From 038cb3b97393ede6e0dc8d9e788108265b58bfd3 Mon Sep 17 00:00:00 2001
From: Jon Beniston <jon@beniston.com>
Date: Tue, 20 Dec 2022 11:31:01 +0000
Subject: [PATCH] Add pinch gesture to GraphicsViewZoom

---
 sdrgui/gui/graphicsviewzoom.cpp | 17 +++++++++++++++++
 sdrgui/gui/graphicsviewzoom.h   |  4 ++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/sdrgui/gui/graphicsviewzoom.cpp b/sdrgui/gui/graphicsviewzoom.cpp
index a210cfb07..4ab6daca5 100644
--- a/sdrgui/gui/graphicsviewzoom.cpp
+++ b/sdrgui/gui/graphicsviewzoom.cpp
@@ -18,6 +18,9 @@
 #include <QMouseEvent>
 #include <QApplication>
 #include <QScrollBar>
+#include <QGestureEvent>
+#include <QPinchGesture>
+
 #include <qmath.h>
 
 #include "graphicsviewzoom.h"
@@ -30,6 +33,7 @@ GraphicsViewZoom::GraphicsViewZoom(QGraphicsView* view) :
 {
     m_view->viewport()->installEventFilter(this);
     m_view->setMouseTracking(true);
+    m_view->viewport()->grabGesture(Qt::PinchGesture);
 }
 
 void GraphicsViewZoom::gentleZoom(double factor)
@@ -79,6 +83,19 @@ bool GraphicsViewZoom::eventFilter(QObject *object, QEvent *event)
             }
         }
     }
+    else if (event->type() == QEvent::Gesture)
+    {
+        QGestureEvent *gestureEvent = static_cast<QGestureEvent *>(event);
+        if (QPinchGesture *pinchGesture = static_cast<QPinchGesture *>(gestureEvent->gesture(Qt::PinchGesture)))
+        {
+            if (pinchGesture->changeFlags() & QPinchGesture::ScaleFactorChanged)
+            {
+                m_view->scale(pinchGesture->scaleFactor(), pinchGesture->scaleFactor());
+                emit zoomed();
+            }
+            return true;
+        }
+    }
 
     Q_UNUSED(object)
     return false;
diff --git a/sdrgui/gui/graphicsviewzoom.h b/sdrgui/gui/graphicsviewzoom.h
index 7751b4454..0e4af0e6b 100644
--- a/sdrgui/gui/graphicsviewzoom.h
+++ b/sdrgui/gui/graphicsviewzoom.h
@@ -23,7 +23,7 @@
 
 #include "export.h"
 
-// GraphicsView that allows scroll wheel to be used for zoom
+// GraphicsView that allows scroll wheel and pinch gesture to be used for zoom
 // https://stackoverflow.com/questions/19113532/qgraphicsview-zooming-in-and-out-under-mouse-position-using-mouse-wheel
 class SDRGUI_API GraphicsViewZoom : public QObject {
     Q_OBJECT
@@ -39,7 +39,7 @@ private:
     Qt::KeyboardModifiers m_modifiers;
     double m_zoomFactorBase;
     QPointF m_targetScenePos, m_targetViewportPos;
-    bool eventFilter(QObject* object, QEvent* event);
+    bool eventFilter(QObject* object, QEvent* event) override;
 
 signals:
     void zoomed();