(WinAPI) FindWindowW always fails

[Виталий Фадеев]

On Thursday, 8 October 2020 at 19:39:05 UTC, Deen O'Connor wrote:
> I was coding my project, and at some point it required to get 
> widow rectangle. GetWindowRect function returned 
> ERROR_INVALID_WINDOW_HANDLE (0x578) error. This is where i 
> detected the error. I then checked what the return value of 
> FindWindowW was, and it was 0. GetLastError showed that there 
> was ERROR_NOT_ALL_ASSIGNED (0x514) error.
>
> So, to re-create the error, i did the following:
> 1 - Opened an app that has a window. In my case this was 
> x32dbg, i chose it because it has a short window name without 
> any spaces.
> 2 - Wrote a small program to check if the error will happen 
> again:
> import std.stdio;
> import std.conv;
> import core.sys.windows.windows;
>
> void main(string[] args) {
>     wstring wndName = "x32dbg";
>     HWND hWnd = FindWindowW(null, cast(wchar*)&wndName);
>     if (hWnd is null) {
>         writeln("Error 0x" ~ to!string(GetLastError(), 16) ~ " 
> in FindWindowW()!");
>     } else {
>         writeln("x32dbg window: 0x" ~ to!string(cast(uint)hWnd, 
> 16));
>     }
> }
> 3 - Ran this code with rdmd
>
> Output said that there was an error.
> This also happened with every window i tried to find no matter 
> what. FindWindowA also failed.
>
> The only reason i'm writing this is because i can find the 
> window with x32dbg and a very similar C++ code works fine.
> So, am i doing something wrong, or is this a bug?

I using like this:

                 HWND hwnd = FindWindow( "Window", "Panel" );

                 if ( hwnd )
                 {
                     PostMessage( hwnd, APP_MAIN_MENU, 0, 0 );
                 }

>     wstring wndName = "x32dbg";
>     HWND hWnd = FindWindowW(null, cast(wchar*)&wndName);

I think some like this...

LPCWSTR toLPCWSTR( string s ) nothrow // const wchar_t*
{
     import std.utf : toUTFz, toUTF16z, UTFException;
     try                        { return toUTF16z( s ); }
     catch ( UTFException e )   { return "ERR"w.ptr; }
     catch ( Exception e )      { return "ERR"w.ptr; }
}
alias toLPCWSTR toPCWSTR;

wstring wndName = "x32dbg";
HWND hWnd = FindWindowW( null, wndName.toLPCWSTR );