Allow xdg-settings to set the default OS handler for url protocols.

scripts/xdg-settings

 #!/bin/sh
 #---------------------------------------------
 #   xdg-settings
 #
 #   Utility script to get various settings from the desktop environment.
 #
 #   Refer to the usage() function below for usage.
 #
 #   Copyright 2009, Google Inc.
 #
@@ skipping 17 matching lines @@
 #   ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 #   OTHER DEALINGS IN THE SOFTWARE.
 #
 #---------------------------------------------
 
 manualpage()
 {
 cat << _MANUALPAGE
 Name
 
-xdg-settings - get various settings from the desktop environment
+   xdg-settings - get various settings from the desktop
+   environment
 
 Synopsis
 
-xdg-settings { get | check | set } {property} [value]
+   xdg-settings { get | check | set } {property} [subproperty]
+   [value]
 
-xdg-settings { --help | --list | --manual | --version }
+   xdg-settings { --help | --list | --manual | --version }
 
 Description
 
-xdg-settings gets various settings from the desktop environment. For instance,
-desktop environments often provide proxy configuration and default web browser
-settings. Using xdg-settings these parameters can be extracted for use by
-applications that do not use the desktop environment's libraries (which would
-use the settings natively).
+   xdg-settings gets various settings from the desktop
+   environment. For instance, desktop environments often provide
+   proxy configuration and default web browser settings. Using
+   xdg-settings these parameters can be extracted for use by
+   applications that do not use the desktop environment's
+   libraries (which would use the settings natively).
 
-xdg-settings is for use inside a desktop session only. It is not recommended to
-use xdg-settings as root.
+   xdg-settings is for use inside a desktop session only. It is
+   not recommended to use xdg-settings as root.
 
 Options
 
---help
-    Show command synopsis.
---list
-    List all properties xdg-settings knows about.
---manual
-    Show this manualpage.
---version
-    Show the xdg-utils version information.
+   --help
+          Show command synopsis.
+
+   --list
+          List all properties xdg-settings knows about.
+
+   --manual
+          Show this manualpage.
+
+   --version
+          Show the xdg-utils version information.
+
+Properties
+
+   When using xdg-settings to get, check or set a destkop setting,
+   properties and possibly sub-properties are used to specify the
+   setting to be changed.
+
+   Some properties (such as default-web-browser) fully describe
+   the setting to be changed. Other properties (such as
+   default-url-scheme-handler) require more information (in this
+   case the actual scheme to set the default handler for) which
+   must be provided in a sub-property.
 
 Exit Codes
 
-An exit code of 0 indicates success while a non-zero exit code indicates
-failure. The following failure codes can be returned:
+   An exit code of 0 indicates success while a non-zero exit code
+   indicates failure. The following failure codes can be returned:
 
-1
-    Error in command line syntax.
-2
-    One of the files passed on the command line did not exist.
-3
-    A required tool could not be found.
-4
-    The action failed.
+   1
+          Error in command line syntax.
+
+   2
+          One of the files passed on the command line did not
+          exist.
+
+   3
+          A required tool could not be found.
+
+   4
+          The action failed.
 
 Examples
 
-Get the desktop file name of the current default web browser
-
+   Get the desktop file name of the current default web browser
         xdg-settings get default-web-browser
 
-
-Check whether the default web browser is firefox.desktop, which can be false
-even if "get default-web-browser" says that is the current value (if only some
-of the underlying settings actually reflect that value)
-
+   Check whether the default web browser is firefox.desktop, which
+   can be false even if "get default-web-browser" says that is the
+   current value (if only some of the underlying settings actually
+   reflect that value)
         xdg-settings check default-web-browser firefox.desktop
 
-
-Set the default web browser to google-chrome.desktop
-
+   Set the default web browser to google-chrome.desktop
         xdg-settings set default-web-browser google-chrome.desktop
 
-
+   Set the default mailto URL scheme handler to be
+   evolution.desktop
+        xdg-settings set default-url-scheme-handler evolution.desktop
 _MANUALPAGE
 }
 
 usage()
 {
 cat << _USAGE
-xdg-settings - get various settings from the desktop environment
+   xdg-settings - get various settings from the desktop
+   environment
 
 Synopsis
 
-xdg-settings { get | check | set } {property} [value]
+   xdg-settings { get | check | set } {property} [subproperty]
+   [value]
 
-xdg-settings { --help | --list | --manual | --version }
+   xdg-settings { --help | --list | --manual | --version }
 
 _USAGE
 }
 
 #@xdg-utils-common@
 
 #----------------------------------------------------------------------------
 #   Common utility functions included in all XDG wrapper scripts
 #----------------------------------------------------------------------------
 
@@ skipping 408 matching lines @@
     mkdir -p "${XDG_DATA_HOME:-$HOME/.local/share}/applications"
     xdg-mime default "$1" "$MIME" || return
     if [ x"`get_browser_mime`" != x"$1" ]; then
         # Put back the original value
         xdg-mime default "$orig" "$MIME"
         exit_failure_operation_failed
     fi
 }
 
 # }}} MIME utilities
+# {{{ KDE utilities
+
+# Reads the KDE configuration setting, compensating for a bug in some versions of kreadconfig.
+read_kde_config()
+{
+    configfile="$1"
+    configsection="$2"
+    configkey="$3"
+    browser="`kreadconfig --file $configfile --group $configsection --key $configkey`"
+    if [ x"$browser" != x ]; then
+        echo "$browser"
+    else
+        # kreadconfig in KDE 4 may not notice Key[$*]=... localized settings, so
+        # check by hand if it didn't find anything (oddly kwriteconfig works
+        # fine though).
+        kdeglobals_dir=`kde${KDE_SESSION_VERSION}-config --path config  | cut -d ':' -f 1`
+        kdeglobals="$kdeglobals_dir/$configfile"
+        [ ! -f "$kdeglobals" ] && return
+        # This will only take the first value if there is more than one.
+        grep "^$configkey"'\[$[^]=]*\]=' "$kdeglobals" | head -n 1 | cut -d= -f 2-
+    fi
+}
+
+# }}} KDE utilities
 # {{{ KDE
 
 # Resolves the KDE browser setting to a binary: if prefixed with !, simply removes it;
 # otherwise, uses desktop_file_to_binary to get the binary out of the desktop file.
 resolve_kde_browser()
 {
     [ -z "$browser" ] && return
     case "$browser" in
       !*)
         echo "${browser#!}"
@@ skipping 13 matching lines @@
       !*)
         desktop="`binary_to_desktop_file "${browser#!}"`"
         basename "$desktop"
         ;;
       *)
         echo "$browser"
         ;;
     esac
 }
 
-# Reads the KDE browser setting, compensating for a bug in some versions of kreadconfig.
 read_kde_browser()
 {
-    browser="`kreadconfig --file kdeglobals --group General --key BrowserApplication`"
-    if [ x"$browser" != x ]; then
-        echo "$browser"
-    else
-        # kreadconfig in KDE 4 may not notice Key[$*]=... localized settings, so
-        # check by hand if it didn't find anything (oddly kwriteconfig works
-        # fine though).
-        kdeglobals_dir=`kde${KDE_SESSION_VERSION}-config --path config  | cut -d ':' -f 1`
-        kdeglobals="$kdeglobals_dir/kdeglobals"
-        [ ! -f "$kdeglobals" ] && return
-        # This will only take the first value if there is more than one.
-        grep '^BrowserApplication\[$[^]=]*\]=' "$kdeglobals" | head -n 1 | cut -d= -f 2-
-    fi
+    read_kde_config kdeglobals General BrowserApplication
 }
 
 get_browser_kde()
 {
     browser="`read_kde_browser`"
     if [ x"$browser" = x ]; then
         # No explicit default browser; KDE will use the MIME type text/html.
         get_browser_mime
     else
         resolve_kde_browser_desktop
@@ skipping 235 matching lines @@
         mv "$temp" "$helpers_rc"
     else
         rm -f "$temp"
         return 1
     fi
 }
 
 # }}} xfce
 # }}} default browser
 
+# {{{ default url scheme handler
+
+exit_unimplemented_default_handler()
+{
+    exit_failure_operation_impossible "default-url-scheme-handler not implemented for $DE"
+}
+
+# {{{ KDE
+
+# Recent versions of KDE support default scheme handler applications using the mime type
+# of x-scheme-handler/scheme. Older versions will not support this but do have support
+# for setting a default mail handler. There is also a system in KDE where .protocol files
+# can be used, however this is not supported by this script.
+# When reading a scheme handler we will use the default mail handler for the mailto scheme,
+# otherwise we will use the mime type x-scheme-handler/scheme.
+
+get_url_scheme_handler_kde()
+{
+    if [ "$1" = "mailto" ]; then
+        handler="`read_kde_config emaildefaults PROFILE_Default EmailClient | first_word`"
+        echo "handler is $handler"
+        if [ x"$handler" != x ]; then
+            binary_to_desktop_file "$handler"
+        else
+            get_browser_mime "x-scheme-handler/$1"
+        fi
+    else 
+        get_browser_mime "x-scheme-handler/$1"
+    fi
+}
+
+check_url_scheme_handler_kde()
+{
+    check="`desktop_file_to_binary "$2"`"
+    if [ -z "$check" ]; then
+        echo no
+        exit_success
+    fi
+    if [ x"$1" = "mailto" ]; then
+        binary="`read_kde_config emaildefaults PROFILE_Default EmailClient`"
+        if [ x"$binary" != x"$check" ]; then
+            echo no
+            exit_success
+        fi
+    fi
+    handler="`get_browser_mime x-scheme-handler/$1`"
+    binary="`desktop_file_to_binary "$handler"`"
+    if [ x"$binary" != x"$check" ]; then
+        echo no
+        exit_success
+    fi
+    echo yes
+    exit_success
+}
+
+set_url_scheme_handler_kde()
+{
+    set_browser_mime "$2" "x-scheme-handler/$1" || return
+    if [ "$1" = "mailto" ]; then
+        binary="`desktop_file_to_binary "$2"`"
+        kwriteconfig --file emaildefaults --group PROFILE_Default --key EmailClient "$binary"
+    fi
+}
+
+# }}} KDE
+# {{{ GNOME
+
+get_url_scheme_handler_gnome()
+{
+    binary="`gconftool-2 --get /desktop/gnome/url-handlers/$1/command | first_word`"
+    if [ x"$binary" != x"" ]; then
+        # gconftool gives the binary (maybe with %s etc. afterward),
+        # but we want the desktop file name, not the binary. So, we
+        # have to find the desktop file to which it corresponds.
+        desktop="`binary_to_desktop_file "$binary"`"
+        basename "$desktop"
+    fi
+}
+
+check_url_scheme_handler_gnome()
+{
+    check="`desktop_file_to_binary "$2"`"
+    if [ -z "$check" ]; then
+        echo no
+        exit_success
+    fi
+    binary="`gconftool-2 --get /desktop/gnome/url-handlers/$1/command | first_word`"
+    if [ x"$binary" != x"$check" ]; then
+        echo no
+        exit_success
+    fi
+    echo yes
+    exit_success
+}
+
+set_url_scheme_handler_gnome()
+{
+    binary="`desktop_file_to_binary "$2"`"
+    [ "$binary" ] || exit_failure_file_missing
+
+    gconftool-2 --type string --set /desktop/gnome/url-handlers/$1/command "$binary %s"
+    gconftool-2 --type bool --set /desktop/gnome/url-handlers/$1/needs_terminal false
+    gconftool-2 --type bool --set /desktop/gnome/url-handlers/$1/enabled true
+}
+
+# }}} GNOME
+# {{{ GNOME 3.x
+
+get_url_scheme_handler_gnome3()
+{
+    get_browser_mime "x-scheme-handler/$1"
+}
+
+check_url_scheme_handler_gnome3()
+{
+    desktop="$2"
+    check="`desktop_file_to_binary "$2"`"
+    if [ -z "$check" ]; then
+        echo no
+        exit_success
+    fi
+    browser="`get_browser_mime "x-scheme-handler/$1"`"
+    if [ x"$browser" != x"$desktop" ]; then
+        echo no
+        exit_success
+    fi
+    echo yes
+    exit_success
+}
+
+set_url_scheme_handler_gnome3()
+{
+    binary="`desktop_file_to_binary "$2"`"
+    [ "$binary" ] || exit_failure_file_missing
+    set_browser_mime "$2" || return
+
+    # Set the default browser.
+    set_browser_mime "$2" "x-scheme-handler/$1" || return
+}
+
+# }}} GNOME 3.x
+# {{{ xfce
+
+get_url_scheme_handler_xfce()
+{
+    exit_unimplemented_default_handler "$1"
+}
+
+check_url_scheme_handler_xfce()
+{
+    exit_unimplemented_default_handler "$1"
+}
+
+set_url_scheme_handler_xfce()
+{
+    exit_unimplemented_default_handler "$1"
+}
+
+# }}} xfce
+# }}} default protocol handler
+
 dispatch_specific()
 {
     # The PROP comments in this function are used to generate the output of
     # the --list option. The formatting is important. Make sure to line up the
     # property descriptions with spaces so that it will look nice.
     if [ x"$op" = x"get" ]; then
         case "$parm" in
           default-web-browser) # PROP:           Default web browser
             get_browser_$DE
             ;;
 
+          default-url-scheme-handler) # PROP:    Default handler for url scheme
+            get_url_scheme_handler_$DE "$1"
+            ;;
+
           *)
             exit_failure_syntax
             ;;
         esac
     elif [ x"$op" = x"check" ]; then
         case "$parm" in
           default-web-browser)
             check_desktop_filename "$1"
             check_browser_$DE "$1"
             ;;
 
+          default-*-handler)
+            check_desktop_filename "$2"
+            check_url_scheme_handler_$DE "$1" "$2"
+            ;;
+
           *)
             exit_failure_syntax
             ;;
         esac
     else # set
-        [ $# -eq 1 ] || exit_failure_syntax "unexpected/missing argument"
         case "$parm" in
           default-web-browser)
+            [ $# -eq 1 ] || exit_failure_syntax "unexpected/missing argument"
             check_desktop_filename "$1"
             set_browser_$DE "$1"
             ;;
 
+          default-*-handler)
+            [ $# -eq 2 ] || exit_failure_syntax "unexpected/missing argument"
+            check_desktop_filename "$2"
+            set_url_scheme_handler_$DE "$1" "$2"
+            ;;
+
           *)
             exit_failure_syntax
             ;;
         esac
     fi
 
     if [ $? -eq 0 ]; then
         exit_success
     else
         exit_failure_operation_failed
@@ skipping 66 matching lines @@
     ;;
 
     generic)
     dispatch_generic "$@"
     ;;
 
     *)
     exit_failure_operation_impossible "unknown desktop environment"
     ;;
 esac