[api-minor] Remove the structTreeLayerFactory in the viewer

Please note that this functionality has never really mattered for the Firefox PDF Viewer, the GENERIC viewer, or even the "simpleviewer"/"singlepageviewer" component-examples. Hence, in practice this means that only the "pageviewer" component-example[1] have ever really utilized this.

Using factories to initialize various layers in the viewer, rather than simply invoking the relevant code directly, seems (at least to me) like a somewhat roundabout way of doing things.
Not only does this lead to more code, both to write and maintain, but since many of the layers have common parameters (e.g. an `AnnotationStorage`-instance) there's also some duplication.

Hence this patch, which removes the `structTreeLayerFactory` and instead uses a lookup-function in the `PDFPageView`-class to access the external viewer-properties as necessary.
Note that this should even be an improvement for the "pageviewer" component-example, since most layers will now work by default rather than require manual configuration.

---
[1] In practice we generally suggest using the "simpleviewer", or "singlepageviewer", since it does *most* things out-of-the-box and given that a lot of functionality really require *a viewer* and not just a single page in order to work.

web/default_factory.js

@@ -21,8 +21,6 @@
 /** @typedef {import("./interfaces").IL10n} IL10n */
 /** @typedef {import("./interfaces").IPDFLinkService} IPDFLinkService */
 // eslint-disable-next-line max-len
-/** @typedef {import("./interfaces").IPDFStructTreeLayerFactory} IPDFStructTreeLayerFactory */
-// eslint-disable-next-line max-len
 /** @typedef {import("./interfaces").IPDFTextLayerFactory} IPDFTextLayerFactory */
 /** @typedef {import("./interfaces").IPDFXfaLayerFactory} IPDFXfaLayerFactory */
 /** @typedef {import("./text_highlighter").TextHighlighter} TextHighlighter */
@@ -30,22 +28,9 @@
 /** @typedef {import("./text_accessibility.js").TextAccessibilityManager} TextAccessibilityManager */
 
 import { SimpleLinkService } from "./pdf_link_service.js";
-import { StructTreeLayerBuilder } from "./struct_tree_layer_builder.js";
 import { TextLayerBuilder } from "./text_layer_builder.js";
 import { XfaLayerBuilder } from "./xfa_layer_builder.js";
 
-/**
- * @implements IPDFStructTreeLayerFactory
- */
-class DefaultStructTreeLayerFactory {
-  /**
-   * @returns {StructTreeLayerBuilder}
-   */
-  createStructTreeLayerBuilder() {
-    return new StructTreeLayerBuilder();
-  }
-}
-
 /**
  * @implements IPDFTextLayerFactory
  */
@@ -100,8 +85,4 @@ class DefaultXfaLayerFactory {
   }
 }
 
-export {
-  DefaultStructTreeLayerFactory,
-  DefaultTextLayerFactory,
-  DefaultXfaLayerFactory,
-};
+export { DefaultTextLayerFactory, DefaultXfaLayerFactory };

web/interfaces.js

@@ -17,8 +17,6 @@
 /** @typedef {import("../src/display/api").PDFPageProxy} PDFPageProxy */
 // eslint-disable-next-line max-len
 /** @typedef {import("../src/display/display_utils").PageViewport} PageViewport */
-// eslint-disable-next-line max-len
-/** @typedef {import("./struct_tree_builder").StructTreeLayerBuilder} StructTreeLayerBuilder */
 /** @typedef {import("./text_highlighter").TextHighlighter} TextHighlighter */
 // eslint-disable-next-line max-len
 /** @typedef {import("./text_layer_builder").TextLayerBuilder} TextLayerBuilder */
@@ -198,16 +196,6 @@ class IPDFXfaLayerFactory {
   createXfaLayerBuilder({ pageDiv, pdfPage, annotationStorage = null }) {}
 }
 
-/**
- * @interface
- */
-class IPDFStructTreeLayerFactory {
-  /**
-   * @returns {StructTreeLayerBuilder}
-   */
-  createStructTreeLayerBuilder() {}
-}
-
 /**
  * @interface
  */
@@ -278,7 +266,6 @@ export {
   IDownloadManager,
   IL10n,
   IPDFLinkService,
-  IPDFStructTreeLayerFactory,
   IPDFTextLayerFactory,
   IPDFXfaLayerFactory,
   IRenderableView,

web/pdf_page_view.js

@@ -20,8 +20,6 @@
 /** @typedef {import("./event_utils").EventBus} EventBus */
 /** @typedef {import("./interfaces").IL10n} IL10n */
 // eslint-disable-next-line max-len
-/** @typedef {import("./interfaces").IPDFStructTreeLayerFactory} IPDFStructTreeLayerFactory */
-// eslint-disable-next-line max-len
 /** @typedef {import("./interfaces").IPDFTextLayerFactory} IPDFTextLayerFactory */
 /** @typedef {import("./interfaces").IPDFXfaLayerFactory} IPDFXfaLayerFactory */
 /** @typedef {import("./interfaces").IRenderableView} IRenderableView */
@@ -53,6 +51,7 @@ import { AnnotationLayerBuilder } from "./annotation_layer_builder.js";
 import { compatibilityParams } from "./app_options.js";
 import { NullL10n } from "./l10n_utils.js";
 import { SimpleLinkService } from "./pdf_link_service.js";
+import { StructTreeLayerBuilder } from "./struct_tree_layer_builder.js";
 import { TextAccessibilityManager } from "./text_accessibility.js";
 
 /**
@@ -76,7 +75,6 @@ import { TextAccessibilityManager } from "./text_accessibility.js";
  *   see also {@link RenderParameters} and {@link GetOperatorListParameters}.
  *   The default value is `AnnotationMode.ENABLE_FORMS`.
  * @property {IPDFXfaLayerFactory} [xfaLayerFactory]
- * @property {IPDFStructTreeLayerFactory} [structTreeLayerFactory]
  * @property {Object} [textHighlighterFactory]
  * @property {string} [imageResourcesPath] - Path for image resources, mainly
  *   for annotation icons. Include trailing slash.
@@ -160,7 +158,6 @@ class PDFPageView {
     this.textLayerFactory = options.textLayerFactory;
     this.xfaLayerFactory = options.xfaLayerFactory;
     this._textHighlighterFactory = options.textHighlighterFactory;
-    this.structTreeLayerFactory = options.structTreeLayerFactory;
     if (
       typeof PDFJSDev === "undefined" ||
       PDFJSDev.test("!PRODUCTION || GENERIC")
@@ -351,9 +348,7 @@ class PDFPageView {
       error,
     });
 
-    if (this.structTreeLayerFactory) {
-      this.#renderStructTreeLayer();
-    }
+    this.#renderStructTreeLayer();
   }
 
   /**
@@ -367,8 +362,7 @@ class PDFPageView {
     if (!this.textLayer) {
       return;
     }
-    this.structTreeLayer ||=
-      this.structTreeLayerFactory.createStructTreeLayerBuilder();
+    this.structTreeLayer ||= new StructTreeLayerBuilder();
 
     const tree = await (!this.structTreeLayer.renderingDone
       ? this.pdfPage.getStructTree()

web/pdf_viewer.component.js

@@ -14,7 +14,6 @@
  */
 
 import {
-  DefaultStructTreeLayerFactory,
   DefaultTextLayerFactory,
   DefaultXfaLayerFactory,
 } from "./default_factory.js";
@@ -60,6 +59,15 @@ class DefaultAnnotationLayerFactory {
   }
 }
 
+class DefaultStructTreeLayerFactory {
+  constructor() {
+    throw new Error(
+      "The `DefaultStructTreeLayerFactory` has been removed, " +
+        "this functionality is automatically enabled when the TextLayer is used."
+    );
+  }
+}
+
 export {
   AnnotationLayerBuilder,
   DefaultAnnotationLayerFactory,

web/pdf_viewer.js

@@ -24,8 +24,6 @@
 /** @typedef {import("./interfaces").IL10n} IL10n */
 /** @typedef {import("./interfaces").IPDFLinkService} IPDFLinkService */
 // eslint-disable-next-line max-len
-/** @typedef {import("./interfaces").IPDFStructTreeLayerFactory} IPDFStructTreeLayerFactory */
-// eslint-disable-next-line max-len
 /** @typedef {import("./interfaces").IPDFTextLayerFactory} IPDFTextLayerFactory */
 /** @typedef {import("./interfaces").IPDFXfaLayerFactory} IPDFXfaLayerFactory */
 // eslint-disable-next-line max-len
@@ -69,7 +67,6 @@ import { NullL10n } from "./l10n_utils.js";
 import { PDFPageView } from "./pdf_page_view.js";
 import { PDFRenderingQueue } from "./pdf_rendering_queue.js";
 import { SimpleLinkService } from "./pdf_link_service.js";
-import { StructTreeLayerBuilder } from "./struct_tree_layer_builder.js";
 import { TextHighlighter } from "./text_highlighter.js";
 import { TextLayerBuilder } from "./text_layer_builder.js";
 import { XfaLayerBuilder } from "./xfa_layer_builder.js";
@@ -206,7 +203,6 @@ class PDFPageViewBuffer {
 /**
  * Simple viewer control to display PDF content/pages.
  *
- * @implements {IPDFStructTreeLayerFactory}
  * @implements {IPDFTextLayerFactory}
  * @implements {IPDFXfaLayerFactory}
  */
@@ -792,7 +788,6 @@ class PDFViewer {
             annotationMode,
             xfaLayerFactory: this,
             textHighlighterFactory: this,
-            structTreeLayerFactory: this,
             imageResourcesPath: this.imageResourcesPath,
             renderer:
               typeof PDFJSDev === "undefined" ||
@@ -1732,13 +1727,6 @@ class PDFViewer {
     });
   }
 
-  /**
-   * @returns {StructTreeLayerBuilder}
-   */
-  createStructTreeLayerBuilder() {
-    return new StructTreeLayerBuilder();
-  }
-
   /**
    * @type {boolean} Whether all pages of the PDF document have identical
    *   widths and heights.