Make sure WillPrint ran before starting printing

src/scripting_api/app_utils.js

@@ -21,8 +21,14 @@ const FORMS_VERSION = 21.00720099;
 const USERACTIVATION_CALLBACKID = 0;
 const USERACTIVATION_MAXTIME_VALIDITY = 5000;
 
+function serializeError(error) {
+  const value = `${error.toString()}\n${error.stack}`;
+  return { command: "error", value };
+}
+
 export {
   FORMS_VERSION,
+  serializeError,
   USERACTIVATION_CALLBACKID,
   USERACTIVATION_MAXTIME_VALIDITY,
   VIEWER_TYPE,

src/scripting_api/doc.js

@@ -16,6 +16,7 @@
 import { createActionsMap } from "./common.js";
 import { PDFObject } from "./pdf_object.js";
 import { PrintParams } from "./print_params.js";
+import { serializeError } from "./app_utils.js";
 import { ZoomType } from "./constants.js";
 
 const DOC_EXTERNAL = false;
@@ -126,19 +127,28 @@ class Doc extends PDFObject {
   }
 
   _dispatchDocEvent(name) {
-    if (name === "Open") {
+    switch (name) {
+      case "Open":
         this._disableSaving = true;
         this._runActions("OpenAction");
         this._disableSaving = false;
-    } else if (name === "WillPrint") {
+        break;
+      case "WillPrint":
         this._disablePrinting = true;
+        try {
           this._runActions(name);
+        } catch (error) {
+          this._send(serializeError(error));
+        }
+        this._send({ command: "WillPrintFinished" });
         this._disablePrinting = false;
-    } else if (name === "WillSave") {
+        break;
+      case "WillSave":
         this._disableSaving = true;
         this._runActions(name);
         this._disableSaving = false;
-    } else {
+        break;
+      default:
         this._runActions(name);
     }
   }

src/scripting_api/initialization.js

@@ -34,6 +34,7 @@ import { Color } from "./color.js";
 import { Console } from "./console.js";
 import { Doc } from "./doc.js";
 import { ProxyHandler } from "./proxy.js";
+import { serializeError } from "./app_utils.js";
 import { Util } from "./util.js";
 
 function initSandbox(params) {
@@ -214,8 +215,7 @@ function initSandbox(params) {
     try {
       functions[name](args);
     } catch (error) {
-      const value = `${error.toString()}\n${error.stack}`;
+      send(serializeError(error));
-      send({ command: "error", value });
     }
   };
 }

web/pdf_scripting_manager.js

@@ -51,6 +51,8 @@ class PDFScriptingManager {
 
   #scripting = null;
 
+  #willPrintCapability = null;
+
   /**
    * @param {PDFScriptingManagerOptions} options
    */
@@ -203,10 +205,23 @@ class PDFScriptingManager {
   }
 
   async dispatchWillPrint() {
-    return this.#scripting?.dispatchEventInSandbox({
+    if (!this.#scripting) {
+      return;
+    }
+    await this.#willPrintCapability?.promise;
+    this.#willPrintCapability = new PromiseCapability();
+    try {
+      await this.#scripting.dispatchEventInSandbox({
         id: "doc",
         name: "WillPrint",
       });
+    } catch (ex) {
+      this.#willPrintCapability.resolve();
+      this.#willPrintCapability = null;
+      throw ex;
+    }
+
+    await this.#willPrintCapability.promise;
   }
 
   async dispatchDidPrint() {
@@ -306,6 +321,10 @@ class PDFScriptingManager {
             pdfViewer.decreaseScale();
           }
           break;
+        case "WillPrintFinished":
+          this.#willPrintCapability?.resolve();
+          this.#willPrintCapability = null;
+          break;
       }
       return;
     }
@@ -432,6 +451,9 @@ class PDFScriptingManager {
       await this.#scripting.destroySandbox();
     } catch {}
 
+    this.#willPrintCapability?.reject(new Error("Scripting destroyed."));
+    this.#willPrintCapability = null;
+
     for (const [name, listener] of this._internalEvents) {
       this.#eventBus._off(name, listener);
     }