tab_elems configuration setting for tab customization

[Walther-MD]

Implements the "tab_elems" configuration setting which allows user to choose the elements that are displayed in the gtk tabs (T - title, C - close button, F - favicon / spinner), as per task https://github.com/conformal/xombrero/issues/8

[marcopeereboom]

I corrected some style issues here: https://github.com/conformal/xombrero/tree/Walther-MD-master

This can't go in in it's current form because it alters the default behavior. For example, my spinners disappeared. These diffs are great but we try really hard to never ever alter default behavior.

[Walther-MD]

I... can modify the behaviour, but I need a suggestion/guide on what to do. Currently, when a favicon is displayed, they share the very same space with the spinner, and this patch keeps that behaviour intact. However, when there is no favicon, where should a spinner be displayed? The idea is to let the user choose.

Should I add a fourth letter, (S)pinner, so the user can independently choose where the elements go (Favicon, Spinner, Text, Close button)? But then it makes no sense to have the favicon vanish/reappear when the spinner does if they aren't in the same location.

Should I instead just force the display of a spinner even if the favicon is not specified? If so, then where does it go? The idea is to be able to customize the answer to that question. So should "S" be added only if no "F" is specified? That is, if a Favicon location is set, then that implicitly includes (and invalidates) Spinner location, and if not, then you can use S to determine where the spinner appears while loading?

If it weren't because the display of the Favicon and Spinner are so closely related, the answer to these questions would be a lot more obvious. If a logical suggestion is given, I can implement that and repush.

[marcopeereboom]

So what I want is the default behavior to remain the same. The options you add are all gravy to me. The default behavior is no favicon on the tabs and a spinner on the right of the text that goes away once the page is loaded. That is what I want to remain intact. Same is true for the compact mode.

Current users would be displeased if their tabs suddenly changed. I am very big on no new surprises.

So all that said, I'd love this diff to be whooped into shape style wise and by default not alter any behavior and then it'll be good to go.

[Walther-MD]

I added a "S" tab-element key, which stands for spinner, this makes it possible to keep the previous default behaviour, and allows showing the spinner even when no favicon is shown. However, the S and F elements will conflict and only one can be used at a time.

[svgeof4695]

Is there something still holding up this commit? I would like at least the functionality to change the order of the Title and Close button to have the button on the right (for the same reasons Walther-MD gave in the original report). This commit would do that (and much more).