Merge pull request #21 from cwollenhaupt/develop

C#/fpCefSharp/fpEventSubscriber.cs

@@ -0,0 +1,99 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Linq.Expressions;
+using System.Linq;
+using System.Reflection;
+using System.Threading.Tasks;
+
+namespace fpCefSharp
+{
+    /// <summary>
+    /// FoxPro interop access to .NET events. Handles all events of a source object for subsequent retrieval by a FoxPro client.
+    /// </summary>
+    /// <remarks>For a FoxPro program to be notified of events, it should use `wwDotNetBridge.InvokeMethodAsync` to call
+    /// <see cref="WaitForEvent"/>. When <see cref="WaitForEvent"/> asynchronously completes, the FoxPro program should
+    /// handle the event it returns and then call <see cref="WaitForEvent"/> again to wait for the next event.
+    /// The FoxPro class `EventSubscription`, which is returned by `SubscribeToEvents`, encapsulates this async wait loop.
+    ///
+    /// NOTE: This code is based on wwDotNetBridge from Rick Strahl and Edward Brey. It's the same code as in pull request
+    ///       #26 for wwDotNetBridge, the class name aside. This code can be removed after the pull request is merged and
+    ///       the FoxPro code has been updated to use the built-in mechanism of wwDotNetBridge.
+    /// </remarks>
+    public class fpEventSubscriber : IDisposable
+    {
+        private readonly object _source;
+        private readonly List<DelegateInfo> _eventHandlers = new List<DelegateInfo>();
+        private readonly ConcurrentQueue<fpRaisedEvent> _raisedEvents = new ConcurrentQueue<fpRaisedEvent>();
+        private TaskCompletionSource<fpRaisedEvent> _completion = new TaskCompletionSource<fpRaisedEvent>();
+
+        public fpEventSubscriber(object source, String prefix = "", dynamic vfp = null)
+        {
+            // Indicates that initially the client is not waiting.
+            _completion.SetResult(null);
+
+            // For each event, adds a handler that calls QueueInteropEvent.
+            _source = source;
+            foreach (var ev in source.GetType().GetEvents())
+            {
+                // handler is a PRIVATE variable defined in EventSubscription.Setup().
+                Boolean hasMethod = vfp?.Eval($"PEMSTATUS(m.handler, '{prefix}{ev.Name}', 5)");
+                if (!hasMethod)
+                    continue;
+
+                var eventParams = ev.EventHandlerType.GetMethod("Invoke").GetParameters().Select(p => Expression.Parameter(p.ParameterType)).ToArray();
+                var eventHandlerLambda = Expression.Lambda(ev.EventHandlerType,
+                    Expression.Call(
+                        instance: Expression.Constant(this),
+                        method: typeof(fpEventSubscriber).GetMethod(nameof(QueueInteropEvent), BindingFlags.NonPublic | BindingFlags.Instance),
+                        arg0: Expression.Constant(ev.Name),
+                        arg1: Expression.NewArrayInit(typeof(object), eventParams.Select(p => Expression.Convert(p, typeof(object))))),
+                    eventParams);
+                var eventHandler = eventHandlerLambda.Compile();
+                ev.AddEventHandler(source, eventHandler);
+                _eventHandlers.Add(new DelegateInfo(eventHandler, ev));
+            }
+        }
+
+        class DelegateInfo
+        {
+            public DelegateInfo(Delegate handler, EventInfo eventInfo)
+            {
+                Delegate = handler;
+                EventInfo = eventInfo;
+            }
+
+            public Delegate Delegate { get; }
+            public EventInfo EventInfo { get; }
+        }
+
+        public void Dispose()
+        {
+            foreach (var item in _eventHandlers)
+                item.EventInfo.RemoveEventHandler(_source, item.Delegate);
+            _completion.TrySetCanceled();
+        }
+
+        private void QueueInteropEvent(string name, object[] parameters)
+        {
+            var interopEvent = new fpRaisedEvent { Name = name, Params = parameters };
+            if (!_completion.TrySetResult(interopEvent))
+                _raisedEvents.Enqueue(interopEvent);
+        }
+
+        /// <summary>
+        /// Waits until an event is raised, or returns immediately if a queued event is available.
+        /// </summary>
+        /// <returns>The next event, or null if this subscriber has been disposed.</returns>
+        public fpRaisedEvent WaitForEvent()
+        {
+            if (_raisedEvents.TryDequeue(out var interopEvent)) return interopEvent;
+            _completion = new TaskCompletionSource<fpRaisedEvent>();
+            var task = _completion.Task;
+
+            task.Wait();
+
+            return task.IsCanceled ? null : task.Result;
+        }
+    }
+}

C#/fpCefSharp/fpRaisedEvent.cs

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+namespace fpCefSharp
+{
+    public class fpRaisedEvent
+    {
+        public string Name { get; internal set; }
+        public object[] Params { get; internal set; }
+    }
+}

Demos/Demo_Events.PRG

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+*========================================================================================
+* Respond to events in the browser
+*========================================================================================
+
+	LOCAL loConfig, loEvents
+	loConfig = CREATEOBJECT("MyHandler")
+	loEvents = CreateObject("MyEvents")
+
+	Local loForm
+	DO FORM ShowHtml WITH "https://myApp/index.html", m.loConfig Name loForm
+	loEvents.AddProperty ("oCefSharpBrowser", m.loForm.oCefSharpBrowser)
+	loForm.oCefSharpBrowser.HandleEvents (m.loEvents)
+
+DEFINE CLASS MyHandler as Custom
+
+	index_html = ""
+
+	PROCEDURE Init
+		TEXT TO This.index_html NoShow
+			<html>
+				<script>
+					function changeTitle () {
+						window.top.document.title = new Date().toLocaleString();
+					}
+				</script>
+			  <button onclick="changeTitle();">Change title</button>
+			</html>	
+		ENDTEXT 
+
+	Procedure TitleChangedEvent (m.tcTitle)
+	MessageBox("TitleChangedEvent: " + m.tcTitle)
+
+ENDDEFINE
+
+
+Define Class MyEvents as Custom
+
+Procedure OnTitleChanged (toSender, toEventArgs)
+	This.oCefSharpBrowser.HandleTitleChangedEvent (m.toSender, m.toEventArgs)
+
+EndDefine