I've fixed this on my version, but thought it would be a good amendment for DDgui.
Currently there's no way to set the caret colour. As I changed my colour scheme to use a black window, the caret is invisible.
I set up a caret colour variable and changed the RGB(0,0,0) on line 1605 to use the variable instead.
Variable font kerning size may also be useful. (Again, I've updated this locally in my version)
What do you mean by font kerning size?
Setting the caret colour is not what I have thought about. But I will use a global variable instead, so you have a tweak for that:
GLOBAL gDDguiCaretColour%
By kerning size I mean the size of the gap between two letters (e.g. 2 pixels between letters might look good on a small font, but 10 might be appropriate when the font is much bigger)
OK, I'll add an argument to the ddgui_update_font or so function.