Bug 216811 [Markers] ExtendedMarkersView#setFocus doesn't
The result is that focus is lost if you drag the view to another stack... The most common implementation seems to be 'viewer.getControl().setFocus()... To test: select an element in the Problems or Tasks view. Drag the view to a new location (could be in an existing stack or a new one) notice that while the view is the active view the arrow keys don't navigate...
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/views/markers/ExtendedMarkersView.java
preservedSelection.clear();
		if (selection instanceof IStructuredSelection) {
			IStructuredSelection structured = (IStructuredSelection) selection;
			Iterator iterator = structured.iterator();
			while (iterator.hasNext()) {
				MarkerItem next = (MarkerItem) iterator.next();
				if (next.isConcrete()) {
					preservedSelection.add(new MarkerSelectionEntry(next));
					getCategoriesToExpand().add(next.getParent());
				} else
					getCategoriesToExpand().add(next);
			}
		}
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.part.ViewPart#saveState(org.eclipse.ui.IMemento)
	 */
	public void saveState(IMemento memento) {
		super.saveState(memento);
		memento.putString(TAG_GENERATOR, builder.getGenerator().getId());
		if (!getCategoriesToExpand().isEmpty()) {
			IMemento expanded = memento.createChild(TAG_EXPANDED);
			Iterator categories = getCategoriesToExpand().iterator();
			while (categories.hasNext()) {
				expanded.createChild(TAG_CATEGORY, (String) categories.next());
			}
		}
		builder.saveState(memento);