Better timeline UX

Scrolling on the timeline now supports modifiers CTRL and SHIFT.

* CTRL + wheel will now scale in/out the frame range as if you used the scrollbar
* SHIFT + wheel will now pan the frame range as if you used the scrollbar
* Without a modifier it works as before, scroll up/down

See https://github.com/orgs/friction2d/discussions/58#discussioncomment-6769336

src/app/GUI/BoxesList/OptimalScrollArea/scrollarea.cpp

@@ -58,8 +58,10 @@ void ScrollArea::resizeEvent(QResizeEvent *e) {
     QScrollArea::resizeEvent(e);
 }
 #include "GUI/global.h"
-void ScrollArea::callWheelEvent(QWheelEvent *event) {
-    if(event->angleDelta().y() > 0) {
+void ScrollArea::callWheelEvent(QWheelEvent *event)
+{
+    if (event->modifiers() & Qt::CTRL || event->modifiers() & Qt::SHIFT) { return; }
+    if (event->angleDelta().y() > 0) {
         scrollBy(0, -eSizesUI::widget);
     } else {
         scrollBy(0, eSizesUI::widget);

src/app/GUI/animationwidgetscrollbar.cpp

@@ -304,6 +304,31 @@ void FrameScrollBar::setCanvasFrameRange(const FrameRange &range) {
     update();
 }
 
+void FrameScrollBar::callWheelEvent(QWheelEvent *event)
+{
+    if (!mRange) { return; }
+    bool triggered = false;
+    if (event->modifiers() & Qt::CTRL) {
+        int newFramesSpan = mViewedFramesSpan;
+        if (event->angleDelta().y() > 0) { newFramesSpan *= 0.85; }
+        else { newFramesSpan *= 1.15; }
+        setFramesSpan(newFramesSpan);
+        triggered = true;
+   } else if (event->modifiers() & Qt::SHIFT) {
+        if (event->angleDelta().y() > 0) {
+            setFirstViewedFrame(mFirstViewedFrame - mViewedFramesSpan/20);
+            triggered = true;
+        } else {
+            setFirstViewedFrame(mFirstViewedFrame + mViewedFramesSpan/20);
+            triggered = true;
+        }
+    }
+    if (!triggered) { return; }
+
+    emitTriggeredChange();
+    update();
+}
+
 void FrameScrollBar::emitChange() {
     emit frameRangeChange(getViewedRange());
 }

src/app/GUI/animationwidgetscrollbar.h

@@ -59,6 +59,8 @@ class FrameScrollBar : public QWidget {
     void setDisplayedFrameRange(const FrameRange& range);
     void setViewedFrameRange(const FrameRange& range);
     void setCanvasFrameRange(const FrameRange& range);
+    void callWheelEvent(QWheelEvent *event);
+
 protected:
     qreal posToFrame(int xPos);
     void paintEvent(QPaintEvent *);

src/app/GUI/timelinewidget.cpp

@@ -284,6 +284,8 @@ TimelineWidget::TimelineWidget(Document &document,
 
     connect(mFrameRangeScrollBar, &FrameScrollBar::triggeredFrameRangeChange,
             this, &TimelineWidget::setViewedFrameRange);
+    connect(mKeysView, &KeysView::wheelEventSignal,
+            mFrameRangeScrollBar, &FrameScrollBar::callWheelEvent);
     mKeysViewLayout->addWidget(mFrameRangeScrollBar);
     //mSceneChooser->setCurrentScene(mDocument.fActiveScene); // why?