In August 2007, some X users wanted the function keys (F1–F12) to have explicit modifier-key variants (“shift levels”) for internationalization purposes.
So after three years of silence and a little discussion, it got implemented in xkeyboard-config in June 2011. The new levels got filled with “VoidSymbol” as a placeholder.
Saying “VoidSymbol” when you mean “F1” might be a bad idea, as some users noticed.
Fortunately there was already an obvious fix (2011 Oct), and people really did think it worked.
Alas, some users still had symptoms.
In September 2012, the discussion had a breakthrough, which led to changes in GTK+ and in xkeyboard-config.
And finally, after a system update this past November, I could—for the first time in over a year—use Shift+F3 to search backwards in my browser again.
- xkeyboard-config 2.4.1 until 2.7
- gtk+ until 2.24.13 / 3.5.14