Parse math expression in textboxes

[ChristianGreiner]

I would find it useful if you could perform calculation in text-fields in the editor.

For example: You want to center an image on the x-coordinate:
Just type in the textbox "423/2" and the result (211,5) gets stored in the property.

[SirePi]

Even better, have some (even hardcoded) variables that allow dynamic evaluation such as WindowWidth, WindowHeight, etc..

But I think this would require an extensive rewrite of the property

[ilexp]

Thought about this for a bit and I'm skeptical, because

• this is an open-ended feature that might lead to a full expression eval in those text boxes, a place that really shouldn't be allowed to execute arbitrary code.
• the utility of it is rather low / nice2have.
• using variables suggests data binding and dynamic self-updates when the variable changes, which simply isn't there, nor easily possible.

If we limit it to pure math, i.e. only numbers and (add / subtract / multiply / divide / power) then the above points do not apply, but even then we would need to clearly define scope.

• Are expressions limited to two operands and immediately evaluated?
• Are arbitrary lengths allowed and evaluation is deferred until done with editing?
• What about operator precedence?
• Should there be "brackets" and nesting?
• Are there math functions like sqrt? Where and how are they defined?
• How is all of this communicated to the user?

As far as I'm concerned I'd keep the scope as small as possible for maintenance reasons and make sure all of the code is in a static class that takes a string and returns a float - consciously limiting the system to simple math only, starting with the API choice.

One more thing to consider is whether we really want to open that topic, as every feature has the potential to raise new and more expectations. And this one could mean a lot of added complexity, so if we do it, we need to somehow make sure it doesn't raise the kind of expectation that would make this an open-ended topic.