Zoom - gedit plugin
This plugin for Gedit - GNOME text editor - adds the ability to change the font size using either the menu bar, keyboard shortcuts or <Ctrl>+mousewheel in a same manner as Firefox, LibreOffice and other applications.
It is included in the Gmate package, a set of plugins and improvements to make Gedit a powerfull programmer text editor.
Download the file gedit-zoom-version.tar.gz and extract the package into the ~/.gnome2/gedit/plugins directory, or - for a system-wide deployment - into /usr/lib/gedit-2/plugins (the path may be different, depending on your distribution).
Then activate and configure the plugin through Edit -> Preferences -> Plugins.
It proved helpful for development to check out the git-repository to your favorite location and create symlinks in your personal plugins directory to the necessary files and directories. There is a make target, that accomplishes this:
$ make install-dev
See the LICENSE file.
If the font size is changed through Edit -> Preferences -> Font & Colors, then these changes are not yet recognized by this plugin. Therefore changing the zoom level still calculates with the fontsize when gedit was last started. Restarting gedit fixes this annoyance.