Setting wallpaper on windows

[ihoss]

Nope, not C:\Bliss.bmp or Bliss.bmp in the same folder. It could be that the functon expects something else than a char pointer.

[wysota]

It might require a wchar pointer. I suggest using this function first to query for the existing wallpaper. This way you'll be able to see how the path is stored in the buffer you provide.

[ihoss]

#include <iostream>
#include <stdio.h>
#include <string>
#include <Windows.h>
using namespace std;
 
int main () {
  char *path = "C:\\Bliss.bmp";
  bool ret = SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, 
			path,
			//NULL,
			//0);
			//SPIF_SENDCHANGE);
			//SPIF_SENDWININICHANGE);
			SPIF_UPDATEINIFILE | SPIF_SENDWININICHANGE);
  cout<<"the function returned "<<(ret ? "true" : "false");
  char* str = NULL;	// function allocates the mem with LocalAlloc(), used with LocalFree()
  int msg_ret = FormatMessage(	FORMAT_MESSAGE_ALLOCATE_BUFFER |	// let the function alloc string mem
						FORMAT_MESSAGE_FROM_SYSTEM |	// use system message and not a passed one
						FORMAT_MESSAGE_IGNORE_INSERTS,	// ignore and "inserts"
						NULL, 
						GetLastError(),			// get the error
						MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),	// default language 
						(CHAR*)&str, 
						0, 
						NULL);
  cout<<"\n"<<str;
  cout<<"\n"<<path;
  return 0;
}

#include <iostream>
#include <stdio.h>
#include <string>
#include <Windows.h>
using namespace std;

int main () {
  char *path = "C:\\Bliss.bmp";
  bool ret = SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, 
			path,
			//NULL,
			//0);
			//SPIF_SENDCHANGE);
			//SPIF_SENDWININICHANGE);
			SPIF_UPDATEINIFILE | SPIF_SENDWININICHANGE);
  cout<<"the function returned "<<(ret ? "true" : "false");
  char* str = NULL;	// function allocates the mem with LocalAlloc(), used with LocalFree()
  int msg_ret = FormatMessage(	FORMAT_MESSAGE_ALLOCATE_BUFFER |	// let the function alloc string mem
						FORMAT_MESSAGE_FROM_SYSTEM |	// use system message and not a passed one
						FORMAT_MESSAGE_IGNORE_INSERTS,	// ignore and "inserts"
						NULL, 
						GetLastError(),			// get the error
						MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),	// default language 
						(CHAR*)&str, 
						0, 
						NULL);
  cout<<"\n"<<str;
  cout<<"\n"<<path;
  return 0;
}

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That code actually works! Great!

But it does not work in QT.

[wysota]

What do you mean "in Qt"? There is no "in Qt" The only problem that might arise is that some macro is included that influences the behaviour of something else, but this is not really a problem with Qt. Reordering includes might help in such situation.

[ihoss]

Well, it works in its own little cpp file, but when I try to include it in the QT project, it won't work. I have tried to rearrange the includes, but it has no effects. I've also set the namespace to std, but it does not seem to be required to make the little cpp compile.

edit: There is one strange thing though. In the little cpp i have to use CHAR as the 5th argument in the FormatMessage function, but in the "qt" program i have to use WCHAR. That is kinda strange when I include the same files and compile it with the same compiler.

[ihoss]

I tried to include the little cpp in the main project and just call the function from the application. It didn't work. I've also made sure both are compiled with mingw, and it only works when it is on its own.

[ChristianEhrlicher]

Use SystemParametersInfoA or convert your QString properly to a WCHAR array with QString::utf16().

[ihoss]

Wow, adding that A fixed the problem! Thanks a lot Christian. Thanks also to wysota for keeping dialog going

[IGHOR]

Use SystemParametersInfoA or convert your QString properly to a WCHAR array with QString::utf16().

Thank's for this!
IT work's:
QString screenPath="C:\\screen.bmp";
SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, (PVOID)screenPath.utf16(), SPIF_SENDWININICHANGE | SPIF_UPDATEINIFILE)