Use save to get message info when triggering an action

Instead of always calling save_current on the screen, it is better to call
save when the record has been modified. This allows to get message information
about failure or success but only if the record needed to be saved.

issue7430
review38231002

src/tab.js

@@ -559,7 +559,11 @@
                             'tabindex': -1
                         }).append(action.name))
                         .click(function() {
-                            screen.save_current().then(function() {
+                            var prm = jQuery.when();
+                            if (this.screen.modified()) {
+                                prm = this.save();
+                            }
+                            prm.then(function() {
                                 var exec_action = jQuery.extend({}, action);
                                 var record_id = null;
                                 if (screen.current_record) {
@@ -579,11 +583,11 @@
                                 Sao.Action.exec_action(exec_action, data,
                                     screen.context());
                             });
-                        })
+                        }.bind(this))
                         .appendTo(menu);
-                    });
-                });
-            });
+                    }.bind(this));
+                }.bind(this));
+            }.bind(this));
             return toolbar;
         },
         _close_allowed: function() {
@@ -623,7 +627,7 @@
         save: function() {
             var access = Sao.common.MODELACCESS.get(this.screen.model_name);
             if (!(access.write || access.create)) {
-                return jQuery.when();
+                return jQuery.Deferred().reject();
             }
             return this.screen.save_current().then(
                     function() {
@@ -634,6 +638,7 @@
                     function() {
                         this.info_bar.message(
                             this.screen.invalid_message(), 'danger');
+                        return jQuery.Deferred().reject();
                     }.bind(this));
         },
         switch_: function() {