Improve PDF password prompt cancellation handling

BlazorBootstrap.Demo.RCL/Components/Pages/Demos/PdfViewer/PdfViewer_Demo_05_Password_Protected_B_Prompt_For_Password.razor

@@ -1,6 +1,8 @@
 @if (showPdfViewer)
 {
-    <PdfViewer Class="mb-3" Url="@($"../{DemoStringConstants.StaticAssets_Docs_Path}/pdf_password_protected.pdf")" PromptForPassword="true" />
+    <PdfViewer Class="mb-3"
+               Url="@($"../{DemoStringConstants.StaticAssets_Docs_Path}/pdf_password_protected.pdf")"
+               OnDocumentLoadError="OnDocumentLoadError" />
 }
 else
 {
@@ -9,4 +11,6 @@ else
 
 @code {
     private bool showPdfViewer = false;
+
+    private void OnDocumentLoadError(string errorMessage) => showPdfViewer = false;
 }

blazorbootstrap/wwwroot/blazor.bootstrap.pdf.js

@@ -210,15 +210,30 @@ export function initialize(dotNetHelper, elementId, scale, rotation, url, passwo
 
     // begin loading document
     const loadingTask = pdfJS.getDocument(options);
+    let passwordPromptCanceled = false;
 
     // handle password only when required (optional password support)
     loadingTask.onPassword = function (updatePassword, reason) {
+        if (passwordPromptCanceled) return;
+
         if (reason === pdfJS.PasswordResponses.NEED_PASSWORD) {
             // only prompt if PDF actually requires password
             const password = prompt("This PDF is password protected. Enter password:");
+            if (password === null) {
+                passwordPromptCanceled = true;
+                loadingTask.destroy();
+                dotNetHelper.invokeMethodAsync('DocumentLoadError', "Password prompt canceled.");
+                return;
+            }
             updatePassword(password);
         } else if (reason === pdfJS.PasswordResponses.INCORRECT_PASSWORD) {
             const password = prompt("Incorrect password. Please try again:");
+            if (password === null) {
+                passwordPromptCanceled = true;
+                loadingTask.destroy();
+                dotNetHelper.invokeMethodAsync('DocumentLoadError', "Password prompt canceled.");
+                return;
+            }
             updatePassword(password);
         }
     };