Well, they could just make a C extension to Electron that draws a blinking colored line (that's all it is) using the OSes arbitrary drawing facilities.

No need to have an official OS caret function (especially if you're not a native text field, and caret aside, the rest of your text editing will be different/broken in subtle ways compared to the OS).

I'm not aware of any system where one can create that caret without a text edit control to hold it. That means that, if the standard text edit control isn't suited for what you want to do, you can't have the caret.

Certainly, on the original Mac OS (a system on which I worked on OS patches for detecting the location of the caret) the method that application used for drawing the caret varied widely. I've seen it implemented by drawing a line, by drawing a rectangle, either in one go or in two parts (that happened in applications that supported a split caret, even if the caret wasn't split), with various transfer modes. Slanted carets typically were application-specific, too.

> I'm not aware of any system where one can create that caret without a text edit control to hold it.

Windows allows this. In a parent comment I posted a link to the API docs. All Windows requires is a window to hold the caret, it doesn't care what kind of window it is.