feat(ipub): soundtrack support with fade transition

this replaces the ipub-content element, and makes ipub publications
limited/containerized into one element.

.epub/example/OEBPS/scripts/ipub.js

@@ -4,36 +4,166 @@ class IPUBElement extends HTMLElement {
   static observedAttributes = ["id"];
 
   connectedCallback() {
-    this.ensureID();
+    this.#ensureID();
   }
 
   attributeChangedCallback(_name, _oldValue, _newValue) {
-    this.ensureID();
+    this.#ensureID();
   }
 
-  ensureID() {
-    if (this.id) {
+  /**
+   * @private
+   */
+  #ensureID() {
+    if (!this.id) {
+      this.id = hashFromHTML(this);
+    }
+  }
+}
+
+class IPUBAudio extends IPUBElement {
+  static elementName = "ipub-audio";
+
+  /**
+   * @param {boolean} [forced=false]
+   * @throws {Error}
+   * @returns {Promise<void>}
+   */
+  play(forced = false) {
+    if (!this.#audioElement.readyState > HTMLMediaElement.HAVE_CURRENT_DATA) {
+      throw new Error("IPUBAudio: audio is not ready");
+    }
+    if (forced) {
+      this.setAttribute("forced", "true");
+    }
+    return this.#audioElement.play();
+  }
+
+  /**
+   * @param {boolean} [forced=false]
+   */
+  pause(forced = false) {
+    if (forced) {
+      this.setAttribute("forced", "true");
+    }
+    this.#audioElement.pause();
+  }
+
+  /**
+   * @param {boolean} state
+   */
+  setLoop(state) {
+    this.#audioElement.loop = state;
+  }
+
+  /**
+   * @returns {boolean}
+   */
+  getLoop() {
+    return this.#audioElement.loop;
+  }
+
+  connectedCallback() {
+    super.connectedCallback();
+
+    const audio = this.querySelector("audio");
+    if (!audio) {
+      console.error("IPUBAudio: Missing child <audio> element");
       return;
     }
 
-    // INFO: Hash algorithm by Joe Freeman & Cristian Sanchez at StackOverflow:
-    // https://stackoverflow.com/a/16348977
-    // https://stackoverflow.com/a/3426956
-    //
-    // Licensed under CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0/)
+    this.#audioElement = audio;
+  }
 
-    let hash = 0;
-    this.innerHTML.split("").forEach((char) => {
-      hash = char.charCodeAt(0) + ((hash << 5) - hash);
-    });
+  /**
+   * @private
+   * @type {HTMLAudioElement}
+   */
+  #audioElement;
 
-    let id = "";
-    for (let i = 0; i < 3; i++) {
-      id += ((hash >> (i * 8)) & 0xff).toString(16).padStart(2, "0");
+  /**
+   * @param {number} volume
+   * @param {Object} options
+   * @param {number} [options.fadetime=0]
+   * @param {() => void} [options.onfinish=() => {}]
+   */
+  setVolume(volume, { fadetimeMS = 0, onFinishFade = () => {} } = {}) {
+    if (fadetimeMS === 0) {
+      this.#audioElement.volume = volume / 100;
+      return;
     }
 
-    this.id = id;
+    if (this.#isFading) {
+      return;
+    }
+
+    this.#onFinishFade = onFinishFade;
+
+    const diff = volume - this.#audioElement.volume * 100;
+    const ticks = diff < 0 ? Math.abs(diff) : diff;
+    let tick = 0;
+
+    const interval = fadetimeMS / ticks;
+
+    this.#isFading = true;
+    this.#fadeTask = setInterval(() => {
+      tick++;
+
+      const cancel = () => {
+        this.#isFading = false;
+        if (onFinishFade) {
+          onFinishFade();
+        }
+        clearInterval(this.#fadeTask);
+        this.#onFinishFade = null;
+      };
+
+      if (!this.#audioElement) {
+        cancel();
+        console.error("IPUBAudio: Missing child <audio> element");
+        return;
+      }
+
+      if (ticks < tick) {
+        cancel();
+        return;
+      }
+
+      if (volume === this.getVolume()) {
+        cancel();
+        return;
+      }
+
+      if (diff === 0) {
+        cancel();
+        return;
+      }
+
+      const nvol =
+        (diff > 0
+          ? Math.ceil(this.#audioElement.volume * 100 + 1)
+          : Math.floor(this.#audioElement.volume * 100 - 1)) / 100;
+
+      if (nvol > 1 || nvol < 0) {
+        cancel();
+        return;
+      }
+
+      this.#audioElement.volume = nvol;
+    }, interval);
   }
+
+  /**
+   * @returns {number}
+   */
+  getVolume() {
+    return Math.floor((this.#audioElement?.volume ?? 0) * 100);
+  }
+
+  #isFading = false;
+  #fadeTask = 0;
+  /** @type {() => void | null} */
+  #onFinishFade = null;
 }
 
 class IPUBBackground extends IPUBElement {
@@ -43,49 +173,84 @@ class IPUBBackground extends IPUBElement {
   /**
    * @private
    */
-  static #observer = (() => {
-    /** @type {Map<string, IPUBBackground>} */
-    const instancesOnScreen = new Map();
-
-    document.addEventListener("scroll", () => {
-      for (const [_, instance] of instancesOnScreen) {
-        const perc = getPercentageInView(
-          instance.querySelector("img") || instance,
+  static #instancesOnScreen = {
+    /** @type {Map<IPUBBody, Set<IPUBBackground>>} */
+    map: new Map(),
+    /**
+     * @param {IPUBBackground} background
+     */
+    add(background) {
+      const body = getAncestor(background, IPUBBody.elementName);
+      if (!body) {
+        console.error(
+          `IPUBBackground: ${background.id} does not have a valid ipub-body ancestor`,
         );
-        instance.fade(perc);
+        return;
       }
-    });
 
-    return new IntersectionObserver((entries) =>
-      entries.forEach((e) => {
-        let instance = e.target.parentElement;
+      let set = this.map.get(body);
+      if (!set) {
+        set = new Set();
+        body.addEventListener("scroll", () => {
+          for (const instance of set.values()) {
+            const perc = getPercentageInView(
+              instance.querySelector("img") || instance,
+            );
+            instance.fade(perc);
+          }
+        });
+      }
+      set.add(background);
+      this.map.set(body, set);
+    },
+    /**
+     * @param {IPUBBackground} background
+     */
+    remove(background) {
+      const body = getAncestor(background, IPUBBody.elementName);
+      if (!body) {
+        console.error(
+          `IPUBBackground: ${background.id} does not have a valid ipub-body ancestor`,
+        );
+        return;
+      }
 
-        if (
-          instance.tagName.toLowerCase() !==
-          IPUBBackground.elementName.toLowerCase()
-        ) {
-          instance = instance.parentElement;
-        }
+      const set = this.map.get(body);
+      if (!set) {
+        return;
+      }
 
-        if (
-          instance.tagName.toLowerCase() !==
-          IPUBBackground.elementName.toLowerCase()
-        ) {
-          console.error(
-            "IPUBBackground: malformed <ipub-background> element",
-            e.target,
-          );
-          return;
-        }
+      set.delete(background);
 
-        if (e.intersectionRatio > 0 && instance.id) {
-          instancesOnScreen.set(instance.id, instance);
-        } else if (instance.id) {
-          instancesOnScreen.delete(instance.id);
-        }
-      }),
-    );
-  })();
+      if (set.size === 0) {
+        this.map.delete(body);
+      }
+    },
+  };
+  static addToScreen() {}
+
+  /**
+   * @private
+   */
+  static #observer = new IntersectionObserver((entries) => {
+    for (const { intersectionRatio, target: image } of entries) {
+      const instance = getAncestor(image, IPUBBackground.elementName);
+
+      if (!instance) {
+        console.error(
+          "IPUBBackground: malformed <ipub-background> element",
+          image,
+        );
+        return;
+      }
+
+      if (intersectionRatio > 0 && instance.id) {
+        IPUBBackground.#instancesOnScreen.add(instance);
+      } else if (instance.id) {
+        IPUBBackground.#instancesOnScreen.remove(instance);
+      }
+    }
+  });
 
   connectedCallback() {
     super.connectedCallback();
@@ -141,8 +306,6 @@ class IPUBBackground extends IPUBElement {
    * @returns {void | Promise<void>}
    */
   fade(perc) {
-    console.debug(`IPUBBackground: ${this.id} is ${perc} on screen`);
-
     if (!this.style.getPropertyValue("--ipub-fade")) {
       this.style.setProperty("--ipub-fade", `${perc}%`);
       return;
@@ -159,8 +322,109 @@ class IPUBBackground extends IPUBElement {
   }
 }
 
-class IPUBContent extends IPUBElement {
-  static elementName = "ipub-content";
+class IPUBBody extends IPUBElement {
+  static elementName = "ipub-body";
+
+  static defineContentElements() {
+    for (const e of [
+      IPUBAudio,
+      IPUBBackground,
+      IPUBImage,
+      IPUBInteraction,
+      IPUBSoundtrack,
+    ]) {
+      console.info(`IPUBBody: Defining custom element <${e.elementName}>`);
+      globalThis.customElements.define(e.elementName, e);
+    }
+  }
+
+  connectedCallback() {
+    super.connectedCallback();
+
+    this.setAttribute("aria-busy", "true");
+
+    // TODO?: Move IPUBCover's "can-play" logic to here
+
+    console.log("IPUBBody: Defining custom element <ipub-cover>");
+    globalThis.customElements.define(IPUBCover.elementName, IPUBCover);
+
+    /** @type {IPUBCover} */
+    const cover = this.querySelector("ipub-cover");
+    if (!cover) {
+      // TODO: automatically create IPUBCover element if it doesn't exists
+      console.error("IPUBBody: Document doesn't has <ipub-cover> element");
+      IPUBBody.defineContentElements();
+    }
+    cover.onclose = IPUBBody.defineContentElements;
+
+    this.setAttribute("aria-busy", "false");
+  }
+}
+
+globalThis.addEventListener("load", () => {
+  console.info("IPUB: Starting IPUB elements");
+
+  console.log("IPUB: Defining custom element <ipub-body>");
+  globalThis.customElements.define(IPUBBody.elementName, IPUBBody);
+});
+
+class IPUBCover extends IPUBElement {
+  static elementName = "ipub-cover";
+
+  /**
+   * @type {() => void} callback
+   */
+  onclose = () => {};
+
+  connectedCallback() {
+    super.connectedCallback();
+
+    console.debug("IPUBCover: Setting up cover");
+    this.setAttribute("aria-busy", "true");
+
+    const dialog = this.querySelector("dialog");
+
+    // HACK: Test if we can autoplay interactions, soundtracks, etc
+
+    /** @type {HTMLMediaElement | null} */
+    const media =
+      this.parentElement.querySelector("audio") ??
+      this.parentElement.querySelector("video");
+
+    if (!media) {
+      return;
+    }
+
+    const pastVolume = media.volume;
+    media.volume = 0.1; // don't let the user hear the test audio
+
+    media
+      .play()
+      .then(() => {
+        media.pause();
+        media.volume = pastVolume;
+        media.currentTime = 0;
+
+        console.debug("IPUBCover: Can autoplay interactions, removing cover");
+        dialog.close();
+        this.onclose();
+      })
+      .catch(() => {
+        console.debug(
+          "IPUBCover: Cannot autoplay interactions, covering content",
+        );
+
+        dialog.show();
+
+        dialog.parentElement.addEventListener("click", () => {
+          dialog.close();
+          this.onclose();
+        });
+
+        this.setAttribute("aria-busy", "false");
+        return;
+      });
+  }
 }
 
 class IPUBImage extends IPUBElement {
@@ -171,72 +435,174 @@ class IPUBInteraction extends IPUBElement {
   static elementName = "ipub-interaction";
 }
 
-globalThis.addEventListener("load", () => {
-  console.info("IPUB: STARTING DEFINITIONS");
+class IPUBSoundtrack extends IPUBElement {
+  static elementName = "ipub-soundtrack";
 
-  [IPUBBackground, IPUBContent, IPUBImage, IPUBInteraction].forEach((e) => {
-    console.info(`IPUB: Defining custom element <${e.elementName}>`);
-    globalThis.customElements.define(e.elementName, e);
-  });
+  // TODO: Toggle automatic soundtrack playing
 
-  console.info("IPUB: FINISHED DEFINITIONS");
+  /**
+   * @private
+   */
+  static #player = setInterval(() => {
+    const last = Array.from(this.#onScreenStack).pop();
+    if (!last) {
+      // TODO: Fallback to previous soundtrack if there's no audio
+      return;
+    }
 
-  /** @type {Map<string, Element>} */
-  const onScreenMap = new Map();
+    // TODO: Get siblings based by group OR parent
+    /** @type {NodeListOf<IPUBSoundtrack> | undefined} */
+    const siblings = last.parentElement?.querySelectorAll(
+      IPUBSoundtrack.elementName,
+    );
 
-  const observer = new IntersectionObserver((entries) => {
-    entries.forEach((e) => {
-      if (e.intersectionRatio > 0) {
-        // console.debug(
-        //   `IntersectionObserver: adding element #${e.target.id} to onScreenMap`,
-        // );
-        onScreenMap.set(e.target.id, e.target);
-      } else {
-        // console.debug(
-        //   `IntersectionObserver: removing element #${e.target.id} to onScreenMap`,
-        // );
-        onScreenMap.delete(e.target.id);
+    try {
+      if (siblings) {
+        siblings.forEach((el) => {
+          if (el !== last) {
+            el.fadeOut();
+          }
+        });
+      }
+      last.fadeIn();
+    } catch (e) {
+      // TODO: Fallback to previous soundtrack on error
+      console.error(
+        `IPUBSoundtrack: error while trying to play audio, error: ${e}`,
+        {
+          error: e,
+          audio: audio,
+        },
+      );
+    }
+  }, 1000);
+
+  /**
+   * @private
+   */
+  static #observer = (() => {
+    return new IntersectionObserver((entries) => {
+      for (const { intersectionRatio, target, time } of entries) {
+        /** @type {IPUBSoundtrack} */
+        const soundtrack = target;
+
+        if (intersectionRatio > 0) {
+          console.debug(`${soundtrack.id} is on screen at ${time}`, soundtrack);
+          this.#onScreenStack.add(soundtrack);
+        } else {
+          console.debug(
+            `${soundtrack.id} is not on screen ${time}`,
+            soundtrack,
+          );
+          this.#onScreenStack.delete(soundtrack);
+        }
       }
     });
-  });
+  })();
 
-  for (const element of document.querySelectorAll(
-    `[data-ipub-trigger="on-screen"]`,
-  )) {
-    observer.observe(element);
+  /**
+   * @private
+   * @type {Set<IPUBSoundtrack>}
+   */
+  static #onScreenStack = new Set();
+
+  /**
+   * @throws {Error}
+   */
+  fadeIn() {
+    /** @type {IPUBAudio | undefined} */
+    const audio = this.querySelector(IPUBAudio.elementName);
+    if (!audio) {
+      throw new Error("IPUBSoundtrack.fadeIn: missing audio element");
+    }
+
+    // TODO: Global volume settings
+
+    audio.play();
+    audio.setVolume(10, { fadetimeMS: IPUBSoundtrack.FADE_TIME_MS });
   }
 
-  document.addEventListener("scroll", async () => {
-    for (const [id, element] of onScreenMap) {
-      const perc = getPercentageInView(element);
-      // console.debug(`Element #${id} is now ${perc}% on screen`);
-
-      const played = element.getAttribute("data-ipub-trigger-played") == "true";
-
-      if (perc >= 100 && !played) {
-        await playIpubElement(element);
-        element.setAttribute("data-ipub-trigger-played", "true");
-      }
+  /**
+   * @throws {Error}
+   */
+  fadeOut() {
+    /** @type {IPUBAudio | undefined} */
+    const audio = this.querySelector(IPUBAudio.elementName);
+    if (!audio) {
+      throw new Error("IPUBSoundtrack.fadeIn: missing audio element");
     }
-  });
-});
+
+    audio.setVolume(0, {
+      fadetimeMS: IPUBSoundtrack.FADE_TIME_MS,
+      onFinishFade: () => {
+        audio.pause();
+      },
+    });
+  }
+
+  /** @type {Readonly<number>} */
+  static FADE_TIME_MS = 1000 * 3;
+
+  connectedCallback() {
+    super.connectedCallback();
+
+    /** @type {IPUBAudio | undefined} */
+    const audio = this.querySelector(IPUBAudio.elementName);
+    if (audio) {
+      audio.setVolume(0);
+    } else {
+      console.error("IPUBSoundtrack: missing audio element");
+      return;
+    }
+
+    IPUBSoundtrack.#observer.observe(this);
+  }
+
+  // TODO(guz013): Handle if element is moved, it's group should be updated
+}
 
 /**
- * @param {Element} element
+ * @param {HTMLElement} el
+ * @param {string} tagName
+ * @returns {HTMLElement | undefined}
  */
-async function playIpubElement(element) {
-  switch (element.tagName) {
-    case "audio": {
-      /** @type {HTMLAudioElement} */
-      const audio = element;
-
-      // await audio.play();
-
-      break;
-    }
-    default:
-      break;
+function getAncestor(el, tagName) {
+  if (!el.parentElement) {
+    return undefined;
   }
+  if (el.parentElement.tagName.toLowerCase() === tagName.toLowerCase()) {
+    return el.parentElement;
+  }
+  return getAncestor(el.parentElement, tagName);
+}
+
+/**
+ * @param {Readonly<Element>} el
+ * @param {number} [length=6]
+ * @returns {string}
+ *
+ * @copyright This function contains code from a hash algorithm by
+ * {@link https://stackoverflow.com/a/16348977|Joe Freeman} and
+ * {@link https://stackoverflow.com/a/3426956|Cristian Sanchez} at
+ * StackOverflow, licensed under {@link https://creativecommons.org/licenses/by-sa/3.0/|CC BY-SA 3.0}.
+ */
+function hashFromHTML(el, length = 6) {
+  const hexLength = length / 2;
+  if (hexLength % 2 !== 0) {
+    hexLength + 1;
+  }
+
+  let hash = 0;
+  for (const char of el.innerHTML) {
+    hash = char.charCodeAt(0) + ((hash << 5) - hash);
+  }
+
+  let hex = "";
+  for (let i = 0; i < hexLength; i++) {
+    hex += ((hash >> (i * 8)) & 0xff).toString(16).padStart(2, "0");
+  }
+
+  return hex.substring(0, length);
 }
 
 /**
@@ -274,3 +640,4 @@ function getPercentageInView(element) {
 
   return Math.round((inView / globalThis.innerHeight) * 100);
 }
+

.epub/example/OEBPS/sections/section0001.xhtml

@@ -9,8 +9,19 @@
     </script>
   </head>
   <body xmlns:epub="http://www.idpf.org/2007/ops" class="body">
-    <ipub-content style="--ipub-padding: 10%;">
-      <main>
+    <ipub-body style="--ipub-padding: 10%;">
+      <ipub-cover>
+        <dialog>
+          <header>
+            <h1>Test comic</h1>
+            <form method="dialog">
+              <p>Click anywhere to 
+              <button>start Reading</button></p>
+            </form>
+          </header>
+        </dialog>
+      </ipub-cover>
+      <main id="content">
         <ipub-background id="background0001">
           <img src="../images/background0001.jpg" width="100" height="100" />
         </ipub-background>
@@ -25,60 +36,35 @@
             rel="external nofollow noopener noreferrer" target="_blank" />
           </ipub-interaction>
         </ipub-image>
-        <section data-ipub-element="page" id="page02">
-          <span data-ipub-element="image">
-            <img src="../images/image0002.png" />
-          </span>
-          <!-- 
-          This in the UI would be an "Area Interaction". The editor would first place
-          the first top-left point, and then the bottom-right one, to select an area/size
-          of the interaction.
-
-          The element wound not have a "action" per say, but would have a "on screen" trigger,
-          which in itself would have the action "play sound".
-        -->
-          <audio data-ipub-element="interaction" data-ipub-trigger="on-screen" controls="true"
-          volume="0" style="--ipub-x: 20%; --ipub-y: 25%; --ipub-width: 50%; --ipub-height: 50%;"
-          id="int-audio0001">
-            <source src="../audios/audio0001.wav.disable" />
-          </audio>
-        </section>
+        <ipub-image>
+          <img src="../images/image0002.png" />
+        </ipub-image>
         <ipub-background id="background0002">
           <picture>
             <img src="../images/background0002.jpg" />
           </picture>
         </ipub-background>
-        <section data-ipub-element="page" id="page03">
-          <span data-ipub-element="image">
-            <img src="../images/image0003.png" />
-          </span>
-        </section>
-        <section data-ipub-element="page" id="page04">
-          <span data-ipub-element="image">
-            <img src="../images/image0004.png" />
-          </span>
-        </section>
+        <ipub-image>
+          <img src="../images/image0003.png" />
+        </ipub-image>
+        <ipub-image>
+          <img src="../images/image0004.png" />
+        </ipub-image>
         <ipub-background id="background0003">
           <picture>
             <img src="../images/background0003.jpg" />
           </picture>
         </ipub-background>
-        <section data-ipub-element="page" id="page02">
-          <span data-ipub-element="image">
-            <img src="../images/image0002.png" />
-          </span>
-        </section>
-        <section data-ipub-element="page" id="page04">
-          <span data-ipub-element="image">
-            <img src="../images/image0003.png" />
-          </span>
-        </section>
-        <section data-ipub-element="page" id="page04">
-          <span data-ipub-element="image">
-            <img src="../images/image0004.png" />
-          </span>
-        </section>
+        <ipub-image>
+          <img src="../images/image0002.png" />
+        </ipub-image>
+        <ipub-image>
+          <img src="../images/image0003.png" />
+        </ipub-image>
+        <ipub-image>
+          <img src="../images/image0004.png" />
+        </ipub-image>
       </main>
-    </ipub-content>
+    </ipub-body>
   </body>
 </html>

.epub/example/OEBPS/styles/stylesheet.css

@@ -8,9 +8,45 @@
   margin: 0;
 
   max-width: 100vw;
+  max-height: 100vh;
+  overflow: clip;
+  display: flex;
+
+  --z-cover: 9;
+ipub-cover > dialog[open] {
+  --ipub-accent-color: #fff;
+  z-index: var(--z-cover);
+  background-color: transparent;
+  border: none;
+
+  display: inline-block;
+  position: absolute;
+  backdrop-filter: blur(1rem);
+  background-image: linear-gradient(
+    rgba(from var(--ipub-accent-color) r g b / 0) 0%,
+    rgba(from var(--ipub-accent-color) r g b / 0.5)
+      calc(100% + calc(var(--ipub-fade, 50%) * -1))
+  );
+  top: 0;
+  left: 0;
+  width: 100%;
+  height: 100%;
 }
 
-ipub-content {
+ipub-body {
+  max-width: 100%;
+  max-height: 100%;
+
+  position: relative;
+
+  display: flex;
+  flex-direction: column;
+
+  overflow: scroll;
+  &:has(ipub-cover > dialog[open]) {
+    overflow: hidden;
+  }
+
   --ipub-padding: 0%;
   --ipub-gap: 0%;
   --ipub-padding-x: var(--ipub-padding, 0%);
@@ -98,13 +134,14 @@ ipub-background {
 
 ipub-image {
   position: relative;
-  display: block;
+  display: inline-block;
   flex-direction: column;
 
   width: var(--ipub-width, unset);
   height: var(--ipub-height, unset);
 
   img {
+    display: block;
     max-width: 100%;
     max-height: 100%;
   }
@@ -146,44 +183,3 @@ ipub-interaction {
     --ipub-radius: 100%;
   }
 }
-
-[data-ipub-element="image"] {
-  width: var(--ipub-width, unset);
-  height: var(--ipub-height, unset);
-  background-image: var(--ipub-image, unset);
-  background-repeat: no-repeat;
-  background-size: cover;
-  display: block;
-
-  img {
-    max-width: 100%;
-    max-height: 100%;
-  }
-}
-
-[data-ipub-element="interaction"] {
-  position: absolute;
-  left: var(--ipub-x, 0%);
-  top: var(--ipub-y, 0%);
-  border-radius: var(--ipub-radius, unset);
-  width: var(--ipub-width, unset);
-  height: var(--ipub-height, unset);
-  transform: translate(
-    var(--ipub-origin-offset-x, 0%),
-    var(--ipub-origin-offset-y, 0%)
-  );
-  aspect-ratio: var(--ipub-ratio, unset);
-  /* 
-  * The opacity would be, by default, zero. Here it is 0.3 for easier debugging and
-  * showing of the example ebook 
-  */
-  background-color: red;
-  opacity: 0.3;
-}
-
-a[data-ipub-element="interaction"] {
-  /* The text inside the interaction anchor are for accessibility purposes */
-  font-size: 0px;
-}
-
-}