private Scalar getScalar(Varnode vn) {
		if (vn == null) {
			return null;
		}

		if (!(vn.getHigh() instanceof HighConstant)) {
			return null;
		}

		HighConstant hv = (HighConstant) vn.getHigh();
		long offset = vn.getOffset();
		int sz = vn.getSize();
		boolean isSigned = true;
		if (hv.getDataType() instanceof AbstractIntegerDataType) {
			isSigned = ((AbstractIntegerDataType) hv.getDataType()).isSigned();
		}

		if (sz > 8) {
			return null; // our Scalar can currently only handle long values
		}

		return new Scalar(sz * 8, offset, isSigned);
	}
A hover service to show tool tip text for hovering over a function name in the decompiler.
The tooltip shows the function signature per the listing.
Ghidra/Features/Decompiler/src/main/java/ghidra/app/decompiler/component/hover/FunctionSignatureDecompilerHover.java