[gparted] Replace deprecated gtk_show_uri() method for help window (!82)

[Mike Fleetwood <mfleetwo src gnome org>]

commit 26f4dc504ab6837d717b1f047edc3853b1c67a5f
Author: Curtis Gedak <gedakc gmail com>
Date:   Sat May 15 11:52:50 2021 -0600

    Replace deprecated gtk_show_uri() method for help window (!82)
    
    The gtk_show_uri() [1] method was deprecated as of gtk3 version 3.22 and
    has been replaced with gtk_show_uri_on_window [2].
    
    [1] https://developer.gnome.org/gtk3/stable/gtk3-Filesystem-utilities.html#gtk-show-uri
    [2] https://developer.gnome.org/gtk3/stable/gtk-migrating-2-to-3.html#id-1.6.3.3.7
    
    Note that AppInfo::launch_uris() has been removed because with
    glib/glibmm >= 2.58 AppInfo::launch_uris() always reports success even
    when yelp is not launched and in such cases prevents the dialog
    reporting the error from being displayed.
    
    Closes !82 - Replace deprecated gtk_show_uri() method for help window

 configure.ac       | 12 ++++++++
 src/Win_GParted.cc | 81 ++++++++++++++++++++++++++++--------------------------
 2 files changed, 54 insertions(+), 39 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 4cd0c85e..22e2c93a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -266,6 +266,18 @@ PKG_CHECK_EXISTS(
 )
 
 
+dnl Check for gtk+-3.0 >= 3.22 to determine availability of gtk_show_uri_on_window() function.
+AC_MSG_CHECKING([for gtk_show_uri_on_window() function])
+PKG_CHECK_EXISTS(
+       [gtk+-3.0 >= 3.22.0],
+       [AC_DEFINE([HAVE_GTK_SHOW_URI_ON_WINDOW], 1,
+                  [Define to 1 if gtk provides gtk_show_uri_on_window function.])
+        AC_MSG_RESULT([yes])
+       ],
+       [AC_MSG_RESULT([no])]
+)
+
+
 dnl Definitions for building of and with gtest.  Gets flags for pthread via earlier
 dnl gthread package check.
 GTEST_CPPFLAGS="-DGTEST_HAS_PTHREAD=1"
diff --git a/src/Win_GParted.cc b/src/Win_GParted.cc
index f15d29f4..f2d1975a 100644
--- a/src/Win_GParted.cc
+++ b/src/Win_GParted.cc
@@ -1778,52 +1778,55 @@ void Win_GParted::show_resize_readonly( const Glib::ustring & path )
 void Win_GParted::show_help(const Glib::ustring & filename /* E.g., "gparted" */,
                             const Glib::ustring & link_id  /* For context sensitive help */)
 {
-       GError *error1 = NULL;
-       GdkScreen *gscreen = NULL ;
-
+       // Build uri string
        Glib::ustring uri = "help:" + filename;
        if (link_id.size() > 0)
                uri = uri + "/" + link_id;
 
-       gscreen = get_window()->get_screen()->gobj();
-       gtk_show_uri(gscreen, uri.c_str(), gtk_get_current_event_time(), &error1);
-       if (error1 != NULL)
-       {
-               //Try opening yelp application directly
-
-               Glib::RefPtr<Gio::AppInfo> yelp
-                       = Gio::AppInfo::create_from_commandline("yelp", "", 
Gio::APP_INFO_CREATE_SUPPORTS_URIS);
-
-               Glib::RefPtr<Gdk::AppLaunchContext> context
-                       = get_window()->get_display()->get_app_launch_context();
-
-               context->set_timestamp(gtk_get_current_event_time());
-
-               bool launched = false;
-               Glib::ustring error2_msg;
-               try
-               {
-                       launched = yelp->launch_uris(std::vector<std::string>(1, uri), context);
-               }
-               catch (Glib::Error& e)
-               {
-                       error2_msg = e.what();
-               }
+       // Check if yelp is available to provide a useful error message.
+       // Missing yelp is the most common cause of failure to display help.
+       //
+       // This early check is performed because failure of gtk_show_uri*()
+       // method only provides a generic "Operation not permitted" message.
+       if (Glib::find_program_in_path("yelp").empty())
+       {
+               Gtk::MessageDialog errorDialog(*this,
+                                              _("Unable to open GParted Manual help file"),
+                                              false, Gtk::MESSAGE_ERROR, Gtk::BUTTONS_OK, true);
+               Glib::ustring sec_text(_("Command yelp not found."));
+               sec_text.append("\n");
+               sec_text.append("\n");
+               sec_text.append(_("Install yelp and try again."));
+               errorDialog.set_secondary_text(sec_text, true);
+               errorDialog.run();
+               return;
+       }
 
-               if (!launched)
-               {
-                       Gtk::MessageDialog dialog(*this,
-                                                 _( "Unable to open GParted Manual help file" ),
-                                                 false,
-                                                 Gtk::MESSAGE_ERROR,
-                                                 Gtk::BUTTONS_OK,
-                                                 true);
-                       dialog.set_secondary_text(error2_msg);
-                       dialog.run();
-               }
+       GError *error = NULL;
 
-               g_clear_error(&error1);
+       // Display help window
+#if HAVE_GTK_SHOW_URI_ON_WINDOW
+       // NULL is provided for the gtk_show_uri_on_window() parent window
+       // so that failures to launch yelp are reported.
+       // https://gitlab.gnome.org/GNOME/gparted/-/merge_requests/82#note_1106114
+       gtk_show_uri_on_window(NULL, uri.c_str(), gtk_get_current_event_time(), &error);
+#else
+       GdkScreen *gscreen = gscreen = gdk_screen_get_default();
+       gtk_show_uri(gscreen, uri.c_str(), gtk_get_current_event_time(), &error);
+#endif
+       if (error != NULL)
+       {
+               Gtk::MessageDialog errorDialog(*this,
+                                              _("Failed to open GParted Manual help file"),
+                                              false,
+                                              Gtk::MESSAGE_ERROR,
+                                              Gtk::BUTTONS_OK,
+                                              true);
+               errorDialog.set_secondary_text(error->message);
+               errorDialog.run();
        }
+
+       g_clear_error(&error);
 }
 
 void Win_GParted::menu_help_contents()