Bug 33550 [Dialogs] Dialog should support remembering size and position
There are several dialogs that remember its size and position. Since restore the size and considering screen size and font changes isn't trivial JFace's Dialog class should support remembering and restoring size and position. These would realy ease the task for subclasses. May be you can steel the code from OpenTypeSelectionDialog.
bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/Dialog.java
*/
    protected int convertVerticalDLUsToPixels(int dlus) {
        
        if (fontMetrics == null)
            return 0;
        return convertVerticalDLUsToPixels(fontMetrics, dlus);
    }
    /**
     * Returns the number of pixels corresponding to the width of the given
     * number of characters.
     * <p>
     * This method may only be called after <code>initializeDialogUnits</code>
     * has been called.
     * </p>
     * <p>
     * Clients may call this framework method, but should not override it.
     * </p>
     * 
     * @param chars
     *            the number of characters
     * @return the number of pixels
     */
    protected int convertWidthInCharsToPixels(int chars) {
        
        if (fontMetrics == null)
            return 0;
        return convertWidthInCharsToPixels(fontMetrics, chars);
    }
    /**
     * Creates a new button with the given id.