C++ Win32 no window, yes on task manager

I'm having problems with my code...the code doesn't show a window, but is in the taskbar manager list...any ideas

// CWnd32.h

Code:

---

#include <windows.h>
#include <string>

using std::string;

class CWnd32 
{
public:
        int ShowUI(const string &,int,int,int,bool);
        BOOL InitInstance(HINSTANCE,const string &);
        CWnd32();
        virtual ~CWnd32();

private:
        WNDCLASSEX m_wcx;
        HWND hwnd;

protected:
        static LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
        LRESULT CALLBACK fakeWndProc(UINT,WPARAM,LPARAM);

};

---

// CWnd32.cpp

Code:

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#include "Wnd32.h"

CWnd32::~CWnd32()
{
        UnregisterClass(m_wcx.lpszClassName, m_wcx.hInstance);
        if (hwnd) DestroyWindow(hwnd);
}

CWnd32::CWnd32()
{
        ZeroMemory(&m_wcx,sizeof(WNDCLASSEX));
}

BOOL CWnd32::InitInstance(HINSTANCE _hInstance, const string &strClass)
{
        m_wcx.cbSize = sizeof(WNDCLASSEX);
        m_wcx.cbClsExtra = 0;
        m_wcx.cbWndExtra = 0;
        m_wcx.hInstance = _hInstance;
        m_wcx.lpszClassName = strClass.c_str();
        m_wcx.lpszMenuName = 0;
        m_wcx.lpfnWndProc = CWnd32::WndProc;
        m_wcx.style = CS_DBLCLKS|CS_HREDRAW|CS_VREDRAW;
        m_wcx.hIcon = LoadIcon(NULL, IDI_APPLICATION);
        m_wcx.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
        m_wcx.hCursor = LoadCursor(NULL, IDC_ARROW);
        m_wcx.hbrBackground = GetSysColorBrush(COLOR_BTNFACE);
        return RegisterClassEx(&m_wcx);
}

int CWnd32::ShowUI(const string &strTitle,int w,int h,int nShow,bool centre)
{
        hwnd = CreateWindow(m_wcx.lpszClassName,strTitle.c_str(),WS_POPUPWINDOW|WS_CAPTION|WS_MINIMIZEBOX|WS_CLIPCHILDREN|WS_CLIPSIBLINGS,1,2,w,h,NULL,NULL,m_wcx.hInstance,this);
        if (!hwnd) return -2;
        ShowWindow(hwnd,nShow);
        UpdateWindow(hwnd);
        return 0;
}

LRESULT CALLBACK CWnd32::WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
        CWnd32 *self;
        if (msg == WM_NCCREATE)
        {
                self = (CWnd32*)((LPCREATESTRUCT)lParam)->lpCreateParams;
                SetWindowLong(hWnd,GWL_USERDATA,(LONG)self);
        }
        else
        {
                self = (CWnd32*)GetWindowLong(hWnd,GWL_USERDATA);
                if(!self) return DefWindowProc(hWnd,msg,wParam,lParam);
        }
        self->hwnd = hWnd;
        return self->fakeWndProc(msg,wParam,lParam);
}

LRESULT CALLBACK CWnd32::fakeWndProc(UINT msg, WPARAM wParam, LPARAM lParam)
{
        switch (msg)
        {
        case WM_CREATE:
                {
                        return 0;
                }
        case WM_COMMAND:
                {
                        return 0;
                }
        case WM_CLOSE:
                {
                        DestroyWindow(hwnd);
                        return 0;
                }
        case WM_DESTROY:
                {
                        PostQuitMessage(0);
                        return 0;
                }
        }
        return DefWindowProc(hwnd,msg,wParam,lParam);
}

---

// main.cpp

Code:

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#include "Wnd32.h"

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)
{
        int ret_val = -1;
        CWnd32 *ptr = new CWnd32;
        if (ptr->InitInstance(hInstance,"my_damn_class"))
        {
                MSG Msg;
                // show the main window
                ptr->ShowUI("hola",150,150,nShowCmd,true);
                while(GetMessage(&Msg,0,0,0))
                {
                        TranslateMessage(&Msg);
                        DispatchMessage(&Msg);
                }
                ret_val = Msg.wParam;
        }
        delete ptr;
        return ret_val;
}

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You're not passing your window's handle to GetMessage().

Ignore that, because its wrong.

As for your problem, why didn't you check the return of your showui function and use GetLastError() to see why it's failing? Hint: It's 1407 which means "Invalid window class", also the return from c_str() is only valid as long as you don't modify the std::string it came from. It being destroyed counts as being modified.

@adeyblue: Thanks, I modified the code so I pass the class string...thanks :)

Quote:

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Originally Posted by adeyblue

Ignore that, because its wrong.

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Oh, yeah? Do you mean that window handle shouldn't be passed to GetMessage()?!

Quote:

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Originally Posted by Sipher

Oh, yeah? Do you mean that window handle shouldn't be passed to GetMessage()?!

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Not necessary, according to msdn => GetMessage:

Quote:

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A handle to the window whose messages are to be retrieved. The window must belong to the current thread.

If hWnd is NULL, GetMessage retrieves messages for any window that belongs to the current thread, and any messages on the current thread's message queue whose hwnd value is NULL (see the MSG structure). Therefore if hWnd is NULL, both window messages and thread messages are processed.

If hWnd is -1, GetMessage retrieves only messages on the current thread's message queue whose hwnd value is NULL, that is, thread messages as posted by PostMessage (when the hWnd parameter is NULL) or PostThreadMessage.

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Since my windows in the only in my current thread

I see... Man, you never know enough! :)

Quote:

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Originally Posted by Sipher

I see... Man, you never know enough! :)

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Thing is, if you pass a window handle to GetMessage() it will only retrieve messages for that window... works like a charm in single window applications but not so handy if you have dialogs and other windows open...

One filtering trick I sometimes use is...

Code:

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GetMessage(GetForegroundWindow(),0,0);

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if I don't want messaging going on in background windows ...