When you switch the tab or window while sequencer is running, the drawing stops but new steps get added to the stepList. When the window gains focus, these steps get drawn frame by frame until stepList is back at event horizon.
You can see this in the sequencer demo: The pointer rushes through the steps after you click on another tab (wait few sec.) and back to the demo.
Possible solution would be to check document.hasFocus() and skip adding to stepList if false.
When you switch the tab or window while sequencer is running, the drawing stops but new steps get added to the stepList. When the window gains focus, these steps get drawn frame by frame until stepList is back at event horizon. You can see this in the sequencer demo: The pointer rushes through the steps after you click on another tab (wait few sec.) and back to the demo. Possible solution would be to check document.hasFocus() and skip adding to stepList if false.