system tray icons loaded from GResource broken w/ Cinnamon

[albrechtd]

I have a question (not sure if its actually a bug in my code, a “special” Cinnamon feature or an issue there) regarding the Freedesktop system tray icons in Cinnamon's notification area.

In my application, I create a tray icon using the XAppStatusIcon object, setting the icon from a GResource. This works fine on XFCE and kde (and maybe others?), but fails on Cinnamon. As example, see the attached trivial code (xapp-test.tar.gz, just say maketo build it):

• run ./sample – displays a stock icon, which woks fine on Cinnamon, XFCE and kde plasma.
• run ./sample x which should display the custom icon from the resource. Works perfectly on XFCE and kde plasma, but cinnamon displays an “icon missing” icon, although the screen's default icon theme “knows” it.

Interestingly, if I store the custom icon in a file and set it by calling xapp_status_icon_set_icon_name(status_icon, "/path/to/sample-icon.png"), it is displayed correctly in Cinnamon.

I ran the tests on Debian testing, but see the same effent on stable and LMDE.

Any idea what goes wrong in my code?

[mtwebster]

The gtk_icon_theme_add_resource_path() call only adds the icon to the theme for that process.

In Cinnamon, the icon to be rendered in the panel comes from the Cinnamon process.

Are saying this exact sample app works in XFCE and kde? If so, it's probably resorting to its fallback (GtkStatusIcon/XEmbed) which renders icons process-local, and tells the X server how to get it (if you remove the xapp-status-applet from your panel, the icon will probably start working, and show up in the systray applet instead, if you have that applet enabled).

There's really no way around this, currently, we'd need to add a way for XAppStatusIcon to be provided with pixel data directly from the theme. This is something we deliberately avoided - any necessary icons should be added to the 'hicolor' theme with some sort of app-specific prefix.. this way they end up available in whichever is the current icon theme.

[albrechtd]

Thanks a lot for your detailed explanations!

Are saying this exact sample app works in XFCE and kde?

Yes. Its a minimal stripped-down sample of another application. I only noticed the problem because one user complained that the icon was missing in LMDE — everyone else was apparently using Xfce, KDE, etc., where it works fine.

If so, it's probably resorting to its fallback (GtkStatusIcon/XEmbed) which renders icons process-local, and tells the X server how to get it (if you remove the xapp-status-applet from your panel, the icon will probably start working, and show up in the systray applet instead, if you have that applet enabled).

At least for XFCE, libsystray.so doesn't reference GtkStatusIcon or XEmbed. Didn't look into the sources, though. To be honest, I have no idea what libxapp does internally (and I didn't care, as it does apparently work on other desktops). The example code does not use any other code than Gtk (excluding the deprecated GtkStatusIcon) and libxapp. IOW, libxapp seems “somehow” to be able to push the icon to the XFCE panel (i.e. libsystray.so); same for kde.

There's really no way around this, currently, we'd need to add a way for XAppStatusIcon to be provided with pixel data directly from the theme. This is something we deliberately avoided - any necessary icons should be added to the 'hicolor' theme with some sort of app-specific prefix.. this way they end up available in whichever is the current icon theme.

Well, yes, exactly the additional packaging of extra files (in the real world there is more than one) is what I wanted to avoid using GResource… Maybe a clumsy workaround is to detect Cinnamon, and iff it is used dump the resource to a temp file which is then loaded with its full path (which, as I noted, seems to work). Hmmm…

[mtwebster]

You can run your app with:

XAPP_DEBUG=StatusIcon <youapp>

It will tell you what 'mode' it's working in - it will say fallback (GtkStatusIcon) or native (dbus).

[albrechtd]

Thanks again for your insight!

You can run your app with:

XAPP_DEBUG=StatusIcon <youapp>

It will tell you what 'mode' it's working in - it will say fallback (GtkStatusIcon) or native (dbus).

I can confirm that it's native for Cinnamon and GtkStatusIcon for xfce and kde (had to re-build the Debian package, btw., as the original one does not define ENABLE_DEBUG, i.e. the environment variable is not recognised…). I also monitored the dbus, and on kde (but not xfce) the application seems to expose the icon pixmap using org.freedesktop.StatusNotifierItem.IconPixmap (but didn't try to convert the hex bytes into a real image). No idea if this interface might be a general solution for replacing the deprecated GtkStatusIcon, though; probably a question for the xapp developers.

Anyway, it appears that I really should re-write my application – which is sad as GResource does really simplify life a lot! And in any case, it would be really helpful if the xapp docs would mention these limitations.