1. Introduction
2. EnumWindows
3. SendMessage
4. SendMessage vs PostMessage
5. Conclusion

Comments

1. ayesha aslam
   24 Feb 2009 at 06:29
   Hi all ! I am developing an application in Visual C# to retrieve data from textboxes, listboxes, statusbars,... etc of open windows in any system... Currently i am using winndows api **Sendmessage **to pass handle of the window and passing its parameter **message ** as WM_COPY (to copy data from textboxes, listboxes, statusbars,... etc ) but its value &H301 is not recognized... What shoulf i do to get the correct output ??? Can anyone help ??? Regards, Ayesha
2. borgy manotoy
   27 Jul 2007 at 10:07
   Hi All,
   
   I wanna ask about the equivalent of SendKey if I will use SendMessage:
   
   Ex.
   
       If ctr2 <= length Then
           myKeys(ctr2) = Mid$(myString, ctr2, 1)
           SendKeys myKeys(ctr2)
           ctr2 = ctr2 + 1
       Else
   
   I tried converting SendKey with SendMessage but nothing happens:
   
   myHWnd is the handle I got from Finding the window. What I want to do is to send specific keys to the specified application (myKeys(ctr2)) as if I am using sendKeys.
   
   SendMessage myHWnd, WM_KEYDOWN, 0, myKeys(ctr2)
   
   
   It didn't send keys to notepad.
   
   
   I really cannot understand SendMessage and I really need your help guys... I am only a newbie in VB.
   
   Thank you,
   
   Gwapo
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
3. andy wang
   13 Jul 2007 at 08:21
   you said you can't get selected text from html file..etc ,may be you havn't find the right handle of area which can be edit.
4. Fernando Escobar
   10 Jul 2007 at 00:06

   Hi,

   About this subject, I´m trying to define the size of an image captured from a generic camera.

   I'm using the SendMessage and SetWindowPos functions with the following instructions:

   To initialize the camera:

   Private Sub PreviewVideo(ByVal pbCtrl As PictureBox)

   On Error GoTo treaterror:

                              
           mHwnd = capCreateCaptureWindowA("Teste", WS_VISIBLE Or WS_CHILD, 0, 0, 100, 100, pbCtrl.hwnd, 0)
          
           If SendMessage(mHwnd, WM_CAP_DRIVER_CONNECT, 0, 0) Then
                SendMessage mHwnd, WM_CAP_SET_SCALE, False, 0
               '---set the preview rate (ms)---
               SendMessage mHwnd, WM_CAP_SET_PREVIEWRATE, 30, 0
               '---start previewing the image---
               SendMessage mHwnd, WM_CAP_SET_PREVIEW, True, 0
               '---resize window to fit in PictureBox control---
               SetWindowPos mHwnd, HWND_BOTTOM, 0, 0, pbCtrl.ScaleWidth, pbCtrl.ScaleHeight, SWP_NOMOVE Or SWP_NOZORDER
              
                   
           Else
               '--error connecting to video source---
               MsgBox "Problema na conexão com a câmera. Contate o suporte!! - " & Err.Description
               DestroyWindow mHwnd
           End If
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   

           Exit Sub
          
   treaterror:
   
   

   MsgBox "Problema na conexão com a câmera. Contate suporte!!!" & Err.Description

      
   End Sub
   

   To capture the image:

   Private Sub cmdCapturar_Click()

   SendMessage mHwnd, GET_FRAME, 0, 0
   SendMessage mHwnd, COPY, 0, 0
   Picture1.Picture = Clipboard.GetData
   Clipboard.Clear
   'Timer1.Enabled = False
   
   
   
   

   End Sub

   Please note that I don't want just want to fit the image to the window. I need its real size to be the window's size. (What is happenning is that I see one image on the PictureBox passed as a parameter the sub PreviewVideo but the captured image is much larger than it.)

   Thank you in advance,

5. erictioh
   21 Jan 2006 at 17:15
   i'm doing something similar to this thread starter. below is my code:
   
   Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
   
          prevWindow = 0
   
          Call GetCursorPos(mousePT)
          X = mousePT.X
          Y = mousePT.Y
          Label2.Text = "(" & X & "," & Y & ")"
          hWnd = WindowFromPoint(X, Y)
   
          className = Space(255) ' Make room in the string to receive the information.
          retValue = GetClassName(hWnd, className, 255)
   
          windowText = Space(255)
          GetWindowText(hWnd, windowText, 255)
   
          Label1.Text = hWnd
   
      End Sub
   
   this is a function which will constantly called by timer, and i have 2 labels on my form which is label 1 and and label2
   you can see that i print the handle number (hWnd) using label1, but when i run the program no matter where i point the mouse to but the hwnd value is still the same, why?
6. DavidChiu
   09 Jun 2005 at 11:27

   Quote:

   [1]Posted by arshad on 29 Jun 2004 12:18 PM[/1]
   Hi Riaz,
   Could you plz explain me how did u fetch data from MS-Word.
   I can able to get typed text from notepad using sendmessage API.
   Same API Could not work for MS-word.
   Thanks,
   Arshad.
   Quote:

   [1]Posted by riyazfarz on 3 Sep 2003 02:33 AM[/1]
   Hi,
   

   
   Yes I could fetch data from MS- word, Notepad etc. But I am not able to fetch from HTML file. Any idea for getting from this.
   

   
   Anyway thanks for your valuable help.
   

   
   Regards
   

   
   Riaz
   

   
   

   
   

   
   I used SendMessage(hwnd, WM_COPY, 0, 0). And I meet the above problem, too!
   I cann't get selected text for HTML file/VC/PDF file/SourceInsight File......
   

7. Sunil K
   13 Oct 2004 at 02:35
   hi, Have u got the solution?
   i m also looking for the same...
   Can you help me some how more ?
   I have developed a dictionary & now I want let user use it with a very simple way.
   I wish to have a word under mouse cursor from any other windows application. my program will search definition for that word & will show at mouse cursor when user press Ctrl key or in any other special window automatically.
   For the same I was searching for, I come across you. I want just any children of any window ( like..notepad, wordpad, word, or explorer or just any edit control.)
   Hopes u got my requirement. Simply I have a definition dictionary & want to synchronize it with text under mouse cursor.
   althogh u have given a nice idea that how to go for it but can u pls show it with a code pls.
   I 'll. be greatly thankful to you, if you can illustrate it with few sample source code (Visual Basic only).
   
   if u got it pls help me.
   Thanks & have a nice time.
   
   Sunil.
   
   
8. Sunil K
   13 Oct 2004 at 02:28
   Hi there !
   how are u?
   
    Can you help me some how more ?
   I have developed a dictionary & now I want let user use it with a very simple way.
   I wish to have a word under mouse cursor from any other windows application. my program will search definition for that word & will show at mouse cursor when user press Ctrl key or in any other special window automatically.
   For the same I was searching for, I come across you. I want just any children of any window ( like..notepad, wordpad, word, or explorer or just any edit control.)
   Hopes u got my requirement. Simply I have a definition dictionary & want to synchronize it with text under mouse cursor.
   althogh u have given a nice idea that how to go for it but can u pls show it with a code pls.
   I 'll. be greatly thankful to you, if you can illustrate it with few sample source code (Visual Basic only).
   
   Thanks & have a nice time.
   Sunil.
   
9. arshad
   29 Jun 2004 at 12:18

   Hi Riaz,
   Could you plz explain me how did u fetch data from MS-Word.
   I can able to get typed text from notepad using sendmessage API.
   Same API Could not work for MS-word.
   Thanks,
   Arshad.
   

   Quote:

   [1]Posted by riyazfarz on 3 Sep 2003 02:33 AM[/1]
   Hi,
   

   
   Yes I could fetch data from MS- word, Notepad etc. But I am not able to fetch from HTML file. Any idea for getting from this.
   

   
   Anyway thanks for your valuable help.
   

   
   Regards
   

   
   Riaz
   

10. riyazfarz
    03 Sep 2003 at 02:33

    Hi,
    

    
    Yes I could fetch data from MS- word, Notepad etc. But I am not able to fetch from HTML file. Any idea for getting from this.
    

    
    Anyway thanks for your valuable help.
    

    
    Regards
    

    
    Riaz

11. hadi3000
    21 Aug 2003 at 15:58

    Quote:

    [1]Posted by koo9 on 11 Jul 2003 03:10 PM[/1]
    like the Gator client, it allow user the hold down a key e.g. ctrl and click on any text in any windows, it will pop up a definition for the clicked text, how do they do it? does it use the WM_GETTEXT as well?
    

    
    

    
    I was able to do that using the SENDMESSAGE, GETCURSORPOS and WINDOWFROMPOINT functions.
    Basicly what you need to do is first get the cursor's position using GETCURSORPOS which will return the x and y location. Pass those coordibates to WINDOWFROMPOINT and it will return the window handle in which the cursor is currently highlighting the text. Since you now have the correct handle of the window (this window can be anything...notepad...explorer...etc...) you then use the SENDMESSAGE function as such:
    SENDMESSAGE FoundWindow.hWnd, WM_COPY, 0, 0 where 'FoundWindow' is the handle returned by WINDOWFROMPOINT.
    

    
    NOTE: This method needs a constant loop to keep checking the mouse cursor position (using a timer control).
    This works when a text is highlighted and the mouse cursor is still above it. If you want to do this using the CTRL key you might have to resort to GETASYNCKEYSTATE also.
    

    
    If you succeed in developing a better code i'd be glad to see it

12. koo9
    11 Jul 2003 at 15:10

    like the Gator client, it allow user the hold down a key e.g. ctrl and click on any text in any windows, it will pop up a definition for the clicked text, how do they do it? does it use the WM_GETTEXT as well?

13. ktran
    14 Apr 2003 at 04:28

    I'm using this api to send a custom message between 2 VB exe's.  The called exe is subclassed to listen to the custom message.  In the calling exe, I'm trying to pass a string in the 4th parameter.  At this stage the 2nd exe is already running.  The api call keeps crashing the 2nd exe.  Can it be done across exe's or only within the same exe, thanks.

14. king_preetham
    15 Mar 2002 at 18:02
    I have the following code:
    The PostMessage function works, while the SendMessage function does not..WHY???
    
    //*********************************
       PROCESS_INFORMATION* pi;
       pi = (PROCESS_INFORMATION*)malloc(sizeof(PROCESS_INFORMATION));
       STARTUPINFO si;
       si.cb=sizeof(si);
       si.lpReserved=NULL;
       si.lpDesktop=NULL;
       si.lpTitle=NULL,
       si.dwFlags=STARTF_FORCEONFEEDBACK;
       si.cbReserved2=0;
       si.lpReserved2=NULL;
       BOOL bres = CreateProcess(NULL, "calc.exe", NULL,NULL,NULL,
                                 CREATE_NEW_CONSOLE | NORMAL_PRIORITY_CLASS,
                                 NULL,NULL,&si,pi);
       if(!bres)
       {
           return;
       }
    
       HWND hWnd;
       EnumThreadWindows(pi->dwThreadId, EnumProc, (LPARAM)&hWnd);
       SetFocus(hWnd);
       //LRESULT lr1 = SendMessage(hWnd, WM_KEYDOWN, 38, 0);
       //LRESULT lr2 = SendMessage(hWnd, WM_KEYUP, 38, 1);
       
       BOOL bp = PostMessage(hWnd, 256, 53, 393217);
       LRESULT lr1 = SendMessage(hWnd, 256, 53, 393217);
    //*************************************************
15. Developer Fusion Bot
    01 Jan 1999 at 00:00

    This thread is for discussions of Enum Windows & SendMessage API.