CODEWITHSUNDEEP
c++-cli
anetworknoobie
anetworknoobie

Reputation: 169

CLI/C++ How to get window handle?

I need to get the handle of another window.

Here is the code for it:

private: System::Void btn_find_Click(System::Object^  sender, System::EventArgs^  e) {
             array<Process^>^ ps = Process::GetProcessesByName("Notepad");
             IntPtr X = ps[0]->MainWindowHandle;
             LPRECT rect;
             if (GetWindowRect(static_cast<HWND>(X.ToPointer()), rect)){
                 DEBUGBOX->Text = "OK!";
             }
             else
             {
                 //DEBUGBOX is a text box
                 DEBUGBOX->Text = ps[0]->MainWindowTitle;

                 //the following code is from MSDN, it is used to
                 //show a message box about the error
                 //P.S. I have no idea why it has to be this complicated
                 LPVOID lpMsgBuf;
                 LPVOID lpDisplayBuf;
                 DWORD dw = GetLastError();
                 LPTSTR lpszFunction = TEXT("GetWindowRect");
                 FormatMessage(
                     FORMAT_MESSAGE_ALLOCATE_BUFFER |
                     FORMAT_MESSAGE_FROM_SYSTEM |
                     FORMAT_MESSAGE_IGNORE_INSERTS,
                     NULL,
                     dw,
                     MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                     (LPTSTR)&lpMsgBuf,
                     0, NULL);
                 lpDisplayBuf = (LPVOID)LocalAlloc(LMEM_ZEROINIT,
                     (lstrlen((LPCTSTR)lpMsgBuf) + lstrlen((LPCTSTR)lpszFunction) + 40) * sizeof(TCHAR));
                 StringCchPrintf((LPTSTR)lpDisplayBuf,
                     LocalSize(lpDisplayBuf) / sizeof(TCHAR),
                     TEXT("%s failed with error %d: %s"),
                     lpszFunction, dw, lpMsgBuf);
                 using MessageBox = System::Windows::Forms::MessageBox;
                 MessageBox::Show(gcnew System::String((LPCTSTR)lpDisplayBuf));
                 LocalFree(lpMsgBuf);
                 LocalFree(lpDisplayBuf);
             }
}

Currently it can find the process which is "Notepad" without a problem, but GetWindowRect function will fail, and goes to the cumbersome error message handling code, giving me "error 1400: Invalid window handle".

I have done some searching but I cannot find why it does not work. I suspect the static_cast from IntPtr to HWND, the code is from internet but seems legit.

I need the handle for some later operations as well.

Upvotes: 3

Views: 12508

Answers (1)

BuCkETBoSS
BuCkETBoSS

Reputation: 21

if u know the name of the title bar of the window then try FindWindowA

HWND handle;
handle=FindWindowA(NULL, "Calculator");

https://msdn.microsoft.com/en-us/library/windows/desktop/ms633499(v=vs.85).aspx

Upvotes: 2

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