Remove "Use round tabs" for tabs support

[vogella]

IIRC a while ago @sratz and I discussed that rounded tabs support in CSS is relatively complex.

How useful is our CSS based rounded tab support? Can we retire it? AFAIK our UI is not API.

[vogella]

@merks WDYT?

[vogella]

@sratz @BeckerWdf WDYT?

[BeckerWdf]

I am not a big fan of the rounded tabs. So I am find with retiring it.

[HeikoKlare]

I am also in favor of getting rid of those rounded tabs in case no one requiring them or finding them appealing steps up.
I can second that this style introduces quite some complexity. And since not many people seem to be using it, it also has some visual visual flaws. We had a hard time improving the appearance of the highlight line for HiDPI environments, which was also caused by the complexity of rounded tabs. And while doing that, we also found that the shapes used for rendering the tab headers (the background, the outline, the keyline and so on) are not properly aligned, in particular when using round tabs.

Is this question only about removing the functionality from the CSS-based rendering (CTabRendering) or do we also want to simplify the renderer of SWT (CTabFolderRenderer), which does currently always render rounded tabs?

[vogella]

This request is for CTabRendering, if we should also change the SWT renderer, I suggest a new issue in the SWT repo. I'm in favor of such a change in SWT.

[HannesWell]

IIRC @azoitl also is working with special tabs in GEF. Maybe this is also interesting for you?

[azoitl]

@HannesWell thx for tagging me here. I have a student who is investigating vertical tabs for CTabFolder. Removing the rounded edges in both Eclipse Platform and SWT would greatly reduce the effort for him. Especially as the CTabFolderRenderer has options to switch between rounded and not rounded rendering which makes the code extremely ugly.