Bug 125327 [Dialogs] Error message shown in the InputDialog is not fully visible
When an error message returned by InputValidator is long, InputDialog displays it partially. My suggestion is to create error label with SWT.WRAP flag, or something like this.
bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/InputDialog.java
super.buttonPressed(buttonId);
    }
    /*
     * (non-Javadoc)
     * 
     * @see org.eclipse.jface.window.Window#configureShell(org.eclipse.swt.widgets.Shell)
     */
    protected void configureShell(Shell shell) {
        super.configureShell(shell);
        if (title != null) {
			shell.setText(title);
		}
    }
    /*
     * (non-Javadoc)
     * 
     * @see org.eclipse.jface.dialogs.Dialog#createButtonsForButtonBar(org.eclipse.swt.widgets.Composite)
     */
    protected void createButtonsForButtonBar(Composite parent) {
        
        okButton = createButton(parent, IDialogConstants.OK_ID,
                IDialogConstants.OK_LABEL, true);
        createButton(parent, IDialogConstants.CANCEL_ID,
                IDialogConstants.CANCEL_LABEL, false);
        
        
        text.setFocus();
        if (value != null) {
            text.setText(value);
            text.selectAll();