非常经典的“设备内容”程序

说到windows程序设计， 这个程序非常经典， 弄透了它：

#include <windows.h>
#define NUMLINES ((int)(sizeof devcaps / sizeof devcaps[0]))

struct {
    int iIndex;
    TCHAR* szLabel;
    TCHAR* szDesc;
} devcaps[] = {
    HORZSIZE, TEXT("HORZSIZE"), TEXT("width in millimeters:"),
        VERTSIZE, TEXT("VERTSIZE"), TEXT("height in millimeters:"),
        HORZRES, TEXT("HORZRES"), TEXT("width in pixels:"),
        VERTRES, TEXT("VERTRES"), TEXT("height in pexels:"),
        BITSPIXEL, TEXT("BITSPIXEL"), TEXT("color bits per pixel:"),
        PLANES, TEXT("PLANES"), TEXT("number of color planes:"),
        NUMBRUSHES, TEXT("NUMBRUSHES"), TEXT("number of device brushes:"),
        NUMPENS, TEXT("NUMPENS"), TEXT("number of device pens:"),
        NUMMARKERS, TEXT("NUMKARKERS"), TEXT("number of device markers:"),
        NUMFONTS, TEXT("NUMFONTS"), TEXT("number of device fonts:"),
        NUMCOLORS, TEXT("NUMCOLORS"), TEXT("number of device colors:"),
        PDEVICESIZE, TEXT("PDEVICESIZE"), TEXT("size of device structure:"),
        ASPECTX, TEXT("ASPECTX"), TEXT("relative width of pixel:"),
        ASPECTY, TEXT("ASPECTY"), TEXT("relative height of pixel:"),
        LOGPIXELSX, TEXT("LOGPIXELSZ"), TEXT("horizontal dots per inch:"),
        LOGPIXELSY, TEXT("LOGPIXELSY"), TEXT("vertical dots per inch:")
};

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
int WINAPI WinMain(HINSTANCE hInstance,
                 HINSTANCE hPrevInstance,
                 PSTR szCmdLine,
                 int iCmdShow) {
    static TCHAR szAppName[] = TEXT("DevCaps1");
    HWND hwnd;
    MSG msg;
    WNDCLASS wndclass;
    
    wndclass.style = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc = WndProc;
    wndclass.cbClsExtra = 0;
    wndclass.cbWndExtra = 0;
    wndclass.hInstance = hInstance;
    wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = szAppName;
    
    if(!RegisterClass(&wndclass)) {
        MessageBox(NULL, TEXT("This program requires window NT!"),
            szAppName, MB_ICONERROR);
        return 0;
    }
    
    hwnd = CreateWindow(szAppName,
         TEXT("Devince Capabilities"),
             WS_OVERLAPPEDWINDOW,
             CW_USEDEFAULT,
             CW_USEDEFAULT,
             CW_USEDEFAULT,
             CW_USEDEFAULT,
             NULL,
             NULL,
             hInstance,
             NULL);
    ShowWindow(hwnd, iCmdShow);
    UpdateWindow(hwnd);
    
    while(GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    
    return msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd,
                         UINT message,
                         WPARAM wParam,
                         LPARAM lParam) {
    static int cxChar, cxCaps, cyChar;
    TCHAR szBuffer[10];
    HDC hdc;
    int i;
    PAINTSTRUCT ps;
    TEXTMETRIC tm;
    
    switch(message) {
    case WM_CREATE:
        hdc = GetDC(hwnd);
        GetTextMetrics(hdc, &tm);
        cxChar = tm.tmAveCharWidth;
        cxCaps = ((tm.tmPitchAndFamily) & 1 ? 3 : 2) * cxChar / 2;
        cyChar = tm.tmHeight + tm.tmExternalLeading;
        ReleaseDC(hwnd, hdc);
        return 0;
        
    case WM_PAINT:
        hdc = BeginPaint(hwnd, &ps);
        for(i = 0; i < NUMLINES; i++) {
            TextOut(hdc, 0, cyChar * i,
                devcaps[i].szLabel,
                lstrlen(devcaps[i].szLabel));
            
            TextOut(hdc, 14 * cxCaps, cyChar * i,
                devcaps[i].szDesc,
                lstrlen(devcaps[i].szDesc));
            
            SetTextAlign(hdc, TA_RIGHT | TA_TOP);
            TextOut(hdc, 14 * cxCaps + 35 * cxChar, cyChar * i,
                szBuffer, wsprintf(szBuffer, TEXT("%5d"),
                GetDeviceCaps(hdc, devcaps[i].iIndex
                )));
            SetTextAlign(hdc, TA_LEFT | TA_TOP);
        }
        
        EndPaint(hwnd, &ps);
        return 0;
        
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }
    
    return DefWindowProc(hwnd, message, wParam, lParam);
}