HOW-TO: Sending real keystrokes to another application

Question

Hey everybody I have been struggeling a lot lately with finding a convenient and reliable solution for my problem. My little voice recognition program handles my speech inputs quite properly and according to the speech command I give I want it to send defined keystrokes (associated to the speech command) to a target windows process e.g Play focuses Windam and sends a X char for playing. This all works kinda ok with SendKeys.SendWait(X). But I have figured that its kinda unreliable because of the timing issues involved in bringing the application window to the foreground to send the keystroke via SendKeys.SendWait (this method only supports sending to the active application). This becomes even more apparent when during gameplay. Right now I am using a bunch of code snippets like [DllImport(user32.dll)] public static extern bool SetForegroundWindow(IntPtr hWnd); to bring the target window to foreground; To send the keys the code is here: private void sendKeystroke(IntPtr HWnd string translatedKeystroke) { IntPtr cwHandle = Win32.GetForegroundWindow(); if (HWnd != IntPtr.Zero) { Win32.SetForegroundWindow(HWnd); SendKeys.Send(translatedKeystroke); Win32.SetForegroundWindow(cwHandle); } } HWnd being the targetProcessHandle; translatedKeystroke is the format SendKeys.Send() requires. I switch to the targetApp send the key then back again. SendWait() didnt improve the situtation! This all kinda works but not reliably... (SendKeys.Send() doesnt support the NUMPAD keys for example) so I was looking around for better solutions. I came across the whole [DllImport(user32.dllCharSet=CharSet.Auto)] public static extern int SendMessage(IntPtr hWnd int wMsg char wParam IntPtr lParam); dilemma which gives me a headache now for a couple of days. Is there anyone out there who can explain to me how to send KeysStrokes likes ALT+L to another application via the whole SendMessage + VirtualKeyscodes wParam. lParam chaos? Yes I was able to make SendMessage work with WM_CLOSE for example to close an app but its different with emulating real keystrokes imho. I believe an app requires 3 messages to process a char. WM_KEYDOWN WM_CHAR WM_KEYUP. Now my question is how to format the SendMessages to make that happen. Please anyone point me to the right direction so that I can get this blocker out of my way. Please anyone... I am really desperate now ;( Thanks & Regards Sören

Soeren Geier · Answer

Hi Alan thanks again for guiding me the right way with my previous posts and your improvement suggestions. I just restarted working on the program and sadly came to find that the whole postMessage idea doesnt properly work with Winamp (CTRL+D) for example or Firefox (CTRL+T). It works flawless with World of Warcraft (what I initially had it built for) to post keystrokes of all kinds (e.g. CTRL+1 ALT+K whatever) directly into the process's message queue but Winamp seems to intercept CTRL SHIFT ALT entirely. Normal keystrokes like lxbv even NUMPAD0 etc arrive at Winamp and get executed but CTRL+SHIFT ALT dont ;( I took the time to inspect what Messages get sent out by Winamp using Winspector (to sniff Messages) and the Virtual Keycodes sent from my program to Winamp and when pressed directly in Winamp are identical... Is it that native Win32 applications handle Message processing differently? Or maybe special keys like CTRL+ALT+SHIFT are specially hooked? Hmm... Any ideas? ^^

Alan · Answer

Pleased to hear that's working OK for you :) With regard to your mapVirtualKey() method the virtual keys for the letters A to Z are in fact the same as their ascii values i.e. 65 to 90. So you could save some work with: private byte mapVirtualKey(string keyString) { if (keyString[0] >= 65 && keyString[0] { return (byte)keyString[0]; } else { switch (keyString) { // deal with other cases } } } If you need to send numerals I think that the virtual keycodes for 0 to 9 are also the same as their ascii values i.e. 48 to 57.

Soeren Geier · Answer

Hey Thanks for your answer. After playing around with lotsa of approaches of sending keys reliably to another process (that runs in the background) I found the following solution most satisfying. private void pressKeys(IntPtr HWnd SpeechCommand spc) { foreach (SpeechCommandKeystroke spck in spc) { byte[] byteArray = spck.VKencodedKeys; foreach (byte b in byteArray) { Win32.PostMessage(HWnd WM_KEYDOWN b 0); } foreach (byte b in byteArray) { Win32.PostMessage(HWnd WM_KEYUP b 0); } //Console.WriteLine(spck.delayAfter.Seconds.ToString()); System.Threading.Thread.Sleep(spck.delayAfter); } } I pass in an obj that holds some information. Then this object can have keystrokeObjects (spck) associated with it. The spck object then has an byte array which holds the VirtualKeycodes for the keystroke e.g. ALT F. I iterate through it and send 2 messages per found bytecode. To translate the keystrokes into virual key code I use a simple switch statement (which I am not happy with): private const int VK_A = 0x41; private const int VK_B = 0x42; private const int VK_C = 0x43; private byte mapVirtualKey(string keyString) { switch (keyString) { case A: return VK_A; case B: return VK_B; case C: return VK_C; .... This basically works all fine for me since I'd prefer to not bring the other process to the foreground which is why I keep posting into its message queue. If you see things that could be improved at first sight let me know ;) I am also wondering if there is a more slicker way to program mapVirtualKey(). All code is still subject to change due to outstanding code optimizations but the core functionality of sendign keys to somewhere works like this. Thanks

Alan · Answer

To send Alt + letter you can use the WM_SYSKEYDOWN message and set the 29th bit of lParam to 1: const uint WM_SYSKEYDOWN = 0x104; // send Alt + F PostMessage(hWnd WM_SYSKEYDOWN VkKeyScan('F') 1 In theory the following combinations should work for Ctrl + F and Shift + F: const uint WM_KEYUP = 0x101; const int VK_SHIFT = 0x10; const int VK_CONTROL = 0x11; PostMessage(hWnd WM_KEYDOWN VK_CONTROL 0); PostMessage(hWnd WM_KEYDOWN VkKeyScan('F') 0); PostMessage(hWnd WM_KEYUP VkKeyScan('F') 0); PostMessage(hWnd WM_KEYUP VK_CONTROL 0); PostMessage(hWnd WM_KEYDOWN VK_SHIFT 0); PostMessage(hWnd WM_KEYDOWN VkKeyScan('F') 0); PostMessage(hWnd WM_KEYUP VkKeyScan('F') 0); PostMessage(hWnd WM_KEYUP VK_SHIFT 0); but disappointlingly they didn't when I tried them :( I also tried various values for the lParam parameter but that made no difference. Unless someone else knows how to do this it looks like PostMessage() is going to be at best a partial solution. Personally I tend to use the unmanaged keybd_event() method for sending keystrokes to other applications as this doesn't have the same synchronization problems as the managed SendKeys class. However the other application needs to have the focus for this to work which is not ideal for your application.

Soeren Geier · Answer

Thank you... this has pointed me to the right direction... as stated in that thread as well I now still need to know how to translate ALT CONTROL SHIFT key .. I assume I have to do something like Win32.PostMessage(HWnd WM_SYSKEYDOWN VK_ALT 1); Win32.PostMessage(HWnd WM_KEYDOWN Win32.VkKeyScan('c') 0); Win32.PostMessage(HWnd WM_KEYUP Win32.VkKeyScan('c') 0); Win32.PostMessage(HWnd WM_SYSKEYUP VK_ALT 0); I dont understand how to calculate the high-bit low-bit information and how totranslate virtual-key code for these special keys. If you could elaborate on that I'd be so happy ;) Thanks for that!

Alan · Answer

You'd be better using PostMessage rather than SendMessage so that the other application won't necessarily need to have the focus. There's an example of usage on this thread: http://www.c-sharpcorner.com/Forums/ShowMessages.aspx?ThreadID=40478