Thread: MultiThreaded GUI.

Here is a quick example. As you can see both windows are added to the task bar and the user won't know if it is the same program or seperate programs (well he can guese because the windows look similar and have the same icon but you can change that).

Code:

#include <windows.h>

const char szClassName[] = "Window Class";

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch(msg)
    {
        case WM_CLOSE:
            DestroyWindow(hwnd);
        break;
        case WM_DESTROY:
            PostQuitMessage(0);
        break;
        default:
            return DefWindowProc(hwnd, msg, wParam, lParam);
    }
    return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    WNDCLASSEX wc;
    MSG Msg;

    
    wc.cbSize = sizeof(WNDCLASSEX);
    wc.style  = 0;
    wc.lpfnWndProc = &WndProc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = hInstance;
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
    wc.lpszMenuName = NULL;
    wc.lpszClassName = szClassName;
    wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);

	RegisterClassEx(&wc);

	HWND hwnd1 = CreateWindowEx(WS_EX_CLIENTEDGE, szClassName, "Window 1", WS_OVERLAPPEDWINDOW | WS_VISIBLE, CW_USEDEFAULT, CW_USEDEFAULT, 100, 100, NULL, NULL, hInstance, NULL);
	HWND hWnd2 = CreateWindowEx(WS_EX_CLIENTEDGE, szClassName, "Window 2", WS_OVERLAPPEDWINDOW | WS_VISIBLE, CW_USEDEFAULT, CW_USEDEFAULT, 200, 200, NULL, NULL, hInstance, NULL);

	ShowWindow(hwnd1, nCmdShow);
    UpdateWindow(hwnd1);
	ShowWindow(hWnd2, nCmdShow);
	UpdateWindow(hWnd2);

	while(GetMessage(&Msg, NULL, 0, 0) > 0)
    {
        TranslateMessage(&Msg);
        DispatchMessage(&Msg);
    }
    return Msg.wParam;
}

You will probably want to create seperate window procedures for each window.

Ok, seems like this is a wee bit more complicated for me. I'm using a more complex class, like the one in foosyerdoos.fsnet.co.uk and it seems like it's not working as i have been debugging for a couple hours.

I got to a point where it says "failed to create wnd". Which means i can register WNDCLASSEX, but i cannot create the window or something. I guess something to do with something getting lost because of having such complicated classes.

So i have two classes. One is a windows program that works fine, then at a certain part a function is activated, which activates WINAPI WinMain2 (the other program), and tries to make it. However things aren't going too well.

Ill keep debugging.

EDIT:
Here's exactly what I did. It compiled and linked great (im using DevC++), but it fails to "create wnd". The following code is like the main.cpp of my FIRST program. It's suppose to launch the second program, which is included in another class Called CppWnd2.

The class functions i used are self-explanatory and work great.

Code:

CppWnd2 App2;
int CppWnd::LaunchSecondProgram(){
    HINSTANCE hInstance;
    App2.SetInstance(hInstance);
//give the wnd a class name to register with os
       App2.SetWndClassName(TEXT("WndClass"));
//give the wnd a caption
       App2.SetWndCaption(TEXT("Second Program"));
       CoInitialize(NULL);
//register and create wnd,checking the return value to ensure that a valid wnd handle has
//been made.
       if (App2.Create(hAppWnd)) // Parent Handle.
    {
    MSG Msg;    //a simple structure for storing message information
    //start message loop
    while (GetMessage(&Msg,NULL,0,0))
        {
            //translate and dispatch other messages
            TranslateMessage(&Msg);
            DispatchMessage(&Msg);
        }
    CoUninitialize();
    return Msg.wParam;
    }
    return 0;
}
LRESULT CALLBACK MainWndProc2(HWND hwnd,UINT Message,WPARAM wParam,LPARAM lParam)
{
//just send the message and other parameters to the class function for handling
return App2.CppWndProc2(hwnd,Message,wParam,lParam);
}

EDIT AGAIN: i fixed the code, so no errors anymore. There is no error. The only problem is when i launch the other program, it just closes the parent window on me and doesn't show any other window. The program just dissappears!!! Everything gets interpretted till the CreateWindowEx is called for this window.

I set window style to: WS_CAPTION | WS_POPUPWINDOW;
and class style to: CS_HREDRAW|CS_VREDRAW;

The hwnd that is returned... works great, no error messages, and hwnd is NOT null. However, they just dissappear... I think something to do with the styles i set.
Well i hear the error message, i hear a sound that's familiar to a messagebox MB_ICONERROR. However, i can't see it O_O.