Add support for password-protected PDFs

Enhanced the `PdfViewer` component to support password-protected PDFs and improved error handling for document loading. Key changes include:

- Added a `Password` parameter to the `PdfViewer` component and updated the `OnAfterRenderAsync` method to pass it to JavaScript interop.
- Introduced the `OnDocumentLoadError` event callback to handle document loading errors.
- Updated `blazor.bootstrap.pdf.js` to support password prompts and handle password-related exceptions.
- Modified `PdfViewer_Demo_01_Examples.razor` to test password-protected PDFs with a local file path.
- Added a sample encrypted PDF (`pdf_password_protected.pdf`) for testing.
- Improved metadata and font handling in the sample PDF.
- Enhanced code robustness with null checks and better documentation.

NOTE: This commit message is auto-generated using GitHub Copilot.

Author: gvreddy04

BlazorBootstrap.Demo.RCL/Components/Pages/PdfViewer/PdfViewer_Demo_01_Examples.razor

@@ -1,7 +1,7 @@
 <p>@eventLog</p>
 
 <PdfViewer Class="mb-3"
-           Url="https://raw.githubusercontent.com/mozilla/pdf.js/ba2edeae/web/compressed.tracemonkey-pldi-09.pdf"
+           Url="file:///D:/Badri/Scanned%20Docs/Badri_EAadhaar_GADD2014.pdf"
            OnDocumentLoaded="OnDocumentLoaded"
            OnPageChanged="OnPageChanged" />
 

BlazorBootstrap.Demo.RCL/wwwroot/docs/pdf_password_protected.pdf

@@ -32,7 +32,7 @@ public partial class PdfViewer : BlazorBootstrapComponentBase
     protected override async Task OnAfterRenderAsync(bool firstRender)
     {
         if (firstRender)
-            await PdfViewerJsInterop.InitializeAsync(objRef!, Id!, scale, rotation, Url!);
+            await PdfViewerJsInterop.InitializeAsync(objRef!, Id!, scale, rotation, Url!, Password!);
 
         await base.OnAfterRenderAsync(firstRender);
     }
@@ -73,6 +73,15 @@ public void DocumentLoaded(PdfViewerModel pdfViewerModel)
             OnDocumentLoaded.InvokeAsync(new PdfViewerEventArgs(pageNumber, pagesCount));
     }
 
+    [JSInvokable]
+    public void DocumentLoadError(string errorMessage)
+    {
+        if(string.IsNullOrEmpty(errorMessage)) return;
+
+        if (OnDocumentLoadError.HasDelegate)
+            OnDocumentLoadError.InvokeAsync(errorMessage);
+    }
+
     [JSInvokable]
     public void SetPdfViewerMetaData(PdfViewerModel pdfViewerModel)
     {
@@ -207,6 +216,12 @@ private async Task ZoomOutAsync()
     [Parameter]
     public EventCallback<PdfViewerEventArgs> OnDocumentLoaded { get; set; }
 
+    /// <summary>
+    /// This event fires if there is an error loading the PDF document.
+    /// </summary>
+    [Parameter]
+    public EventCallback<string> OnDocumentLoadError { get; set; }
+
     /// <summary>
     /// This event fires immediately after the page is changed.
     /// </summary>
@@ -222,6 +237,15 @@ private async Task ZoomOutAsync()
     [Parameter]
     public Orientation Orientation { get; set; } = Orientation.Portrait;
 
+    /// <summary>
+    /// Gets or sets the password used for the PDF document if it is password-protected.
+    /// </summary>
+    /// <remarks>
+    /// Default value is <see langword="null"/>.
+    /// </remarks>
+    [Parameter]
+    public string? Password { get; set; }
+
     /// <summary>
     /// Provides JavaScript interop functionality for the PDF viewer.
     /// </summary>

blazorbootstrap/Components/PdfViewer/PdfViewer.razor.cs

@@ -40,10 +40,10 @@ public async Task GotoPageAsync(object objRef, string elementId, int gotoPageNum
         await module.InvokeVoidAsync("gotoPage", objRef, elementId, gotoPageNum);
     }
 
-    public async Task InitializeAsync(object objRef, string elementId, double scale, double rotation, string url)
+    public async Task InitializeAsync(object objRef, string elementId, double scale, double rotation, string url, string password)
     {
         var module = await moduleTask.Value;
-        await module.InvokeVoidAsync("initialize", objRef, elementId, scale, rotation, url);
+        await module.InvokeVoidAsync("initialize", objRef, elementId, scale, rotation, url, password);
     }
 
     public async Task LastPageAsync(object objRef, string elementId)

blazorbootstrap/Components/PdfViewer/PdfViewerJsInterop.cs

@@ -194,17 +194,57 @@ pageRotateCwButton.disabled = this.pagesCount === 0;
 pageRotateCcwButton.disabled = this.pagesCount === 0;
 */
 
-export function initialize(dotNetHelper, elementId, scale, rotation, url) {
+export function initialize(dotNetHelper, elementId, scale, rotation, url, password = null) {
     const pdf = new Pdf(elementId);
     pdf.scale = scale;
     pdf.rotation = rotation;
 
-    pdfJS.getDocument(url).promise.then(function (doc) {
-        pdf.pdfDoc = doc;
-        pdf.pagesCount = doc.numPages;
-        renderPage(pdf, pdf.pageNum);
-        dotNetHelper.invokeMethodAsync('DocumentLoaded', { pagesCount: pdf.pagesCount, pageNumber: pdf.pageNum });
-    });
+    // prepare loading options (optional password allowed)
+    const options = { url };
+    if (password) {
+        options.password = password; // pre-supply if user already has it
+    }
+
+    // begin loading document
+    const loadingTask = pdfJS.getDocument(options);
+
+    // handle password only when required (optional password support)
+    loadingTask.onPassword = function (updatePassword, reason) {
+        if (reason === pdfJS.PasswordResponses.NEED_PASSWORD) {
+            // only prompt if PDF actually requires password
+            const password = prompt("This PDF is password protected. Enter password:");
+            updatePassword(password);
+        } else if (reason === pdfJS.PasswordResponses.INCORRECT_PASSWORD) {
+            const password = prompt("Incorrect password. Please try again:");
+            updatePassword(password);
+        }
+    };
+
+    // handle the promise
+    loadingTask
+        .promise
+        .then(function (doc) {
+            pdf.pdfDoc = doc;
+            pdf.pagesCount = doc.numPages;
+            renderPage(pdf, pdf.pageNum);
+
+            // notify .NET side that document is loaded
+            dotNetHelper.invokeMethodAsync('DocumentLoaded', {
+                pagesCount: pdf.pagesCount,
+                pageNumber: pdf.pageNum
+            });
+        })
+        .catch(function (error) {
+            console.error("PDF loading error:", error);
+
+            // handle password exceptions specifically
+            if (error.name === "PasswordException") {
+                console.error("Password required but not provided");
+            }
+
+            // notify .NET side that document loading failed
+            dotNetHelper.invokeMethodAsync('DocumentLoadError', error.message);
+        });
 }
 
 function isDomSupported() {