How to multiply a Unit by a number?
The Unit type exists to represent a length, and contains two different informations: a value and a unit or type. The unit can be absolute (pixels, centimeters, etc.) or relative (percentage, em). They are not lengths in the physical sense because in the relative case, they vary depending on the context. This is just how HTML works with lengths.
So every property that will end up representing a length should be of type Unit.
Now, while Unit is a value type (a struct, if you prefer, as opposed to a class), it lacks the basic arithmetic operators. You can't add two Units, but that's normal, because they may have different units (again, they are not lengths in the physical sense), but you can't multiply them by a number either without writing some code.
An example where you would want to do that is for example the Menu control where we have the possibility to indent the submenus. A menu of depth three will have to be indented by three times the indent property value.
We're doing it more or less this way:
Unit
Multiply(Unit indent, int depth) {if (indent.IsEmpty) {
return Unit.Empty;
}
if (indent.Value == 0) {
return indent;
}
double indentValue = indent.Value * depth;
// I'd love not to hardcode this but Unit.MaxValue is currently private.
if (indentValue < 32767) {
return new Unit(indentValue, indent.Type);
}
else {
return new Unit(32767, indent.Type);
}
}