Syncfusion HTMLUI研究一

HTMLUI可以加载HTML页面，并且相比WebKit等占用资源特别少

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<body marginheight="0" marginwidth="0" bgcolor="#ffffff">
<div>
    <span style="font:Bold">12121</span>
    <span style="font:Bold;Color:Blue">121212</span>
    <span style="font:Bold;Color:Blue">121212</span>
</div>
<hr></hr>
<div>
    <span style="font:Bold;font-size:9pt">1212</span>
    <span style="font:Bold;font-size:9pt">1221</span>
    <span style="font:Bold;font-size:9pt">1212</span>
</div>
<p>
    <span style="font:Bold;font-size:9pt">12121</span>
    
    <span id="aaa" style="24px;height:24px;"></span>
    
    <span style="font:Bold;font-size:9pt">121212</span>
</p>
</div>
</body>
</html>

（1）HTMLUI源码中绘制部分

/// <summary>
/// Starts the drawing of the document from the start element.
/// </summary>
/// <param name="e">Paint event data.</param>
private void ProcessDraw(PaintEventArgs e)
{
    if (e == null)
        throw new ArgumentNullException("e");

    if (m_startDrawElement == null)
    {
        this.RenderRoot.DrawElement(e);
    }
    else
    {
        m_startDrawElement.DrawElement(e);

        // Reset start element.
        m_startDrawElement = null;
    }
}

如果m_startDrawElement为null，在根html tag下绘制，否则在指定元素下绘制。
（2）FlowLayoutPanel中使用HTMLUI时，要先用一个UserControl或者其它控件作为HTMLUI的父控件，不然滚动时会出现花屏现象。

（3）动态改变HTMLUI元素内容代码

private void htmluiControl1_PreRenderDocument(object sender, Syncfusion.Windows.Forms.HTMLUI.PreRenderDocumentArgs e)
        {
            Hashtable htmlelements = new Hashtable();
            htmlelements = e.Document.ElementsByUserID;
            Label lable=new Label();
            lable.Text = "1";
            lable.Width = 24;
            lable.Height = 24;
            lable.BackColor = Color.Red;
            BaseElement aaa = htmlelements["aaa"] as BaseElement;
                new CustomControlBase(aaa, lable);

        }

        private void ChangeLableValue(HTMLUIControl htmluiControl,string str)
        {

            var v = htmluiControl.Document.GetElementsByUserIdHash()["aaa"];
            Label v1= htmluiControl.Document.GetControlByElement((IHTMLElement) v) as Label;
            v1.Text = str;
        }

（4）有时创建会报线程间操作无效: 从不是创建控件“”的线程访问它，经检查原因在PreRenderDocument,修改PreRenderDocument如下。

private void htmluiControl1_PreRenderDocument(object sender, Syncfusion.Windows.Forms.HTMLUI.PreRenderDocumentArgs e)
        {
            Hashtable htmlelements = new Hashtable();
            htmlelements = e.Document.ElementsByUserID;

            Action<Hashtable> action = (data) =>
            {
                Label lable = new Label();
                lable.Text = "1";
                lable.Width = 24;
                lable.Height = 24;
                lable.BackColor = Color.Red;
                BaseElement aaa = htmlelements["aaa"] as BaseElement;
                new CustomControlBase(aaa, lable);
            };
            Invoke(action, htmlelements);

        }

一起研究的来群：616945527