Creating Responsive Windows winapi c++

Question

I am just learning to create a gui using the winapi, but i have run into an issue. I can create a window like this

#include "stdafx.h"
#include <windows.h>

int main()
{
    HWND hwnd = CreateWindow(L"STATIC",NULL,WS_VISIBLE|WS_SYSMENU|WS_CAPTION,0,0,600,600,NULL,NULL,NULL,NULL);
    UpdateWindow(hwnd);
    MSG msg;

    while(GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    _gettch();
}

But the windows will not close when the close button is clicked, and the window can not be dragged around or moved. I was wondering how i would enable these features of the window.

Answer 1

Static windows are not there for normal windows, you should try and look up how to register and handle your own class with RegisterWindowEx then use the same class name to create a window. You have to have your own window procedure in order to handle messages. All window classes registered by the system run their own default window procudure and as far as I know none of them handle WM_CLOSE ( that is the close button ) this is why you can't close it.

For you main windows always use something like WS_OVERLAPPEDWINDOW so it'll be clear if it's okay or not and from that eliminate the flags you don't need.

How you set it up :

WNDCLASSEX wndcls;
HWND hMainWnd;

// Register your own window class
    ZeroMemory(&wndcls,sizeof(WNDCLASSEX));
    wndcls.cbSize=sizeof(WNDCLASSEX);
    wndcls.style=CS_VREDRAW+CS_HREDRAW;
    wndcls.lpfnWndProc=&appWndFunc;
    wndcls.hInstance=hInstance;
    wndcls.hIcon=hMainIcon;     // or just LoadIcon(hInstance,MAKEINTRESOURCE(IDI_MAIN_ICON))
    wndcls.hIconSm=hMainIcon;
    wndcls.hCursor=LoadCursor((HINSTANCE)NULL,IDC_ARROW);
    wndcls.hbrBackground=(HBRUSH)COLOR_APPWORKSPACE;
    wndcls.lpszClassName="myWndClass";
    if (RegisterClassEx(&wndcls)==0)
    {
        // failed to register class name
        return false;
    }

// Create window with your own class
    hMainWnd=CreateWindowEx(0,\
                            "myWndClass","widnow title",\
                            WS_OVERLAPPEDWINDOW|WS_VISIBLE,\
                            0,\
                            0,\
                            250,\
                            250,\
                            hMainWnd,NULL,hInstance,NULL);

    if (hMainWnd==(HWND)NULL)
    {
        // failed to create main window
        return false;
    }

Then your main loop :

bool bAppMainLoop=false
while(!bAppMainLoop)
{
    WaitMessage();
    while(PeekMessage(&emsg,NULL,0,0,PM_NOREMOVE))
    {
        if(GetMessage(&emsg,NULL,0,0)==0)
        {
            bAppMainLoop=true;
            break;
        }
        TranslateMessage(&emsg);
        DispatchMessage(&emsg);
    }
}

This is a bit more than usual setup, so let me explain , in order to not burn CPU, you wait for a message with WaitMessage, it'll block until something happens, like move window, click, paint etc. PeekMessage will return true if there is a message so calling it in a while loop will make sure it drains the message quene, GetMessage will obtain the message if it returns 0 it means that your app called the PostQuitMessage(0) so a WM_QUIT arrived was found in the message loop that means it's time to break out from the message loop. The rest Translate and Dispatch does what it name says.

Finally you need your own window procedure :

LRESULT CALLBACK appWndFunc(HWND hWnd,UINT uMsg,WPARAM wParam,LPARAM lParam)
{
    if (uMsg==WM_CLOSE)
    {
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hWnd,uMsg,wParam,lParam);
}

DefWindowProc is essential that handles all commonly occurring messages from the system, thus you don't need to handle those here. You simply respond to the WM_CLOSE message which is sent when you want to close the window and post a quit message into the message loop that you will catch and exit.

Additional info : It's not required to release your stuff since windows does that for you so it wont be locked the next time you start your program , but it's a good practice to at least Unregister your window class after your main loop.

Btw that is the wrong main function : WinMain that is the correct one. Plus to avoid even more bugs make sure you compile a windows GUI application.