Mais Sobre Ícones

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

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain(HINSTANCE hI, HINSTANCE hPI, PSTR szCL, int iCS) {
    TCHAR    szAppName[] = TEXT("IconDemo");
    HWND     hwnd;
    MSG      msg;
    WNDCLASS wndclass;

    wndclass.style         = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc   = WndProc;
    wndclass.cbClsExtra    = 0;
    wndclass.cbWndExtra    = 0;
    wndclass.hInstance     = hI;
    wndclass.hIcon         = LoadIcon(hI, MAKEINTRESOURCE(IDI_ICON));
    wndclass.hCursor       = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH) WHITE_BRUSH;
    wndclass.lpszMenuName  = NULL;
    wndclass.lpszClassName = szAppName;

    if(!RegisterClass(&wndclass)) {
        MessageBox(NULL, TEXT("Windows NT"), szAppName, MB_ICONERROR);
        return 0;
    }

    hwnd = CreateWindow(szAppName, TEXT("Icon Demo"),
                        WS_OVERLAPPEDWINDOW,
                        CW_USEDEFAULT, CW_USEDEFAULT,
                        CW_USEDEFAULT, CW_USEDEFAULT,
                        NULL, NULL, hI, NULL);

    ShowWindow(hwnd, iCS);
    UpdateWindow(hwnd);

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

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) {
    static HICON hIcon;
    static int cxIcon, cyIcon, cxClient, cyClient;
    HDC hdc;
    HINSTANCE hI;
    PAINTSTRUCT ps;
    int x, y;

    switch(msg) {
        case WM_CREATE:
            hI = ((LPCREATESTRUCT) lp)->hInstance;
            hIcon = LoadIcon(hI, MAKEINTRESOURCE(IDI_ICON));
            cxIcon = GetSystemMetrics(SM_CXICON);
            cyIcon = GetSystemMetrics(SM_CYICON);
            return 0;
        case WM_SIZE:
            cxClient = LOWORD(lp);
            cyClient = HIWORD(lp);
            return 0;
        case WM_PAINT:
            hdc = BeginPaint(hwnd, &ps);

            for(y=0; y<cyClient; y+=cyIcon)
                for(x=0; x<cxClient; x+=cxIcon)
                DrawIcon(hdc, x, y, hIcon);
            EndPaint(hwnd, &ps);
            return 0;
        case WM_DESTROY:
            PostQuitMessage(0);
            return 0;
    }
    return DefWindowProc(hwnd, msg, wp, lp);
}