Add address label to request payment QR Code (QT)

In the Receive 'Tab' of the QT wallet, when 'Show'ing a previously requested payment, add a label underneath the QR Code showing the bitcoin address where the funds will go to.

This way the user can be sure that the QR code scanner app the user using is reading the correct bitcoin address, preventing funds to be stolen.

Includes fix for HiDPI screens by @jonasschnelli.

4 files changed, 20 insertions, 7 deletions

diff --git a/src/qt/forms/receiverequestdialog.ui b/src/qt/forms/receiverequestdialog.ui
index 1e484dd9a..4163f4189 100644
--- a/src/qt/forms/receiverequestdialog.ui
+++ b/src/qt/forms/receiverequestdialog.ui
@@ -22,7 +22,7 @@
      <property name="minimumSize">
       <size>
        <width>300</width>
-       <height>300</height>
+       <height>320</height>
       </size>
      </property>
      <property name="toolTip">
diff --git a/src/qt/guiconstants.h b/src/qt/guiconstants.h
index 4b2c10dd4..bab9923d2 100644
--- a/src/qt/guiconstants.h
+++ b/src/qt/guiconstants.h
@@ -43,7 +43,7 @@ static const int TOOLTIP_WRAP_THRESHOLD = 80;
 static const int MAX_URI_LENGTH = 255;
 
 /* QRCodeDialog -- size of exported QR Code image */
-#define EXPORT_IMAGE_SIZE 256
+#define QR_IMAGE_SIZE 300
 
 /* Number of frames in spinner animation */
 #define SPINNER_FRAMES 36
diff --git a/src/qt/receiverequestdialog.cpp b/src/qt/receiverequestdialog.cpp
index a1e9156ee..b13ea3df7 100644
--- a/src/qt/receiverequestdialog.cpp
+++ b/src/qt/receiverequestdialog.cpp
@@ -45,7 +45,7 @@ QImage QRImageWidget::exportImage()
 {
     if(!pixmap())
         return QImage();
-    return pixmap()->toImage().scaled(EXPORT_IMAGE_SIZE, EXPORT_IMAGE_SIZE);
+    return pixmap()->toImage();
 }
 
 void QRImageWidget::mousePressEvent(QMouseEvent *event)
@@ -166,20 +166,32 @@ void ReceiveRequestDialog::update()
                 ui->lblQRCode->setText(tr("Error encoding URI into QR Code."));
                 return;
             }
-            QImage myImage = QImage(code->width + 8, code->width + 8, QImage::Format_RGB32);
-            myImage.fill(0xffffff);
+            QImage qrImage = QImage(code->width + 8, code->width + 8, QImage::Format_RGB32);
+            qrImage.fill(0xffffff);
             unsigned char *p = code->data;
             for (int y = 0; y < code->width; y++)
             {
                 for (int x = 0; x < code->width; x++)
                 {
-                    myImage.setPixel(x + 4, y + 4, ((*p & 1) ? 0x0 : 0xffffff));
+                    qrImage.setPixel(x + 4, y + 4, ((*p & 1) ? 0x0 : 0xffffff));
                     p++;
                 }
             }
             QRcode_free(code);
 
-            ui->lblQRCode->setPixmap(QPixmap::fromImage(myImage).scaled(300, 300));
+            QImage qrAddrImage = QImage(QR_IMAGE_SIZE, QR_IMAGE_SIZE+20, QImage::Format_RGB32);
+            qrAddrImage.fill(0xffffff);
+            QPainter painter(&qrAddrImage);
+            painter.drawImage(0, 0, qrImage.scaled(QR_IMAGE_SIZE, QR_IMAGE_SIZE));
+            QFont font = GUIUtil::fixedPitchFont();
+            font.setPixelSize(12);
+            painter.setFont(font);
+            QRect paddedRect = qrAddrImage.rect();
+            paddedRect.setHeight(QR_IMAGE_SIZE+12);
+            painter.drawText(paddedRect, Qt::AlignBottom|Qt::AlignCenter, info.address);
+            painter.end();
+
+            ui->lblQRCode->setPixmap(QPixmap::fromImage(qrAddrImage));
             ui->btnSaveAs->setEnabled(true);
         }
     }
diff --git a/src/qt/receiverequestdialog.h b/src/qt/receiverequestdialog.h
index 4cab4caff..676745a85 100644
--- a/src/qt/receiverequestdialog.h
+++ b/src/qt/receiverequestdialog.h
@@ -10,6 +10,7 @@
 #include <QDialog>
 #include <QImage>
 #include <QLabel>
+#include <QPainter>
 
 class OptionsModel;