Bug 304211 StackRenderer does not set eagerly created controls to the item
Right-clicking on a Java element and then using 'Open Declaration' opens an editor on the specified file but its content is not shown. Switching tabs or selecting items in the 'Outline' view does _not_ help. Seems to be calling IWorkbenchPage's APIs properly. No idea yet as to what's going on over here.
bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/workbench/ui/renderers/swt/StackRenderer.java
MElementContainer<MUIElement> stack = part.getParent();
		CTabFolder ctf = (CTabFolder) stack.getWidget();
		if (ctf == null)
			return null;
		CTabItem[] items = ctf.getItems();
		for (int i = 0; i < items.length; i++) {
			if (items[i].getData(OWNING_ME) == part)
				return items[i];
		}
		return null;
	}
	@Override
	public void hideChild(MElementContainer<MUIElement> parentElement,
			MUIElement child) {
		super.hideChild(parentElement, child);
		if (!(((MUIElement) parentElement) instanceof MPartStack)
				|| !(child instanceof MPart))
			return;
		CTabFolder ctf = (CTabFolder) parentElement.getWidget();
		if (ctf == null)
			return;
		
		CTabItem[] items = ctf.getItems();
		for (int i = 0; i < items.length; i++) {
			if (items[i].getData(OWNING_ME) == child) {
				items[i].setControl(null);
				items[i].dispose();
			}
		}