Wt::WPaintedWidget

来自：http://www.webtoolkit.eu/wt/doc/reference/html/classWt_1_1WPaintedWidget.html#_details

Detailed Description

A widget that is painted using vector graphics.

【 WPaintedWidget的用途是做为一个widget，容许用户使用向量图在其上做画。】

A painted widget is rendered from basic drawing primitives. Rendering is done not on the server but on the browser, using different rendering methods:

【WPaintedWidget渲染自基本的绘图元素，渲染发生在浏览器端，而不是服务器端，可能采用如下渲染方法：】

Browser	Methods	Default method
Firefox 1.5+	HtmlCanvas, InlineSVG	HtmlCanvas
Internet Explorer 6.0+	InlineVML	InlineVML
Safari	HtmlCanvas, InlineSVG	HtmlCanvas
Opera	InlineSVG, HtmlCanvas*	InlineSVG
other	?	HtmlCanvas

* HtmlCanvas occasionally suffers from rendering artefacts in Opera.

The different rendering methods correspond to different WPaintDevice implementations, from which this widget choses a suitable one depending on the browser capabilities and configuration.

【不一样的渲染方法对应不一样的 WPaintDevice 实现，WPaintedWidget 会根据浏览器能力和配置自动选择适合的渲染方法。 】

If no JavaScript is available, the JavaScript-based HtmlCanvas will not be used, and InlineSVG will be used instead. The method used may be changed by using setPreferredMethod().

【若是禁用 JavaScript， 那么基于 JavaScript 的 HtmlCanvas 将不会被采用，而使用 InlineSVG 代替。咱们能够使用 setPreferredMethod() 方法改变渲染方法。 】

InlineSVG requires that the document is rendered as XHTML. This must be enabled in the configuration file using the <send-xhtml-mime-type> option. By default, this option is off.

【InlineSVG 须要 文档做为 XHTML 渲染，这就要求配置文件中必须设置 <send-xhtml-mime-type> 选项，默认状况下，这个选项是被关闭的。 】

To use a WPaintedWidget, you must derive from it and reimplement paintEvent(WPaintDevice *paintDevice). To paint on a WPaintDevice, you will need to use a WPainter. Repainting is triggered by calling the update() method.

【要想使用 WPaintedWidget，你必须定义继承于它的子类，并从新实现 paintEvent(WPaintDevice *paintDevice) 。要想在 WPaintDevice 做画，你须要使用  WPainter 。Repainting 是由 update()  引起的。 】

Usage example:【示例】

class MyPaintedWidget : public Wt::WPaintedWidget
 {
 public:
   MyPaintedWidget(Wt::WContainerWidget *parent = 0)
     : Wt::WPaintedWidget(parent),
       foo_(100)
   {
      resize(200, 200); // provide a default size
   }

   void setFoo(int foo) {
      foo_ = foo;
      update(); // trigger a repaint
   }

 protected:
   void paintEvent(Wt::WPaintDevice *paintDevice) {
     Wt::WPainter painter(paintDevice);
     painter.drawLine(20, 20, foo_, foo_);
     ...
   }

 private:
   int foo_;
 };

CSS

Styling through CSS is not applicable.

Note:【注意】

A WPaintedWidget requires that it is given a size using resize() or by a layout manager.

         【 WPaintedWidget 须要被指定尺寸，或指定布局管理器】

See also:

WImage

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