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 this, in VB and C#, and to some extent how to do it in c++. I am currently calling the SystemParametersInfo with what seems to be all the correct arguments (no compiler errors) and it fails. No great crash of cymbals, just a 0 returned. GetLastError() returns an equally enlightening 0.

Below is the code I am using (In a slightly modified form, so you do not have to view the object internals).

#include <windows.h>
#include <iostream>
#include <QString>

void setWall()
{
    QString filepath = "C:\\Documents and Settings\\Owner\\My Documents\\Wallpapers\\wallpaper.png";
    char path[150];
    strcpy(path, currentFilePath.toStdString().c_str());
    char *pathp;
    pathp = path;

    cout << path;

    int result;
    result = SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, pathp, SPIF_UPDATEINIFILE);

    if (result)
    {
        cout << "Wallpaper set";
    }
    else
    {
        cout << "Wallpaper not set";
        cout << "SPI returned" << result;
    }
}

Millisecond

Answer 1

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.

Republic

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";

Normie

Answer 3

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;
}

Purnell

Answer 4

std::string file_path = "C:\\Image.png";
LPVOID FilePath = (LPVOID)file_path.c_str();
SystemParametersInfoA(SPI_SETDESKWALLPAPER, 0, FilePathBuffer, SPIF_UPDATEINIFILE | SPIF_SENDCHANGE);

Clarindaclarine

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