Copy strings from editcontrols

This is a discussion on Copy strings from editcontrols within the C++ Programming forums, part of the General Programming Boards category; Why doesent this work? All I get in my messagebox is... no nothing. Code: // Get the length of the ...

  1. #1
    Registered User Drogin's Avatar
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    Copy strings from editcontrols

    Why doesent this work? All I get in my messagebox is... no nothing.

    Code:
    // Get the length of the line
    int length=SendMessage(hwndDlgIP,EM_LINELENGTH,0,0);
    
    //Make ready the buffer
    char *buffer=new char [length+1];
    
    //Add the terminating zero
    buffer[length+1]='\0';
    
    //Copy the string
    SendMessage(hwndDlgIP,EM_GETLINE,0,(LPARAM)buffer);
    
    //Show it
    MessageBox(NULL,buffer,"test",MB_OK);
    
    //Dont forget to delete trash
    delete buffer;

  2. #2
    Registered User ventolin's Avatar
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    Is there any text in the actual edit control? Is length >= 0?

    Is the hwndDlgIP a valid HWND? Try doing a GetDlgItem(hwnd,EDIT_CONTROLID) for a valid hwnd value.

  3. #3
    Registered User Drogin's Avatar
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    Yes. I tested to MessageBox-out the length variable, and it worked.

    Which means; I do have a valid HWND, and I do have a length...
    So what could the problem be?

  4. #4
    Registered User ventolin's Avatar
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    Try calling GetLastError() after each SendMessage. Check the return values for any possible problems with the two SendMessages.

    Remember HWNDs can be valid for the window, but if you havent retrienved the correct Dialog Controls handle - the send message wont appear to work.

    How have you determined the hwnd for this control? Please print this code.

    Where abouts are you doing this piece of code? inside the WM_COMMAND message loop? Print the whole section/function so i can easily see what is going wrong.
    Last edited by ventolin; 10-30-2005 at 03:19 PM.

  5. #5
    VA National Guard The Brain's Avatar
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    Excerpt from MSDN:

    EM_GETLINE Message

    The EM_GETLINE message copies a line of text from an edit control and places it in a specified buffer. You can send this message to either an edit control or a rich edit control.

    Syntax

    To send this message, call the SendMessage function as follows.

    lResult = SendMessage( // returns LRESULT in lResult
    (HWND) hWndControl, // handle to destination control
    (UINT) EM_GETLINE, // message ID
    (WPARAM) wParam, // = (WPARAM) () wParam;
    (LPARAM) lParam // = (LPARAM) (LPCTSTR) lParam;
    );

    Parameters

    wParam
    Specifies the zero-based index of the line to retrieve from a multiline edit control. A value of zero specifies the topmost line. This parameter is ignored by a single-line edit control.

    lParam
    Pointer to the buffer that receives a copy of the line. Before sending the message, set the first word of this buffer to the size, in TCHARs, of the buffer. For ANSI text, this is the number of bytes; for Unicode text, this is the number of characters. The size in the first word is overwritten by the copied line.

    Return Value

    The return value is the number of TCHARs copied. The return value is zero if the line number specified by the wParam parameter is greater than the number of lines in the edit control.

    Remarks

    Edit controls: The copied line does not contain a terminating null character.

    Rich edit controls: Supported in Microsoft Rich Edit 1.0 and later. The copied line does not contain a terminating null character, unless no text was copied. If no text was copied, the message places a null character at the beginning of the buffer. For information about the compatibility of rich edit versions with the various system versions, see About Rich Edit Controls.
    • "Problem Solving C++, The Object of Programming" -Walter Savitch
    • "Data Structures and Other Objects using C++" -Walter Savitch
    • "Assembly Language for Intel-Based Computers" -Kip Irvine
    • "Programming Windows, 5th edition" -Charles Petzold
    • "Visual C++ MFC Programming by Example" -John E. Swanke
    • "Network Programming Windows" -Jones/Ohlund
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    • "Mathmatics for 3D Game Programming & Computer Graphics" -Eric Lengyel

  6. #6
    Registered User Drogin's Avatar
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    Code:
    Before sending the message, set the first word of this
    buffer to the size, in TCHARs, of the buffer. For ANSI text, this is 
    the number of bytes; for Unicode text,
     this is the number of characters. The size in the first word is
    overwritten by the copied line.
    Yeah, thats probably it! ...though i didnt understand what they ment... Can someone show a examplecode?
    Last edited by Drogin; 10-31-2005 at 03:03 AM.

  7. #7
    Reverse Engineer maxorator's Avatar
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    Wouldn't it be easier to just use GetWindowText?
    Or are you sure you want just one line?

  8. #8
    Registered User Drogin's Avatar
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    I am sure i just want one line..

  9. #9
    Reverse Engineer maxorator's Avatar
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    So you have a multiline edit control?

  10. #10
    Registered User Drogin's Avatar
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    yeap.

  11. #11
    Registered User Drogin's Avatar
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    So, what im after is how to initalize the buffer, so that the first WORD, is the length you wan to copy?

  12. #12
    Yes, my avatar is stolen anonytmouse's Avatar
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    Code:
    // Get the length of the line (truncated to a WORD)...
    WORD length = (WORD) SendMessage(hwndDlgIP, EM_LINELENGTH, 0, 0);
    
    // Allocate a buffer, make sure there is room for the buffer size
    // even if length is zero...
    char *buffer = new char[length + 1 + sizeof(WORD)];
    
    // Copy the buffer size to the first WORD of the buffer...
    CopyMemory(buffer, &length, sizeof(WORD));
    
    // Copy the string...
    SendMessage(hwndDlgIP, EM_GETLINE, 0, (LPARAM) buffer);
    
    // Add the terminating zero...
    buffer[length] = '\0';
    
    // Show it...
    MessageBox(NULL, buffer, "test", MB_OK);
    
    // Dont forget to delete trash...
    delete buffer;

  13. #13
    VA National Guard The Brain's Avatar
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    Thumbs up anonytmouse = wicked awesome

    I've been banging my head against a wall for two days..


    anonytmouse.. you are a genius.


    Code:
    void EditBoxFileParser(HWND hwnd, HWND hEdit)
    {
         
         int iCount; 
         WORD iLength;          
         TCHAR **Lines;
         
         //Get Number of Lines in Edit Field
         iCount = SendMessage(hEdit, EM_GETLINECOUNT, 0, 0);
         
         if(!iCount)
         
              return;
         
         Lines = new TCHAR*[iCount];
         
         //Populate 2D array - Lines[RowIndex][LineText]
         for(int i=0; i<iCount; i++)
         {     
              iLength = (WORD)SendMessage(hEdit, EM_LINELENGTH, i, 0);
              Lines[i] = new TCHAR[iLength+sizeof(WORD)+1];
              CopyMemory(Lines[i], &iLength, sizeof(WORD));
              SendMessage(hEdit, EM_GETLINE, i, (LPARAM)Lines[i]);
              Lines[i][iLength] = '\0';
         }   
         
         MessageBox(NULL, Lines[3], "test", MB_OK); 
                   
    }

    my only question is.. why does it have to be this hard..?? why wouldn't it work they way Drogin had it set up...??? (which seems to be the intuitively easy way to do it)
    Last edited by The Brain; 10-31-2005 at 04:34 PM.
    • "Problem Solving C++, The Object of Programming" -Walter Savitch
    • "Data Structures and Other Objects using C++" -Walter Savitch
    • "Assembly Language for Intel-Based Computers" -Kip Irvine
    • "Programming Windows, 5th edition" -Charles Petzold
    • "Visual C++ MFC Programming by Example" -John E. Swanke
    • "Network Programming Windows" -Jones/Ohlund
    • "Sams Teach Yourself Game Programming in 24 Hours" -Michael Morrison
    • "Mathmatics for 3D Game Programming & Computer Graphics" -Eric Lengyel

  14. #14
    Registered User Drogin's Avatar
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    I completely agree. This dirty old C-functions copying memory and manually adding termanationg zero's and all... I thought that escaping such was the positive side of windows

  15. #15
    Registered User Drogin's Avatar
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    but why
    Code:
    buffer[length] = '\0';
    and not

    Code:
    buffer[length+1] = '\0';
    The length variable does not include the terminating zero...

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