The trick for me was just using a hidden input and updating the state of an in game input box. The code is ancient by today's standards but uses a reasonably simple technique to get the selection bounds of the text.
It works with auto complete on phones and has been stable for a decade.
hidden input box is something I heard before from some hacker-ish old collegues - seems to be a powerful and reliable approach to store state & enable communication between components!
Oops, I worded my comment poorly -- it's not a hidden input, but rather a "CSS-visibility-hidden textbox input". Hidden inputs are useful but something completely different.
One of the frustrating things about web dev, I find, is the staggering gulf between apparently nearly identical tasks and unpredictability of it. So often I will find myself on gwernnet asking Said Achmiz, 'this letter is a little too far left in Safari, can we fix that?' and the answer is 'yes but fixing that would require shipping our own browser in a virtual machine.' ¯\_(ツ)_/¯
Actually, I came up with that all on my own after I noted to myself that capture-recapture would work; and it amused me so much that I resolved to try to come up with a proper list filling out the idea. I did get some of the other ideas from LLMs, though.
