add cover-image-alt to book html output

Author: cscheid

src/project/types/book/book-render.ts

@@ -75,6 +75,7 @@ import {
   isMultiFileBookFormat,
   isNumberedChapter,
   kBookCoverImage,
+  kBookCoverImageAlt,
 } from "./book-shared.ts";
 import { bookCrossrefsPostRender } from "./book-crossrefs.ts";
 import { bookBibliographyPostRender } from "./book-bibliography.ts";
@@ -148,9 +149,15 @@ export function bookPandocRenderer(
               | undefined;
 
           if (coverImage) {
+            const coverImageAlt =
+              (file.recipe.format.metadata[kBookCoverImageAlt] ||
+                bookConfig(kBookCoverImageAlt, project.config)) as
+                  | string
+                  | undefined;
             const title = file.recipe.format.metadata[kTitle] || "";
+            const alt = coverImageAlt ? ` fig-alt="${coverImageAlt}"` : "";
             file.executeResult.markdown =
-              `![](${coverImage} "${title}"){.quarto-cover-image}\n\n` +
+              `![](${coverImage} "${title}"){.quarto-cover-image${alt}}\n\n` +
               file.executeResult.markdown;
           }
 

src/project/types/book/book-shared.ts

@@ -29,10 +29,12 @@ export type BookConfigKey =
   | "date"
   | "date-format"
   | "abstract"
-  | "cover-image";
+  | "cover-image"
+  | "cover-image-alt";
 
 export const kBook = "book";
 export const kBookCoverImage = "cover-image";
+export const kBookCoverImageAlt = "cover-image-alt";
 
 export interface BookExtension {
   // bool extensions are single file by default but can elect to be multi file

src/resources/editor/tools/vs-code.mjs

@@ -16356,6 +16356,11 @@ var require_yaml_intelligence_resources = __commonJS({
                     description: "Cover image (used in HTML and ePub formats)"
                   }
                 },
+                "cover-image-alt": {
+                  string: {
+                    description: "Alternative text for cover image (used in HTML format)"
+                  }
+                },
                 sharing: {
                   maybeArrayOf: {
                     enum: [

src/resources/editor/tools/yaml/web-worker.js

@@ -9335,6 +9335,11 @@
                 "description": "Cover image (used in HTML and ePub formats)"
               }
             },
+            "cover-image-alt": {
+              "string": {
+                "description": "Alternative text for cover image (used in HTML format)"
+              }
+            },
             "sharing": {
               "maybeArrayOf": {
                 "enum": [

src/resources/editor/tools/yaml/yaml-intelligence-resources.json

@@ -84,6 +84,9 @@
         cover-image:
           path:
             description: "Cover image (used in HTML and ePub formats)"
+        cover-image-alt:
+          string:
+            description: "Alternative text for cover image (used in HTML format)"
         sharing:
           maybeArrayOf:
             enum: [twitter, facebook, linkedin]