[pitivi] preset: Allow creating a new preset only when a preset is selected

[Thibault Saunier <tsaunier src gnome org>]

commit fa369837bbe4787dccac7379991c7eb7519a0801
Author: Alexandru Băluț <alexandru balut gmail com>
Date:   Sun Oct 11 00:23:38 2015 +0200

    preset: Allow creating a new preset only when a preset is selected
    
    Differential Revision: https://phabricator.freedesktop.org/D369
    Reviewed-by: Thibault Saunier <tsaunier gnome org>

 pitivi/preset.py  |    4 ++++
 pitivi/project.py |    3 +++
 2 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/pitivi/preset.py b/pitivi/preset.py
index f09d453..7bceed6 100644
--- a/pitivi/preset.py
+++ b/pitivi/preset.py
@@ -332,6 +332,10 @@ class PresetManager(Loggable):
             return False
         return True
 
+    def isNewButtonSensitive(self):
+        """Whether the New button should be enabled"""
+        return bool(self.cur_preset)
+
     def _projectToPreset(self, project):
         raise NotImplementedError()
 
diff --git a/pitivi/project.py b/pitivi/project.py
index 4aaf185..cfc00e6 100644
--- a/pitivi/project.py
+++ b/pitivi/project.py
@@ -1621,6 +1621,9 @@ class ProjectSettingsDialog():
         can_remove = mgr.isRemoveButtonSensitive()
         self.preset_actions[button]["remove"].set_enabled(can_remove)
 
+        can_create_new = mgr.isNewButtonSensitive()
+        self.preset_actions[button]["new"].set_enabled(can_create_new)
+
     def _loadPresets(self, mgr, combo, button):
         """Set up the specified treeview to display the specified presets.