Pan with Middle mouse button in remote view

Allow panning with middle mouse button regardless of the current
interaction mode.

This reduces the need to switch the interaction mode in the remote view
when the area where the user wants to look at is out of the view.

ui/remoteviewwidget.cpp

@@ -1029,6 +1029,15 @@ void RemoteViewWidget::mousePressEvent(QMouseEvent *event)
 {
     m_currentMousePosition = mapToSource(QPointF(event->pos()));
 
+    // Initiate the middle mouse button panning that works regarless of the interaction mode
+    if(event->button() == Qt::MiddleButton) {
+        m_mouseDownPosition = event->pos() - QPoint(m_x, m_y);
+        m_cursorBeforeMmbPan = cursor();
+        setCursor(Qt::ClosedHandCursor);
+        QWidget::mousePressEvent(event);
+        return;
+    }
+
     switch (m_interactionMode) {
     case NoInteraction:
         break;
@@ -1075,12 +1084,29 @@ void RemoteViewWidget::mouseReleaseEvent(QMouseEvent *event)
 {
     m_currentMousePosition = mapToSource(QPointF(event->pos()));
 
+    if (event->button() == Qt::MiddleButton) {
+        // In view interaction, set the open hand cursor if the user hasn't
+        // initiated LMB panning in the meantime. Otherwise, bring back the
+        // original cursor.
+        if(m_interactionMode == ViewInteraction) {
+            if(!(event->buttons() & Qt::LeftButton)) {
+                setCursor(Qt::OpenHandCursor);
+            }
+        } else {
+            setCursor(m_cursorBeforeMmbPan);
+        }
+        QWidget::mouseReleaseEvent(event);
+        return;
+    }
+
     switch (m_interactionMode) {
     case NoInteraction:
     case ElementPicking:
         break;
     case ViewInteraction:
-        setCursor(Qt::OpenHandCursor);
+        if (!(event->buttons() & Qt::MiddleButton)) {
+            setCursor(Qt::OpenHandCursor);
+        }
         break;
     case Measuring:
         if (event->buttons() & Qt::LeftButton)
@@ -1122,6 +1148,17 @@ void RemoteViewWidget::mouseMoveEvent(QMouseEvent *event)
 {
     m_currentMousePosition = mapToSource(QPointF(event->pos()));
 
+    auto handlePan = [this](QPoint mousePos) {
+        m_x = mousePos.x() - m_mouseDownPosition.x();
+        m_y = mousePos.y() - m_mouseDownPosition.y();
+        clampPanPosition();
+        updateUserViewport();
+    };
+
+    if (event->buttons() & Qt::MiddleButton) {
+        handlePan(event->pos());
+    }
+
     switch (m_interactionMode) {
     case NoInteraction:
     case ElementPicking:
@@ -1130,18 +1167,17 @@ void RemoteViewWidget::mouseMoveEvent(QMouseEvent *event)
         if (event->buttons() != Qt::LeftButton) {
             break;
         }
-        m_x = event->x() - m_mouseDownPosition.x();
-        m_y = event->y() - m_mouseDownPosition.y();
-        clampPanPosition();
-        updateUserViewport();
+        handlePan(event->pos());
         break;
     case Measuring:
         if (event->buttons() & Qt::LeftButton) {
             m_measurementEndPosition = mapToSource(event->pos());
         }
         break;
     case InputRedirection:
-        sendMouseEvent(event);
+        if (!(event->buttons() & Qt::MiddleButton)) {
+            sendMouseEvent(event);
+        }
         break;
     case ColorPicking:
         // label should be always fully inside the remoteviewwidget

ui/remoteviewwidget.h

@@ -229,6 +229,7 @@ private slots:
     QPointF m_currentMousePosition; // in view coordinates
     QPoint m_measurementStartPosition; // in source coordinates
     QPoint m_measurementEndPosition; // in source coordinates
+    QCursor m_cursorBeforeMmbPan;
     bool m_hasMeasurement;
     ObjectIdsFilterProxyModel *m_pickProxyModel;
     VisibilityFilterProxyModel *m_invisibleItemsProxyModel;