标题：WHATSIZE程式
简介
Windows的小历史：第一篇如何写作Windows程式的介绍文章出现在《Microsoft Systems Journal》1986年12月号上。在那篇文章中，范例程式叫做WSZ（「what size：什么尺寸」），它以图素、英寸和毫米为单位显示了显示区域的大小。那个程式的更简易版本是WHATSIZE，如程式5-6所示。程式显示了以五种度量映射方式显示的视窗显示区域的大小。
具体程式
程式5-6  WHATSIZE
WHATSIZE.C
/*------------------------------------------------------------
WHATSIZE.C -- What Size is the Window?
(c) Charles Petzold, 1998
----------------------------------------------------------*/
#include <windows.h>
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT ("WhatSize") ;
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 Windows NT!"),
szAppName, MB_ICONERROR) ;
return 0 ;
}
hwnd = CreateWindow (szAppName, TEXT ("What Size is the Window?"),
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 Show (HWND hwnd, HDC hdc, int xText, int yText, int iMapMode,
TCHAR * szMapMode)
{
TCHAR szBuffer [60] ;
RECT  rect ;
SaveDC (hdc) ;
SetMapMode (hdc, iMapMode) ;
GetClientRect (hwnd, &rect) ;
DPtoLP (hdc, (PPOINT) &rect, 2) ;
RestoreDC (hdc, -1) ;
TextOut (        hdc, xText, yText, szBuffer,
wsprintf (szBuffer, TEXT ("%-20s %7d %7d %7d %7d"), szMapMode,
rect.left, rect.right, rect.top, rect.bottom)) ;
}  
LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
static TCHAR szHeading [] =
TEXT ("Mapping Mode        Left        Right        Top  Bottom") ;
static TCHAR szUndLine [] = 
TEXT ("------------   ----   -----         ---  ------") ;
static int   cxChar, cyChar ;
HDC                 hdc ;
PAINTSTRUCT        ps ;
TEXTMETRIC        tm ;
switch (message)
{
case        WM_CREATE:
hdc = GetDC (hwnd) ;
SelectObject (hdc, GetStockObject (SYSTEM_FIXED_FONT)) ;
GetTextMetrics (hdc, &tm) ;
cxChar = tm.tmAveCharWidth ;
cyChar = tm.tmHeight + tm.tmExternalLeading ;
ReleaseDC (hwnd, hdc) ;
return 0 ;
case        WM_PAINT:
hdc = BeginPaint (hwnd, &ps) ;
SelectObject (hdc, GetStockObject (SYSTEM_FIXED_FONT)) ;
SetMapMode (hdc, MM_ANISOTROPIC) ;
SetWindowExtEx (hdc, 1, 1, NULL) ;
SetViewportExtEx (hdc, cxChar, cyChar, NULL) ;
TextOut (hdc, 1, 1, szHeading, lstrlen (szHeading)) ;
TextOut (hdc, 1, 2, szUndLine, lstrlen (szUndLine)) ;
Show (hwnd, hdc, 1, 3, MM_TEXT,        TEXT ("TEXT (pixels)")) ;
Show (hwnd, hdc, 1, 4, MM_LOMETRIC,        TEXT ("LOMETRIC (.1 mm)")) ;
Show (hwnd, hdc, 1, 5, MM_HIMETRIC,        TEXT ("HIMETRIC (.01 mm)")) ;
Show (hwnd, hdc, 1, 6, MM_LOENGLISH, TEXT ("LOENGLISH (.01 in)")) ;
Show (hwnd, hdc, 1, 7, MM_HIENGLISH,TEXT ("HIENGLISH (.001 in)")) ;
Show (hwnd, hdc, 1, 8, MM_TWIPS,        EXT ("TWIPS (1/1440 in)")) ;
EndPaint (hwnd, &ps) ;
return 0 ;
case        WM_DESTROY:
PostQuitMessage (0) ;
return 0 ;
}
return DefWindowProc (hwnd, message, wParam, lParam) ;
}
评价
这个程式看似麻烦其实原理很简单