Eclipse e4 M4 has introduce a new look and feel for the tabs in the workbench. See Eclipse e4 M4 New and Noteworthy. Unfortunately the news and noteworthy document did not give information how to enable this feature.
The e4 mailing list has recently discussed this topic and Remy Suen was kind enough to provide this information. To turn this feature on you have to add the tag “newtablook” to your PartStack.
For example if you create an new e4 application with the e4 wizard you can add this tag via:
<children xsi:type="application:PartSashContainer" xmi:id="_vTa8kiuFEd-PeMLywHTM-g" id="_vTa8kiuFEd-PeMLywHTM-g">
<children xsi:type="application:PartStack" xmi:id="_vTa8kyuFEd-PeMLywHTM-g" id="_vTa8kyuFEd-PeMLywHTM-g">
<tags>newtablook</tags>
<children xsi:type="application:Part" xmi:id="_vTa8lCuFEd-PeMLywHTM-g" id="_vTa8lCuFEd-PeMLywHTM-g" label="Main"/>
</children>
This lead to the following result:

Compared to the “old” look and feel.

For this topic see also Bug 305147 which discusses to move this feature to the CSS styling capabilities.
Eclipse e4 M4 has introduce a new look and feel for the tabs in the workbench. See Eclipse e4 M4 New and Noteworthy. Unfortunately the news and noteworthy document did not give information how to enable this feature.
The e4 mailing list has recently discussed this topic and Remy Suen was kind enough to provide ...