Bug 59037 [Navigator] Package explorer flicker when switching/closing editors
If 'Link with editor' is active I see a lot of redrawing going on in the Package Explorer view when I switch between editors (or close an open editor). If the file opened in the second editor already appears in the Package Explorer, it is simply selected and there is no flicker. If, however, the view has to be scrolled to show the second file, I see a lot of redrawing before the view is shown in the new position. The Outline view also seems to draw a white background before drawing the content for the active editor, but it's not nearly as annoying as the Package Explorer (it's true that hte PAckage Explorer has much more items, though).
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractTreeViewer.java
* Recursively collects all expanded elements from the given widget.
     * 
     * @param result
     *           a list (element type: <code>Object</code>) into which to
     *           collect the elements
     * @param widget
     *           the widget
     */
    private void internalCollectExpanded(List result, Widget widget) {
        Item[] items = getChildren(widget);
        for (int i = 0; i < items.length; i++) {
            Item item = items[i];
            if (getExpanded(item)) {
                Object data = item.getData();
                if (data != null)
                    result.add(data);
            }
            internalCollectExpanded(result, item);
        }
    }
    /**
     * Tries to create a path of tree items for the given element. This method
     * recursively walks up towards the root of the tree and assumes that
     * <code>getParent</code> returns the correct parent of an element.
     * 
     * @param element
     *           the element
     * @param expand
     *           <code>true</code> if all nodes on the path should be
     *           expanded, and <code>false</code> otherwise