Change wallpaper programmatically using c++ and windows api

Question

I\'ve been trying to write an application, using Qt and mingw32, to download images and set them as the background Wallpaper. I have read several articles online about how to do

Answer 1

You cn use SetTimer to trigger a change.

#define STRICT 1 
#include <windows.h>
#include <iostream.h>

VOID CALLBACK TimerProc(HWND hWnd, UINT nMsg, UINT nIDEvent, DWORD dwTime) 
{

  LPWSTR wallpaper_file = L"C:\\Wallpapers\\wallpaper.png";
  int return_value = SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, wallpaper_file, SPIF_UPDATEINIFILE);


  cout << "Programmatically change the desktop wallpaper periodically: " << dwTime << '\n';
  cout.flush();
}

int main(int argc, char *argv[], char *envp[]) 
{
    int Counter=0;
    MSG Msg;

    UINT TimerId = SetTimer(NULL, 0, 2000, &TimerProc); //2000 milliseconds

    cout << "TimerId: " << TimerId << '\n';
   if (!TimerId)
    return 16;

   while (GetMessage(&Msg, NULL, 0, 0)) 
   {
        ++Counter;
        if (Msg.message == WM_TIMER)
        cout << "Counter: " << Counter << "; timer message\n";
        else
        cout << "Counter: " << Counter << "; message: " << Msg.message << '\n';
        DispatchMessage(&Msg);
    }

   KillTimer(NULL, TimerId);
return 0;
}

Answer 2

"C:\Documents and Settings\Owner\My Documents\Wallpapers\wallpaper.png";

shouldn't this be:

"C:\\Documents and Settings\\Owner\\My Documents\\Wallpapers\\wallpaper.png";

Answer 3

It could be that SystemParametersInfo is expecting an LPWSTR (a pointer to wchar_t).

Try this:

LPWSTR test = L"C:\\Documents and Settings\\Owner\\My Documents\\Wallpapers\\wallpaper.png";

result = SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, test, SPIF_UPDATEINIFILE);

If this works (try it with a few different files just to make sure), you'll need to convert your char * to a LPWSTR. I'm not sure if Qt offers these services, but one function that may help is MultiByteToWideChar.