmpty())
+    {
+        exportImage().save(fn);
+    }
+}
+
+void QRImageWidget::copyImage()
+{
+    QApplication::clipboard()->setImage(exportImage());
+}
+
 ReceiveRequestDialog::ReceiveRequestDialog(const QString &addr, const QString &label, quint64 amount, const QString &message, QWidget *parent) :
     QDialog(parent),
     ui(new Ui::ReceiveRequestDialog),
@@ -42,6 +88,8 @@ ReceiveRequestDialog::ReceiveRequestDialog(const QString &addr, const QString &l
     ui->lblQRCode->setVisible(false);
 #endif
 
+    connect(ui->btnSaveAs, SIGNAL(clicked()), ui->lblQRCode, SLOT(saveImage()));
+
     genCode();
 }
 
@@ -77,7 +125,7 @@ void ReceiveRequestDialog::genCode()
             ui->lblQRCode->setText(tr("Error encoding URI into QR Code."));
             return;
         }
-        myImage = QImage(code->width + 8, code->width + 8, QImage::Format_RGB32);
+        QImage myImage = QImage(code->width + 8, code->width + 8, QImage::Format_RGB32);
         myImage.fill(0xffffff);
         unsigned char *p = code->data;
         for (int y = 0; y < code->width; y++)
@@ -147,15 +195,6 @@ void ReceiveRequestDialog::on_lnMessage_textChanged()
     genCode();
 }
 
-void ReceiveRequestDialog::on_btnSaveAs_clicked()
-{
-#ifdef USE_QRCODE
-    QString fn = GUIUtil::getSaveFileName(this, tr("Save QR Code"), QString(), tr("PNG Images (*.png)"));
-    if (!fn.isEmpty())
-        myImage.scaled(EXPORT_IMAGE_SIZE, EXPORT_IMAGE_SIZE).save(fn);
-#endif
-}
-
 void ReceiveRequestDialog::updateDisplayUnit()
 {
     if (model)

src/qt/receiverequestdialog.h

@@ -3,12 +3,32 @@
 
 #include <QDialog>
 #include <QImage>
+#include <QLabel>
 
 namespace Ui {
     class ReceiveRequestDialog;
 }
 class OptionsModel;
 
+/* Label widget for QR code. This image can be dragged, dropped, copied and saved
+ * to disk.
+ */
+class QRImageWidget : public QLabel
+{
+    Q_OBJECT
+
+public:
+    explicit QRImageWidget(QWidget *parent = 0);
+    QImage exportImage();
+
+public slots:
+    void saveImage();
+    void copyImage();
+
+protected:
+    virtual void mousePressEvent(QMouseEvent *event);
+};
+
 class ReceiveRequestDialog : public QDialog
 {
     Q_OBJECT
@@ -23,7 +43,6 @@ private slots:
     void on_lnReqAmount_textChanged();
     void on_lnLabel_textChanged();
     void on_lnMessage_textChanged();
-    void on_btnSaveAs_clicked();
 
     void updateDisplayUnit();
 
@@ -31,7 +50,6 @@ private:
     Ui::ReceiveRequestDialog *ui;
     OptionsModel *model;
     QString address;
-    QImage myImage;
 
     void genCode();
     QString getURI();