I want to bind C-= in Emacs but Emacs sees it as "=". Emacs is 24.3 running in gnome-terminal on Ubuntu 14.10. xev sees that Control is pressed but C-v C-= in bash prints only "=". I assume that either Unity, GTK or gnome-terminal is swallowing the key but do not know how to look further.
My first thought was that Ctrl++ ("Zoom In") could be failing to pass the key through when the shift modifier is not pressed. However, the other size adjustment keys can be captured and disabling this shortcut does not help.
Terminology note: Emacs and Bash use the prefix C- to indicate holding Ctrl. Gnome uses Ctrl+. I've mixed them in my description as appropriate.