navigator view draw viewport rect

graphicsview.cpp

@@ -104,6 +104,7 @@ void GraphicsView::resetTransform()
 
 void GraphicsView::zoomView(qreal scaleFactor)
 {
+    m_enableFitInView = false;
     m_scaleFactor *= scaleFactor;
     reapplyViewTransform();
     emit navigatorViewRequired(!isThingSmallerThanWindowWith(transform()), m_rotateAngle);
@@ -175,12 +176,9 @@ void GraphicsView::mouseReleaseEvent(QMouseEvent *event)
 
 void GraphicsView::wheelEvent(QWheelEvent *event)
 {
-    m_enableFitInView = false;
-    if (event->delta() > 0) {
-        zoomView(1.25);
-    } else {
-        zoomView(0.8);
-    }
+    event->ignore();
+
+    return QGraphicsView::wheelEvent(event);
 }
 
 void GraphicsView::resizeEvent(QResizeEvent *event)
@@ -243,6 +241,17 @@ void GraphicsView::dropEvent(QDropEvent *event)
     }
 }
 
+void GraphicsView::paintEvent(QPaintEvent *event)
+{
+    // A little dirty hack way to get the viewport "pan" event
+    // but still doesn't works well with gif which scaled up bigger than the window.
+    if (event->rect() == this->rect() && !isThingSmallerThanWindowWith(transform())) {
+        emit viewportRectChanged();
+//        qDebug() << "paintEvent" << event << QObject::sender();
+    }
+    return QGraphicsView::paintEvent(event);
+}
+
 bool GraphicsView::isThingSmallerThanWindowWith(const QTransform &transform) const
 {
     return rect().size().expandedTo(transform.mapRect(sceneRect()).size().toSize())

graphicsview.h

@@ -33,6 +33,7 @@ public:
 
 signals:
     void navigatorViewRequired(bool required, qreal angle);
+    void viewportRectChanged();
 
 public slots:
     void toggleCheckerboard();
@@ -48,6 +49,8 @@ private:
     void dragMoveEvent(QDragMoveEvent *event) override;
     void dropEvent(QDropEvent *event) override;
 
+    void paintEvent(QPaintEvent *event) override;
+
     bool isThingSmallerThanWindowWith(const QTransform &transform) const;
     bool shouldIgnoreMousePressMoveEvent(const QMouseEvent *event) const;
     void setCheckerboardEnabled(bool enabled);

mainwindow.cpp

@@ -48,6 +48,7 @@ MainWindow::MainWindow(QWidget *parent) :
     m_gv = new NavigatorView(this);
     m_gv->setFixedSize(250, 160);
     m_gv->setScene(scene);
+    m_gv->setMainView(m_graphicsView);
     m_gv->fitInView(m_gv->sceneRect(), Qt::KeepAspectRatio);
 
     connect(m_graphicsView, &GraphicsView::navigatorViewRequired,
@@ -58,6 +59,9 @@ MainWindow::MainWindow(QWidget *parent) :
         m_gv->setVisible(required);
     });
 
+    connect(m_graphicsView, &GraphicsView::viewportRectChanged,
+            m_gv, &NavigatorView::updateMainViewportRegion);
+
     m_closeButton = new QPushButton(m_graphicsView);
     m_closeButton->setFlat(true);
     m_closeButton->setFixedSize(50, 50);
@@ -211,6 +215,15 @@ void MainWindow::mouseDoubleClickEvent(QMouseEvent *event)
     return QMainWindow::mouseDoubleClickEvent(event);
 }
 
+void MainWindow::wheelEvent(QWheelEvent *event)
+{
+    if (event->delta() > 0) {
+        m_graphicsView->zoomView(1.25);
+    } else {
+        m_graphicsView->zoomView(0.8);
+    }
+}
+
 void MainWindow::resizeEvent(QResizeEvent *event)
 {
     updateWidgetsPosition();

mainwindow.h

@@ -33,6 +33,7 @@ protected slots:
     void mouseMoveEvent(QMouseEvent *event) override;
     void mouseReleaseEvent(QMouseEvent *event) override;
     void mouseDoubleClickEvent(QMouseEvent *event) override;
+    void wheelEvent(QWheelEvent *event) override;
     void resizeEvent(QResizeEvent *event) override;
 
     bool nativeEvent(const QByteArray& eventType, void* message, long* result) override;

navigatorview.cpp

@@ -1,9 +1,13 @@
 #include "navigatorview.h"
 
+#include "graphicsview.h"
+
 #include <QMouseEvent>
+#include <QDebug>
 
 NavigatorView::NavigatorView(QWidget *parent)
     : QGraphicsView (parent)
+    , m_viewportRegion(this->rect())
 {
     setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
     setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
@@ -11,8 +15,31 @@ NavigatorView::NavigatorView(QWidget *parent)
                   "border-radius: 3px;");
 }
 
+// doesn't take or manage its ownership
+void NavigatorView::setMainView(GraphicsView *mainView)
+{
+    m_mainView = mainView;
+}
+
+void NavigatorView::updateMainViewportRegion()
+{
+    if (m_mainView != nullptr) {
+        m_viewportRegion = mapFromScene(m_mainView->mapToScene(m_mainView->rect()));
+        qDebug() << m_mainView->rect() << m_mainView->mapToScene(m_mainView->rect()) << m_viewportRegion;
+    }
+}
+
 void NavigatorView::wheelEvent(QWheelEvent *event)
 {
     event->ignore();
     return QGraphicsView::wheelEvent(event);
 }
+
+void NavigatorView::paintEvent(QPaintEvent *event)
+{
+    QGraphicsView::paintEvent(event);
+
+    QPainter painter(viewport());
+    painter.setPen(QPen(Qt::gray, 2));
+    painter.drawRect(m_viewportRegion.boundingRect());
+}

navigatorview.h

@@ -3,14 +3,24 @@
 
 #include <QGraphicsView>
 
+class GraphicsView;
 class NavigatorView : public QGraphicsView
 {
     Q_OBJECT
 public:
     NavigatorView(QWidget *parent = nullptr);
 
+    void setMainView(GraphicsView *mainView);
+
+public slots:
+    void updateMainViewportRegion();
+
 private:
     void wheelEvent(QWheelEvent *event) override;
+    void paintEvent(QPaintEvent *event) override;
+
+    QPolygon m_viewportRegion;
+    QGraphicsView *m_mainView = nullptr;
 };
 
 #endif // NAVIGATORVIEW_H