[LyX/master] #12434 add event handler for pinch-to-zoom gesture

[Stephan Witt]

commit d4324034300f73f76e5ac34fb1e7653fa6e2ddf5
Author: Stephan Witt <sw...@lyx.org>
Date:   Mon Jan 3 07:37:03 2022 +0100

    #12434 add event handler for pinch-to-zoom gesture
---
 src/frontends/qt/GuiView.cpp |   20 ++++++++++++++++++++
 1 files changed, 20 insertions(+), 0 deletions(-)

diff --git a/src/frontends/qt/GuiView.cpp b/src/frontends/qt/GuiView.cpp
index ffcbc3d..791a2c2 100644
--- a/src/frontends/qt/GuiView.cpp
+++ b/src/frontends/qt/GuiView.cpp
@@ -110,6 +110,8 @@
 #include <QTimer>
 #include <QUrl>
 #include <QWindowStateChangeEvent>
+#include <QGestureEvent>
+#include <QPinchGesture>
 
 
 // sync with GuiAlert.cpp
@@ -694,6 +696,9 @@ GuiView::GuiView(int id)
        connect(statusBar(), SIGNAL(customContextMenuRequested(QPoint)),
                this, SLOT(showZoomContextMenu()));
 
+       // enable pinch to zoom
+       grabGesture(Qt::PinchGesture);
+
        int const iconheight = max(int(d.normalIconSize), fm.height());
        QSize const iconsize(iconheight, iconheight);
 
@@ -1621,6 +1626,21 @@ bool GuiView::event(QEvent * e)
                return QMainWindow::event(e);
        }
 
+       case QEvent::Gesture: {
+               QGestureEvent *ge = static_cast<QGestureEvent*>(e);
+               QGesture *gp = ge->gesture(Qt::PinchGesture);
+               if (gp) {
+                       QPinchGesture *pinch = static_cast<QPinchGesture *>(gp);
+                       QPinchGesture::ChangeFlags changeFlags = 
pinch->changeFlags();
+                       if (changeFlags & QPinchGesture::ScaleFactorChanged) {
+                               qreal factor = 
lyxrc.currentZoom*pinch->scaleFactor();
+                               //factor = ceil(factor/20)*20;
+                               zoomValueChanged(factor);
+                       }
+               }
+               return QMainWindow::event(e);
+       }
+
        default:
                return QMainWindow::event(e);
        }
-- 
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