Theme Deletes only work for unused themes

openlp/core/lib/plugin.py

@@ -254,3 +254,9 @@ class Plugin(QtCore.QObject):
             self.mediadock.insert_dock(self.media_item, self.icon, self.weight)
         if self.settings_tab:
             self.settings.insertTab(self.settings_tab, self.weight)
+
+    def can_delete_theme(self, theme):
+        """
+        Called to ask the plugin if a theme can be deleted
+        """
+        return True

openlp/core/ui/thememanager.py

@@ -180,6 +180,19 @@ class ThemeManager(QtGui.QWidget):
                     self.trUtf8('You are unable to delete the default theme!'),
                     QtGui.QMessageBox.StandardButtons(QtGui.QMessageBox.Ok))
             else:
+                for plugin in self.parent.plugin_manager.plugins:
+                    if not plugin.can_delete_theme(theme):
+                        QtGui.QMessageBox.critical(
+                            self, self.trUtf8('Error'),
+                            self.trUtf8('theme %s is use in %s plugin' % (theme, plugin.name)),
+                            QtGui.QMessageBox.StandardButtons(QtGui.QMessageBox.Ok))
+                        return
+                if unicode(self.parent.ServiceManagerContents.ThemeComboBox.currentText()) == theme:
+                    QtGui.QMessageBox.critical(
+                        self, self.trUtf8('Error'),
+                        self.trUtf8('theme %s is use Service Manager' % theme),
+                        QtGui.QMessageBox.StandardButtons(QtGui.QMessageBox.Ok))
+                    return
                 self.themelist.remove(theme)
                 th = theme + u'.png'
                 row = self.ThemeListWidget.row(item)

openlp/plugins/bibles/bibleplugin.py

@@ -92,3 +92,9 @@ class BiblePlugin(Plugin):
             'plugin allows bible verses from different sources to be '
             'displayed on the screen during the service.')
         return about_text
+
+
+    def can_delete_theme(self, theme):
+        if self.settings_tab.bible_theme == theme:
+            return False
+        return True

openlp/plugins/custom/customplugin.py

@@ -72,3 +72,8 @@ class CustomPlugin(Plugin):
             'songs are.  This plugin provides greater freedom over the '
             'songs plugin.<br>')
         return about_text
+
+    def can_delete_theme(self, theme):
+        if len(self.custommanager.get_customs_for_theme(theme)) == 0:
+            return True
+        return False

openlp/plugins/custom/lib/manager.py

@@ -105,3 +105,6 @@ class CustomManager():
                 return False
         else:
             return True
+
+    def get_customs_for_theme(self, theme):
+        return self.session.query(CustomSlide).filter(CustomSlide.theme_name == theme).all()

openlp/plugins/songs/lib/manager.py

@@ -237,3 +237,6 @@ class SongManager():
             self.session.rollback()
             log.exception(u'Could not delete book from song database')
             return False
+
+    def get_songs_for_theme(self, theme):
+        return self.session.query(Song).filter(Song.theme_name == theme).all()

openlp/plugins/songs/songsplugin.py

@@ -179,3 +179,8 @@ class SongsPlugin(Plugin):
         about_text = self.trUtf8('<b>Song Plugin</b> <br>This plugin allows '
             'Songs to be managed and displayed.<br>')
         return about_text
+
+    def can_delete_theme(self, theme):
+        if len(self.songmanager.get_songs_for_theme(theme)) == 0:
+            return True
+        return False