Question

I’m trying to use the mciSendString function to open and close the cd tray in Qt. Here is the code:

#include <windows.h>
MCIERROR mciSendString(LPCTSTR lpszCommand, LPTSTR lpszReturnString, UINT cchReturn, HANDLE hwndCallback);
void OpenCD()
{
    mciSendString((LPCTSTR)"set cdaudio door open",(LPTSTR)NULL, (UINT)0, (HANDLE)NULL);
}
void CloseCD()
{
    mciSendString((LPCTSTR)"set cdaudio door closed",(LPTSTR)NULL, (UINT)0, (HANDLE)NULL);
}    

But I get this error: “ undefined reference to `mciSendStringW(wchar_t const*, wchar_t*, unsigned int, void*)’ ”
How can I fix this error and use the mciSendString function without any problem?

Answer 1

Try add one of the next lines to pro-file:

LIBS += path_to_lib/Winmm.lib

or

LIBS += path_to_lib/Winmm.dll

Also you can include Mmsystem.h and Windows.h

Link

For example:
Pro file inludes link to lib-file from installed SDK:

LIBS += $$quote(C:\\Program Files\\Microsoft SDKs\\Windows\\v7.0A\\Lib\\WinMM.lib)

In cpp-file:

#include "Windows.h"
#include "mmsystem.h"
//MCIERROR mciSendString(LPCTSTR lpszCommand, LPTSTR lpszReturnString, UINT cchReturn, HANDLE hwndCallback);
...
void MainWindow::on_pushButton_clicked() {
   mciSendString((LPCTSTR)"set cdaudio door open",(LPTSTR)NULL, (UINT)0, (HWND__*)0);
}