[Editor] Add a tooltip showing the alt text when hovering the alt-text button (bug 1844952)

l10n/en-US/viewer.properties

@@ -265,9 +265,9 @@ editor_ink2_aria_label=Draw Editor
 editor_ink_canvas_aria_label=User-created image
 
 # Alt-text dialog
-# LOCALIZATION NOTE (alt_text_button_label): Alternative text (alt text) helps
+# LOCALIZATION NOTE (editor_alt_text_button_label): Alternative text (alt text) helps
 # when people can't see the image.
-alt_text_button_label=Alt text
+editor_alt_text_button_label=Alt text
 editor_alt_text_dialog_label=Choose an option
 editor_alt_text_dialog_description=Alt text (alternative text) helps when people can’t see the image or when it doesn’t load.
 editor_alt_text_enter_description_label=Enter a description
@@ -276,3 +276,4 @@ editor_alt_text_mark_decorative_label=Mark as decorative
 editor_alt_text_mark_decorative_description=This is best for images that aren’t informative, like borders or stylistic elements.
 editor_alt_text_cancel_button=Cancel
 editor_alt_text_save_button=Save
+editor_alt_text_decorative_tooltip=Marked as decorative

src/display/editor/editor.js

@@ -40,7 +40,9 @@ class AnnotationEditor {
 
   #altTextButton = null;
 
-  #altTextAriaDescription = null;
+  #altTextTooltip = null;
+
+  #altTextTooltipTimeout = null;
 
   #keepAspectRatio = false;
 
@@ -142,7 +144,10 @@ class AnnotationEditor {
    */
   static initialize(l10n, options = null) {
     AnnotationEditor._l10nPromise ||= new Map(
-      ["alt_text_button_label"].map(str => [str, l10n.get(str)])
+      [
+        "editor_alt_text_button_label",
+        "editor_alt_text_decorative_tooltip",
+      ].map(str => [str, l10n.get(str)])
     );
     if (options?.strings) {
       for (const str of options.strings) {
@@ -818,9 +823,11 @@ class AnnotationEditor {
     }
     const altText = (this.#altTextButton = document.createElement("button"));
     altText.className = "altText";
-    AnnotationEditor._l10nPromise.get("alt_text_button_label").then(msg => {
-      altText.textContent = msg;
-    });
+    AnnotationEditor._l10nPromise
+      .get("editor_alt_text_button_label")
+      .then(msg => {
+        altText.textContent = msg;
+      });
     altText.tabIndex = "0";
     altText.addEventListener(
       "click",
@@ -836,6 +843,18 @@ class AnnotationEditor {
         this._uiManager.editAltText(this);
       }
     });
+    const DELAY_TO_SHOW_TOOLTIP = 500;
+    altText.addEventListener("mouseenter", () => {
+      this.#altTextTooltipTimeout = setTimeout(() => {
+        this.#altTextTooltipTimeout = null;
+        this.#altTextTooltip?.classList.add("show");
+      }, DELAY_TO_SHOW_TOOLTIP);
+    });
+    altText.addEventListener("mouseleave", () => {
+      clearTimeout(this.#altTextTooltipTimeout);
+      this.#altTextTooltipTimeout = null;
+      this.#altTextTooltip?.classList.remove("show");
+    });
     this.#setAltTextButtonState();
     this.div.append(altText);
     if (!AnnotationEditor.SMALL_EDITOR_SIZE) {
@@ -849,36 +868,30 @@ class AnnotationEditor {
     }
   }
 
-  #setAltTextButtonState() {
+  async #setAltTextButtonState() {
     const button = this.#altTextButton;
-    if (!button) {
+    if (!button || (!this.#altTextDecorative && !this.#altText)) {
       return;
     }
-    // TODO: remove the aria-describedby once the tooltip stuff is implemented:
-    // the tooltip willl contain a span with the description, hence we could use
-    // it.
-    if (this.#altTextDecorative) {
-      button.classList.add("done");
-      button.title = "";
-      if (this.#altTextAriaDescription) {
-        button.removeAttribute("aria-describedby");
-        this.#altTextAriaDescription.remove();
-        this.#altTextAriaDescription = null;
-      }
-    } else if (this.#altText) {
-      button.classList.add("done");
-      button.title = this.#altText;
-      let description = this.#altTextAriaDescription;
-      if (!description) {
-        this.#altTextAriaDescription = description =
-          document.createElement("span");
-        description.className = "description";
-        const id = (description.id = `${this.id}-alt-text`);
-        button.append(description);
-        button.setAttribute("aria-describedby", id);
-      }
-      description.innerText = this.#altText;
+    let tooltip = this.#altTextTooltip;
+    if (!tooltip) {
+      this.#altTextTooltip = tooltip = document.createElement("span");
+      tooltip.className = "tooltip";
+      tooltip.setAttribute("role", "tooltip");
+      const id = (tooltip.id = `alt-text-tooltip-${this.id}`);
+      button.append(tooltip);
+      button.setAttribute("aria-describedby", id);
     }
+    button.classList.add("done");
+    if (this.#altTextDecorative) {
+      tooltip.innerText = await AnnotationEditor._l10nPromise.get(
+        "editor_alt_text_decorative_tooltip"
+      );
+      tooltip.classList.add("decorative");
+      return;
+    }
+    tooltip.innerText = this.#altText;
+    tooltip.classList.remove("decorative");
   }
 
   getClientDimensions() {

web/annotation_editor_layer_builder.css

@@ -529,13 +529,53 @@
     mask-image: var(--alt-text-done-image);
   }
 
-  & .description {
-    position: absolute;
-    top: 0;
-    left: 0;
+  & .tooltip {
     display: none;
-    width: 0;
-    height: 0;
+
+    &.decorative {
+      font-style: italic;
+    }
+
+    &.show {
+      --alt-text-tooltip-bg: #f0f0f4;
+      --alt-text-tooltip-fg: #15141a;
+      --alt-text-tooltip-border: #8f8f9d;
+      --alt-text-tooltip-shadow: 0px 2px 6px 0px rgba(58, 57, 68, 0.2);
+
+      @media (prefers-color-scheme: dark) {
+        --alt-text-tooltip-bg: #1c1b22;
+        --alt-text-tooltip-fg: #fbfbfe;
+        --alt-text-tooltip-shadow: 0px 2px 6px 0px #15141a;
+      }
+
+      @media screen and (forced-colors: active) {
+        --alt-text-tooltip-bg: Canvas;
+        --alt-text-tooltip-fg: CanvasText;
+        --alt-text-tooltip-border: CanvasText;
+        --alt-text-tooltip-shadow: none;
+      }
+
+      display: inline-flex;
+      flex-direction: column;
+      align-items: center;
+      justify-content: center;
+      position: absolute;
+      top: calc(100% + 2px);
+      inset-inline-start: 0;
+      padding-block: 2px 3px;
+      padding-inline: 3px;
+      max-width: 300px;
+      width: max-content;
+      height: auto;
+      font-size: 12px;
+
+      border: 0.5px solid var(--alt-text-tooltip-border);
+      background: var(--alt-text-tooltip-bg);
+      box-shadow: var(--alt-text-tooltip-shadow);
+      color: var(--alt-text-tooltip-fg);
+
+      pointer-events: none;
+    }
   }
 }
 

web/l10n_utils.js

@@ -82,7 +82,8 @@ const DEFAULT_L10N_STRINGS = {
   editor_free_text2_aria_label: "Text Editor",
   editor_ink2_aria_label: "Draw Editor",
   editor_ink_canvas_aria_label: "User-created image",
-  alt_text_button_label: "Alt text",
+  editor_alt_text_button_label: "Alt text",
+  editor_alt_text_decorative_tooltip: "Marked as decorative",
 };
 if (typeof PDFJSDev === "undefined" || !PDFJSDev.test("MOZCENTRAL")) {
   DEFAULT_L10N_STRINGS.print_progress_percent = "{{progress}}%";