EnumPropsEx Error

This is a discussion on EnumPropsEx Error within the Windows Programming forums, part of the Platform Specific Boards category; Hello, I am trying to get the properties of a Microsoft's Notepad.exe window. I have an instance of this application ...

  1. #1
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    May 2008
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    EnumPropsEx Error

    Hello,

    I am trying to get the properties of a Microsoft's Notepad.exe window. I have an instance of this application running when I execute the code below.

    Code:
    #include <iostream>
    #include <windows.h>
    
    using namespace std;
    
    BOOL CALLBACK PropEnumProcEx(HWND hwnd, LPTSTR lpszString, HANDLE hData, ULONG_PTR dwData) {
      cout << "Property Label: " << lpszString << "." << endl;
      return true;
    }
    
    int main()
    {
        HWND hNote = FindWindow("Notepad", NULL);
        cout << "Notepad's handle: " << hNote << endl;
        EnumPropsEx(hNote, PropEnumProcEx, 0);
        cout << "Done" << endl;
        return 0;
    }
    The output is:

    Notepad's handle: 0x7e0b7e
    Property Label:

    Then i receive a "properties.exe has encountered a problem and needs to close. We are sorry for the inconvenience." Windows error message.

    {P.S. my program is called properties.exe}

    If I don't have a reference to lpszString in the callback function then the code executes as expected through to the end. I suspect I am not using the pointer of the string correctly...?

    If someone could shed some light that would be appreciated.

    Thanks,

  2. #2
    Registered User Codeplug's Avatar
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    Posts
    4,669
    Check return value of FindWindow().

    The incoming string may be a "global atom". See SetProp(). Check the high word before assuming it's a string.

    Call EnumPropsExA() since your code is expecting char strings (instead of wchar_t).

    gg
    Last edited by Codeplug; 05-30-2008 at 11:09 PM.

  3. #3
    Registered User
    Join Date
    May 2008
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    Yes, indeed it is an atom; namely, an integer atom.

    I changed the callback procedure to the following:
    Code:
    BOOL CALLBACK PropEnumProcEx(HWND hwnd, LPTSTR lpszString, HANDLE hData, ULONG_PTR dwData) {
      if (HIWORD(lpszString) == 0) {
        WORD the_atom = LOWORD(lpszString);
        char buffy[100] = {0};
        GetAtomName(the_atom, buffy, 100);
        cout << "It is an atom: " << buffy << endl;
        cout << "Data: " << hData << endl;
      }else {
        cout << "Property Label: " << lpszString << "." << endl;
      }
      return true;
    }
    I have two follow-ups.

    1. Winspector Spy shows there are two integer atoms, but I only get 1. What is going on here?
    2. What can I do with the hData handle?


    Thanks for your assistance,

  4. #4
    Registered User Codeplug's Avatar
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    4,669
    1. A global atom not used in SetProp(), or in another window...?
    2. It's whatever was passed to SetProp(), so you can't do much unless you know what it is.

    gg

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