One can autostart an application such that it launches on session start with an xdg desktop file in ~/.config/autostart (or /etc/xdg/autostart).

But my application (a python/gtk/webkit/html5 app) when autostarted has a unity (and a unity-2d) launcher icon that is a gray question mark, even though:

• when I find it in dash, the dash shows the icon I specify in my main desktop file (in /usr/share/applications)
• when I launch it from dash, the launcher shows the icon I specify in my main desktop file
• when I add it as a favorite, the launcher shows the proper icon

There are two cases where I get the gray question mark icon:

• autostart
• launch from terminal (this use case is not essential though and doesn't involve the desktop file anyway: but should/does ubuntu have an xdg desktop file interpreter à la #!/usr/bin/desktop or something)

So: what is needed such unity (3d/2d) launcher panel shows the icon specified in an autostart desktop file?