From caef959fe448727bb29be75ec1e2fb537b0b0d6d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ferenc=20G=C3=A9czi?= <ferenc.gm@gmail.com>
Date: Thu, 30 Nov 2023 00:00:04 +0000
Subject: [PATCH] [qt] Add support for touchscreen pinch zoom
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Signed-off-by: Ferenc Géczi <ferenc.gm@gmail.com>
---
 qt/mainwindow.cpp           |  4 ++++
 qt/qt_common/map_widget.cpp | 33 +++++++++++++++++++++++++++++++++
 qt/qt_common/map_widget.hpp |  7 +++++++
 3 files changed, 44 insertions(+)

diff --git a/qt/mainwindow.cpp b/qt/mainwindow.cpp
index 88a75d4d51..7d8247c481 100644
--- a/qt/mainwindow.cpp
+++ b/qt/mainwindow.cpp
@@ -123,6 +123,10 @@ MainWindow::MainWindow(Framework & framework,
   int const height = m_screenshotMode ? static_cast<int>(screenshotParams->m_height) : 0;
   m_pDrawWidget = new DrawWidget(framework, std::move(screenshotParams), this);
 
+  QList<Qt::GestureType> gestures;
+  gestures << Qt::PinchGesture;
+  m_pDrawWidget->grabGestures(gestures);
+
   setCentralWidget(m_pDrawWidget);
 
   if (m_screenshotMode)
diff --git a/qt/qt_common/map_widget.cpp b/qt/qt_common/map_widget.cpp
index bfb95e01a1..10abbf1165 100644
--- a/qt/qt_common/map_widget.cpp
+++ b/qt/qt_common/map_widget.cpp
@@ -15,6 +15,7 @@
 #include <functional>
 #include <string>
 
+#include <QGesture>
 #include <QOpenGLShaderProgram>
 #include <QOpenGLBuffer>
 #include <QOpenGLVertexArrayObject>
@@ -557,4 +558,36 @@ void MapWidget::wheelEvent(QWheelEvent * e)
   m_framework.Scale(exp(e->angleDelta().y() / 3.0 / 360.0), m2::PointD(L2D(pos.x()), L2D(pos.y())), false);
 }
 
+void MapWidget::grabGestures(const QList<Qt::GestureType> &gestures)
+{
+  for (Qt::GestureType gesture : gestures)
+    grabGesture(gesture);
+}
+
+bool MapWidget::event(QEvent *event)
+{
+  if (event->type() == QEvent::Gesture)
+    return gestureEvent(static_cast<QGestureEvent*>(event));
+  return QWidget::event(event);
+}
+
+bool MapWidget::gestureEvent(QGestureEvent *event)
+{
+  if (QGesture *pinch = event->gesture(Qt::PinchGesture))
+    pinchTriggered(static_cast<QPinchGesture *>(pinch));
+  return true;
+}
+
+void MapWidget::pinchTriggered(QPinchGesture *gesture)
+{
+  QPinchGesture::ChangeFlags changeFlags = gesture->changeFlags();
+  m2::PointD centerPoint = m_framework.GetVisiblePixelCenter();
+  if (changeFlags & QPinchGesture::ScaleFactorChanged)
+  {
+    qreal totalScaleFactor = gesture->totalScaleFactor();
+
+    if (totalScaleFactor != 1.0)
+      m_framework.Scale((totalScaleFactor > 1.0) ? Framework::SCALE_MAG : Framework::SCALE_MIN, true);
+  }
+}
 } // namespace qt::common
diff --git a/qt/qt_common/map_widget.hpp b/qt/qt_common/map_widget.hpp
index 8ad231f143..f2ee2d58a7 100644
--- a/qt/qt_common/map_widget.hpp
+++ b/qt/qt_common/map_widget.hpp
@@ -13,6 +13,8 @@
 #include <memory>
 
 class Framework;
+class QGestureEvent;
+class QPinchGesture;
 class QMouseEvent;
 class QWidget;
 class ScreenBase;
@@ -35,6 +37,7 @@ public:
   void BindHotkeys(QWidget & parent);
   void BindSlider(ScaleSlider & slider);
   void CreateEngine();
+  void grabGestures(const QList<Qt::GestureType> &gestures);
 
 signals:
   void OnContextMenuRequested(QPoint const & p);
@@ -79,6 +82,10 @@ protected:
   void paintGL() override;
   void resizeGL(int width, int height) override;
 
+  bool event(QEvent * event) override;
+  bool gestureEvent(QGestureEvent * event);
+  void pinchTriggered(QPinchGesture * gesture);
+
   void mouseDoubleClickEvent(QMouseEvent * e) override;
   void mousePressEvent(QMouseEvent * e) override;
   void mouseMoveEvent(QMouseEvent * e) override;