I use Xournal to edit pdfs, either to highlight important words or to add some annotations.
Some pdfs have a (dark) coloured background, so it would be nice to add some annotations in white colour. The problem is, selecting a white text colour makes the text you are writing and editing unreadable until you press enter.
My current workaround is slecting an other textcolor, writing the text and switching back to white.
I have an idea for a better solution: let the editor area of the text white but make it semitransparent (independent from the text colour). So a white text is always readable expect on a white background (which makes no sense to write white text on white background). Furthermore this gives the user a better feeling how his text might look after pressing enter and would prevent him to write for example black text on black background.