Bug 87111 [Dialogs] Feature: add general-purpose page change notification for dialogs
New dynamic help pane attaches itself to all the dialogs that JFace provides. Some of these dialogs manage multiple pages but dynamic help has no way of registering for page change notification. Examples of dialogs that exhibit this behaviour are WizardDialog, PreferenceDialog, LaunchConfigurationDialog (in Debug), PropertiesDialog etc. Attached is the code for the following proposed enhancement: 1) A new interface 'IBaseDialogPage' that interfaces like IDialogPage and ILaunchConfigurationTab can extend 2) A class PageChangedEvent for page change notification 3) A new interface 'IPageChangeProvider' 4) A new interface 'IPageChangedListener' In the attached patch, WizardDialog and PreferenceDialog implement IPageChangeProvider and notify page changed listeners whenever current page changes. This allows dynamic help to update its content and show the relevant help for the currently selected page. Since IBaseDialogPage is now a base interface for IDialogPage, two methods (getTitle() and getControl()) are moved up from IDialogPage. This is consistent with ILaunchConfigurationTab and does not clash with any existing method.
bundles/org.eclipse.jface/src/org/eclipse/jface/wizard/WizardDialog.java
private String pageMessage;
    private int pageMessageType = IMessageProvider.NONE;
    private String pageDescription;
    
    private ProgressMonitorPart progressMonitorPart;
    private Cursor waitCursor;
    private Cursor arrowCursor;
    private MessageDialog windowClosingDialog;
    
    private Button backButton;
    private Button nextButton;
    private Button finishButton;
    private Button cancelButton;
    private Button helpButton;
    private SelectionAdapter cancelListener;
    private boolean isMovingToPreviousPage = false;
    private Composite pageContainer;
    private PageContainerFillLayout pageContainerLayout = new PageContainerFillLayout(
            5, 5, 300, 225);
    private int pageWidth = SWT.DEFAULT;
    private int pageHeight = SWT.DEFAULT;
    private static final String FOCUS_CONTROL = "focusControl"; 
    private boolean lockedUI = false;
    /**
     * A layout for a container which includes several pages, like
     * a notebook, wizard, or preference dialog. The size computed by
     * this layout is the maximum width and height of all pages currently
     * inserted into the container.
     */
    protected class PageContainerFillLayout extends Layout {