LightweightSystem分析

*LightweightSystem概述

---功能

draw2d的核心功能,在draw2d和SWT之间的桥梁.内容包括figure的绘制,事件转发,图形更新.

---由3个主要组成成分,

root figure,event dispatcher,update manager

下面通过源码分析功能

*root figure

---在构造器初始化时被自动创建,作为自定义figure的容器,

	protected RootFigure createRootFigure() {
		RootFigure f = new RootFigure();
		f.addNotify();
		f.setOpaque(true);
		f.setLayoutManager(new StackLayout());　//
		return f;
	}

---自定义的figure通过setContents(IFigure figure)设置

	public void setContents(IFigure figure) {
		if (contents != null) 
			root.remove(contents); //root figure only contains a child
		contents = figure;
		root.add(contents); 
	}

figure的层次结构,root figure ->自定义figure->孩子们

*event dispatcher

---默认的事件调度器是SWTEventDispatcher

---功能,将Canvas上的注册SWT事件,通过dispatcher传给对应的figure(获取焦点的figure)

---实现原理

１.LightweightSystem.addListeners() //实现canvas添加各种SWT事件监听器,这个监听器为内部类LightweightSystem.EventHandler

2.EventHandler调用dispatcher处理

		/** @see MouseTrackListener#mouseHover(MouseEvent) */
		public void mouseHover(MouseEvent e) {
			getEventDispatcher().dispatchMouseHover(e);
		}

3.dispatcher调用对应的figure完成处理

对应上面方法的后续处理实现

	/**
	 * @see EventDispatcher#dispatchMouseHover(org.eclipse.swt.events.MouseEvent)
	 */
	public void dispatchMouseHover(org.eclipse.swt.events.MouseEvent me) {
		receive(me);
		if (mouseTarget != null)
			mouseTarget.handleMouseHover(currentEvent);
		/*
		 * Check Tooltip source. Get Tooltip source's Figure. Set that tooltip
		 * as the lws contents on the helper.
		 */
		if (hoverSource != null) {
			toolTipHelper = getToolTipHelper();
			IFigure tip = hoverSource.getToolTip();
			Control control = (Control) me.getSource();
			org.eclipse.swt.graphics.Point absolute;
			absolute = control.toDisplay(new org.eclipse.swt.graphics.Point(
					me.x, me.y));
			toolTipHelper.displayToolTipNear(hoverSource, tip, absolute.x,
					absolute.y);
		}
	}

*update manager

---功能

绘制和更新figure的内容

---默认的实现private UpdateManager manager = new DeferredUpdateManager();
---实现原理

1.LightweightSystem初始化过程中,

在初始化canvas时,配置update manager

	/**
	 * Sets the LightweightSystem's control to the passed Canvas.
	 * 
	 * @param c
	 *            the canvas
	 * @since 2.0
	 */
	public void setControl(Canvas c) {
		if (canvas == c)
			return;
		canvas = c;
		if ((c.getStyle() & SWT.DOUBLE_BUFFERED) != 0)
			getUpdateManager().setGraphicsSource(
					new NativeGraphicsSource(canvas));
		else
			getUpdateManager().setGraphicsSource(
					new BufferedGraphicsSource(canvas));　//配置图形上下文,实质是GC
		getEventDispatcher().setControl(c);
		addListeners();

		// Size the root figure and contents to the current control's size
		Rectangle r = new Rectangle(canvas.getClientArea());
		r.setLocation(0, 0);
		root.setBounds(r);
		root.revalidate();
	}

初始化root时配置,配置root figure

	/**
	 * Sets this LightweightSystem's root figure.
	 * 
	 * @param root
	 *            the new root figure
	 */
	protected void setRootPaneFigure(RootFigure root) {
		getUpdateManager().setRoot(root); //设置root
		this.root = root;
	}

2.在Canvas的ControlListener时触发update manager,就是在Canvas上有move和resize的情况时发生

	/**
	 * Resizes and revalidates the root figure when the control is resized.
	 */
	protected void controlResized() {
		if (ignoreResize > 0)
			return;
		Rectangle r = new Rectangle(canvas.getClientArea());
		r.setLocation(0, 0);
		root.setBounds(r);
		root.revalidate();
		getUpdateManager().performUpdate();　//执行update manager,完成更新
	}

*总结

---draw2d的一切都是从Canvas开始的,将功能分成figure的图形展现,update manager的更新机制,和dispatcher的SWT事件转发机制.

所有这些功能在LightweightSystem中集成.