Well, this is a functionality I need (studying cell structure and processes in biology). I can easily replace the output of lt and gt special character output in an xhtml file. However, that doesn't help me with any other form of output.
Image/Audio support is easy to implement in the user-interface however would require some dramatic changes to the file format. Storing images in the XML file is troublesome (base64 encoded files would litter the xml file) and saving them alongside the xml would litter the file system. A possible option is to save in a zip/gzip container. Regardless, it would be some time before this feature can be fully implemented.
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Image/Audio support is easy to implement in the user-interface however would require some dramatic changes to the file format. Storing images in the XML file is troublesome (base64 encoded files would litter the xml file) and saving them alongside the xml would litter the file system. A possible option is to save in a zip/gzip container. Regardless, it would be some time before this feature can be fully implemented.