Ubuntu-MATE 20.04.1, Menu & Mime System problems

[David LaVerne]

Bug Report, Ubuntu-MATE 20.04.1, Menu & Mime System

I am not sure where the actual error lies -
It might be in the packaging and installation of Brave for Ubuntu-MATE;
It might be in the Main Menu editor, 'mozo'
    mozo-1.24.0/Mozo;
It might be Preferred Applications, 'mate-default-applications-properties'
    mate-control-center-1.24.0/capplets/default-appplications;
It might be the library call that Preferred Applications uses to populate
    its combo boxes - g_app_info_get_all_for_type();
It might be the Add to Panel, 'mate-panel'
    mate-panel-1.24.0/mate-panel;
It might be the library call that Add to Panel uses to get the menu items,
    which is, or is buried in - matemenu_tree_new();
Or it might be that an intermediate file/cache is not created correctly
    an (unknown to me) intermediate program;
It may be some files get messed up by something else.

Since it is between several programs,etc, I am going to post the details
here on LaunchPad, and put shorter posts on the github locations for the
individual programs, linking to here.

Previously have seen a similar issue with Preferred Applications not
showing available Applications even though they (Firefox, Evolution,
Rhythmbox) are installed, and files (*.desktop, menu, mime) appear
to be correct. See: https://ubuntu-mate.community/t/23387
This problem has been around for a while; a forum entry from Jul '16
mentions the behavior: https://ubuntu-mate.community/t/7669
A post here suggest testing it against a guest session; I did and the
new user had the correct Preferred Applications combo boxes, so it
would appear to be a user profile settings issue, but all the files
in ~/.config and ~/.local seem to be correct.
Possibly/probably related issues:
    https://bugs.launchpad.net/ubuntu-mate/+bug/1800585 (2018/10/30)
    https://bugs.launchpad.net/ubuntu-mate/+bug/1898706 (2020/10/06)
    https://bugs.launchpad.net/ubuntu-mate/+bug/1903355 (2020/11/06)
The software (README) has github locations for bug tracking:
    https://github.com/mate-desktop/mozo/issues
 https://github.com/mate-desktop/mate-control-center/issues
    https://github.com/mate-desktop/mate-panel/issues

This newest incident was a brand new install. Installed system from USB,
did Software Updater (left out Firefox). Rebooted, Welcome -> Utilities
and -> Software Boutique: Brave, Wireshark, Synaptic Package Manager;
remove Firefox; no Evolution, no Thunderbird, no LibreOffice, ...
Welcome -> Browser Selection is Brave

In setting up the Panel at the top, Classic Menu,
    Add to Panel -> Application Launcher
        Brave is *NOT* in the Application Menu/List
Brave is *NOT* in Menu -> Applications -> Internet (but Wireshark is)
Brave is *NOT* listed for Run Application applet
Brave *IS* listed in the Preferred Applications combo box (Web Browser)
Brave *IS* listed in System -> Preferences -> Look and Feel -> Main Menu
    under Applications -> Internet -> Brave Web Broswer
It is simultaneously *NOT* listed in the Menu itself

Went back into Look and Feel -> Main Menu; poked around a bit (IIRC),
    looked at Properties of Brave and exitted.
Brave now *IS* listed in Menu
Brave is *NOT* in Preferred Applications (combo box empty)
Right-click on .html does offer "Open with Brave Web Browser" in submenu.

------------------------------------------------------------------------------

Note: in mate-panel-1.24.0/mate-panel/panel-addto.c, line 1335-6
        g_signal_connect (dialog->addto_dialog, "destroy",
     G_CALLBACK (panel_addto_dialog_destroy), dialog);
does not say
                          G_OBJECT (dialog->addto_dialog)
as all the other calls to g_signal_connect do.
Probably an error.

------------------------------------------------------------------------------

I looked at all the files involved: menu and mime and desktop, in all
the various places:
    ~/.config, ~/.local/share,
    /etc/menu, /etc/xdg/menus,
    /usr/share/applications, /usr/share/mate, /usr/share/mate-menu,
        /usr/share/menu, /usr/share/mime,
    /usr/local/share, /usr/local/share/mime,
    /usr/lib/mate-menu, /usr/lib/menu,
    /var/lib/snapd/desktop
None of them seem to be missing, and none of them seem to be missing
appropriate content; but this is after Brave reappeared in the Menu, so
only Preferred Applications is messed up right now.

As things stand, I can find nothing wrong with the files that would
explain the Preferred Applications issue, although I have not looked at
(have not gotten) the code for g_app_info_get_all_for_type(), it appears
that the files which (I assume) would be used
    /usr/share/applications/brave-browser.desktop
    ~/.local/share/applications/brave-browser.desktop
are there with the correct MimeType (x-scheme-handler/http) listed and
Categories (Network;WebBrowser;) for the Menu shown.
They are the same except the local one has "NoDisplay=false" in it.
The one status command I can think of,
    xdg-mime query default x-scheme-handler/http
returns
    brave-browser.desktop
I am at a loss to explain the Preferred Applications empty combo box,
which is why I suspect g_app_info_get_all_for_type().
I can leave this disk as it is for probably several weeks, if there are
any questions about files, content, or behavior.

Since it is relatively early in the Install process, I can re-install on
another (smaller) disk, following the same (written down) procedure, and
try to capture why Brave is not in the Menu. I don't have the code for
matemenu_tree_new() nor whatever library calls it makes, so it again will
come down to files and content (is brave-browser.desktop there, in the
correct place, and with the correct Category).