Editing expressions with negative integer values in them

[meurigbeynon]

When you're editing a scalar value in a formula which is preceded by a -, the cursor behaves oddly.
So when editing the expression

 carfloor4button is button with boxbx is car.boxbx - 40, boxby is car.boxby-20;

  you find that trying to change the second - to a + starts editing the following '20', whilst taking out the space between the '-' and the '40' and then trying to restore it results in '-4 0'

[knicos]

Difficult to resolve. I've specifically bound the minus sign to the number in the highlighter in order to allow number dragging of negatives. If I don't then number dragging can't go negative easily... would require more work.

[knicos]

Note to self: perhaps use custom attributes on the span element.