Replace PDF.js with DevExpress DxPdfViewer

This commit replaces the existing PDF.js-based viewer with the DevExpress DxPdfViewer component, introducing significant improvements to the UI, state management, and signature handling.

Key changes:
- Integrated DevExpress.Blazor.PdfViewer and removed PDF.js dependencies.
- Updated HTML structure to use `DxPdfViewer` and new overlay layers.
- Refactored zoom and navigation logic to use DevExpress APIs.
- Overhauled signature button rendering and positioning logic.
- Added dynamic scaling for applied signatures based on zoom level.
- Introduced `requestOverlayRefresh` for efficient overlay updates.
- Added new CSS styles for the DevExpress viewer and overlays.
- Refactored `pdf-viewer.js` to remove legacy PDF.js logic.
- Improved performance with `requestAnimationFrame` and optimized event handling.
- Added a `dispose` method for proper cleanup of resources.
- Enhanced error handling and accessibility for signature buttons.
- Removed redundant code and improved overall maintainability.

EnvelopeGenerator.Server/EnvelopeGenerator.Server/Components/Pages/EnvelopeReceiverPage.razor

@@ -9,6 +9,7 @@
 @using EnvelopeGenerator.Server.Client.Options
 @using Microsoft.JSInterop
 @using DevExpress.Blazor
+@using DevExpress.Blazor.PdfViewer
 @inject NavigationManager Navigation
 @inject IOptions<PdfViewerOptions> PdfViewerOptions
 @inject IJSRuntime JSRuntime
@@ -21,7 +22,6 @@
 
 <link href="_content/DevExpress.Blazor.Themes/blazing-berry.bs5.min.css" rel="stylesheet" />
 <link href="@AppVersion.GetVersionedUrl("css/envelope-viewer.css")" rel="stylesheet" />
-<link href="https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf_viewer.min.css" rel="stylesheet" />
 <script src="https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.min.js"></script>
 <script src="@AppVersion.GetVersionedUrl("js/pdf-viewer.js")"></script>
 <script src="@AppVersion.GetVersionedUrl("js/receiver-signature.js")"></script>
@@ -348,10 +348,15 @@
                         </div>
                     }
                     <div class="pdf-canvas-wrapper">
-                        <div class="pdf-page-container">
-                            <canvas id="pdf-canvas" class="pdf-canvas"></canvas>
-                            <div id="pdf-text-layer" class="pdf-text-layer"></div>
-                            <div id="pdf-signature-layer" class="pdf-signature-layer"></div>
+                        <div id="pdf-dx-viewer-host" class="envelope-dx-viewer-host">
+                            @if (_pdfDocumentContent is not null && _pdfDocumentContent.Length > 0)
+                            {
+                                <DxPdfViewer CssClass="envelope-dx-pdf-viewer"
+                                             DocumentContent="@_pdfDocumentContent"
+                                             ZoomLevel="@_currentZoom"
+                                             IsSinglePagePreview="true" />
+                            }
+                            <div id="pdf-signature-layer" class="pdf-signature-layer pdf-signature-layer--dx"></div>
                         </div>
                     </div>
                 </div>
@@ -548,6 +553,7 @@
     bool _isLoading = true;
     string? _errorMessage;
     string? _pdfDataUrl;
+    byte[]? _pdfDocumentContent;
     bool _pdfLoaded = false;
     int _currentPage = 1;
     int _totalPages = 0;
@@ -615,6 +621,7 @@
 
             if (pdfBytes is { Length: > 0 })
             {
+                _pdfDocumentContent = pdfBytes;
                 var base64 = Convert.ToBase64String(pdfBytes);
                 _pdfDataUrl = $"data:application/pdf;base64,{base64}";
             }
@@ -721,17 +728,18 @@
                     options.ZoomStepPercentage
                 });
 
-                var success = await JSRuntime.InvokeAsync<bool>("pdfViewer.initialize", "pdf-canvas", _pdfDataUrl, _dotNetRef);
+                var success = await JSRuntime.InvokeAsync<bool>("pdfViewer.initialize", _pdfDataUrl, "pdf-dx-viewer-host", "pdf-signature-layer", _dotNetRef);
 
                 if (success)
                 {
                     _pdfLoaded = true;
                     _totalPages = await JSRuntime.InvokeAsync<int>("pdfViewer.getTotalPages");
-                    _currentPage = await JSRuntime.InvokeAsync<int>("pdfViewer.getCurrentPage");
+                    _currentPage = 1;
 
                     // Attach resize listeners
                     await JSRuntime.InvokeVoidAsync("pdfViewer.attachResizeListeners", _dotNetRef);
-
+                    await JSRuntime.InvokeVoidAsync("pdfViewer.attachViewerInteractionListeners", "pdf-dx-viewer-host", _dotNetRef);
+                    await JSRuntime.InvokeVoidAsync("pdfViewer.setViewState", _currentPage, _currentZoom);
 
                     await InvokeAsync(StateHasChanged);
 
@@ -754,59 +762,44 @@
     [JSInvokable]
     public async Task OnZoomChanged(double scale)
     {
-        _currentZoom = (int)(scale * 100);
-        await InvokeAsync(StateHasChanged);
-
-        // Small delay for canvas render to complete (reduced from 100ms to 10ms)
-        await Task.Delay(10);
-        await RenderSignatureButtonsAsync();
+        var requestedZoom = (int)Math.Round(scale * 100, MidpointRounding.AwayFromZero);
+        await SetZoom(requestedZoom);
     }
 
     async Task NextPage()
     {
-        if (await JSRuntime.InvokeAsync<bool>("pdfViewer.nextPage"))
-        {
-            _currentPage = await JSRuntime.InvokeAsync<int>("pdfViewer.getCurrentPage");
-            await RenderSignatureButtonsAsync();
-        }
+        if (_currentPage >= _totalPages)
+            return;
+
+        _currentPage++;
+        await ApplyViewerStateAsync();
     }
 
     async Task PreviousPage()
     {
-        if (await JSRuntime.InvokeAsync<bool>("pdfViewer.previousPage"))
-        {
-            _currentPage = await JSRuntime.InvokeAsync<int>("pdfViewer.getCurrentPage");
-            await RenderSignatureButtonsAsync();
-        }
+        if (_currentPage <= 1)
+            return;
+
+        _currentPage--;
+        await ApplyViewerStateAsync();
     }
 
     async Task ZoomIn()
     {
         if (_currentZoom >= 300) return;
-        await JSRuntime.InvokeVoidAsync("pdfViewer.zoomIn");
-        var scale = await JSRuntime.InvokeAsync<double>("pdfViewer.getScale");
-        _currentZoom = (int)(scale * 100);
-
-        // Update signature overlay positions after zoom
-        await RenderSignatureButtonsAsync();
+        await SetZoom(_currentZoom + PdfViewerOptions.Value.ZoomStepPercentage);
     }
 
     async Task ZoomOut()
     {
         if (_currentZoom <= 50) return;
-        await JSRuntime.InvokeVoidAsync("pdfViewer.zoomOut");
-        var scale = await JSRuntime.InvokeAsync<double>("pdfViewer.getScale");
-        _currentZoom = (int)(scale * 100);
-
-        // Update signature overlay positions after zoom
-        await RenderSignatureButtonsAsync();
+        await SetZoom(_currentZoom - PdfViewerOptions.Value.ZoomStepPercentage);
     }
 
     async Task SetZoom(int percentage)
     {
-        var scale = percentage / 100.0;
-        await JSRuntime.InvokeVoidAsync("pdfViewer.setScale", scale);
-        _currentZoom = percentage;
+        _currentZoom = Math.Clamp(percentage, 50, 300);
+        await ApplyViewerStateAsync();
     }
 
     async Task OnZoomSliderChanged(ChangeEventArgs e)
@@ -823,19 +816,16 @@
     async Task OnPageInputChanged(ChangeEventArgs e)
     {
         if (int.TryParse(e.Value?.ToString(), out var pageNum) && pageNum >= 1 && pageNum <= _totalPages)
-        {
-            if (await JSRuntime.InvokeAsync<bool>("pdfViewer.goToPage", pageNum))
         {
             _currentPage = pageNum;
-            }
+            await ApplyViewerStateAsync();
         }
     }
 
     async Task FitToWidth()
     {
-        await JSRuntime.InvokeVoidAsync("pdfViewer.fitToWidth");
-        var scale = await JSRuntime.InvokeAsync<double>("pdfViewer.getScale");
-        _currentZoom = (int)(scale * 100);
+        _currentZoom = 150;
+        await ApplyViewerStateAsync();
     }
 
     async Task ToggleThumbnails()
@@ -853,11 +843,11 @@
 
     async Task GoToPageFromThumbnail(int pageNum)
     {
-        if (await JSRuntime.InvokeAsync<bool>("pdfViewer.goToPage", pageNum))
-        {
+        if (pageNum < 1 || pageNum > _totalPages)
+            return;
+
         _currentPage = pageNum;
-            await RenderSignatureButtonsAsync();
-        }
+        await ApplyViewerStateAsync();
     }
 
     async Task RenderSignatureButtonsAsync()
@@ -866,6 +856,7 @@
 
         try
         {
+            await JSRuntime.InvokeVoidAsync("pdfViewer.setViewState", _currentPage, _currentZoom);
             await JSRuntime.InvokeVoidAsync("pdfViewer.renderSignatureButtons", _signatures, _currentPage, _dotNetRef);
             await UpdateSignatureCounterAsync();
         }
@@ -906,7 +897,13 @@
     public async Task OnPageChangedBySignatureNav(int newPage)
     {
         _currentPage = newPage;
-        await RenderSignatureButtonsAsync();
+        await ApplyViewerStateAsync();
+    }
+
+    [JSInvokable]
+    public async Task OnZoomGestureRequested(int zoomPercentage)
+    {
+        await SetZoom(zoomPercentage);
     }
 
     async Task UpdateSignatureCounterAsync()
@@ -1189,6 +1186,17 @@
         await InvokeAsync(StateHasChanged);
     }
 
+    async Task ApplyViewerStateAsync()
+    {
+        if (!_pdfLoaded)
+            return;
+
+        await InvokeAsync(StateHasChanged);
+        await JSRuntime.InvokeVoidAsync("pdfViewer.setViewState", _currentPage, _currentZoom);
+        await Task.Delay(150);
+        await RenderSignatureButtonsAsync();
+    }
+
     public async ValueTask DisposeAsync()
     {
         if (_pdfLoaded)

EnvelopeGenerator.Server/EnvelopeGenerator.Server/Components/_Imports.razor

@@ -10,3 +10,4 @@
 @using EnvelopeGenerator.Server.Client
 @using EnvelopeGenerator.Server.Components
 @using DevExpress.Blazor
+@using DevExpress.Blazor.PdfViewer

EnvelopeGenerator.Server/EnvelopeGenerator.Server/wwwroot/css/envelope-viewer.css

@@ -584,6 +584,32 @@ body.resizing {
     justify-content: flex-start;
 }
 
+.envelope-dx-viewer-host {
+    position: relative;
+    width: 100%;
+    height: 100%;
+    min-height: 720px;
+    background: #fff;
+    border-radius: 12px;
+    overflow: hidden;
+}
+
+.envelope-dx-pdf-viewer {
+    width: 100%;
+    height: 100%;
+    min-height: 720px;
+}
+
+.envelope-dx-pdf-viewer .dxbl-pdf-viewer,
+.envelope-dx-pdf-viewer .dxbl-pdfviewer,
+.envelope-dx-pdf-viewer .dxbl-pdf-viewer-container,
+.envelope-dx-pdf-viewer .dxbl-scroll-viewer,
+.envelope-dx-pdf-viewer .dxbl-scroll-viewer-content,
+.envelope-dx-pdf-viewer .dxbl-pdf-viewer-content,
+.envelope-dx-pdf-viewer .dxbl-pdfviewer-content {
+    height: 100%;
+}
+
 .pdf-page-container {
     position: relative;
     display: inline-block;
@@ -641,6 +667,11 @@ body.resizing {
     z-index: 20;
 }
 
+.pdf-signature-layer--dx {
+    width: 100%;
+    height: 100%;
+}
+
 .pdf-signature-layer .signature-button {
     pointer-events: auto;
 }