Wt::WPaintedWidget-优快云博客

WPaintedWidget是一种向量绘图组件，它在浏览器端渲染并可根据浏览器类型自动选择渲染方式，如HtmlCanvas或InlineSVG。该组件需通过派生类实现paintEvent方法来绘制图形。

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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的用途是作为一个widget，允许用户使用向量图在其上作画。】

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，可能采用以下渲染方法：】

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.

【不同的渲染方法对应不同的 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().

【如果禁用 JavaScript，那么基于 JavaScript 的 HtmlCanvas 将不会被采用，而使用 InlineSVG 代替。我们可以使用 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 需要文档作为 XHTML 渲染，这就要求配置文件中必须设置 <send-xhtml-mime-type> 选项，默认情况下，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，并重新实现 paintEvent(WPaintDevice *paintDevice) 。要想在 WPaintDevice 作画，你需要使用 WPainter 。Repainting 是由 update() 引发的。】

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_;
 };