small qweb optimisation: reuse bound handlers if possible

web/static/src/ts/core/component.ts

@@ -33,6 +33,7 @@ interface Meta<T extends WEnv> {
   renderId: number;
   renderProps: any;
   renderPromise: Promise<VNode> | null;
+  boundHandlers: { [key: number]: any };
 }
 
 const patch = init([sdListeners, sdAttrs]);
@@ -100,7 +101,8 @@ export class Component<
       cmap: {},
       renderId: 1,
       renderPromise: null,
-      renderProps: props
+      renderProps: props,
+      boundHandlers: {}
     };
   }
 
@@ -251,7 +253,10 @@ export class Component<
     this.__widget__.renderId++;
     const promises: Promise<void>[] = [];
     const template = this.inlineTemplate || this.template;
-    let vnode = this.env.qweb.render(template, this, { promises });
+    let vnode = this.env.qweb.render(template, this, {
+      promises,
+      handlers: this.__widget__.boundHandlers
+    });
 
     // this part is critical for the patching process to be done correctly. The
     // tricky part is that a child widget can be rerendered on its own, which

web/static/src/ts/core/qweb_vdom.ts

@@ -722,10 +722,11 @@ const onDirective: Directive = {
       return "";
     });
     ctx.addLine(
-      `p${nodeID}.on = {${eventName}: context['${handler}'].bind(owner${
+      `extra.handlers[${nodeID}] = extra.handlers[${nodeID}] || context['${handler}'].bind(owner${
         extraArgs ? ", " + qweb._formatExpression(extraArgs) : ""
-      })};`
+      });`
     );
+    ctx.addLine(`p${nodeID}.on = {${eventName}: extra.handlers[${nodeID}]};`);
   }
 };