viewer: respond to wheel events for moving and zooming

app/widget/handmovableview/handmovableview.cpp

@@ -150,16 +150,21 @@ const HandMovableView::DragMode &HandMovableView::GetDefaultDragMode() const
   return default_drag_mode_;
 }
 
-bool HandMovableView::WheelEventIsAZoomEvent(QWheelEvent *event) const
+bool HandMovableView::WheelEventIsAZoomEvent(QWheelEvent *event)
 {
   return (static_cast<bool>(event->modifiers() & Qt::ControlModifier) == !OLIVE_CONFIG("ScrollZooms").toBool());
 }
 
+qreal HandMovableView::GetScrollZoomMultiplier(QWheelEvent *event)
+{
+  return 1.0 + (static_cast<qreal>(event->angleDelta().x() + event->angleDelta().y()) * 0.001);
+}
+
 void HandMovableView::wheelEvent(QWheelEvent *event)
 {
   if (WheelEventIsAZoomEvent(event)) {
     if (!event->angleDelta().isNull()) {
-      qreal multiplier = 1.0 + (static_cast<qreal>(event->angleDelta().x() + event->angleDelta().y()) * 0.001);
+      qreal multiplier = GetScrollZoomMultiplier(event);
 
       QPointF cursor_pos;
 #if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)

app/widget/handmovableview/handmovableview.h

@@ -34,6 +34,10 @@ class HandMovableView : public QGraphicsView
 public:
   HandMovableView(QWidget* parent = nullptr);
 
+  static bool WheelEventIsAZoomEvent(QWheelEvent* event);
+
+  static qreal GetScrollZoomMultiplier(QWheelEvent* event);
+
 protected:
   virtual void ToolChangedEvent(Tool::Item tool){Q_UNUSED(tool)}
 
@@ -44,8 +48,6 @@ protected:
   void SetDefaultDragMode(DragMode mode);
   const DragMode& GetDefaultDragMode() const;
 
-  bool WheelEventIsAZoomEvent(QWheelEvent* event) const;
-
   virtual void wheelEvent(QWheelEvent* event) override;
 
   virtual void ZoomIntoCursorPosition(QWheelEvent* event, double multiplier, const QPointF &cursor_pos);

app/widget/viewer/viewer.cpp

@@ -1373,10 +1373,10 @@ void ViewerWidget::ShowContextMenu(const QPoint &pos)
       Menu* zoom_menu = new Menu(tr("Zoom"), &menu);
       menu.addMenu(zoom_menu);
 
-      int zoom_levels[] = {10, 25, 50, 75, 100, 150, 200, 400};
       zoom_menu->addAction(tr("Fit"))->setData(0);
-      for (int i=0;i<8;i++) {
-        zoom_menu->addAction(tr("%1%").arg(zoom_levels[i]))->setData(zoom_levels[i]);
+      for (int i=0;i<ViewerSizer::kZoomLevelCount;i++) {
+        int z = ViewerSizer::kZoomLevels[i];
+        zoom_menu->addAction(tr("%1%").arg(z))->setData(z);
       }
 
       connect(zoom_menu, &QMenu::triggered, this, &ViewerWidget::SetZoomFromMenu);

app/widget/viewer/viewersizer.cpp

@@ -20,7 +20,12 @@
 
 #include "viewersizer.h"
 
+#include <QApplication>
+#include <QEvent>
 #include <QMatrix4x4>
+#include <QWheelEvent>
+
+#include "widget/handmovableview/handmovableview.h"
 
 namespace olive {
 
@@ -30,7 +35,8 @@ ViewerSizer::ViewerSizer(QWidget *parent) :
   width_(0),
   height_(0),
   pixel_aspect_(1),
-  zoom_(0)
+  zoom_(0),
+  current_widget_scale_(0)
 {
   horiz_scrollbar_ = new QScrollBar(Qt::Horizontal, this);
   horiz_scrollbar_->setVisible(false);
@@ -52,6 +58,7 @@ void ViewerSizer::SetWidget(QWidget *widget)
 
   if (widget_ != nullptr) {
     widget_->setParent(this);
+    widget_->installEventFilter(this);
 
     UpdateSize();
   }
@@ -90,6 +97,51 @@ void ViewerSizer::HandDragMove(int x, int y)
   }
 }
 
+bool ViewerSizer::eventFilter(QObject *watched, QEvent *event)
+{
+  if (watched == widget_) {
+    if (event->type() == QEvent::Wheel) {
+      QWheelEvent *w = static_cast<QWheelEvent*>(event);
+
+      if (HandMovableView::WheelEventIsAZoomEvent(w)) {
+        int x = w->angleDelta().x() + w->angleDelta().y();
+
+        int current_percent = zoom_;
+        if (current_percent == 0) {
+          // Currently set to "fit"
+          current_percent = current_widget_scale_;
+        }
+
+        if (x > 0) {
+          // Zoom in
+          for (int i=kZoomLevelCount-2; i>=0; i--) {
+            if (current_percent >= kZoomLevels[i]) {
+              SetZoom(kZoomLevels[i+1]);
+              break;
+            }
+          }
+        } else if (x < 0) {
+          // Zoom out
+          for (int i=1; i<kZoomLevelCount; i++) {
+            if (current_percent <= kZoomLevels[i]) {
+              SetZoom(kZoomLevels[i-1]);
+              break;
+            }
+          }
+        }
+      } else {
+        // Pass scroll values to scrollbars
+        QPoint p = w->pixelDelta();
+        horiz_scrollbar_->setValue(horiz_scrollbar_->value() - p.x());
+        vert_scrollbar_->setValue(vert_scrollbar_->value() - p.y());
+      }
+      return true;
+    }
+  }
+
+  return QWidget::eventFilter(watched, event);
+}
+
 void ViewerSizer::resizeEvent(QResizeEvent *event)
 {
   QWidget::resizeEvent(event);
@@ -169,6 +221,8 @@ void ViewerSizer::UpdateSize()
 
   }
 
+  current_widget_scale_ = current_scale * 100;
+
   if (zoom_ > 0) {
 
     // Scale to get to the requested zoom

app/widget/viewer/viewersizer.h

@@ -51,6 +51,9 @@ public:
    */
   void SetWidget(QWidget* widget);
 
+  static constexpr int kZoomLevelCount = 8;
+  static constexpr int kZoomLevels[kZoomLevelCount] = {10, 25, 50, 75, 100, 150, 200, 400};
+
 public slots:
   /**
    * @brief Set resolution to use
@@ -73,6 +76,8 @@ public slots:
 
   void HandDragMove(int x, int y);
 
+  virtual bool eventFilter(QObject *watched, QEvent *event) override;
+
 signals:
   void RequestScale(const QMatrix4x4& matrix);
 
@@ -111,6 +116,7 @@ private:
    * @brief Internal zoom value
    */
   int zoom_;
+  int current_widget_scale_;
 
   QScrollBar* horiz_scrollbar_;
   QScrollBar* vert_scrollbar_;