feat(ipub): make sticky and fade backgrounds the default

This makes the random hex ID logic shared between all elements

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

@@ -1,7 +1,185 @@
 "use strict";
 
+class IPUBElement extends HTMLElement {
+  static observedAttributes = ["id"];
+
+  connectedCallback() {
+    this.ensureID();
+  }
+
+  attributeChangedCallback(_name, _oldValue, _newValue) {
+    this.ensureID();
+  }
+
+  ensureID() {
+    if (this.id) {
+      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/)
+
+    let hash = 0;
+    this.innerHTML.split("").forEach((char) => {
+      hash = char.charCodeAt(0) + ((hash << 5) - hash);
+    });
+
+    let id = "";
+    for (let i = 0; i < 3; i++) {
+      id += ((hash >> (i * 8)) & 0xff).toString(16).padStart(2, "0");
+    }
+
+    this.id = id;
+  }
+}
+
+class IPUBBackground extends IPUBElement {
+  static elementName = "ipub-background";
+  static observedAttributes = ["nofade"].concat(super.observedAttributes);
+
+  /**
+   * @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,
+        );
+        instance.fade(perc);
+      }
+    });
+
+    return new IntersectionObserver((entries) =>
+      entries.forEach((e) => {
+        let instance = e.target.parentElement;
+
+        if (
+          instance.tagName.toLowerCase() !==
+          IPUBBackground.elementName.toLowerCase()
+        ) {
+          instance = instance.parentElement;
+        }
+
+        if (
+          instance.tagName.toLowerCase() !==
+          IPUBBackground.elementName.toLowerCase()
+        ) {
+          console.error(
+            "IPUBBackground: malformed <ipub-background> element",
+            e.target,
+          );
+          return;
+        }
+
+        if (e.intersectionRatio > 0 && instance.id) {
+          instancesOnScreen.set(instance.id, instance);
+        } else if (instance.id) {
+          instancesOnScreen.delete(instance.id);
+        }
+      }),
+    );
+  })();
+
+  connectedCallback() {
+    super.connectedCallback();
+
+    const image = this.querySelector("img");
+    if (!image) {
+      console.error("IPUBBackground: missing <img> element inside background");
+      return;
+    }
+
+    // INFO: We don't need to fade the first background
+    if (this.matches(":first-of-type") || this.hasAttribute("nofade")) {
+      IPUBBackground.#observer.unobserve(image);
+      return;
+    }
+
+    IPUBBackground.#observer.observe(image);
+    const perc = getPercentageInView(image);
+    if (perc > 0) {
+      this.fade(perc);
+    }
+  }
+
+  attributeChangedCallback(name, _oldValue, _newValue) {
+    super.attributeChangedCallback();
+
+    if (name !== "nofade") {
+      return;
+    }
+
+    const image = this.querySelector("img");
+    if (!image) {
+      console.error("IPUBBackground: missing <img> element inside background");
+      return;
+    }
+
+    // INFO: We don't need to fade the first background
+    if (this.matches(":first-of-type") || this.hasAttribute("nofade")) {
+      IPUBBackground.#observer.unobserve(image);
+      return;
+    }
+
+    IPUBBackground.#observer.observe(image);
+    const perc = getPercentageInView(image);
+    if (perc > 0) {
+      this.fade(perc);
+    }
+  }
+
+  /**
+   * @param {number} perc
+   * @throws {Error}
+   * @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;
+    }
+
+    const currentPerc = this.style.getPropertyValue("--ipub-fade");
+    if (currentPerc === "100%" && perc >= 100) {
+      return;
+    }
+
+    if (perc % 10 === 0) {
+      this.style.setProperty("--ipub-fade", `${perc}%`);
+    }
+  }
+}
+
+class IPUBContent extends IPUBElement {
+  static elementName = "ipub-content";
+}
+
+class IPUBImage extends IPUBElement {
+  static elementName = "ipub-image";
+}
+
+class IPUBInteraction extends IPUBElement {
+  static elementName = "ipub-interaction";
+}
+
 globalThis.addEventListener("load", () => {
-  console.log("IPUB SCRIPT LOADED");
+  console.info("IPUB: STARTING DEFINITIONS");
+
+  [IPUBBackground, IPUBContent, IPUBImage, IPUBInteraction].forEach((e) => {
+    console.info(`IPUB: Defining custom element <${e.elementName}>`);
+    globalThis.customElements.define(e.elementName, e);
+  });
+
+  console.info("IPUB: FINISHED DEFINITIONS");
 
   /** @type {Map<string, Element>} */
   const onScreenMap = new Map();
@@ -9,14 +187,14 @@ globalThis.addEventListener("load", () => {
   const observer = new IntersectionObserver((entries) => {
     entries.forEach((e) => {
       if (e.intersectionRatio > 0) {
-        console.debug(
-          `IntersectionObserver: adding element #${e.target.id} to onScreenMap`,
-        );
+        // console.debug(
+        //   `IntersectionObserver: adding element #${e.target.id} to onScreenMap`,
+        // );
         onScreenMap.set(e.target.id, e.target);
       } else {
-        console.debug(
-          `IntersectionObserver: removing element #${e.target.id} to onScreenMap`,
-        );
+        // console.debug(
+        //   `IntersectionObserver: removing element #${e.target.id} to onScreenMap`,
+        // );
         onScreenMap.delete(e.target.id);
       }
     });
@@ -31,7 +209,7 @@ globalThis.addEventListener("load", () => {
   document.addEventListener("scroll", async () => {
     for (const [id, element] of onScreenMap) {
       const perc = getPercentageInView(element);
-      console.debug(`Element #${id} is now ${perc}% on screen`);
+      // console.debug(`Element #${id} is now ${perc}% on screen`);
 
       const played = element.getAttribute("data-ipub-trigger-played") == "true";
 
@@ -52,7 +230,7 @@ async function playIpubElement(element) {
       /** @type {HTMLAudioElement} */
       const audio = element;
 
-      await audio.play();
+      // await audio.play();
 
       break;
     }

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

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <html xmlns="http://www.w3.org/1999/xhtml">
   <head>
-    <meta name="x-ipub-version" content="1.0" />
+    <meta name="x-ipub-version" content="0.1" />
     <link href="../styles/stylesheet.css" rel="stylesheet" type="text/css" />
     <!-- <script type="module" src="../scripts/ipub.js" fetchpriority="high"></script> -->
     <script defer="true" src="../scripts/ipub.js" fetchpriority="high">
@@ -9,89 +9,76 @@
     </script>
   </head>
   <body xmlns:epub="http://www.idpf.org/2007/ops" class="body">
-    <main data-ipub-element="content">
-      <section data-ipub-element="page" id="page01">
-        <span data-ipub-element="image">
+    <ipub-content style="--ipub-padding: 10%;">
+      <main>
+        <ipub-background id="background0001">
+          <img src="../images/background0001.jpg" width="100" height="100" />
+        </ipub-background>
+        <ipub-image>
           <img src="../images/image0001.png" />
-        </span>
-        <!-- 
-        This in the UI would be an "Point Interaction" or just "Interaction". The
-        editor can just place it on some point the page, and adjust it's size.
+          <ipub-interaction style="--ipub-y:88.5%;--ipub-x:6%" circle="">
+            <a href="https://krita.org" referrerpolicy="same-origin"
+            rel="external nofollow noopener noreferrer" target="_blank" />
+          </ipub-interaction>
+          <ipub-interaction style="--ipub-y:93.5%;--ipub-x:81.5%;--ipub-size:13%;">
+            <a href="https://guz.one" referrerpolicy="same-origin"
+            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 action is "open link", this action should have a warning to the reader, 
-        to make sure they don't open malicious links.
-      -->
-        <!-- 
-        The "rel" will have "nofollow", "noopener" and "noreferrer" when the link
-        is to a domain different from the project's one.
-      -->
-        <a data-ipub-element="interaction" data-ipub-variant="point"
-        style="--ipub-x:6%;--ipub-y:88.5%;--ipub-width:10%;--ipub-radius:100%;--ipub-origin-offset-x:-50%;--ipub-origin-offset-y:-50%;--ipub-ratio:1/1;"
-        id="int-httpsguzone" href="https://krita.org" target="_blank" referrerpolicy="same-origin"
-        rel="external nofollow noopener noreferrer">
-        <!-- 
-
-        This would be generated if the editor doesn't specify a accessibility text,
-        the in quotations text would be fetched from the site's title when the link is created
-        if possible.
-      -->
-        Go to "Krita | Digital Paiting. Creative Freedom"</a>
-        <!-- 
-        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 action is "go to page".
-      -->
-        <a data-ipub-element="interaction" data-ipub-variant="area"
-        style="--ipub-x:76%;--ipub-y:90%;--ipub-width:11.5%;--ipub-height:8%;" id="int-httpsguzone"
-        href="section0001.xhtml#page03">
-        <!-- 
-        This would be generated if the editor doesn't specify a accessibility text.
-        The in quotations text would be the title of the page if it has one, otherwise
-        it's ID is used (RFC, we could just place the text as "Go to page", since the IDs.
-        may not be human-readable).
-      -->
-        Go to page "page03"</a>
-        <!-- 
-        TODO: Analyse if area and point interactions should be saved as the same type of element
-        and if the "data-ipub-variant" should be a thing. This pretty much depends on how much
-        we want the editor to "guess" what controls to provide the user with.
-      -->
-      </section>
-      <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>
-      <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>
-      <section data-ipub-element="page" id="page02">
-        <span data-ipub-element="image">
-          <img src="../images/image0002.png" />
-        </span>
-      </section>
-    </main>
+          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-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-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>
+      </main>
+    </ipub-content>
   </body>
 </html>

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

@@ -1,22 +1,164 @@
 .body {
   -epub-writing-mode: horizontal-tb;
   -webkit-writing-mode: horizontal-tb;
-  /* direction: ltr; */
-  direction: rtl;
+  direction: ltr;
+  /* direction: rtl; */
   writing-mode: horizontal-tb;
+  position: relative;
+  margin: 0;
 
   max-width: 100vw;
 }
 
-[data-ipub-element="page"] {
-  display: flex;
-  flex-direction: column;
+ipub-content {
+  --ipub-padding: 0%;
+  --ipub-gap: 0%;
+  --ipub-padding-x: var(--ipub-padding, 0%);
+  --ipub-padding-y: var(--ipub-padding, 0%);
+  --ipub-padding-t: var(--ipub-padding-y, 0%);
+  --ipub-padding-r: var(--ipub-padding-x, 0%);
+  --ipub-padding-b: var(--ipub-padding-y, 0%);
+  --ipub-padding-l: var(--ipub-padding-x, 0%);
+
+  & > article,
+  & > main,
+  & > section {
+    position: relative;
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+
+    & > *:first-child:not(ipub-background),
+    & > ipub-background:first-child + *:first-of-type {
+      margin-top: var(--ipub-padding-t);
+    }
+
+    & > *:not(ipub-background) {
+      margin-top: calc(var(--ipub-gap) / 2);
+      margin-right: var(--ipub-padding-r);
+      margin-left: var(--ipub-padding-l);
+      margin-bottom: calc(var(--ipub-gap) / 2);
+    }
+
+    & > *:last-child:not(ipub-background),
+    & > ipub-background:last-child + *:last-of-type {
+      margin-bottom: var(--ipub-padding-b);
+    }
+  }
+}
+
+ipub-background {
+  --ipub-width: 100vw;
+  --ipub-height: 100vh;
+
+  &[sticky] {
+    display: inline-block;
+    top: 0;
+    left: 0;
+    width: 0;
+    height: 0;
+    position: sticky;
+    align-self: start;
+  }
+
+  &[fade] img {
+    /* For testing */
+    /* background-image: linear-gradient( */
+    /*   rgba(266, 0, 0, 1) 0%, */
+    /*   rgba(0, 266, 0, 1) calc(100% + calc(var(--ipub-fade, 100%) * -1)), */
+    /*   rgba(266, 0, 266, 1) 100% */
+    /* ) !important; */
+    --mask: linear-gradient(
+      rgba(0, 0, 0, 0) 0%,
+      rgba(0, 0, 0, 1) calc(100% + calc(var(--ipub-fade, 100%) * -1))
+    ) !important;
+    /* background-image: var(--mask); */
+    mask-image: var(--mask);
+    -webkit-mask-image: var(--mask);
+  }
+
+  & > picture {
+    display: block;
+    width: var(--ipub-width);
+    height: var(--ipub-height);
+    & > img {
+      object-fit: cover;
+      width: 100%;
+      height: 100%;
+    }
+  }
+  /* Support standalone img element */
+  & > img {
+    display: block;
+    object-fit: cover;
+    width: var(--ipub-width);
+    height: var(--ipub-height);
+  }
+}
+
+ipub-image {
   position: relative;
+  display: block;
+  flex-direction: column;
+
+  width: var(--ipub-width, unset);
+  height: var(--ipub-height, unset);
+
+  img {
+    max-width: 100%;
+    max-height: 100%;
+  }
+}
+
+ipub-interaction {
+  position: absolute;
+
+  --ipub-x: 0px;
+  --ipub-y: 0px;
+  --ipub-size: 10%;
+  --ipub-width: var(--ipub-size, unset);
+  --ipub-height: unset;
+  --ipub-ratio: 1/1;
+
+  left: var(--ipub-x);
+  top: var(--ipub-y);
+
+  width: var(--ipub-width);
+  height: var(--ipub-height);
+  aspect-ratio: var(--ipub-ratio, unset);
+  transform: translate(var(--ipub-offset-x, -50%), var(--ipub-offset-y, -50%));
+
+  & > * {
+    display: block;
+    width: 100%;
+    height: 100%;
+
+    border-radius: var(--ipub-radius, 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;
+  }
+  &[circle] {
+    --ipub-radius: 100%;
+  }
 }
 
 [data-ipub-element="image"] {
   width: var(--ipub-width, unset);
-  height: 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"] {
@@ -44,7 +186,4 @@ a[data-ipub-element="interaction"] {
   font-size: 0px;
 }
 
-img {
-  max-width: 100%;
-  max-height: 100%;
 }