From e26cbe331a352c743635e5ca2b92d9454a6ac770 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Zolt=C3=A1n=20Kov=C3=A1cs?= <zoltan@geogebra.org>
Date: Mon, 8 Jul 2019 14:17:07 +0200
Subject: [PATCH] Implement zooming with the mouse wheel

---
 src/ui/fractalwidget.cpp |  6 ++++++
 src/ui/fractalwidget.h   |  1 +
 src/ui/mainwindow.cpp    | 18 ++++++++++++++++++
 src/ui/mainwindow.h      |  3 +++
 4 files changed, 28 insertions(+)

diff --git a/src/ui/fractalwidget.cpp b/src/ui/fractalwidget.cpp
index 5500a71e..c54e37b2 100644
--- a/src/ui/fractalwidget.cpp
+++ b/src/ui/fractalwidget.cpp
@@ -87,3 +87,9 @@ void FractalWidget::mouseMoveEvent(QMouseEvent *event)
     m_mousePosition = event->pos();
     event->ignore();
 }
+
+void FractalWidget::wheelEvent(QWheelEvent *event)
+{
+    m_mousePosition = event->pos();
+    event->ignore();
+}
diff --git a/src/ui/fractalwidget.h b/src/ui/fractalwidget.h
index 2c1a13fc..643566e8 100644
--- a/src/ui/fractalwidget.h
+++ b/src/ui/fractalwidget.h
@@ -23,6 +23,7 @@ class FractalWidget: public QWidget
     void mousePressEvent(QMouseEvent * event);
     void mouseReleaseEvent(QMouseEvent * event);
     void resizeEvent(QResizeEvent * event);
+    void wheelEvent(QWheelEvent *event);
 #ifdef USE_OPENGL
     void paintGL();
     void resizeGL (int w, int h);
diff --git a/src/ui/mainwindow.cpp b/src/ui/mainwindow.cpp
index 886e6472..e3a45a94 100644
--- a/src/ui/mainwindow.cpp
+++ b/src/ui/mainwindow.cpp
@@ -217,6 +217,18 @@ int MainWindow::mouseButtons()
         if (m_mouseButtons & Qt::RightButton)
             mouseButtons |= BUTTON3;
     }
+    // handle mouse wheel operations
+    if (m_mouseWheel > 0)
+        mouseButtons |= BUTTON1;
+    if (m_mouseWheel < 0)
+        mouseButtons |= BUTTON3;
+    if (m_mouseWheel != 0) {
+        timespec timenow;
+        clock_gettime(CLOCK_REALTIME, &timenow);
+        long elapsed = timenow.tv_sec * 1.0e9 + timenow.tv_nsec - wheeltimer.tv_sec * 1.0e9 - wheeltimer.tv_nsec;
+        if (elapsed > 1.0e9) // timing is hardcoded here
+            m_mouseWheel = 0;
+    }
     return mouseButtons;
 }
 
@@ -235,6 +247,12 @@ void MainWindow::mouseReleaseEvent(QMouseEvent *event)
     m_mouseButtons = event->buttons();
 }
 
+void MainWindow::wheelEvent(QWheelEvent *event)
+{
+    m_mouseWheel = event->delta();
+    clock_gettime(CLOCK_REALTIME, &wheeltimer);
+}
+
 void MainWindow::keyPressEvent(QKeyEvent *event)
 {
     m_keyboardModifiers = event->modifiers();
diff --git a/src/ui/mainwindow.h b/src/ui/mainwindow.h
index 4ea9ba9d..973cfa63 100644
--- a/src/ui/mainwindow.h
+++ b/src/ui/mainwindow.h
@@ -8,6 +8,8 @@ class MainWindow:public QMainWindow  {
     Q_OBJECT
 private:
     Qt::MouseButtons m_mouseButtons = 0;
+    int m_mouseWheel = 0;
+    timespec wheeltimer;
     Qt::KeyboardModifiers m_keyboardModifiers = 0;
     int m_keyCombination = 0;
     FractalWidget * m_fractalWidget;
@@ -18,6 +20,7 @@ class MainWindow:public QMainWindow  {
     void closeEvent(QCloseEvent *);
     void mousePressEvent(QMouseEvent * event);
     void mouseReleaseEvent(QMouseEvent * event);
+    void wheelEvent(QWheelEvent *event);
     void keyPressEvent(QKeyEvent * event);
     void keyReleaseEvent(QKeyEvent * event);
 private slots: