Question

I am confused. Sometimes when I initiate my window, the Handle returned is good. and sometimes its not. Here is my code

void GXRenderManager::InitWindows()
{
    WNDCLASSEX wndcex;

    wndcex.cbSize   = sizeof(WNDCLASSEX);
    wndcex.style    = CS_HREDRAW | CS_VREDRAW;
    wndcex.lpfnWndProc = GXRenderManager::WndProc;
    wndcex.cbClsExtra = 0;
    wndcex.cbWndExtra = 0;
    wndcex.hInstance = *GXRenderManager::hinstance;
    wndcex.hIcon = LoadIcon(NULL,IDI_APPLICATION);
    wndcex.hCursor  =   LoadCursor(NULL,IDC_ARROW);
    wndcex.hbrBackground    = (HBRUSH)(COLOR_WINDOW+1);
    wndcex.lpszMenuName = NULL;
    wndcex.lpszClassName = L"GXRenderClass";
    wndcex.hIconSm  =   LoadIcon(NULL, IDI_APPLICATION);

    if(!RegisterClassEx(&wndcex))
        throw GXWindowsException(L"Failed To Register Window");

    //EDIT AREA: This is a static size for window. Needs to be changed for dynamic size
    RECT rectangle = {0,0,GXRenderManager::width,GXRenderManager::height};
    AdjustWindowRect(&rectangle, WS_OVERLAPPEDWINDOW, FALSE);

    HWND tempWin;

    tempWin = CreateWindowEx(WS_EX_CLIENTEDGE,L"GXRenderClass",L"GXRender Engine",
        WS_OVERLAPPEDWINDOW,CW_USEDEFAULT,CW_USEDEFAULT, 
        (rectangle.right - rectangle.left),
        (rectangle.bottom - rectangle.top), NULL, NULL,*GXRenderManager::hinstance, NULL);

    if(!tempWin)
        GXWindowsException(L"GX had an issue creating a window.");

    GXRenderManager::mainWindow = &tempWin;

    ShowWindow(*GXRenderManager::mainWindow, *GXRenderManager::nCmdShow);

}

Sometimes GXRenderManager::mainWindow returns a number, but most of the time it returns a “expression can not be evaluated. Any takers ??

[edit]

the header

#ifndef GXRM
#define GXRM
#include <windows.h>
#include "DeviceEnum.h"
#include "GXRenderDevice.h"
#include "GXExceptions.h"

class GXRenderManager {

public:
    static int Ignite(HINSTANCE*, int*, GXDEVICE , int w = 800, int h = 600);
    static GXRenderer* Device();
    static void InitWindows();
    static LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);

    static int Run();

private:
    bool running;
    static GXRenderer *renderDevice;

protected:
    static HINSTANCE * hinstance;
    static int *nCmdShow;
    static HWND mainWindow;
    static int width;
    static int height;

};

#endif

.cpp

GXRenderManager::mainWindow is a static member . Prior to the responses below. I updated the code to the following…

void GXRenderManager::InitWindows()
{
    WNDCLASSEX wndcex;

    wndcex.cbSize   = sizeof(WNDCLASSEX);
    wndcex.style    = CS_HREDRAW | CS_VREDRAW;
    wndcex.lpfnWndProc = GXRenderManager::WndProc;
    wndcex.cbClsExtra = 0;
    wndcex.cbWndExtra = 0;
    wndcex.hInstance = *GXRenderManager::hinstance;
    wndcex.hIcon = LoadIcon(NULL,IDI_APPLICATION);
    wndcex.hCursor  =   LoadCursor(NULL,IDC_ARROW);
    wndcex.hbrBackground    = (HBRUSH)(COLOR_WINDOW+1);
    wndcex.lpszMenuName = NULL;
    wndcex.lpszClassName = L"GXRenderClass";
    wndcex.hIconSm  =   LoadIcon(NULL, IDI_APPLICATION);

    if(!RegisterClassEx(&wndcex))
        throw GXWindowsException(L"Failed To Register Window");

    //EDIT AREA: This is a static size for window. Needs to be changed for dynamic size
    RECT rectangle = {0,0,GXRenderManager::width,GXRenderManager::height};
    AdjustWindowRect(&rectangle, WS_OVERLAPPEDWINDOW, FALSE);

    HWND tempWin;

    tempWin = CreateWindowEx(WS_EX_CLIENTEDGE,L"GXRenderClass",L"GXRender Engine",
        WS_OVERLAPPEDWINDOW,CW_USEDEFAULT,CW_USEDEFAULT, 
        (rectangle.right - rectangle.left),
        (rectangle.bottom - rectangle.top), NULL, NULL,*GXRenderManager::hinstance, NULL);

    if(!tempWin)
        GXWindowsException(L"GX had an issue creating a window.");

    GXRenderManager::mainWindow = tempWin;

    ShowWindow(GXRenderManager::mainWindow, *GXRenderManager::nCmdShow);

}

Still I see the same issue.

Answer 1

You are saving a pointer to a local variable (tempWin) and expecting that will be valid after you return from the InitWindows() function. Instead of making GXRenderManager::mainWindow a pointer, declare it as an actual data member. So:

class GXRenderManager {
    ...
    HWND mainWindow; // not a pointer
    ...
};

GXRenderManager::mainWindow = tempWin;

ShowWindow(GXRenderManager::mainWindow, *GXRenderManager::nCmdShow);

I suspect you might have a similar problem with nCmdShow, but you haven’t shown enough of your code to tell.