深入浅出Web Page Editor之二:布局引擎的四个层次

1. 简介


  •  CSS层
  •  HTML层
  •  Tag Converter层
  •  Edit层


2. CSS层


2.1. ICSSStyle


2.2. Figure和Layout



EditPart层 Figure层
ElementEditPart CSSFigure
DocumentEditPart FlowPage
TextEditPart CSSTextFigure


2.3. 一些不被由css所决定的绘制内容

ITagEditInfo接口可以提供一信息以让绘制引擎决定是否给一个元素绘制边框。至于如何绘制边框,可以找到BorderUtil:: drawBorderDecorator()中去一探究竟。默认情况下,BODY和HTML标签在任何状态下都会被一个虚线框包络着。一个标签是否需要画边框,是由它的TagConverter的_needBorderDecorator属性所决定的。在CSSFigure的paintBorder中有如下的代码:

	protected void paintBorder(Graphics graphics) {
		CSSLayout layout = (CSSLayout) getLayoutManager();
		if (layout != null && !layout.handlingBorderForBlock()) {

		ICSSStyle style = this.getCSSStyle();
		if (style != null) {
			CSSBorder border1 = new CSSBorder(this.getCSSStyle());
			border1.paint(this, graphics, NO_INSETS);

			// draw a border for those special elements like <h:form>, etc.
			ITagEditInfo editInfo = (ITagEditInfo) style

			if (editInfo != null && editInfo.needBorderDecorator()) {
				BorderUtil.drawBorderDecorator(this, graphics);


这里的HTMl层指的是在布局引擎中的HTML部分,它实际上就是一个中间层,指导如何根据Element建模中的数据来初始化其对应Figure。对应到代码上,就是形形色色的****FigureHandler。其创建过程可以在FigureFactory:: createFigureHandler中找到。

	private static IFigureHandler createFigureHandler(Element ele) {
		String tag = ele.getTagName();
		if ("input".equalsIgnoreCase(tag)) { //$NON-NLS-1$
			return new InputFigureHandler();
		} else if ("select".equalsIgnoreCase(tag)) { //$NON-NLS-1$
			return new SelectFigureHandler();
		} else if ("img".equalsIgnoreCase(tag)) { //$NON-NLS-1$
			return new ImgFigureHandler();
		} else if ("object".equalsIgnoreCase(tag)) { //$NON-NLS-1$
			return new ObjectFigureHandler();
		} else if ("textarea".equalsIgnoreCase(tag)) { //$NON-NLS-1$
			return new TextareaFigureHandler();
		} else if ("br".equalsIgnoreCase(tag)) { //$NON-NLS-1$
			return new BRFigureHandler();
		} else if (!HTMLUtil.isVisualHtmlElement(tag)) {
			return new HiddenFigureHandler(getSharedHTMLImage(ele));
		else {
			return new DefaultFigureHandler();


public void updateFigure(Element node, CSSFigure oldFigure) {
    ICSSWidgetProvider provider = initializeWidgetProvider(node);
    .setFixedLayoutManager(new CSSWidgetLayout(oldFigure, provider));


4.Tag converter层

在WPE中有一个tag converter机制。这个机制可以把一些用户自定定的html标签转化到标准的标签上,以方便绘制。它是工作在GEF的model层的。

	protected Element doConvertRefresh() {
		Element result = createElement(getHostElement().getTagName());
		ConverterUtil.copyAllAttributes(getHostElement(), result, null);
		if (!internalIsWidget(result)) {
			copyChildren(getHostElement(), result);
		} else {
			dumCopyChildren(getHostElement(), result);
		return result;

例如,如果开发人员想要创建一个“<abc></abc>”控件。通过tag converter机制可以把它在绘制的时候转换成<div><input/></div>的形式,就不用再专门去为这个控件写绘图的代码了。虽然已经经过了转换,但是其实数据的真实模型并没有发生改变。始终谨记,convter之后的标签仅仅是为了绘图方便。




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