I am trying to make some syntax colouring for Visual Studio 2022, when displaying BBC Basic V from the Acorn Archimedes. This is a language that had its heyday in the late 80s and early 90s. I’ve copied the TextMate tmLanguage file from .BAT files and got it to handle BASIC V and Arm assembler keywords like LDR, IF, SUB, ELSE etc. That’s great. But I don’t understand how to add code folding. In BBC Basic, a procedure is typically defined in code as

    DEFPROCname
        <some mix of BBC Basic and assembler> 
    ENDPROC

This is where the textmate syntax has me baffled. MS adding a json wrapper to everything isn’t helping.

Right at the end of the basicv.tmLanguage file I’ve made, I added

    <key>foldingStartMarker</key>
    <string>DEFPROC*</string>

right before the final but it doesn’t appear to work.

The file is being picked up by Visual Studio 2022, because keywords are showing up in blue.