Create window with WNDCLASSEX? [Cpp]

Question

First here is my code... well actually it is pretty much copied and pasted from Microsoft tutorial that I am trying to learn from...

CreateWindow.h

#ifndef CreateWindow_H
#define CreateWindow_H

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

using namespace std;

int WINAPI WinMain(HINSTANCE hInstance,
                   HINSTANCE hPrevInstance,
                   LPSTR lpCmdLine,
                   int nCmdShow);

#endif

CreateWindow.cpp

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

// Global variables

// The main window class name.
static TCHAR szWindowClass[] = _T("win32app");

// The string that appears in the application's title bar.
static TCHAR szTitle[] = _T("Win32 Guided Tour Application");

HINSTANCE hInst;

// Forward declarations of functions included in this code module:
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);


int WINAPI WinMain(HINSTANCE hInstance,
                   HINSTANCE hPrevInstance,
                   LPSTR lpCmdLine,
                   int nCmdShow) {
    WNDCLASSEX wcex;

    wcex.cbSize = sizeof(WNDCLASSEX);
    wcex.style          = CS_HREDRAW | CS_VREDRAW;
    wcex.lpfnWndProc    = WndProc;
    wcex.cbClsExtra     = 0;
    wcex.cbWndExtra     = 0;
    wcex.hInstance      = hInstance;
    wcex.hIcon          = LoadIcon(hInstance, static_cast<WORD>(MAKEINTRESOURCE(IDI_APPLICATION)));
    wcex.hCursor        = LoadCursor(NULL, IDC_ARROW);
    wcex.hbrBackground  = (HBRUSH)(COLOR_WINDOW+1);
    wcex.lpszMenuName   = NULL;
    wcex.lpszClassName  = szWindowClass;
    wcex.hIconSm        = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_APPLICATION));

    if (!RegisterClassEx(&wcex)) {
        MessageBox(NULL,
                   _T("Call to RegisterClassEx failed!"),
                   _T("Win32 Guided Tour"),
                   NULL);

        return 1;
    }

    hInst = hInstance; // Store instance handle in our global variable

    // The parameters to CreateWindow explained:
    // szWindowClass: the name of the application
    // szTitle: the text that appears in the title bar
    // WS_OVERLAPPEDWINDOW: the type of window to create
    // CW_USEDEFAULT, CW_USEDEFAULT: initial position (x, y)
    // 500, 100: initial size (width, length)
    // NULL: the parent of this window
    // NULL: this application dows not have a menu bar
    // hInstance: the first parameter from WinMain
    // NULL: not used in this application
    HWND hWnd = CreateWindow(
                    szWindowClass,
                    szTitle,
                    WS_OVERLAPPEDWINDOW,
                    CW_USEDEFAULT, CW_USEDEFAULT,
                    500, 100,
                    NULL,
                    NULL,
                    hInstance,
                    NULL
                );

    if (!hWnd) {
        MessageBox(NULL,
                   _T("Call to CreateWindow failed!"),
                   _T("Win32 Guided Tour"),
                   NULL);

        return 1;
    }

    // The parameters to ShowWindow explained:
    // hWnd: the value returned from CreateWindow
    // nCmdShow: the fourth parameter from WinMain
    ShowWindow(hWnd,
               nCmdShow);
    UpdateWindow(hWnd);

    // Main message loop:
    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return (int) msg.wParam;
}

Errors:

C:\Users\***\Documents\CodeBlocksProjects\encryptText\CreateWindow.cpp||In function 'int WinMain(HINSTANCE__*, HINSTANCE__*, CHAR*, int)':|
C:\Users\***\Documents\CodeBlocksProjects\encryptText\CreateWindow.cpp|32|error: cast from 'CHAR*' to 'WORD' loses precision|
C:\Users\***\Documents\CodeBlocksProjects\encryptText\CreateWindow.cpp|32|error: invalid static_cast from type 'CHAR*' to type 'WORD'|
C:\Users\***\Documents\CodeBlocksProjects\encryptText\CreateWindow.cpp|37|error: cast from 'CHAR*' to 'WORD' loses precision|
||=== Build finished: 3 errors, 0 warnings ===|

I thought that I would need to do a static_cast, but nothing was working. I even tried using WORD, but still go the error. So I have no idea what to do there.

Also how do I even use this? I read the entire tutorial a couple times.

Tutorial: http://msdn.microsoft.com/en-us/library/bb384843.aspx

I thought you would do something like

// start up the four variables before hand, how ever that is done
WinMain(hInstance, hPrevInstance, lpCmdLine, nCmdShow);

I didn't really get anywhere with that.

Don't get me wrong though... I understand a lot of it, but the things I don't understand ill go ahead and list below.

• _T / TCHAR
• CALLBACK
• How to start up application for actual use
• Fix compiler errors for casting

Answer 1

I'll just answer each of your bullets in turn:

• _T is a macro that evaluates to L<macro_argument> when UNICODE is defined and just <macro_argument> when it is not defined. You would use this macro around string literals so that when UNICODE is defined a wide literal is used (e.g. L"foo") and when it is not defined a "narrow" literal is used (e.g. "foo"). Likewise, TCHAR is a typedef to wchar_t when UNICODE is defined and a typedef to char when it is not defined. See this article on more information about globalization of Windows applications.

• CALLBACK is a define that evaluates to __stdcall. This is a Microsoft-specific extension that modifies the function from the default cdecl calling convention to stdcall. See this article for more information about calling conventions.

• WinMain is the entry point for non-console Windows applications. Technically, the C runtime (CRT) defines the actual entry point called by the operating system and this in turn calls your WinMain. Like main(), it should never be called directly in your code.

• LoadIcon takes a LPCTSTR (wchar_t const* or a char const* depending on UNICODE) for the second parameter. The MAKEINTRESOURCE macro will do the appropriate cast to LPTSTR, so you should not be casting it to a WORD. In fact, you should not be using the MAKEINTRESOURCE macro here at all since IDI_APPLICATION should already be a define to MAKEINTRESOURCE(<some_integer>). Simply LoadIcon(hInstance, IDI_APPLICATION) will do.

Answer 2

You'll find it extremely helpful to not deal with _T, TCHAR, and tchar.h. Those are relics from the days when it was conceivable you might have to have your code run on Windows 95/98 and NT at the same time. I'm assuming this isn't an issue for you. Just make everything UNICODE - you won't regret it. This does mean that all string literals will need to get prefixed with an 'L'. E.g.

L"Win32 Guided Tour"

Now do this:

Add the following two lines to the very top of your source file (before all the includes)

#ifndef UNICODE
#define UNICODE
#endif

#ifndef _UNICODE
#define _UNICODE
#endif

(Or better yet, just make sure UNICODE and _UNICODE are set in your project settings. This is the default in Visual Studio - so if you're running VS2008 or VS2010, then just skip all this).

Now, take out the static_cast in your LoadIcon calls. Your code will compile (and hopefully run) just fine.