Question

How do I change desktop wallpaper?

I tried this

procedure TForm1.Button1Click(Sender: TObject); 
var   
  PicPath: String; 
begin 
  PicPath := 'C:\test.bmp';   
  SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, pChar(PicPath), SPIF_SENDCHANGE) 
end;

But it didn’t work.

Answer 1

I just tried it with D2007 on XP (and also D2009 on Vista), and this code works.
But to catch If and why it is not working, you should test the result code and get the error from Windows:

  if not SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, pChar(PicPath), SPIF_SENDCHANGE)then
    RaiseLastOSError;

In most cases, it will be because the bmp file is not found:

System Error.  Code: 2.
The system cannot find the file specified.