KeyPublisher does not treat all shortcuts equally

Environment

• OS Version: Ubuntu 20.04
• Ignition: Edifice, built from source
• ign-gui branch: main (da55587d6fad56b739efd9c124699863dd22859f), built from source - together with Edifice

Description

Very minor thing, which might as well not by an issue - just something done by design. I do not have any use-case for it currently (just something I noticed when trying out the demo), so please just close this issue if you think it works as it should.

• Expected behavior: All keypresses are published, including "blank space" ("spacebar") key.
• Expected behavior (alternative): All keypresses except bound shortcuts are published.
• Actual behavior: Keys such as 't' (shortcut for Translate mode) or 'r' (shortcut for Rotate mode) are published together with other keys. However, key for "spacebar" (shortcut for pause/play) is not published.

Note: Combinations with holding "ctrl" or "shift" allow "spacebar" key to be published

Steps to reproduce

1. ign gazebo empty.sdf
2. Add Key publisher GUI plugin (manually)
3. ign topic -e -t /keyboard/keypress
4. While Gazebo GUI is in focus, press keys such as 'a' or 'b' - keys are published
5. While Gazebo GUI is in focus, press keys such as 't' (shortcut for translate mode) or 'r' (shortcut for Rotate mode) - keys are published
6. While Gazebo GUI is in focus, press "spacebar" - no key is published