timebasedwidget: rewrote scroll catchup code

Code is much better. Less hacky queuing, implements cooldowns to improve navigation, and introduces a framework so that subclasses can make use of catchup/cooldown code too with any scrollbar they want

app/widget/timebased/timebasedwidget.cpp

@@ -52,6 +52,10 @@ TimeBasedWidget::TimeBasedWidget(bool ruler_text_visible, bool ruler_cache_statu
   connect(scrollbar_, &ResizableScrollBar::ResizeMoved, this, &TimeBasedWidget::ScrollBarResizeMoved);
 
   PassWheelEventsToScrollBar(ruler_);
+
+  catchup_scroll_timer_ = new QTimer(this);
+  catchup_scroll_timer_->setInterval(250); // Hardcoded 1/4 scroll limit value
+  connect(catchup_scroll_timer_, &QTimer::timeout, this, &TimeBasedWidget::CatchUpTimerTimeout);
 }
 
 void TimeBasedWidget::SetScaleAndCenterOnPlayhead(const double &scale)
@@ -217,6 +221,15 @@ void TimeBasedWidget::CatchUpScrollToPoint(int point)
   PageScrollInternal(point, false);
 }
 
+void TimeBasedWidget::CatchUpTimerTimeout()
+{
+  for (auto it=catchup_scroll_values_.cbegin(); it!=catchup_scroll_values_.cend(); it++) {
+    QScrollBar *sb = it.key();
+    const CatchUpScrollData &d = it.value();
+    PageScrollInternal(sb, d.maximum, sb->value() + d.value, false);
+  }
+}
+
 void TimeBasedWidget::AutoUpdateTimebase()
 {
   rational video_tb = viewer_node_->GetVideoParams().frame_rate_as_time_base();
@@ -301,6 +314,36 @@ void TimeBasedWidget::PassWheelEventsToScrollBar(QObject *object)
   object->installEventFilter(this);
 }
 
+void TimeBasedWidget::SetCatchUpScrollValue(QScrollBar *b, int v, int maximum)
+{
+  CatchUpScrollData &cudata = catchup_scroll_values_[b];
+  cudata.value = v;
+  cudata.maximum = maximum;
+
+  static const qint64 min_cooldown = 100; // Hardcoded 1/10 sec cooldown
+  if (QDateTime::currentMSecsSinceEpoch() - cudata.last_forced >= min_cooldown) {
+    QMetaObject::invokeMethod(this, &TimeBasedWidget::CatchUpTimerTimeout, Qt::QueuedConnection);
+    cudata.last_forced = QDateTime::currentMSecsSinceEpoch();
+  }
+
+  if (!catchup_scroll_timer_->isActive()) {
+    catchup_scroll_timer_->start();
+  }
+}
+
+void TimeBasedWidget::SetCatchUpScrollValue(int v)
+{
+  SetCatchUpScrollValue(scrollbar_, v, ruler()->width());
+}
+
+void TimeBasedWidget::StopCatchUpScrollTimer(QScrollBar *b)
+{
+  catchup_scroll_values_.remove(b);
+  if (catchup_scroll_values_.empty()) {
+    catchup_scroll_timer_->stop();
+  }
+}
+
 void TimeBasedWidget::SetTime(const rational &time)
 {
   if (UserIsDraggingPlayhead()) {

app/widget/timebased/timebasedwidget.h

@@ -150,6 +150,14 @@ protected:
 
   void PassWheelEventsToScrollBar(QObject* object);
 
+  void SetCatchUpScrollValue(QScrollBar *b, int v, int maximum);
+  void SetCatchUpScrollValue(int v);
+  void StopCatchUpScrollTimer(QScrollBar *b);
+  void StopCatchUpScrollTimer()
+  {
+    StopCatchUpScrollTimer(scrollbar_);
+  }
+
   virtual const QVector<Block*> *GetSnapBlocks() const { return nullptr; }
   virtual const QVector<KeyframeViewInputConnection*> *GetSnapKeyframes() const { return nullptr; }
   virtual const std::vector<NodeKeyframe*> *GetSnapIgnoreKeyframes() const { return nullptr; }
@@ -228,6 +236,14 @@ private:
   TimelineWorkArea *workarea_;
   TimelineMarkerList *markers_;
 
+  QTimer *catchup_scroll_timer_;
+  struct CatchUpScrollData {
+    qint64 last_forced = 0;
+    int maximum;
+    int value;
+  };
+  QMap<QScrollBar*, CatchUpScrollData> catchup_scroll_values_;
+
 private slots:
   void UpdateMaximumScroll();
 
@@ -247,6 +263,8 @@ private slots:
 
   void CatchUpScrollToPoint(int point);
 
+  void CatchUpTimerTimeout();
+
   void AutoUpdateTimebase();
 
   void ConnectedNodeRemovedFromGraph();