Thank you, Jonathan!

Oh, and for new templates to be picked up by Textastic, you do not need to restart the app. It's sufficient to just add a new file and select the template.

Ah, ok. My answer above was for adding syntax highlighting support for .mxml files. I didn't realize you wanted to add a template.

You need to json-encode the snippet string. So in your case, you need to escape the quote characters and newlines. 

Replace " with \" and newlines with \n

It would something like this:

snippet = "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n<s:WindowedApplication xmlns:fx=\"http://ns.adobe.com/mxml/2009\" \n                       xmlns:s=\"library://ns.adobe.com/flex/spark\" \n                       xmlns:mx=\"library://ns.adobe.com/flex/m\""

What exactly does not work?

You can add your own TextMate-compatible syntax definitions to Textastic. Have a look at the manual: http://www.textasticapp.com/v4/manual/lessons/How_can_I_add_my_own_syntax_definitions__themes_and_templates.html

You can find a Flex TextMate bundle with an .mxml language definition at https://github.com/simongregory/flex-tmbundle

Sorry, but Apple doesn't allow compilers or interpreters in apps that also allow file downloads and file sharing.

Sorry, but I don't speak Russian. Can you please post in English (or German)?

It would sure be nice, but I think it would be out of the scope of Textastic. But it sounds like a good idea for a new app.

The cursor movement happens instantly, but the the scrolling happens after a very short delay. This is not only when using external keyboard, but also when you move the cursor with your finger.

I'll consider improving the behavior.