[Editor] Implement the new alt text flow (bug 1909604)

For the Firefox pdf viewer, we want to use AI to guess an alt-text when adding an image to a pdf.
For now the telemtry stuff is not implemented and will come soon.
In order to test it locally:
 - set enableAltText, enableFakeMLManager and enableUpdatedAddImage to true.
or in Firefox:
 - set browser.ml.enable, pdfjs.enableAltText and pdfjs.enableUpdatedAddImage to true.

gulpfile.mjs

@@ -201,6 +201,7 @@ function createWebpackAlias(defines) {
     "web-annotation_editor_params": "web/annotation_editor_params.js",
     "web-download_manager": "",
     "web-external_services": "",
+    "web-new_alt_text_manager": "web/new_alt_text_manager.js",
     "web-null_l10n": "",
     "web-pdf_attachment_viewer": "web/pdf_attachment_viewer.js",
     "web-pdf_cursor_tools": "web/pdf_cursor_tools.js",

l10n/en-US/viewer.ftl

@@ -416,3 +416,52 @@ pdfjs-editor-colorpicker-red =
 pdfjs-editor-highlight-show-all-button-label = Show all
 pdfjs-editor-highlight-show-all-button =
     .title = Show all
+
+## New alt-text dialog
+## Group note for entire feature: Alternative text (alt text) helps when people can't see the image. This feature includes a tool to create alt text automatically using an AI model that works locally on the user's device to preserve privacy.
+
+# Modal header positioned above a text box where users can edit the alt text.
+pdfjs-editor-new-alt-text-dialog-edit-label = Edit alt text (image description)
+
+# Modal header positioned above a text box where users can edit the alt text.
+pdfjs-editor-new-alt-text-dialog-add-label = Add alt text (image description)
+
+pdfjs-editor-new-alt-text-textarea =
+    .placeholder = Write your description here…
+
+# This text is refers to the alt text box above this description. It offers a definition of alt text.
+pdfjs-editor-new-alt-text-description = Short description for people who can’t see the image or when the image doesn’t load.
+
+# This is a required legal disclaimer that refers to the automatically created text inside the alt text box above this text. It disappears if the text is edited by a human.
+pdfjs-editor-new-alt-text-disclaimer = This alt text was created automatically.
+pdfjs-editor-new-alt-text-disclaimer-learn-more-url = Learn more
+
+pdfjs-new-alt-text-create-automatically-button-label = Create alt text automatically
+pdfjs-editor-new-alt-text-not-now-button = Not now
+pdfjs-editor-new-alt-text-error-title = Couldn’t create alt text automatically
+pdfjs-editor-new-alt-text-error-description = Please write your own alt text or try again later.
+pdfjs-editor-new-alt-text-error-close-button = Close
+
+# Variables:
+#   $totalSize (Number) - the total size (in MB) of the ai model.
+#   $downloadedSize (Number) - the downloaded size (in MB) of the ai model.
+#   $percent (Number) - the percentage of the downloaded size.
+pdfjs-editor-new-alt-text-ai-model-downloading-progress =
+    .aria-valuemin = 0
+    .aria-valuemax = { $totalSize }
+    .aria-valuenow = { $downloadedSize }
+    .aria-valuetext = Downloading alt text AI model ({ $downloadedSize } of { $totalSize } MB)
+
+# This is a button that users can click to edit the alt text they have already added.
+pdfjs-editor-new-alt-text-added-button-label = Alt text added
+
+# This is a button that users can click to open the alt text editor and add alt text when it is not present.
+pdfjs-editor-new-alt-text-missing-button-label = Missing alt text
+
+# This is a button that opens up the alt text modal where users should review the alt text that was automatically generated.
+pdfjs-editor-new-alt-text-to-review-button-label = Review alt text
+
+# "Created automatically" is a prefix that will be added to the beginning of any alt text that has been automatically generated. After the colon, the user will see/hear the actual alt text description. If the alt text has been edited by a human, this prefix will not appear.
+# Variables:
+#   $generatedAltText (String) - the generated alt-text.
+pdfjs-editor-new-alt-text-generated-alt-text-with-disclaimer = Created automatically: { $generatedAltText }

src/display/editor/alt_text.js

@@ -16,7 +16,7 @@
 import { noContextMenu } from "../display_utils.js";
 
 class AltText {
-  #altText = "";
+  #altText = null;
 
   #altTextDecorative = false;
 
@@ -28,12 +28,21 @@ class AltText {
 
   #altTextWasFromKeyBoard = false;
 
+  #badge = null;
+
   #editor = null;
 
+  #guessedText = "";
+
+  #amendedText = "";
+
+  #useNewAltTextFlow = false;
+
   static _l10nPromise = null;
 
   constructor(editor) {
     this.#editor = editor;
+    this.#useNewAltTextFlow = editor._uiManager.useNewAltTextFlow;
   }
 
   static initialize(l10nPromise) {
@@ -43,9 +52,17 @@ class AltText {
   async render() {
     const altText = (this.#altTextButton = document.createElement("button"));
     altText.className = "altText";
-    const msg = await AltText._l10nPromise.get(
-      "pdfjs-editor-alt-text-button-label"
-    );
+    let msg;
+    if (this.#useNewAltTextFlow) {
+      altText.classList.add("new");
+      msg = await AltText._l10nPromise.get(
+        "pdfjs-editor-new-alt-text-missing-button-label"
+      );
+    } else {
+      msg = await AltText._l10nPromise.get(
+        "pdfjs-editor-alt-text-button-label"
+      );
+    }
     altText.textContent = msg;
     altText.setAttribute("aria-label", msg);
     altText.tabIndex = "0";
@@ -84,9 +101,64 @@ class AltText {
   }
 
   isEmpty() {
+    if (this.#useNewAltTextFlow) {
+      return this.#altText === null;
+    }
     return !this.#altText && !this.#altTextDecorative;
   }
 
+  hasData() {
+    if (this.#useNewAltTextFlow) {
+      return this.#altText !== null || !!this.#guessedText;
+    }
+    return this.isEmpty();
+  }
+
+  get guessedText() {
+    return this.#guessedText;
+  }
+
+  async setGuessedText(guessedText) {
+    if (this.#altText !== null) {
+      // The user provided their own alt text, so we don't want to overwrite it.
+      return;
+    }
+    this.#guessedText = guessedText;
+    this.#amendedText = await AltText._l10nPromise.get(
+      "pdfjs-editor-new-alt-text-generated-alt-text-with-disclaimer"
+    )({ generatedAltText: guessedText });
+    this.#setState();
+  }
+
+  toggleAltTextBadge(visibility) {
+    if (!this.#useNewAltTextFlow || this.#altText) {
+      if (this.#badge) {
+        this.#badge.remove();
+        this.#badge = null;
+      }
+      return;
+    }
+    if (!this.#badge) {
+      const badge = (this.#badge = document.createElement("div"));
+      badge.className = "noAltTextBadge";
+      this.#editor.div.append(badge);
+    }
+    this.#badge.classList.toggle("hidden", !visibility);
+  }
+
+  serialize(isForCopying) {
+    let altText = this.#altText;
+    if (!isForCopying && this.#guessedText === altText) {
+      altText = this.#amendedText;
+    }
+    return {
+      altText,
+      decorative: this.#altTextDecorative,
+      guessedText: this.#guessedText,
+      amendedText: this.#amendedText,
+    };
+  }
+
   get data() {
     return {
       altText: this.#altText,
@@ -97,12 +169,18 @@ class AltText {
   /**
    * Set the alt text data.
    */
-  set data({ altText, decorative }) {
+  set data({ altText, decorative, guessedText, amendedText, cancel = false }) {
+    if (guessedText) {
+      this.#guessedText = guessedText;
+      this.#amendedText = amendedText;
+    }
     if (this.#altText === altText && this.#altTextDecorative === decorative) {
       return;
     }
-    this.#altText = altText;
-    this.#altTextDecorative = decorative;
+    if (!cancel) {
+      this.#altText = altText;
+      this.#altTextDecorative = decorative;
+    }
     this.#setState();
   }
 
@@ -121,25 +199,53 @@ class AltText {
     this.#altTextButton?.remove();
     this.#altTextButton = null;
     this.#altTextTooltip = null;
+    this.#badge?.remove();
+    this.#badge = null;
   }
 
   async #setState() {
     const button = this.#altTextButton;
     if (!button) {
       return;
     }
-    if (!this.#altText && !this.#altTextDecorative) {
-      button.classList.remove("done");
-      this.#altTextTooltip?.remove();
-      return;
+
+    if (this.#useNewAltTextFlow) {
+      const type =
+        (this.#altText && "added") ||
+        (this.#altText === null && this.guessedText && "to-review") ||
+        "missing";
+      button.classList.toggle("done", !!this.#altText);
+      AltText._l10nPromise
+        .get(`pdfjs-editor-new-alt-text-${type}-button-label`)
+        .then(msg => {
+          button.setAttribute("aria-label", msg);
+          // We can't just use button.textContent here, because it would remove
+          // the existing tooltip element.
+          for (const child of button.childNodes) {
+            if (child.nodeType === Node.TEXT_NODE) {
+              child.textContent = msg;
+              break;
+            }
+          }
+        });
+      if (!this.#altText) {
+        this.#altTextTooltip?.remove();
+        return;
+      }
+    } else {
+      if (!this.#altText && !this.#altTextDecorative) {
+        button.classList.remove("done");
+        this.#altTextTooltip?.remove();
+        return;
+      }
+      button.classList.add("done");
+      AltText._l10nPromise
+        .get("pdfjs-editor-alt-text-edit-button-label")
+        .then(msg => {
+          button.setAttribute("aria-label", msg);
+        });
     }
-    button.classList.add("done");
 
-    AltText._l10nPromise
-      .get("pdfjs-editor-alt-text-edit-button-label")
-      .then(msg => {
-        button.setAttribute("aria-label", msg);
-      });
     let tooltip = this.#altTextTooltip;
     if (!tooltip) {
       this.#altTextTooltip = tooltip = document.createElement("span");