From c21036aa0e894d5665bf0fbbf36f69dbbdaff99d Mon Sep 17 00:00:00 2001
From: Brian <bpcampbell@gmail.com>
Date: Thu, 3 Mar 2016 18:57:21 -0500
Subject: [PATCH] Handle multiple context menu selections - Fixes #770

The problem is that multiple context menu selections spawn multiple .exe
(invoked). Each invoked .exe sets the InstanceProxy variables in the
running .exe and tells it to start a thread to process. But, there is no
waiting, so the InstanceProxy variables get clobbered before they can
get used.
This fix uses a semaphore to control the invoked .exe. There is only one
entry allowed forcing invoked .exe to wait until any other invoked .exe
is finished running and releases the semaphore.
---
 .../ApplicationInstanceManager.cs                        | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/ShareX.HelpersLib/SingleInstanceApplication/ApplicationInstanceManager.cs b/ShareX.HelpersLib/SingleInstanceApplication/ApplicationInstanceManager.cs
index 4531ee38e..dfe677101 100644
--- a/ShareX.HelpersLib/SingleInstanceApplication/ApplicationInstanceManager.cs
+++ b/ShareX.HelpersLib/SingleInstanceApplication/ApplicationInstanceManager.cs
@@ -34,10 +34,13 @@ namespace SingleInstanceApplication
 {
     public static class ApplicationInstanceManager
     {
+        private static Semaphore semaphore;
+
         [DebuggerStepThrough]
         public static bool CreateSingleInstance(string name, EventHandler<InstanceCallbackEventArgs> callback, string[] args)
         {
             string eventName = string.Format("{0}-{1}", Environment.MachineName, name);
+            string semaphoreName = string.Format("{0}{1}", eventName, "Semaphore");
 
             InstanceProxy.IsFirstInstance = false;
             InstanceProxy.CommandLineArgs = args;
@@ -46,9 +49,13 @@ public static bool CreateSingleInstance(string name, EventHandler<InstanceCallba
             {
                 using (EventWaitHandle eventWaitHandle = EventWaitHandle.OpenExisting(eventName))
                 {
+                    semaphore = Semaphore.OpenExisting(semaphoreName);
+                    semaphore.WaitOne();
                     UpdateRemoteObject(name);
 
                     if (eventWaitHandle != null) eventWaitHandle.Set();
+
+                    semaphore.Release();
                 }
 
                 Environment.Exit(0);
@@ -59,6 +66,7 @@ public static bool CreateSingleInstance(string name, EventHandler<InstanceCallba
 
                 using (EventWaitHandle eventWaitHandle = new EventWaitHandle(false, EventResetMode.AutoReset, eventName))
                 {
+                    semaphore = new Semaphore(1, 1, semaphoreName);
                     ThreadPool.RegisterWaitForSingleObject(eventWaitHandle, WaitOrTimerCallback, callback, Timeout.Infinite, false);
                 }
 
@@ -107,6 +115,7 @@ private static void RegisterRemoteType(string uri)
             process.Exited += delegate
             {
                 ChannelServices.UnregisterChannel(serverChannel);
+                semaphore.Close();
             };
         }