Phoenity for Thunderbird was created by Lim Chee Aun with the assistance of Chris Neale. I made minor modifications to make it compatible with Thunderbird 1.5. The theme is now compatible with Thunderbird 2.0a1 and 3.0a1.
This theme incorporates some subskins from Phoenity Firefox described in:
http://phoenity.com/subskins.html
But now there is no need to look for userChrome.css file! Since version 0.1.8, the sub-skins can be selected from the "About Phoenity" dialog found through the themes window (Phoenity Thunderbird must be the active theme for showing the About Phoenity dialog).
The indent and outdent icons were corrected in version 0.2.3 after a problem was noticed by DaveM (thank you, DaveM).
Thanks to Wolfey I became aware that the icon in the Mark toolbar button is incorrect when using small icons. Thank will be fixed for version 0.2.4 of this theme. Release 0.2.4 will also include some support within the theme for some extensions such as "Mail Redirect," "abcTajpu," and "DownloadThemAll!"
Regarding another request from Wolfey: I am not sure about what to do regarding the color of non-compatible extensions, because forcing a color is not good to do with a theme that takes elements from the O.S. theme, i.e., forcing red text could be a problem if the O.S. has red as the background color.
Robert brought up a bug that put me in shame. The file toolbar button was not showing up properly since in releases 0.2.3 and 0.2.4 of the theme. Release 0.2.5 of the theme corrects this problem.
Thanks again to Jakub Lukomski for his assistance and patience. Again, thanks to Lim Chee Aun for creating this theme and his continued oversight.
Extras
