Use flexible font size for QRCode image address

src/qt/guiutil.cpp

@@ -995,6 +995,18 @@ QString formatBytes(uint64_t bytes)
     return QString(QObject::tr("%1 GB")).arg(bytes / 1024 / 1024 / 1024);
 }
 
+qreal calculateIdealFontSize(int width, const QString& text, QFont font, qreal minPointSize, qreal font_size) {
+    while(font_size >= minPointSize) {
+        font.setPointSizeF(font_size);
+        QFontMetrics fm(font);
+        if (fm.width(text) < width) {
+            break;
+        }
+        font_size -= 0.5;
+    }
+    return font_size;
+}
+
 void ClickableLabel::mouseReleaseEvent(QMouseEvent *event)
 {
     Q_EMIT clicked(event->pos());

src/qt/guiutil.h

@@ -201,6 +201,8 @@ namespace GUIUtil
 
     QString formatBytes(uint64_t bytes);
 
+    qreal calculateIdealFontSize(int width, const QString& text, QFont font, qreal minPointSize = 4, qreal startPointSize = 14);
+
     class ClickableLabel : public QLabel
     {
         Q_OBJECT

src/qt/receiverequestdialog.cpp

@@ -183,9 +183,13 @@ void ReceiveRequestDialog::update()
             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();
+
+            // calculate ideal font size
+            qreal font_size = GUIUtil::calculateIdealFontSize(paddedRect.width() - 20, info.address, font);
+            font.setPointSizeF(font_size);
+
+            painter.setFont(font);
             paddedRect.setHeight(QR_IMAGE_SIZE+12);
             painter.drawText(paddedRect, Qt::AlignBottom|Qt::AlignCenter, info.address);
             painter.end();