[RESOLVED] Creating a window in a DLL

So I'm using the code below to create a window from a DLL. I've tried this code in an application, and it worked, but it does not seem to work from a DLL. I get "1" on the return so I know the program is properly loading the DLL, but the window is never created. I've also tested the "double windowt", and was able to change the size of that window so I know I'm passing the argument correctly.

Quote:

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DLL double startup(double windowt,double x1,double y1,double x2,double y2)
{HWND window=(HWND)(DWORD)windowt;
browse=window;
WNDCLASS wc;
//create window
//HINSTANCE hInstance=GetModuleHandle(NULL);
HINSTANCE hInstance = (HINSTANCE)GetWindowLong(window, GWL_HINSTANCE);
wc.style = CS_OWNDC;
wc.lpfnWndProc = NULL;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.hIcon = LoadIcon( NULL, IDI_APPLICATION );
wc.hCursor = LoadCursor( NULL, IDC_ARROW );
wc.hbrBackground = (HBRUSH)GetStockObject( BLACK_BRUSH );
wc.lpszMenuName = NULL;
wc.lpszClassName = "eRun";
RegisterClass( &wc );
HWND hWnd = CreateWindow( "eRun", "eRun Loading...", WS_CAPTION | WS_POPUPWINDOW | WS_VISIBLE,0, 0, x2, y2,NULL, NULL, hInstance, NULL );
return 1;}

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when you create a window in a DLL how do you call it , please write entire code , the way you have gone about creating window , this can only work from WinMain not a DLL

Code:

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DLL double startup(double windowt,double x1,double y1,double x2,double y2)

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Why return a double?

Code:

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DLL double startup(double windowt,double x1,double y1,double x2,double y2)

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I see you mentioned this was for testing. You should remove old testing code that is irrelevant before posting code

Code:

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browse=window;

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Where is browse? If it is global, why?

Code:

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RegisterClass( &wc );

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You should always check for failure. otherwise how you do know this is working?

Code:

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HWND hWnd = CreateWindow( "eRun", "eRun Loading...", WS_CAPTION |  WS_POPUPWINDOW | WS_VISIBLE,0, 0, x2, y2,NULL, NULL, hInstance, NULL );

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Okay you have hWnd which is your handle, but why the new variable?

Code:

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return 1;

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Why are you returing an int of 1? You already expect a double which an int can convert to implicitly, but I am sure returning 1 is not your intended result.

Why is your registration code and creation of a window code in the same function. You should always try to separate code into logical steps as much as possible. For ex,

Code:

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Handle StartUp( int x, int y, int Width, int Height )
{
    HWND WindowHandle = NULL;

    if( SetupWin32() )
    {
        WindowHandle = CreateGuiWindow( x, y, Width, Height );
    }

    return WindowHandle;
)

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You need to check for failure on api calls. If they fail, call GetLastError() and see what the error means on msdn. You also need to fix these errors I have shown you or explain in more detail what they are for.

It is possible to create a window in a dll and have it loop through its own messaging queue. Is this what you are trying to do?

You should always post a complete small example demonstrating your problem.

I'm making this DLL for gamemaker, which only allows you to pass variables in to form of Double and Char. That is why I use so many doubles, and save the HWND browse as a global variable. I called GetLastError() after RegisterClass, Create Window, and "SetWindowPos( hWnd, HWND_TOP, 0, 0, 100, 100, SWP_SHOWWINDOW);" (I added it to test the window). The only error i got was on setwindowpos, and the error was "invalid window handle" so i know it's not working, but I can't pin point the problem.

@aamir121a that is the exact code from the DLL, what needs to be different in a DLL?

When you register your own class, it must have a message pump and a window procedure

What is

Code:

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wc.lpfnWndProc = NULL;

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How do you handle your messages?

I added a message pump and it works perfectly now, thanks for the help :).

Also don't forget to unregister your class since dlls do not unregister classes automatically.

Also are you sure there isn't a better way to pass HWND? Can you at least pass pointers?

I'll make sure to unregister it, thanks :). I'll look into changing the HWND into a double since that is what the gamemaker does when it's sending it's window to the DLL.