[IMP] web: add a generic notification feature inside form views

The notification box remains on the form until either:
 - the user closes it explicitly, or
 - the user edits the record, or
 - the form view is refreshed (switch to another record, or refresh form).

Add a method `once` to `EventDispatcherMixin`, as it is convenient.
Make `FormView` trigger events `to_view_mode` and `to_edit_mode`.

1 files changed, 11 insertions, 0 deletions

diff --git a/addons/web/static/src/js/framework/mixins.js b/addons/web/static/src/js/framework/mixins.js
index e9f9b2c94b0..2f96da09872 100644
--- a/addons/web/static/src/js/framework/mixins.js
+++ b/addons/web/static/src/js/framework/mixins.js
@@ -268,6 +268,17 @@ var EventDispatcherMixin = _.extend({}, ParentedMixin, {
         });
         return this;
     },
+    once: function(events, dest, func) {
+        // similar to this.on(), but func is executed only once
+        var self = this
+        if (typeof func !== "function") {
+            throw new Error("Event handler must be a function.");
+        }
+        self.on(events, dest, function what() {
+            func.apply(this, arguments);
+            self.off(events, dest, what);
+        });
+    },
     trigger: function() {
         this.__edispatcherEvents.trigger.apply(this.__edispatcherEvents, arguments);
         return this;