Question about support for rendering Khmer text correctly in various environments

[mbert]

Of course this is not an "issue", merely a bunch of questions hoping that someone here may be able to help.

While learning Khmer I have also got into Khmer script. I have found that while most word processors can render Khmer texts well, this does not seem to be the case for other environments:

On the Linux command line, of course with Unicode Khmer fonts installed, rendering consonants with foots and vowels are fails: e.g. something like រ្ធី looks like រ with a "+" underneath and the vowel missing altogether. On my Mac this works quite well, even on the command line.

The same effect seems to occur when trying to render PDF files using some PDF rendering library from program code.

Just wondering: do terminal emulators or PDF renderers need some particular functionality for rendering Khmer text correctly?