improved resizable scrollbar functionality

app/widget/resizablescrollbar/resizablescrollbar.cpp

@@ -48,53 +48,23 @@ void ResizableScrollBar::mousePressEvent(QMouseEvent *event)
   if (mouse_handle_state_ == kNotInHandle) {
     QScrollBar::mousePressEvent(event);
   } else {
-    mouse_dragging_ = true;
+    dragging_ = true;
 
-    mouse_drag_start_ = GetActiveMousePos(event);
+    drag_start_point_ = GetActiveMousePos(event);
+
+    emit ResizeBegan(GetActiveBarSize(), (mouse_handle_state_ == kInTopHandle));
   }
 }
 
 void ResizableScrollBar::mouseMoveEvent(QMouseEvent *event)
 {
-  QStyleOptionSlider opt;
-  initStyleOption(&opt);
+  QRect sr = GetScrollBarRect();
 
-  QRect sr = style()->subControlRect(QStyle::CC_ScrollBar, &opt,
-                                     QStyle::SC_ScrollBarSlider, this);
+  if (dragging_) {
+    // Determine how much the cursor has moved
+    int mouse_movement = GetActiveMousePos(event) - drag_start_point_;
 
-  if (mouse_dragging_) {
-    int new_drag_pos = GetActiveMousePos(event);
-    int mouse_movement = new_drag_pos - mouse_drag_start_;
-    mouse_drag_start_ = new_drag_pos;
-
-    if (mouse_handle_state_ == kInTopHandle) {
-      mouse_movement = -mouse_movement;
-    }
-
-    double width_adjustment = static_cast<double>(sr.width() + mouse_movement);
-
-    // Prevent dividing by zero or emitting a negative scale
-    if (width_adjustment > 0) {
-      double scale_multiplier = static_cast<double>(sr.width()) / width_adjustment;
-      emit RequestScale(scale_multiplier);
-
-      if (mouse_handle_state_ == kInTopHandle) {
-        QRect gr = style()->subControlRect(QStyle::CC_ScrollBar, &opt,
-                                           QStyle::SC_ScrollBarGroove, this);
-
-        int slider_min = gr.x();
-        int slider_max = gr.right() - (sr.width() + mouse_movement);
-        int val = QStyle::sliderValueFromPosition(minimum(),
-                                                  maximum(),
-                                                  event->pos().x() - slider_min,
-                                                  slider_max - slider_min,
-                                                  opt.upsideDown);
-
-        setValue(val);
-      } else {
-        setValue(qRound(static_cast<double>(value()) * scale_multiplier));
-      }
-    }
+    emit ResizeMoved(mouse_movement);
 
   } else {
 
@@ -133,13 +103,27 @@ void ResizableScrollBar::mouseMoveEvent(QMouseEvent *event)
 
 void ResizableScrollBar::mouseReleaseEvent(QMouseEvent *event)
 {
-  if (mouse_dragging_) {
-    mouse_dragging_ = false;
+  if (dragging_) {
+    dragging_ = false;
+
+    emit ResizeEnded();
   } else {
     QScrollBar::mouseReleaseEvent(event);
   }
 }
 
+QRect ResizableScrollBar::GetScrollBarRect()
+{
+  // Initialize "style option". I don't know what this does, I just ripped it straight from
+  // Qt source code
+  QStyleOptionSlider opt;
+  initStyleOption(&opt);
+
+  // Determine rect of slider bar
+  return style()->subControlRect(QStyle::CC_ScrollBar, &opt,
+                                 QStyle::SC_ScrollBarSlider, this);
+}
+
 void ResizableScrollBar::Init()
 {
   setSingleStep(20);
@@ -147,7 +131,7 @@ void ResizableScrollBar::Init()
   setMouseTracking(true);
 
   mouse_handle_state_= kNotInHandle;
-  mouse_dragging_ = false;
+  dragging_ = false;
 }
 
 int ResizableScrollBar::GetActiveMousePos(QMouseEvent *event)
@@ -159,4 +143,15 @@ int ResizableScrollBar::GetActiveMousePos(QMouseEvent *event)
   }
 }
 
+int ResizableScrollBar::GetActiveBarSize()
+{
+  QRect sr = GetScrollBarRect();
+
+  if (orientation() == Qt::Horizontal) {
+    return sr.width();
+  } else {
+    return sr.height();
+  }
+}
+
 }

app/widget/resizablescrollbar/resizablescrollbar.h

@@ -35,7 +35,11 @@ public:
   ResizableScrollBar(Qt::Orientation orientation, QWidget* parent = nullptr);
 
 signals:
-  void RequestScale(const double& multiplier);
+  void ResizeBegan(int old_bar_width, bool top_handle);
+
+  void ResizeMoved(int movement);
+
+  void ResizeEnded();
 
 protected:
   virtual void mousePressEvent(QMouseEvent* event) override;
@@ -45,6 +49,8 @@ protected:
   virtual void mouseReleaseEvent(QMouseEvent* event) override;
 
 private:
+  QRect GetScrollBarRect();
+
   static const int kHandleWidth;
 
   enum MouseHandleState {
@@ -57,11 +63,13 @@ private:
 
   int GetActiveMousePos(QMouseEvent* event);
 
+  int GetActiveBarSize();
+
   MouseHandleState mouse_handle_state_;
 
-  bool mouse_dragging_;
+  bool dragging_;
 
-  int mouse_drag_start_;
+  int drag_start_point_;
 
 };
 

app/widget/timebased/timebasedwidget.cpp

@@ -44,7 +44,8 @@ TimeBasedWidget::TimeBasedWidget(bool ruler_text_visible, bool ruler_cache_statu
   connect(ruler_, &TimeRuler::TimeChanged, this, &TimeBasedWidget::SetTimeAndSignal);
 
   scrollbar_ = new ResizableTimelineScrollBar(Qt::Horizontal, this);
-  connect(scrollbar_, &ResizableScrollBar::RequestScale, this, &TimeBasedWidget::ScrollBarResized);
+  connect(scrollbar_, &ResizableScrollBar::ResizeBegan, this, &TimeBasedWidget::ScrollBarResizeBegan);
+  connect(scrollbar_, &ResizableScrollBar::ResizeMoved, this, &TimeBasedWidget::ScrollBarResizeMoved);
 
   PassWheelEventsToScrollBar(ruler_);
 }
@@ -126,7 +127,7 @@ void TimeBasedWidget::ConnectViewerNode(ViewerOutput *node)
 
 void TimeBasedWidget::UpdateMaximumScroll()
 {
-  rational length = (viewer_node_) ? viewer_node_->GetLength() : rational();
+  rational length = (viewer_node_) ? viewer_node_->GetLength() : 0;
 
   if (auto_max_scrollbar_) {
     scrollbar_->setMaximum(qMax(0, qCeil(TimeToScene(length)) - width()));
@@ -137,27 +138,47 @@ void TimeBasedWidget::UpdateMaximumScroll()
   }
 }
 
-void TimeBasedWidget::ScrollBarResized(const double &multiplier)
+void TimeBasedWidget::ScrollBarResizeBegan(int current_bar_width, bool top_handle)
 {
   QScrollBar* bar = static_cast<QScrollBar*>(sender());
 
-  // Our extension area (represented by a TimelineViewEndItem) is NOT scaled, but the ResizableScrollBar doesn't know
-  // this. Here we re-calculate the requested scale knowing that the end item is not affected by scale.
+  scrollbar_start_width_ = current_bar_width;
+  scrollbar_start_value_ = bar->value();
+  scrollbar_start_scale_ = GetScale();
+  scrollbar_top_handle_ = top_handle;
+}
 
-  int current_max = bar->maximum();
-  double proposed_max = static_cast<double>(current_max) * multiplier;
+void TimeBasedWidget::ScrollBarResizeMoved(int movement)
+{
+  ResizableScrollBar* bar = static_cast<ResizableScrollBar*>(sender());
 
-  proposed_max = proposed_max - (bar->width() * 0.5 / multiplier) + (bar->width() * 0.5);
-
-  double corrected_scale;
-
-  if (current_max == 0) {
-    corrected_scale = multiplier;
-  } else {
-    corrected_scale = (proposed_max / static_cast<double>(current_max));
+  // Negate movement for the top handle
+  if (scrollbar_top_handle_) {
+    movement = -movement;
   }
 
-  SetScale(GetScale() * corrected_scale);
+  // The user wants the bar to be this size
+  int proposed_size = scrollbar_start_width_ + movement;
+
+  double ratio = double(scrollbar_start_width_) / double(proposed_size);
+
+  if (ratio > 0) {
+    SetScale(scrollbar_start_scale_ * ratio);
+
+    if (scrollbar_top_handle_) {
+      int viewable_area;
+
+      if (timeline_views_.isEmpty()) {
+        viewable_area = width();
+      } else {
+        viewable_area = timeline_views_.first()->width();
+      }
+
+      bar->setValue((scrollbar_start_value_ + viewable_area) * ratio - viewable_area);
+    } else {
+      bar->setValue(scrollbar_start_value_ * ratio);
+    }
+  }
 }
 
 void TimeBasedWidget::PageScrollToPlayhead()
@@ -492,7 +513,7 @@ void TimeBasedWidget::SetMarker()
   bool ok;
   QString marker_name;
 
-  if (Config::Current()["SetNameWithMarker"].toBool()) {
+  if (Config::Current()[QStringLiteral("SetNameWithMarker")].toBool()) {
     marker_name = QInputDialog::getText(this, tr("Set Marker"), tr("Marker name:"), QLineEdit::Normal, QString(), &ok);
   } else {
     ok = true;

app/widget/timebased/timebasedwidget.h

@@ -205,10 +205,17 @@ private:
 
   QVector<QObject*> wheel_passthrough_objects_;
 
+  int scrollbar_start_width_;
+  double scrollbar_start_value_;
+  double scrollbar_start_scale_;
+  bool scrollbar_top_handle_;
+
 private slots:
   void UpdateMaximumScroll();
 
-  void ScrollBarResized(const double& multiplier);
+  void ScrollBarResizeBegan(int current_bar_width, bool top_handle);
+
+  void ScrollBarResizeMoved(int new_bar_width);
 
   /**
    * @brief Slot to handle page scrolling of the playhead