Method onUpdate

src/component/timeline/SliderTimelineView.ts:592–594

(pointer: TimelineSymbol)

                pointerMoveTo(pointer, me._progressLine, currentIndex, axis, timelineModel, true);
            },
            onUpdate(pointer: TimelineSymbol) {
                pointerMoveTo(pointer, me._progressLine, currentIndex, axis, timelineModel);
            }
        };

        // Reuse when exists, for animation and drag.