Patches xdg-open to decode scheme:// URLs by querying xdg-mime

xdg-open-scheme-handler.diff

--- /usr/bin/xdg-open	2011-10-04 06:49:38.000000000 +0200
+++ /home/towo/bin/xdg-open	2012-11-08 15:05:36.632522149 +0100
@@ -446,8 +446,35 @@
         fi
     fi
 
+    if (echo "$1" | egrep -q '^[a-z]+:'); then
+        scheme=`echo "$1" | cut -d: -f1`;
+        handler=`xdg-mime query default x-scheme-handler/$scheme`;
+        if [ -n "$handler" ] ; then
+            xdg_user_dir="$XDG_DATA_HOME"
+            [ -n "$xdg_user_dir" ] || xdg_user_dir="$HOME/.local/share"
+
+            xdg_system_dirs="$XDG_DATA_DIRS"
+            [ -n "$xdg_system_dirs" ] || xdg_system_dirs=/usr/local/share/:/usr/share/
+
+            for x in `echo "$xdg_user_dir:$xdg_system_dirs" | sed 's/:/ /g'`; do
+                local file="$x/applications/$handler"
+                if [ -r "$file" ] ; then
+                    command="`grep -E "^Exec(\[[^]=]*])?=" "$file" | cut -d= -f 2- | first_word`"
+                    command_exec=`which $command 2>/dev/null`
+                    if [ -x "$command_exec" ] ; then
+                        $command_exec "$1"
+                        if [ $? -eq 0 ]; then
+                            exit_success
+                        fi
+                    fi
+                fi
+            done
+        fi
+    fi
+
     OLDIFS="$IFS"
     IFS=":"
+
     for browser in $BROWSER; do
         IFS="$OLDIFS"
         if [ x"$browser" != x"" ]; then

If xdg-open doesn't detect a desktop environment, it defaults to using the open_generic tree. open_generic tries to see if it's a path/file URL, in which case a wrapper for xdg-mime query is called (the wrapper is reused here). If it doesn't find anything, it just gives up and hands it over to the browser.

But in the case of magnet: urls and such, handing it to the browser is rather counter-productive. Thus this little patch that queries for a relevant x-scheme-handler for the given URL. Be sure to use e.g. xdg-mime default transmission-gtk.desktop x-scheme-handler/magnet to define a local handler for magnet URLs.