Use Gtk.show_uri_on_window when available. Bug 770884.

* src/CMakeLists.txt: Define a macro when Gtk+ 3.22 is available.

* src/client/application/geary-application.vala (GearyApplication): Add
  show_uri method that uses the app's currently active window/screen to
  show the URI on, add a compile-time test to use Gtk.show_uri or
  Gtk.show_uri_on_window as appropriate, make the API nicer to use by
  not having two different error reporting methods. Rework existing uses
  of Gtk.show_uri to use this method.

src/CMakeLists.txt

@@ -593,6 +593,13 @@ if (NOT DEPS_gtk+-3.0_VERSION VERSION_LESS 3.20)
     )
 endif()
 
+if (NOT DEPS_gtk+-3.0_VERSION VERSION_LESS 3.22)
+    set(EXTRA_VALA_OPTIONS
+        ${EXTRA_VALA_OPTIONS}
+        -D GTK_3_22
+    )
+endif()
+
 if (DISABLE_POODLE)
     message(STATUS "POODLE SSLv3 fix: OFF")
     set(EXTRA_VALA_OPTIONS

src/client/application/geary-application.vala

@@ -372,6 +372,25 @@ public class GearyApplication : Gtk.Application {
         }
     }
 
+    /**
+     * Displays a URI on the current active window, if any.
+     */
+    public void show_uri(string uri) throws Error {
+        Gtk.Window? window = get_active_window();
+#if !GTK_3_22
+        bool success = Gtk.show_uri(
+            window != null ? window.get_screen() : null, uri, Gdk.CURRENT_TIME
+        );
+        if (!success) {
+            throw new IOError.FAILED("gtk_show_uri() returned false");
+        }
+#else
+        if (!Gtk.show_uri_on_window(window, uri, Gdk.CURRENT_TIME)) {
+            throw new IOError.FAILED("gtk_show_uri_on_window() returned false");
+        }
+#endif
+    }
+
     // This call will fire "exiting" only if it's not already been fired.
     public void exit(int exitcode = 0) {
         if (exiting_fired)
@@ -481,7 +500,7 @@ public class GearyApplication : Gtk.Application {
     private void on_activate_help() {
         try {
             if (is_installed()) {
-                Gtk.show_uri(null, "ghelp:geary", Gdk.CURRENT_TIME);
+                show_uri("ghelp:geary");
             } else {
                 Pid pid;
                 File exec_dir = get_exec_dir();

src/client/application/geary-controller.vala

@@ -2184,19 +2184,20 @@ public class GearyController : Geary.BaseObject {
     // Opens a link in an external browser.
     private bool open_uri(string _link) {
         string link = _link;
-        
+
         // Support web URLs that ommit the protocol.
         if (!link.contains(":"))
             link = "http://" + link;
-        
-        bool ret = false;
+
+        bool success = true;
         try {
-            ret = Gtk.show_uri(main_window.get_screen(), link, Gdk.CURRENT_TIME);
+            this.application.show_uri(link);
         } catch (Error err) {
-            debug("Unable to open URL. %s", err.message);
+            success = false;
+            debug("Unable to open URL: \"%s\" %s", link, err.message);
         }
-        
-        return ret;
+
+        return success;
     }
 
     internal bool close_composition_windows(bool main_window_only = false) {
@@ -2798,7 +2799,7 @@ public class GearyController : Geary.BaseObject {
             FileUtils.chmod(temporary_filename, (int) (Posix.S_IRUSR | Posix.S_IWUSR));
 
             string temporary_uri = Filename.to_uri(temporary_filename, null);
-            Gtk.show_uri(main_window.get_screen(), temporary_uri, Gdk.CURRENT_TIME);
+            this.application.show_uri(temporary_uri);
         } catch (Error error) {
             ErrorDialog dialog = new ErrorDialog(
                 main_window,