Bug 42587 Left over from content assist
M3 - set preference that content assist should overwrite - open content assist on some word so that the rest of the word is indicated to be overwritten - transfer focus to the content assist widget using TAB - Esc -> overwrite indication is still there
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/text/link/contentassist/CompletionProposalPopup2.java
* Computes the table hight hint for <code>table</code>.
	 * 
	 * @param table the table to compute the height for
	 * @param rows the number of rows to compute the height for
	 * @return the height hint for <code>table</code>
	 */
	private int getTableHeightHint(Table table, int rows) {
		if (table.getFont().equals(JFaceResources.getDefaultFont()))
			table.setFont(JFaceResources.getDialogFont());
		int result= table.getItemHeight() * rows;
		if (table.getLinesVisible())
			result+= table.getGridLineWidth() * (rows - 1);
		
		return result + 4;		
	}
	private boolean validateProposal(IDocument document, ICompletionProposal p, int offset, DocumentEvent event) {
		
		if (p instanceof ICompletionProposalExtension2) {
			ICompletionProposalExtension2 e= (ICompletionProposalExtension2) p;				
			if (e.validate(document, offset, event))
				return true;
		} else if (p instanceof ICompletionProposalExtension) {
			ICompletionProposalExtension e= (ICompletionProposalExtension) p;
			if (e.isValidFor(document, offset))
				return true;
		}
		return false;
	}
	/**
	 * Returns the graphical location at which this popup should be made visible.