icecat "mailto" handler does not work - and cannot be reconfigured by user

[Danny Milosavljevic <dannym@scratchpost.org>]

> Unless I misunderstood what you mean: this already exists.  On the page
> you linked to above look for “reply via email to”.  It’s followed by a
> button.  When you click on it you get a “mailto”-Link.

Whoops. I should have read the page better.

However, clicking on that button in icecat does not send E-Mail for me. 

Monitoring the network interface I can see that it redirects to a mailto: URL. So that's nice.

Checking the application preferences of icecat, it only gives "always ask" (note: it doesn't ask) and not an application for "mailto". (in GuixSD)

Creating my own HTML page with a mailto link doesn't work either.

Therefore, I reported a bug to Guix too.

Bug report follows:

"mailto:" links don't work in icecat.

Checking the icecat source code, there are several ways to handle E-Mail. One of them is as "external helper app". One of those (not sure whether it's the correct one) uses gio's g_app_info_launch_default_for_uri in order to launch helper applications.

There is a test icecat-38.8.0/uriloader/exthandler/tests/unit/test_handlerService.js that does:

  let isLinux = ("@mozilla.org/gio-service;1" in Components.classes);
  if (isLinux) {
    // Check mailto handler from GIO
    // If there isn't one, then we have no mailto handler
    let gIOSvc = Cc["@mozilla.org/gio-service;1"].
                 createInstance(Ci.nsIGIOService);
    try {
      gIOSvc.getAppForURIScheme("mailto");
      noMailto = false;
    } catch (ex) {
      noMailto = true;
    }
  }

And this ./toolkit/system/gnome/nsGIOService.cpp uses g_app_info_launch_default_for_uri .

Therefore, I tried it out:

#include <glib.h>
#include <gio/gio.h>
#include <stdlib.h>

int main() {
        GError* error;
        g_app_info_launch_default_for_uri("mailto:foo@example.com", NULL, &error);
        // g_app_info_launch_default_for_uri("http://www.google.at/", NULL, &error);
        if (error) {
                g_warning("err %s", error->message);
                g_error_free(error);
                return 1;
        } else
                return 0;
}

I get:

** (process:12464): WARNING **: err Operation not supported

If I debug it some more I get:

$ strace -f ./g 2>&1 |grep open |grep -v ENOENT

open("/home/dannym/.local/share//mime/mime.cache", O_RDONLY) = 3
open("/home/dannym/.guix-profile/share/mime/mime.cache", O_RDONLY) = 3
open("/run/current-system/profile/share/mime/mime.cache", O_RDONLY) = 3
open("/home/dannym/.guix-profile/share/mime/mime.cache", O_RDONLY) = 3
open("/run/current-system/profile/share/mime/mime.cache", O_RDONLY) = 3
open("/home/dannym/.guix-profile/lib/gio/modules", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
open("/home/dannym/.guix-profile/lib/gio/modules/giomodule.cache", O_RDONLY) = 4
open("/home/dannym/.guix-profile/lib/gio/modules/libdconfsettings.so", O_RDONLY|O_CLOEXEC) = 4
open("/run/current-system/profile/lib/gio/modules", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
open("/run/current-system/profile/lib/gio/modules/giomodule.cache", O_RDONLY) = 4
open("/gnu/store/6qrijb6cfyvs8svacr0l9a75vcpypr5f-glib-2.48.0/lib/gio/modules", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
open("/gnu/store/4lbgxvsk8xl75hlkjqgrqvmpq74app73-dconf-0.26.0/lib/gio/modules", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
open("/gnu/store/4lbgxvsk8xl75hlkjqgrqvmpq74app73-dconf-0.26.0/lib/gio/modules/giomodule.cache", O_RDONLY) = 4
open("/home/dannym/.guix-profile/lib/gio/modules", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
open("/home/dannym/.guix-profile/lib/gio/modules/giomodule.cache", O_RDONLY) = 4
open("/run/current-system/profile/lib/gio/modules", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
open("/run/current-system/profile/lib/gio/modules/giomodule.cache", O_RDONLY) = 4
open("/gnu/store/m3py3rk71ihlfgvj2kss7054hwfqwkpq-glib-2.48.0/lib/gio/modules", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
[pid 12632] open("/usr/share/locale/locale.alias", O_RDONLY <unfinished ...>
[pid 12632] open("/home/dannym/.config/mimeapps.list", O_RDONLY) = 5
[pid 12632] open("/gnu/store/8m00x5x8ykmar27s9248cmhnkdb2n54a-glibc-2.22/lib/gconv/gconv-modules", O_RDONLY|O_CLOEXEC) = 5
[pid 12632] open("/home/dannym/.local/share/applications", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 5
[pid 12632] open("/home/dannym/.local/share/applications/mimeapps.list", O_RDONLY) = 5
[pid 12632] open("/home/dannym/.local/share/applications/mimeinfo.cache", O_RDONLY) = 5
[pid 12632] open("/home/dannym/.guix-profile/share/applications", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 5
[pid 12632] open("/run/current-system/profile/share/applications", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 5
[pid 12632] open("/run/current-system/profile/share/applications/mimeinfo.cache", O_RDONLY) = 5
[pid 12632] open("/home/dannym/.guix-profile/share/applications", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 5
[pid 12632] open("/run/current-system/profile/share/applications", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 5
[pid 12632] open("/run/current-system/profile/share/applications/mimeinfo.cache", O_RDONLY) = 5

There would be g_app_info_set_as_default_for_type () to set a new default application in nsGIOService - which is exposed and used by ./browser/components/shell/nsGNOMEShellService.cpp on setting icecat up as default browser (so not always).

I'm using Fluxbox.