private void doTopOfFile(EventTrigger trigger) {
		showIndex(BigInteger.ZERO, 0);
		cursorHandler.setCursorPos(0, 0, trigger);
	}
Returns the offset of the cursor from the top of the screen

@return the offset of the cursor from the top of the screen
Ghidra/Framework/Docking/src/main/java/docking/widgets/fieldpanel/FieldPanel.java