Core - Add IDownloadHandler.CanDownload

- Add IDownloadHandler.CanDownload
- Add to Fluent implementation
- Update examples

https://bitbucket.org/chromiumembedded/cef/commits/6d7a6801871cd4fcceb174dfa99a5b46da6253c1

Resolves #4090

Author: amaitland

CefSharp.Core.Runtime/Internals/ClientAdapter.cpp

@@ -990,6 +990,20 @@ namespace CefSharp
             }
         }
 
+        bool ClientAdapter::CanDownload(CefRefPtr<CefBrowser> browser, const CefString& url, const CefString& request_method)
+        {
+            auto handler = _browserControl->DownloadHandler;
+
+            if (handler == nullptr)
+            {
+                return true;
+            }
+
+            auto browserWrapper = GetBrowserWrapper(browser->GetIdentifier(), browser->IsPopup());
+
+            return handler->CanDownload(_browserControl, browserWrapper, StringUtils::ToClr(url), StringUtils::ToClr(request_method));
+        }
+
         void ClientAdapter::OnBeforeDownload(CefRefPtr<CefBrowser> browser, CefRefPtr<CefDownloadItem> download_item,
             const CefString& suggested_name, CefRefPtr<CefBeforeDownloadCallback> callback)
         {

CefSharp.Core.Runtime/Internals/ClientAdapter.h

@@ -187,6 +187,7 @@ namespace CefSharp
             virtual DECL void OnDraggableRegionsChanged(CefRefPtr<CefBrowser> browser, CefRefPtr<CefFrame> frame, const std::vector<CefDraggableRegion>& regions) override;
 
             //CefDownloadHandler
+            virtual DECL bool CanDownload(CefRefPtr<CefBrowser> browser, const CefString & url, const CefString & request_method) override;
             virtual DECL void OnBeforeDownload(CefRefPtr<CefBrowser> browser, CefRefPtr<CefDownloadItem> download_item,
                 const CefString& suggested_name, CefRefPtr<CefBeforeDownloadCallback> callback) override;
             virtual DECL void OnDownloadUpdated(CefRefPtr<CefBrowser> browser, CefRefPtr<CefDownloadItem> download_item,

CefSharp.Core/Fluent/DownloadHandler.cs

@@ -6,6 +6,18 @@
 
 namespace CefSharp.Fluent
 {
+    /// <summary>
+    /// Called before a download begins in response to a user-initiated action
+    /// (e.g. alt + link click or link click that returns a `Content-Disposition:
+    /// attachment` response from the server).
+    /// </summary>
+    /// <param name="chromiumWebBrowser">the ChromiumWebBrowser control</param>
+    /// <param name="browser">The browser instance</param>
+    /// <param name="url">is the target download URL</param>
+    /// <param name="requestMethod">is the target method (GET, POST, etc)</param>
+    /// <returns>Return true to proceed with the download or false to cancel the download.</returns>
+    public delegate bool CanDownloadDelegate(IWebBrowser chromiumWebBrowser, IBrowser browser, string url, string requestMethod);
+
     /// <summary>
     /// Called before a download begins.
     /// </summary>
@@ -30,6 +42,7 @@ namespace CefSharp.Fluent
     /// </summary>
     public class DownloadHandler : Handler.DownloadHandler
     {
+        private CanDownloadDelegate canDownload;
         private OnBeforeDownloadDelegate onBeforeDownload;
         private OnDownloadUpdatedDelegate onDownloadUpdated;
 
@@ -94,6 +107,11 @@ internal DownloadHandler()
 
         }
 
+        internal void SetCanDownload(CanDownloadDelegate action)
+        {
+            canDownload = action;
+        }
+
         internal void SetOnBeforeDownload(OnBeforeDownloadDelegate action)
         {
             onBeforeDownload = action;
@@ -104,6 +122,12 @@ internal void SetOnDownloadUpdated(OnDownloadUpdatedDelegate action)
             onDownloadUpdated = action;
         }
 
+        /// <inheritdoc/>
+        protected override bool CanDownload(IWebBrowser chromiumWebBrowser, IBrowser browser, string url, string requestMethod)
+        {
+            return canDownload?.Invoke(chromiumWebBrowser, browser, url, requestMethod) ?? true;
+        }
+
         /// <inheritdoc/>
         protected override void OnBeforeDownload(IWebBrowser chromiumWebBrowser, IBrowser browser, DownloadItem downloadItem, IBeforeDownloadCallback callback)
         {

CefSharp.Core/Fluent/DownloadHandlerBuilder.cs

@@ -11,6 +11,22 @@ public class DownloadHandlerBuilder
     {
         private readonly DownloadHandler handler = new DownloadHandler();
 
+        /// <summary>
+        /// See <see cref="IDownloadHandler.CanDownload(IWebBrowser, IBrowser, string, string)"/> for details.
+        /// </summary>
+        /// <param name="action">Action to be executed when <see cref="IDownloadHandler.CanDownload(IWebBrowser, IBrowser, string, string)"/>
+        /// is called</param>
+        /// <returns>
+        /// Fluent Builder, call <see cref="Build"/> to create
+        /// a new <see cref="IDownloadHandler"/> instance
+        /// </returns>
+        public DownloadHandlerBuilder CanDownload(CanDownloadDelegate action)
+        {
+            handler.SetCanDownload(action);
+
+            return this;
+        }
+
         /// <summary>
         /// See <see cref="IDownloadHandler.OnBeforeDownload(IWebBrowser, IBrowser, DownloadItem, IBeforeDownloadCallback)"/> for details.
         /// </summary>

CefSharp.Example/Handlers/DownloadHandler.cs

@@ -57,7 +57,7 @@ public BrowserTabUserControl(Action<string, int?> openNewTab, string url, bool m
             browser.MenuHandler = new MenuHandler();
             browser.RequestHandler = new WinFormsRequestHandler(openNewTab);
             browser.JsDialogHandler = new JsDialogHandler();
-            browser.DownloadHandler = new DownloadHandler();
+            browser.DownloadHandler = Fluent.DownloadHandler.AskUser();
             browser.AudioHandler = new CefSharp.Handler.AudioHandler();
             browser.FrameHandler = new CefSharp.Handler.FrameHandler();
 

CefSharp.WinForms.Example/BrowserTabUserControl.cs

@@ -13,6 +13,7 @@
 using CefSharp.Example.JavascriptBinding;
 using CefSharp.Example.ModelBinding;
 using CefSharp.Example.PostMessage;
+using CefSharp.Fluent;
 using CefSharp.Wpf.Example.Handlers;
 using CefSharp.Wpf.Example.ViewModels;
 using CefSharp.Wpf.Experimental.Accessibility;
@@ -131,10 +132,24 @@ public BrowserTabView()
                 }
             };
 
-            var downloadHandler = new DownloadHandler();
-            downloadHandler.OnBeforeDownloadFired += OnBeforeDownloadFired;
-            downloadHandler.OnDownloadUpdatedFired += OnDownloadUpdatedFired;
-            browser.DownloadHandler = downloadHandler;
+            browser.DownloadHandler = DownloadHandler
+                .Create()
+                .CanDownload((chromiumWebBrowser, browser, url, requestMethod) =>
+                {
+                    //All all downloads
+                    return true;
+                })
+                .OnBeforeDownload((chromiumWebBrowser, browser, downloadItem, callback) =>
+                {
+                    UpdateDownloadAction("OnBeforeDownload", downloadItem);
+
+                    callback.Continue("", showDialog: true);
+
+                }).OnDownloadUpdated((chromiumWebBrowser, browser, downloadItem, callback) =>
+                {
+                    UpdateDownloadAction("OnDownloadUpdated", downloadItem);
+                })
+                .Build();
             browser.AudioHandler = new CefSharp.Handler.AudioHandler();
 
             //Read an embedded bitmap into a memory stream then register it as a resource you can then load custom://cefsharp/images/beach.jpg
@@ -238,16 +253,6 @@ private void OnBrowserJavascriptMessageReceived(object sender, JavascriptMessage
 
         }
 
-        private void OnBeforeDownloadFired(object sender, DownloadItem e)
-        {
-            this.UpdateDownloadAction("OnBeforeDownload", e);
-        }
-
-        private void OnDownloadUpdatedFired(object sender, DownloadItem e)
-        {
-            this.UpdateDownloadAction("OnDownloadUpdated", e);
-        }
-
         private void UpdateDownloadAction(string downloadAction, DownloadItem downloadItem)
         {
             this.Dispatcher.InvokeAsync(() =>

CefSharp.Wpf.Example/Views/BrowserTabView.xaml.cs

@@ -10,6 +10,27 @@ namespace CefSharp.Handler
     /// </summary>
     public class DownloadHandler : IDownloadHandler
     {
+        /// <inheritdoc />
+        bool IDownloadHandler.CanDownload(IWebBrowser chromiumWebBrowser, IBrowser browser, string url, string requestMethod)
+        {
+            return CanDownload(chromiumWebBrowser, browser, url, requestMethod);
+        }
+
+        /// <summary>
+        /// Called before a download begins in response to a user-initiated action
+        /// (e.g. alt + link click or link click that returns a `Content-Disposition:
+        /// attachment` response from the server).
+        /// </summary>
+        /// <param name="chromiumWebBrowser">the ChromiumWebBrowser control</param>
+        /// <param name="browser">The browser instance</param>
+        /// <param name="url">is the target download URL</param>
+        /// <param name="requestMethod">is the target method (GET, POST, etc)</param>
+        /// <returns>Return true to proceed with the download or false to cancel the download.</returns>
+        protected virtual bool CanDownload(IWebBrowser chromiumWebBrowser, IBrowser browser, string url, string requestMethod)
+        {
+            return true;
+        }
+
         /// <summary>
         /// Called before a download begins.
         /// </summary>

CefSharp/Handler/DownloadHandler.cs

@@ -10,6 +10,18 @@ namespace CefSharp
     /// </summary>
     public interface IDownloadHandler
     {
+        /// <summary>
+        /// Called before a download begins in response to a user-initiated action
+        /// (e.g. alt + link click or link click that returns a `Content-Disposition:
+        /// attachment` response from the server).
+        /// </summary>
+        /// <param name="chromiumWebBrowser">the ChromiumWebBrowser control</param>
+        /// <param name="browser">The browser instance</param>
+        /// <param name="url">is the target download URL</param>
+        /// <param name="requestMethod">is the target method (GET, POST, etc)</param>
+        /// <returns>Return true to proceed with the download or false to cancel the download.</returns>
+        bool CanDownload(IWebBrowser chromiumWebBrowser, IBrowser browser, string url, string requestMethod);
+
         /// <summary>
         /// Called before a download begins.
         /// </summary>