Sending keystrokes to other *non-focus* application

This is a discussion on Sending keystrokes to other *non-focus* application within the Windows Programming forums, part of the Platform Specific Boards category; In order to send keystorkes or mouse clicks to other application that is not in focus, I found in the ...

  1. #1
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    Sending keystrokes to other *non-focus* application

    In order to send keystorkes or mouse clicks to other application that is not in focus, I found
    in the internet the concept of using SendInput while attaching my application thread to the application I want to control. Here is the short console program code for writing the letter 'g' on the notepad program.
    But still problem - it doesn't put the letter on the notepad... why?

    Code:
    #include "stdafx.h"
    #include "conio.h"
    #include "windows.h"
    
    void sendKey(WORD wVk)
    {
    	INPUT input[2];
    
    	input[0].ki.wVk = wVk;
    	input[0].ki.wScan = 0;
    	input[0].ki.dwFlags = 0; //press down;
    	input[0].ki.time = 0;
    	input[0].ki.dwExtraInfo = 0;
    	input[0].type = INPUT_KEYBOARD;
    
    	input[1].ki.wVk = wVk;
    	input[1].ki.wScan = 0;
    	input[1].ki.dwFlags = KEYEVENTF_KEYUP;
    	input[1].ki.time = 0;
    	input[1].ki.dwExtraInfo = 0;
    	input[1].type = INPUT_KEYBOARD;
    
    	SendInput(2, input, sizeof(INPUT));
    }
    
    int _tmain(int argc, _TCHAR* argv[])
    {
    	TCHAR	sText[1024];
    	HWND	hTargetWnd;
    	DWORD   processID;
    	DWORD	threadID;
    	
    	
    	HWND hNotepadWnd = FindWindow(NULL,  L"Untitled - Notepad");
        hTargetWnd=FindWindowEx(hNotepadWnd,NULL,L"Edit",NULL);
    	threadID = GetWindowThreadProcessId(hTargetWnd , &processID);	
    	if(hTargetWnd)
    	{
    		wsprintf(sText, L"Target window found\nWindow = %p\nprocessID = %x\nThreadID = %x\n",hTargetWnd,processID,threadID);
    		wprintf(L"%s",sText);
    		
    			  if(AttachThreadInput( GetCurrentThreadId(), threadID,true))
    			  {
    				sendKey('G');
    				AttachThreadInput(GetCurrentThreadId(),threadID,   false);
    			  }
    	}
    	else
    	{
    		wprintf(L"Window Notepad wasn't found\n");
    	}
    
    	// if there was SendInput, it also should be seen here
    	while(_kbhit())
    	{
    		wprintf(L"%c",getch());
    	}
    
    	// wait for keystroke to exit
    	while(!_kbhit());
    
    	return 0;
    }
    Last edited by Salem; 08-05-2009 at 11:58 PM. Reason: Removed colour from code - it adds nothing, if you apply it to the whole block

  2. #2
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    If you have the handle to the NotePad application then try posting a WM_CHAR message, for example:

    Code:
          PostMessage( hTargetWnd, WM_CHAR,  'g', 0 );

  3. #3
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    Thanks, that may work.

    I tried to work with PostMessage and the messages are indeed, received by the notepad.
    But I found that in this case, I must know what the target program is designed to receive.
    I tried for example to send WM_LBUTTONDOWN in order to simulate left mouse button click, but the target program didn't react to this even it received it.
    When I checked, using Spy++ the messages it accepts when the mouse is really on it, I found the messages are much more complicated than just WM_LBUTTONDOWN and includes WM_NCHITTEST, WM_SETCURSOR and more. Why it is not just WM_LBUTTONDOWN ? I don't know. it's first time for me in this subject.

    If you can give some description on this behavior and a solution, that will be great.
    Thanks

  4. #4
    Registered User Joelito's Avatar
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    Quote Originally Posted by Scarlet7 View Post
    If you have the handle to the NotePad application then try posting a WM_CHAR message, for example:

    Code:
          PostMessage( hTargetWnd, WM_CHAR,  'g', 0 );
    If I want to send "Alt+B", for example?
    * PC: Intel Core 2 DUO E6550 @ 2.33 GHz with 2 GB RAM: Archlinux-i686 with xfce4.
    * Laptop: Intel Core 2 DUO T6600 @ 2.20 GHz with 4 GB RAM: Archlinux-x86-64 with xfce4.

  5. #5
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by audi02 View Post
    Thanks, that may work.

    I tried to work with PostMessage and the messages are indeed, received by the notepad.
    But I found that in this case, I must know what the target program is designed to receive.
    I tried for example to send WM_LBUTTONDOWN in order to simulate left mouse button click, but the target program didn't react to this even it received it.
    When I checked, using Spy++ the messages it accepts when the mouse is really on it, I found the messages are much more complicated than just WM_LBUTTONDOWN and includes WM_NCHITTEST, WM_SETCURSOR and more. Why it is not just WM_LBUTTONDOWN ? I don't know. it's first time for me in this subject.

    If you can give some description on this behavior and a solution, that will be great.
    Thanks
    I think that WM_SETCURSOR and similar are always given to your program, even if you don't catch them. I would expect Notepad to listen for that so that it knows where you're clicking (to move the cursor to that spot, on a button, etc.)

  6. #6
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    I tried for example to send WM_LBUTTONDOWN in order to simulate left mouse button click, but the target program didn't react to this even it received it.
    What reaction were you expecting, or hoping for on a left mouse button?

    If to bring the NotePad to the top window the use the following:
    Code:
        SetForegroundWindow( hTargetWnd );
    If to set the cursor position then WM_LBUTTONDOWN will work, but only the x y coordinates within the text region, the following will set the cursor coords to x=0 y=0 (top left of window):
    Code:
        PostMessage(hTargetWnd, WM_LBUTTONDOWN, MK_LBUTTON, MAKELPARAM(0,0));
        PostMessage(hTargetWnd, WM_LBUTTONUP, MK_LBUTTON, MAKELPARAM(0,0));
    The following code example will bring the NotePad to the front and write 3 lines the insert some text into line 1:
    Code:
    void SendString(HWND h, char *text)
    {
        int len = strlen(text);
        for(int i = 0; i < len; i++)
            PostMessage(h, WM_CHAR, text[i], 0);
    }
    
    void SetCursor(HWND h, short x, short y )
    {
        PostMessage(h, WM_LBUTTONDOWN, MK_LBUTTON, MAKELPARAM(x,y));
        PostMessage(h, WM_LBUTTONUP, MK_LBUTTON, MAKELPARAM(x,y));
    }
    
    int _tmain(int argc, _TCHAR* argv[])
    {
        ...
    
        SetForegroundWindow(hTargetWnd);
    
        SetCursor(hTargetWnd, 0,0);
    		
        SendString(hTargetWnd, "Hello World line 1\n");
        SendString(hTargetWnd, "Hello World line 2\n");
        SendString(hTargetWnd, "Hello World line 3\n");
    
        SetCursor(hTargetWnd, 20,0);
    
        SendString(hTargetWnd, "(Inserted)");
    
        ...
    }
    Last edited by Scarlet7; 08-06-2009 at 04:44 AM.

  7. #7
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    Thanks Scarlet7.

    1) It works.
    2) I don't want to make the target program (NotePad in this example) focused , so we can use the PostMessage without SetForegroundWindow(hTargetWnd) and SetCursor(hTargetWnd, 0,0)
    3) I found that the reasone I didn't have the corrrect response to WM_LBUTTONDOWN etc' was because I didn't use the correct child window - my mistake!

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