[FIX] qweb: properly supports svg

Snabbdom supports svg, but it adds the namespace at the creation of the
virtual node.  However, owl works slightly differently: it adds children
after creating the parent virtual node.

So, we need to actually call the addNS method after the children nodes
have been created.

As a bonus, this is slightly faster than snabbdom: we only check at
template compilation time once if a node is a svg.

src/qweb/qweb.ts

@@ -2,6 +2,7 @@ import { EventBus } from "../core/event_bus";
 import { h, patch, VNode } from "../vdom/index";
 import { Context } from "./context";
 import { shallowEqual } from "../utils";
+import { addNS } from "../vdom/vdom";
 
 /**
  * Owl QWeb Engine
@@ -93,7 +94,10 @@ const UTILS: Utils = {
     }
     return expr;
   },
-  shallowEqual
+  shallowEqual,
+  addNameSpace(vnode) {
+      addNS(vnode.data, vnode.children, vnode.sel);
+  },
 };
 
 function parseXML(xml: string): Document {
@@ -537,6 +541,10 @@ export class QWeb extends EventBus {
     }
 
     this._compileChildren(node, ctx);
+    if (node.nodeName === 'svg') {
+        ctx.rootContext.shouldDefineUtils = true;
+        ctx.addLine(`utils.addNameSpace(vn${ctx.parentNode});`);
+    }
 
     for (let { directive, value, fullName } of validDirectives) {
       if (directive.finalize) {

src/vdom/vdom.ts

@@ -564,7 +564,7 @@ type VNodeChildElement = VNode | string | number | undefined | null;
 type ArrayOrElement<T> = T | T[];
 type VNodeChildren = ArrayOrElement<VNodeChildElement>;
 
-function addNS(data: any, children: VNodes | undefined, sel: string | undefined): void {
+export function addNS(data: any, children: VNodes | undefined, sel: string | undefined): void {
   data.ns = "http://www.w3.org/2000/svg";
   if (sel !== "foreignObject" && children !== undefined) {
     for (let i = 0, iLen = children.length; i < iLen; ++i) {
@@ -612,13 +612,5 @@ export function h(sel: any, b?: any, c?: any): VNode {
         children[i] = vnode(undefined, undefined, undefined, children[i], undefined);
     }
   }
-  if (
-    sel[0] === "s" &&
-    sel[1] === "v" &&
-    sel[2] === "g" &&
-    (sel.length === 3 || sel[3] === "." || sel[3] === "#")
-  ) {
-    addNS(data, children, sel);
-  }
   return vnode(sel, data, children, text, undefined);
 }