private void updateDropTargets(int numOperands) {
		++numOperands;
		if (dropSupported) {
			for (int i = 0; i < dropTargets.length; i++) {
				dropTargets[i].setActive(i < numOperands);
			}
		}
	}
Enable drop on specified number of operands.
A value of -1 will disable all drop targets.
@param numOperands the number of operands
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/references/InstructionPanel.java