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Render Modes

RadEditor has different render modes that can change the actual HTML markup that is rendered. They are exposed via the RenderMode property that can have four possible values - Classic, Lightweight, Mobile and Auto. This functionality was introduced in the Q3 2014 version.

The possible options are:

  • Classic—this mode is the rendering that has been used before. It remains without changes and it is the default value of the property. In this mode tables and background images (in several sprites) are used to create the layout (including rounded corners and shadows).

  • Lightweight—this mode emphasizes on semantic HTML and CSS3. It reduces the amount of markup the control renders and makes it easier to customize. This also reduces the number of image sprites required by the control. All of this decreases the overall size and complexity of each skin, including custom ones.

  • Mobile—as of Q2 2015, a phone-optimized layout is available. It targets small screens, uses font-icons and the flex-model for positioning and sizing.

  • Auto—this mode makes each control choose the appropriate rendering mode according to the used browser—Classic, Lightweight or Mobile. This functionality was added in Q3 2013.

RadEditor and its child controls (RadWindow and RadToolBar, and RadContextMenu when RenderMode is Lightweight), as well as the other controls included in the Telerik® UI for ASP.NET AJAX suite that utilize render modes, support only one type of render mode per page. This includes mode being set for a standalone RadEditor, RadToolBar, RadWindow and RadWindowManager, RadMenu and RadContextMenu. All such controls must have the same RenderMode on a given page. This also includes instances from user controls and master pages.

Setting Render Mode

There are two ways to configure the rendering mode of the controls:

  • The RenderMode property in the markup or in the code-behind that can be used for a particular instance:


    <telerik:RadEditor ID="RadEditor1" runat="server" RenderMode="Lightweight">


    RadEditor1.RenderMode = Telerik.Web.UI.RenderMode.Lightweight;


    RadEditor1.RenderMode = Telerik.Web.UI.RenderMode.Lightweight   
  • A global setting in the web.config file that will affect the entire application, unless a concrete value is specified for a given control instance:


        <add key="Telerik.Web.UI.Editor.RenderMode" value="lightweight" />
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