[IMP] qweb: add preliminary support for transitions

Still very naive...

Part of #66

doc/animations.md

@@ -0,0 +1,39 @@
+# 🦉 Animations 🦉
+
+
+Animation is a complex topic. There are many different use cases, and many
+solutions and technologies.
+
+## Simple CSS effects
+
+Sometimes, using pure CSS is enough.  For these use cases, Owl is not really
+necessary: it just needs to render a DOM element with a specific class. For
+example:
+
+
+```xml
+<button class="flash" t-on-click="doSomething">Click</button>
+```
+
+with the following CSS:
+
+```css
+.flash {
+  transition: background 0.5s;
+}
+
+.flash:active {
+  background-color: #41454a;
+  transition: background 0s;
+}
+```
+
+will produce a nice flash effect whenever the user click (or activate with the
+keyboard) the button.
+
+## CSS Transitions (single element)
+
+A more complex situation occurs when we want to transition an element in or out
+of the page.  For example, we may want a fade-in and fade-out effect.
+
+The `t-transition` directive is here to help us (see [QWeb documentation](doc/qweb.md#t-transition-directive)).

doc/qweb.md

@@ -16,6 +16,7 @@
     - [Component: `t-widget`, `t-props`](#component-t-widget-t-props)
     - [`t-ref` directive](#t-ref-directive)
     - [`t-key` directive](#t-key-directive)
+    - [`t-transition` directive](#t-transition)
     - [Debugging (`t-debug` and `t-log`)](#debugging-t-debug-and-t-log)
     - [White spaces](#white-spaces)
     - [Root nodes](#root-nodes)
@@ -253,6 +254,54 @@ There are three main use cases:
 - *animations*: give a different identity to a component.  Ex: thread id with
 animations on add/remove message.
 
+### `t-transition` directive
+
+To perform useful transition effects, whenever an element appears or disappears,
+it is necessary to add/remove some css style or class at some precise moment in
+the lifetime of a node.  Since this is not easy to do by hand, Owl `t-transition`
+directive is there to help.
+
+Whenever a node has a `t-transition` directive, with a `name` value, the following
+will happen:
+
+At node creation:
+
+- the css classes `name-enter` and `name-enter-active` will be added before the
+  node is added to the DOM,
+- on the next animation frame: the css class `name-enter` will be removed and the
+  class `name-enter-to` will be added (so they can be used to trigger css
+  transition effects),
+- the css class `name-enter-active` will be removed whenever a css transition
+  ends.
+
+At node destruction:
+- the css classes `name-leave` and `name-leave-active` will be added before the
+  node is removed to the DOM,
+- the css class `name-leave` will be removed on the next animation frame (so it
+  can be used to trigger css transition effects),
+- the css class `name-leave-active` will be removed whenever a css transition
+  ends. Only then will the element be removed from the DOM.
+
+For example, a simple fade in/out effect can be done with this:
+
+```xml
+<div>
+    <div t-if="state.flag" class="square" t-transition="fade">Hello</div>
+</div>
+```
+
+```css
+.fade-enter-active, .fade-leave-active {
+    transition: opacity .5s;
+}
+.fade-enter, .fade-leave-to {
+    opacity: 0;
+}
+```
+
+Note: you will find more information on animations in the [animation](doc/animations.md)
+documentation.
+
 ### Debugging (`t-debug` and `t-log`)
 
 The javascript QWeb implementation provides two useful debugging directives:

doc/readme.md

@@ -11,4 +11,5 @@
 
 ## Miscellaneous
 - [Quick Start](quick_start.md)
+- [Animations](animations.md)
 - [Comparison with React/Vue](comparison.md)

src/qweb.ts

@@ -61,6 +61,37 @@ const UTILS = {
       }
     }
     return classes.join(" ");
+  },
+  nextFrame(cb: () => void) {
+    requestAnimationFrame(() => requestAnimationFrame(cb));
+  },
+  transitionCreate(elm: HTMLElement, name: string) {
+    elm.classList.add(name + "-enter");
+    elm.classList.add(name + "-enter-active");
+  },
+  transitionInsert(elm: HTMLElement, name: string) {
+    const finalize = () => {
+      elm.classList.remove(name + "-enter-active");
+      elm.classList.remove(name + "-enter-to");
+    };
+    elm.addEventListener("transitionend", finalize);
+    this.nextFrame(() => {
+      elm.classList.remove(name + "-enter");
+      elm.classList.add(name + "-enter-to");
+    });
+  },
+  transitionRemove(elm: HTMLElement, name: string, rm: () => void) {
+    elm.classList.add(name + "-leave");
+    elm.classList.add(name + "-leave-active");
+    elm.addEventListener("transitionend", () => {
+      elm.classList.remove(name + "-leave-active");
+      elm.classList.remove(name + "-enter-to");
+      rm();
+    });
+    this.nextFrame(() => {
+      elm.classList.remove(name + "-leave");
+      elm.classList.add(name + "-leave-to");
+    });
   }
 };
 //------------------------------------------------------------------------------
@@ -240,6 +271,7 @@ export class QWeb {
       callDirective,
       onDirective,
       refDirective,
+      transitionDirective,
       debugDirective,
       logDirective,
       widgetDirective
@@ -983,16 +1015,34 @@ const onDirective: Directive = {
 const refDirective: Directive = {
   name: "ref",
   priority: 95,
-  atNodeCreation({ ctx, node }) {
+  atNodeCreation({ ctx, nodeID, value }) {
-    let ref = node.getAttribute("t-ref")!;
+    ctx.addLine(`p${nodeID}.hook = {
-    ctx.addLine(`p${ctx.parentNode}.hook = {
             create: (_, n) => context.refs[${ctx.formatExpression(
-              ref
+              value
             )}] = n.elm,
         };`);
   }
 };
 
+const transitionDirective: Directive = {
+  name: "transition",
+  priority: 96,
+  atNodeCreation({ ctx, value }) {
+    let name = value;
+    ctx.addLine(`p${ctx.parentNode}.hook = {
+        create: (_, n) => {
+          this.utils.transitionCreate(n.elm, '${name}');
+        },
+        insert: vn => {
+          this.utils.transitionInsert(vn.elm, '${name}');
+        },
+        remove: (vn, rm) => {
+          this.utils.transitionRemove(vn.elm, '${name}', rm);
+        }
+      };`);
+  }
+};
+
 const debugDirective: Directive = {
   name: "debug",
   priority: 99,

tests/__snapshots__/qweb.test.ts.snap

@@ -1,5 +1,32 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`animations t-transition, on a simple node 1`] = `
+"function anonymous(context,extra
+) {
+    var h = this.utils.h;
+    var c1 = [], p1 = {key:1};
+    var vn1 = h('div', p1, c1);
+    var c2 = [], p2 = {key:2};
+    var vn2 = h('span', p2, c2);
+    c1.push(vn2);
+    p2.hook = {
+        create: (_, n) => {
+          this.utils.transitionCreate(n.elm, 'chimay');
+        },
+        insert: vn => {
+          this.utils.transitionInsert(vn.elm, 'chimay');
+        },
+        remove: (vn, rm) => {
+          this.utils.transitionRemove(vn.elm, 'chimay', rm);
+        }
+      };
+    c2.push({text: \`blue\`});
+    return vn1;
+}"
+`;
+
+exports[`animations t-transition, on a simple node 2`] = `"<span class=\\"chimay-enter chimay-enter-active\\">blue</span>"`;
+
 exports[`attributes dynamic attribute falsy variable  1`] = `
 "function anonymous(context,extra
 ) {

tests/qweb.test.ts

@@ -1,5 +1,5 @@
-import { patch } from "../src/vdom";
 import { EvalContext, QWeb } from "../src/qweb";
+import { patch } from "../src/vdom";
 import { normalize } from "./helpers";
 
 //------------------------------------------------------------------------------
@@ -1098,12 +1098,12 @@ describe("t-key", () => {
 describe("debugging", () => {
   test("t-debug", () => {
     const consoleLog = console.log;
-    console.log = jest.fn()
+    console.log = jest.fn();
     qweb.addTemplate(
       "test",
       `<div t-debug="1"><t t-if="true"><span t-debug="1">hey</span></t></div>`
     );
-    qweb.render('test');
+    qweb.render("test");
     expect(qweb.templates.test.fn.toString()).toMatchSnapshot();
 
     expect(console.log).toHaveBeenCalledTimes(1);
@@ -1112,7 +1112,7 @@ describe("debugging", () => {
 
   test("t-log", () => {
     const consoleLog = console.log;
-    console.log = jest.fn()
+    console.log = jest.fn();
 
     qweb.addTemplate(
       "test",
@@ -1121,10 +1121,23 @@ describe("debugging", () => {
           <t t-log="foo + 3"/>
         </div>`
     );
-    qweb.render('test');
+    qweb.render("test");
     expect(qweb.templates.test.fn.toString()).toMatchSnapshot();
 
     expect(console.log).toHaveBeenCalledWith(45);
     console.log = consoleLog;
   });
 });
+
+describe("animations", () => {
+  test("t-transition, on a simple node", async () => {
+    // this test does not test much, because it is not easy to test timing
+    // transitions... we should do a little more effort for these tests.
+    qweb.addTemplate(
+      "test",
+      `<div><span t-transition="chimay">blue</span></div>`
+    );
+    let dom: HTMLElement = <HTMLElement>renderToDOM(qweb, "test");
+    expect(dom.innerHTML).toMatchSnapshot();
+  });
+});