validate math formula on text change

[bryanparadis]

I've been writing a lot of formulae and I am new to the software and not sure about syntax. I've been clicking out of the input box to validate. Looks like I could also be pressing enter. It would be nice if this field was validated as I typed instead and so I have opened this draft pull request.

Validation will run on each change with no delay/debounce. Fiddled around with it a bit and didn't seem super heavy. Don't think there are additional side effects but I am not familiar with the codebase.

[bryanparadis]

There are two options for this:

On user and programmatic change

void QLineEdit::textChanged(const QString &text)
This signal is emitted whenever the text changes. The text argument is the new text.
Unlike textEdited(), this signal is also emitted when the text is changed programmatically, for example, by calling setText().
Note: Notifier signal for property text.

On user change only

void QLineEdit::textEdited(const QString &text)
This signal is emitted whenever the text is edited. The text argument is the new text.
Unlike textChanged(), this signal is not emitted when the text is changed programmatically, for example, by calling setText().

[bryanparadis]

I've learned to look at the OK button to see if validation is good or not. Maybe something in the field or beside the field instead would be a better/more coupled indicator?

[jankae]

Thanks, I think some early validation (and possibly also indicating what the problem is if it fails) is a good idea. Most likely I will checkout this PR locally, add some error indicator and then merge this (unless you want to take this on as well)

[bryanparadis]

Thanks, I think some early validation (and possibly also indicating what the problem is if it fails) is a good idea. Most likely I will checkout this PR locally, add some error indicator and then merge this (unless you want to take this on as well)

I added a red background on validation fail to the box and a green on OK. Doesn't look too great. Maybe lighter red and green or some kind of X or checkmark. I can add what I've tried to the branch

[jankae]

I think I found a good way to show the status by adding a label under the formula field. Here is what that looks like with a valid formula:

And here are various errors with invalid formulas:

• Empty formula:
  
• Using a variable name that does not exist:
  
• Using a function that does not exist:
  
• Multiple operators in a row:
  
• Missing parenthesis:
  

The error message comes straight out of the muParserX library, so it is not something I can influence. But I think most errors should at least help a little bit when trying to figure out the problem.

[bryanparadis]

I think I found a good way to show the status by adding a label under the formula field. Here is what that looks...

Oh interesting!

The error message comes straight out of the muParserX library, so it is not something I can influence. But I think most errors should at least help a little bit when trying to figure out the problem.

Yeah. That is true. I hadn't looked into displaying the parser errors I went for background colors. I broke the formula saving though.

Hahaha. Nuked a line I didn't want to

ui->lMathFormula->setText(t.getMathFormula());

[jankae]

I think I'll just merge the original PR + my changes to show the error message. The colors are a nice touch, but I think the error message is more helpful.

I broke the formula saving though.

You just deleted the line which initially fills the QLineEdit with the formula from the trace when opening the dialog.