自己的不足

今天看了windows程序第8章的 DigClock程序，令我感叹不已呀。是一个数字时种，如下：

让我明白了原先我们去的那种老式数字电子表的数字是怎样显示的，那个要显示0-9的数字，通过变换方块的多少来表示0-9的方法，记得以前我也研究过，但是始终没想到作者用那么短的代码实现了。

 

唉，哪位大大能告诉我，为什么作者能用那么短的几个函数把这些数字控制自如，这个需要什么技术？数据结构？我想不是。。。。

/*-----------------------------------------
   DIGCLOCK.c -- Digital Clock
                 (c) Charles Petzold, 1998
  -----------------------------------------*/

#include <windows.h>

#define ID_TIMER    1

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

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     static TCHAR szAppName[] = TEXT ("DigClock") ;
     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 ("Program requires Windows NT!"), 
                      szAppName, MB_ICONERROR) ;
          return 0 ;
     }

     hwnd = CreateWindow (szAppName, TEXT ("Digital Clock"),
                          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 ;
     }

void DisplayDigit (HDC hdc, int iNumber)
{
     static BOOL  fSevenSegment [10][7] = {
                         1, 1, 1, 0, 1, 1, 1,     // 0
                         0, 0, 1, 0, 0, 1, 0,     // 1
                         1, 0, 1, 1, 1, 0, 1,     // 2
                         1, 0, 1, 1, 0, 1, 1,     // 3
                         0, 1, 1, 1, 0, 1, 0,     // 4
                         1, 1, 0, 1, 0, 1, 1,     // 5
                         1, 1, 0, 1, 1, 1, 1,     // 6
                         1, 0, 1, 0, 0, 1, 0,     // 7
                         1, 1, 1, 1, 1, 1, 1,     // 8
                         1, 1, 1, 1, 0, 1, 1 } ;  // 9
     static POINT ptSegment [7][6] = {
                          7,  6,  11,  2,  31,  2,  35,  6,  31, 10,  11, 10,
                          6,  7,  10, 11,  10, 31,   6, 35,   2, 31,   2, 11,
                         36,  7,  40, 11,  40, 31,  36, 35,  32, 31,  32, 11,
                          7, 36,  11, 32,  31, 32,  35, 36,  31, 40,  11, 40,
                          6, 37,  10, 41,  10, 61,   6, 65,   2, 61,   2, 41,
                         36, 37,  40, 41,  40, 61,  36, 65,  32, 61,  32, 41,
                          7, 66,  11, 62,  31, 62,  35, 66,  31, 70,  11, 70 } ;
     int          iSeg ;
     
     for (iSeg = 0 ; iSeg < 7 ; iSeg++)
          if (fSevenSegment [iNumber][iSeg])
               Polygon (hdc, ptSegment [iSeg], 6) ;
}

void DisplayTwoDigits (HDC hdc, int iNumber, BOOL fSuppress)
{
     if (!fSuppress || (iNumber / 10 != 0))
          DisplayDigit (hdc, iNumber / 10) ;

     OffsetWindowOrgEx (hdc, -42, 0, NULL) ;
     DisplayDigit (hdc, iNumber % 10) ;
     OffsetWindowOrgEx (hdc, -42, 0, NULL) ;
}

void DisplayColon (HDC hdc)
{
     POINT ptColon [2][4] = { 2,  21,  6,  17,  10, 21,  6, 25,
                              2,  51,  6,  47,  10, 51,  6, 55 } ;

     Polygon (hdc, ptColon [0], 4) ;
     Polygon (hdc, ptColon [1], 4) ;

     OffsetWindowOrgEx (hdc, -12, 0, NULL) ;
}

void DisplayTime (HDC hdc, BOOL f24Hour, BOOL fSuppress)
{
     SYSTEMTIME st ;

     GetLocalTime (&st) ;

     if (f24Hour)
          DisplayTwoDigits (hdc, st.wHour, fSuppress) ;
     else
          DisplayTwoDigits (hdc, (st.wHour %= 12) ? st.wHour : 12, fSuppress) ;

     DisplayColon (hdc) ;
     DisplayTwoDigits (hdc, st.wMinute, FALSE) ;
     DisplayColon (hdc) ;
     DisplayTwoDigits (hdc, st.wSecond, FALSE) ;
}

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
     static BOOL   f24Hour, fSuppress ;
     static HBRUSH hBrushRed ;
     static int    cxClient, cyClient ;
     HDC           hdc ;
     PAINTSTRUCT   ps ;
     TCHAR         szBuffer [2] ;

     switch (message)
     {
     case WM_CREATE:
          hBrushRed = CreateSolidBrush (RGB (255, 0, 0)) ;
          SetTimer (hwnd, ID_TIMER, 1000, NULL) ;

                                                  // fall through

     case WM_SETTINGCHANGE:
          GetLocaleInfo (LOCALE_USER_DEFAULT, LOCALE_ITIME, szBuffer, 2) ;
          f24Hour = (szBuffer[0] == '1') ;

          GetLocaleInfo (LOCALE_USER_DEFAULT, LOCALE_ITLZERO, szBuffer, 2) ;
          fSuppress = (szBuffer[0] == '0') ;

          InvalidateRect (hwnd, NULL, TRUE) ;
          return 0 ;

     case WM_SIZE:
          cxClient = LOWORD (lParam) ;
          cyClient = HIWORD (lParam) ;
          return 0 ;

     case WM_TIMER:
          InvalidateRect (hwnd, NULL, TRUE) ;
          return 0 ;

     case WM_PAINT:
          hdc = BeginPaint (hwnd, &ps) ;

          SetMapMode (hdc, MM_ISOTROPIC) ;
          SetWindowExtEx (hdc, 276, 72, NULL) ;
          SetViewportExtEx (hdc, cxClient, cyClient, NULL) ;

          SetWindowOrgEx (hdc, 138, 36, NULL) ;
          SetViewportOrgEx (hdc, cxClient / 2, cyClient / 2, NULL) ;

          SelectObject (hdc, GetStockObject (NULL_PEN)) ;
          SelectObject (hdc, hBrushRed) ;

          DisplayTime (hdc, f24Hour, fSuppress) ;

          EndPaint (hwnd, &ps) ;
          return 0 ;

     case WM_DESTROY:
          KillTimer (hwnd, ID_TIMER) ;
          DeleteObject (hBrushRed) ;
          PostQuitMessage (0) ;
          return 0 ;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}