There are quire a few instances when the Flash window for Hookpad briefly flashes white when interacting with it:
- When clicking on the note/chord area
- Adding/removing notes (but not rests)
- Making a note a higher/lower octave than default
- Exiting the Mixer window
- Adding/removing a Youtube video
- Click-dragging to a note/chord’s length
- Toggling the “Stable” button
- Adding/removing an instrument
- Changing time signatures
- Adding lines
- Cancelling the “Open” window
All of these seem to come from the fact that when you do one of the above (on a 1440x900 screen, anyway), the scroll bar on the right-hand side shows up. This underlying issue could be that the Flash player, when the scroll bar appears, automatically resizes, causing the brief white flash.
Windows 10, Google Chrome, on a 1440x900 monitor.