[api-minor] Add basic support for the SetOCGState action (issue 15372)

Note that this patch implements the `SetOCGState`-handling in `PDFLinkService`, rather than as a new method in `OptionalContentConfig`[1], since this action is nothing but a series of `setVisibility`-calls and that it seems quite uncommon in real-world PDF documents.

The new functionality also required some tweaks in the `PDFLayerViewer`, to ensure that the `layersView` in the sidebar is updated correctly when the optional-content visibility changes from "outside" of `PDFLayerViewer`.

---
[1] We can obviously move this code into `OptionalContentConfig` instead, if deemed necessary, but for an initial implementation I figured that doing it this way might be acceptable.

src/core/catalog.js

@@ -329,6 +329,7 @@ class Catalog {
         url: data.url,
         unsafeUrl: data.unsafeUrl,
         newWindow: data.newWindow,
+        setOCGState: data.setOCGState,
         title: stringToPDFString(title),
         color: rgbColor,
         count: Number.isInteger(count) ? count : undefined,
@@ -1533,6 +1534,38 @@ class Catalog {
           }
           break;
 
+        case "SetOCGState":
+          const state = action.get("State");
+          const preserveRB = action.get("PreserveRB");
+
+          if (!Array.isArray(state) || state.length === 0) {
+            break;
+          }
+          const stateArr = [];
+
+          for (const elem of state) {
+            if (elem instanceof Name) {
+              switch (elem.name) {
+                case "ON":
+                case "OFF":
+                case "Toggle":
+                  stateArr.push(elem.name);
+                  break;
+              }
+            } else if (elem instanceof Ref) {
+              stateArr.push(elem.toString());
+            }
+          }
+
+          if (stateArr.length !== state.length) {
+            break; // Some of the original entries are not valid.
+          }
+          resultObj.setOCGState = {
+            state: stateArr,
+            preserveRB: typeof preserveRB === "boolean" ? preserveRB : true,
+          };
+          break;
+
         case "JavaScript":
           const jsAction = action.get("JS");
           let js;

src/display/annotation_layer.js

@@ -597,6 +597,9 @@ class LinkAnnotationElement extends AnnotationElement {
     } else if (data.action) {
       this._bindNamedAction(link, data.action);
       isBound = true;
+    } else if (data.setOCGState) {
+      this.#bindSetOCGState(link, data.setOCGState);
+      isBound = true;
     } else if (data.dest) {
       this._bindLink(link, data.dest);
       isBound = true;
@@ -678,6 +681,20 @@ class LinkAnnotationElement extends AnnotationElement {
     link.className = "internalLink";
   }
 
+  /**
+   * Bind SetOCGState actions to the link element.
+   * @param {Object} link
+   * @param {Object} action
+   */
+  #bindSetOCGState(link, action) {
+    link.href = this.linkService.getAnchorUrl("");
+    link.onclick = () => {
+      this.linkService.executeSetOCGState(action);
+      return false;
+    };
+    link.className = "internalLink";
+  }
+
   /**
    * Bind JS actions to the link element.
    *

src/display/optional_content_config.js

@@ -14,6 +14,7 @@
  */
 
 import { objectFromMap, unreachable, warn } from "../shared/util.js";
+import { MurmurHash3_64 } from "../shared/murmurhash3.js";
 
 const INTERNAL = Symbol("INTERNAL");
 
@@ -44,11 +45,11 @@ class OptionalContentGroup {
 }
 
 class OptionalContentConfig {
-  #cachedHasInitialVisibility = true;
+  #cachedGetHash = null;
 
   #groups = new Map();
 
-  #initialVisibility = null;
+  #initialHash = null;
 
   #order = null;
 
@@ -84,10 +85,7 @@ class OptionalContentConfig {
     }
 
     // The following code must always run *last* in the constructor.
-    this.#initialVisibility = new Map();
-    for (const [id, group] of this.#groups) {
-      this.#initialVisibility.set(id, group.visible);
-    }
+    this.#initialHash = this.getHash();
   }
 
   #evaluateVisibilityExpression(array) {
@@ -206,20 +204,11 @@ class OptionalContentConfig {
     }
     this.#groups.get(id)._setVisible(INTERNAL, !!visible);
 
-    this.#cachedHasInitialVisibility = null;
+    this.#cachedGetHash = null;
   }
 
   get hasInitialVisibility() {
-    if (this.#cachedHasInitialVisibility !== null) {
-      return this.#cachedHasInitialVisibility;
-    }
-    for (const [id, group] of this.#groups) {
-      const visible = this.#initialVisibility.get(id);
-      if (group.visible !== visible) {
-        return (this.#cachedHasInitialVisibility = false);
-      }
-    }
-    return (this.#cachedHasInitialVisibility = true);
+    return this.getHash() === this.#initialHash;
   }
 
   getOrder() {
@@ -239,6 +228,18 @@ class OptionalContentConfig {
   getGroup(id) {
     return this.#groups.get(id) || null;
   }
+
+  getHash() {
+    if (this.#cachedGetHash !== null) {
+      return this.#cachedGetHash;
+    }
+    const hash = new MurmurHash3_64();
+
+    for (const [id, group] of this.#groups) {
+      hash.update(`${id}:${group.visible}`);
+    }
+    return (this.#cachedGetHash = hash.hexdigest());
+  }
 }
 
 export { OptionalContentConfig };