Content Filters

Filters are small code snippets, which are called in a sequence to process the editor content, when the mode (html / design / preview) is changed. Basically, the editor content is supplied to the filter chain and each filter gets a chance to modify it.
Currently the available filters correspond to the following editor properties:

1. StripAbsoluteAnchorPaths - IE converts all relative URLs to absolute and this property allows to control/revert the process
2. StripAbsoluteImagesPaths - IE converts all relative URLs to absolute and this property allows to control/revert the process
3. ConvertTagToLower - (Under IE) converts tag names to lower case, which is XHTML compliant
4. ConvertFontToSpan - convert the found font tags to span tags
5. AllowScripts - (false by default) - allows for (CLIENT or SERVER) script tags to be inserted/submitted with the editor. Eases the developer's job against script attacks.
Note: This property replaces the deprecated AllowServerScripts property.

There is also a sixth unconditional filter that adds quotes around tag attributes (e.g. width = "25"), as IE strips quotes automatically when the editor content is requested.

There are two additional properties, used for fine-tuning the behavior of the StripAbsoluteAnchorPaths and StripAbsoluteImagesPaths filters:
AnchorPathToStrip
ImagesPathToStrip
They are useful in some rare cases when the local absolute path to be stripped cannot be detected properly and has to be specified manually.

The other filters can be modified, detached and re-attached if necessarily on the client using the Filter API.

Implementing Custom Filters

This example has one �ustom Filter implemented. It modifies the editor content so that in HTML mode it is presented with capital letters and in Design mode it is shown in all-small letters. This is a fairly simplistic and unrealistic scenario, but it demonstrates what is necessary for createing and "hooking" a filter to the editor. In real-life scenario the filter would likely employ a number of regular expressions of various complexity that will make the necessary changes to the content.

The two steps for implementing a Custom Filter are:

1. Create a javascript function/class that implements one or more of the three filter methods:
   � GetDesignContent (Called when the editor is switched from some other mode to DESIGN mode)
   � GetHtmlContent (Called when the editor is switched from some other mode to HTML mode)
   � GetPreviewContent (Called when the editor is switched from some other mode to PREVIEW mode)

2. Register the filter with the editor. The best way to do it is to register a OnClientLoad function that instantiates the filter and adds it to the filter manager.