Allow to link widget style definitions, so applying one style might disable the other

[Marek Lewandowski]

This is a follow-up of #13200 issue.

Some styles styles might exclude the others, take alignment class for an example. Having left-align and right-align class, we want to use only one at a time.

What we can do is to add group property to the style definition passed to config.stylesSet.

var stylesSet = [
    { name: 'Left align', type: 'widget', widget: 'image', attributes: { 'class': 'left-align' }, gorup: 'alignment' },
    { name: 'Right align', type: 'widget', widget: 'image', attributes: { 'class': 'right-align' }, gorup: 'alignment' }
];

Scope of the Fix

For the time being let's restrict only to widget system. Later on we might bring support for that for Object styles, that are implemented in core/style.js.

Multiple Groups

Now there possiblty might be a case when style fits (excludes) more than one group. So we should also accept array of groups in such case.

[Szymon Kupś]

Pushed ​branch:t/13818. I've added style groups handling to widget's custom style handler and introduced new method style.removeStylesFromSameGroup().
Also updated stylescombo plugin, checking for edge case when there are styles from multiple groups applied together.

[Tade0]

After some digging I found a way to break something: Switch to source mode and apply conflicting styles this way(via adding classes), then switch back. The result is that the styles are still applied.

I've done some minor style corrections and added the sourcearea plugin to the manual test.

Changes pushed to ​branch:t/13818.

[Wiktor Walc]

Keep in mind that applying stupid operations in source mode can be considered as unsupported edge case. If this was the only reason to fail the review, please check it again, ignoring the case above.

[Marek Lewandowski]

Replying to wwalc:

Keep in mind that applying stupid operations in source mode can be considered as unsupported edge case. If this was the only reason to fail the review, please check it again, ignoring the case above.

+1 on that

[kkrzton]

Apart from the issue mentioned in comment:4 which we decided to skip as it is unsupported edge case, everything looks good.

[kkrzton]

Merged to master with ​c300ed9.

[Marek Lewandowski]

It's actually a new feature rather than a bug fix.