Added initial load page count.

Added cancellation token support for rendering.

src/DtronixPdf/Actions/RenderPageAction.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Drawing;
 using System.Drawing.Imaging;
+using System.Threading;
 using DtronixPdf.Renderer.Dispatcher;
 using PDFiumCore;
 
@@ -14,16 +15,18 @@ namespace DtronixPdf.Actions
         private readonly RenderFlags _flags;
         private readonly Color? _backgroundColor;
         private readonly bool _includeAlpha;
+        private readonly CancellationToken _cancellationToken;
         private readonly ThreadDispatcher _dispatcher;
+        private FpdfBitmapT _bitmap;
 
-        public RenderPageAction(
-            ThreadDispatcher dispatcher,
+        public RenderPageAction(ThreadDispatcher dispatcher,
             FpdfPageT pageInstance,
             float scale,
             Viewport viewport,
             RenderFlags flags,
             Color? backgroundColor,
-            bool includeAlpha)
+            bool includeAlpha,
+            CancellationToken cancellationToken)
         {
             _pageInstance = pageInstance;
             _scale = scale;
@@ -31,28 +34,36 @@ namespace DtronixPdf.Actions
             _flags = flags;
             _backgroundColor = backgroundColor;
             _includeAlpha = includeAlpha;
+            _cancellationToken = cancellationToken;
             _dispatcher = dispatcher;
         }
 
         protected override PdfBitmap OnExecute()
         {
-            
-            var bitmap = fpdfview.FPDFBitmapCreateEx(
-                (int)_viewport.Size.Width,
-                (int)_viewport.Size.Height,
-                (int) (_includeAlpha ? FPDFBitmapFormat.BGRA : FPDFBitmapFormat.BGR) , 
-                IntPtr.Zero, 
-                0);
-
-            if (bitmap == null)
-                throw new Exception("failed to create a bitmap object");
-
-            if(_backgroundColor.HasValue)
-                fpdfview.FPDFBitmapFillRect(
-                    bitmap, 0, 0, (int)_viewport.Size.Width, (int)_viewport.Size.Height, (uint) _backgroundColor.Value.ToArgb());
-
             try
             {
+                _cancellationToken.ThrowIfCancellationRequested();
+
+                _bitmap = fpdfview.FPDFBitmapCreateEx(
+                    (int) _viewport.Size.Width,
+                    (int) _viewport.Size.Height,
+                    (int) (_includeAlpha ? FPDFBitmapFormat.BGRA : FPDFBitmapFormat.BGR),
+                    IntPtr.Zero,
+                    0);
+
+                if (_bitmap == null)
+                    throw new Exception("failed to create a bitmap object");
+
+                _cancellationToken.ThrowIfCancellationRequested();
+
+                if (_backgroundColor.HasValue)
+                {
+                    fpdfview.FPDFBitmapFillRect(
+                        _bitmap, 0, 0, (int) _viewport.Size.Width, (int) _viewport.Size.Height, (uint) _backgroundColor.Value.ToArgb());
+
+                    _cancellationToken.ThrowIfCancellationRequested();
+                }
+
                 // |          | a b 0 |
                 // | matrix = | c d 0 |
                 // |          | e f 1 |
@@ -89,21 +100,29 @@ namespace DtronixPdf.Actions
                 clipping.Bottom = 0;
                 clipping.Top = _viewport.Size.Height;
 
-                fpdfview.FPDF_RenderPageBitmapWithMatrix(bitmap, _pageInstance, matrix, clipping, (int) _flags);
+                fpdfview.FPDF_RenderPageBitmapWithMatrix(_bitmap, _pageInstance, matrix, clipping, (int) _flags);
+
+                // Cancellation check;
+                _cancellationToken.ThrowIfCancellationRequested();
 
                 return new PdfBitmap(
-                    bitmap,
-                    (int)_viewport.Size.Width,
-                    (int)_viewport.Size.Height,
+                    _bitmap,
+                    (int) _viewport.Size.Width,
+                    (int) _viewport.Size.Height,
                     _dispatcher,
                     _includeAlpha ? PixelFormat.Format32bppArgb : PixelFormat.Format24bppRgb,
                     _scale,
                     _viewport);
             }
+            catch (OperationCanceledException)
+            {
+                fpdfview.FPDFBitmapDestroy(_bitmap);
+                throw;
+            }
             catch (Exception ex)
             {
-                fpdfview.FPDFBitmapDestroy(bitmap);
-                throw new Exception("error rendering page", ex);
+                fpdfview.FPDFBitmapDestroy(_bitmap);
+                throw new Exception("Error rendering page. Check inner exception.", ex);
             }
         }
     }

src/DtronixPdf/PdfBitmap.cs

@@ -23,8 +23,6 @@ namespace DtronixPdf
 
         public IntPtr Scan0 { get; }
 
-        public Bitmap Bitmap { get; }
-
         public float Scale { get; }
 
         public Viewport Viewport { get; }
@@ -59,7 +57,11 @@ namespace DtronixPdf
             Scale = scale;
             Viewport = viewport;
             Width = width;
-            Bitmap = new Bitmap(width, height, Stride, format, Scan0);
+        }
+
+        public Bitmap ToBitmap()
+        {
+            return new Bitmap(Width, Height, Stride, Format, Scan0);
         }
 
         public async ValueTask DisposeAsync()
@@ -68,7 +70,6 @@ namespace DtronixPdf
                 return;
 
             IsDisposed = true;
-            Bitmap?.Dispose();
 
             await _dispatcher.QueueForCompletion(() =>
             {

src/DtronixPdf/PdfDocument.cs

@@ -17,6 +17,8 @@ namespace DtronixPdf
 
         private static readonly ThreadDispatcher Dispatcher;
 
+        public int Pages { get; private set; }
+
         static PdfDocument()
         {
             Dispatcher = new ThreadDispatcher();
@@ -33,14 +35,23 @@ namespace DtronixPdf
 
         public static async Task<PdfDocument> Load(string path, string password)
         {
+            int pages = -1;
             var result = await Dispatcher.QueueWithResult(() =>
-                fpdfview.FPDF_LoadDocument(path, password));
+            {
+                var document = fpdfview.FPDF_LoadDocument(path, password);
+                pages = fpdfview.FPDF_GetPageCount(document);
+                return document;
+            });
 
             if (result == null)
                 return null;
 
-            var renderer = new PdfDocument(result);
-            return renderer;
+            var pdfDocument = new PdfDocument(result)
+            {
+                Pages = pages
+            };
+
+            return pdfDocument;
         }
 
         public static async Task<PdfDocument> Create()

src/DtronixPdf/PdfPage.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Drawing;
 using System.Text;
+using System.Threading;
 using System.Threading.Tasks;
 using DtronixPdf.Actions;
 using DtronixPdf.Renderer.Dispatcher;
@@ -95,13 +96,14 @@ namespace DtronixPdf
             float scale,
             Viewport viewport,
             bool alpha,
-            Color? backgroundColor)
+            Color? backgroundColor,
+            CancellationToken cancellationToken)
         {
             if(viewport.IsEmpty)
                 throw new ArgumentException("Viewport is empty", nameof(viewport));
 
             return await _dispatcher.QueueWithResult(
-                new RenderPageAction(_dispatcher, _pageInstance, scale, viewport, flags, backgroundColor, alpha));
+                new RenderPageAction(_dispatcher, _pageInstance, scale, viewport, flags, backgroundColor, alpha, cancellationToken));
         }