head程式

UNⅨ中有一個著名的實用程式叫做head，它顯示檔案開始的幾行。讓我們使用清單方塊為Windows編寫一個類似的程式。如程式9-6所示，HEAD將所有檔案和子目錄列在清單方塊中。您可以挑選某個被選擇的檔案來顯示，方法是在該檔案上使用滑鼠雙擊或者使用Enter鍵按下要選的檔案。您也可以使用這兩種方法之一來改變子目錄。這個程式在HEAD視窗顯示區域的右邊，從檔案的開頭開始顯示，它最多能夠顯示8 KB的內容。

程式9-6HEAD

HEAD.C

/*-------------------------------------------------------------------------

HEAD.C -- Displays beginning (head) of file

(c) Charles Petzold,1998

--------------------------------------------------------------------------*/

#include <windows.h>

#define ID_LIST 1

#define ID_TEXT 2

#define MAXREAD 8192

#define DIRATTR (DDL_READWRITE | DDL_READONLY | DDL_HIDDEN | DDL_SYSTEM | \

DDL_DIRECTORY | DDL_ARCHⅣE| DDL_DRⅣES)

#define DTFLAGS (DT_WORDBREAK | DT_EXPANDTABS | DT_NOCLIP |DT_NOPREFⅨ）

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

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

WNDPROC OldList ;

int WINAPI WinMain (HINSTANCE hInstance,HINSTANCE hPrevInstance,

PSTR szCmdLine,int iCmdShow)

{

static TCHAR szAppName[] = TEXT ("head") ;

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) (COLOR_BTNFACE + 1） ;

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 ("head"),

WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN,

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 BOOL bValidFile ;

static BYTE buffer[MAXREAD] ;

static HWND hwndList,hwndText ;

static RECT rect ;

static TCHAR szFile[MAX_PATH + 1] ;

HANDLE hFile ;

HDC hdc ;

int i,cxChar,cyChar ;

PAINTSTRUCT ps ;

TCHAR szBuffer[MAX_PATH + 1] ;

switch (message)

{

case WM_CREATE :

cxChar = LOWORD (GetDialogBaseUnits ()) ;

cyChar = HIWORD (GetDialogBaseUnits ()) ;

rect.left = 20 * cxChar ;

rect.top=3 * cyChar ;

hwndList = CreateWindow (TEXT ("listbox"),NULL,

WS_CHILDWINDOW | WS_ⅥSIBLE | LBS_STANDARD,

cxChar,cyChar * 3,

cxChar * 13 + GetSystemMetrics (SM_CXVSCROLL),

cyChar * 10,

hwnd,(HMENU) ID_LIST,

（HINSTANCE) GetWindowLong (hwnd,GWL_HINSTANCE),

NULL) ;

GetCurrentDirectory (MAX_PATH + 1,szBuffer) ;

hwndText = CreateWindow (TEXT ("static"),szBuffer,

WS_CHILDWINDOW | WS_ⅥSIBLE | SS_LEFT,

cxChar,cyChar,cxChar * MAX_PATH,cyChar,

hwnd,(HMENU) ID_TEXT,

（HINSTANCE) GetWindowLong (hwnd,GWL_HINSTANCE),

NULL) ;

OldList = (WNDPROC) SetWindowLong (hwndList,GWL_WNDPROC,

（LPARAM) ListProc) ;

SendMessage (hwndList,LB_DIR,DIRATTR,(LPARAM) TEXT ("*.*")) ;

return 0 ;

case WM_SIZE :

rect.right = LOWORD (lParam) ;

rect.bottom = HIWORD (lParam) ;

return 0 ;

case WM_SETFOCUS :

SetFocus (hwndList) ;

return 0 ;

case WM_COMMAND :

if (LOWORD (wParam) == ID_LIST && HIWORD (wParam) == LBN_DBLCLK)

{

if (LB_ERR == (i = SendMessage (hwndList,LB_GETCURSEL,0,0)))

break ;

SendMessage (hwndList,LB_GETTEXT,i,(LPARAM) szBuffer) ;

if (INVALID_HANDLE_VALUE != (hFile = CreateFile (szBuffer,

GENERIC_READ,FILE_SHARE_READ,NULL,

OPEN_EⅪSTING,0,NULL)))

{

CloseHandle (hFile) ;

bValidFile = TRUE ;

lstrcpy (szFile,szBuffer) ;

GetCurrentDirectory (MAX_PATH + 1,szBuffer) ;

if (szBuffer [lstrlen (szBuffer) - 1] != '\\')

lstrcat (szBuffer,TEXT ("\\")) ;

SetWindowText (hwndText,lstrcat (szBuffer,szFile)) ;

}

else

{

bValidFile = FALSE ;

szBuffer [lstrlen (szBuffer) - 1] = '\0' ;

// If setting the directory doesn't work,maybe it's

// a drive change,so try that.

if (!SetCurrentDirectory (szBuffer + 1））

{

szBuffer [3] = ':' ;

szBuffer [4] = '\0' ;

SetCurrentDirectory (szBuffer + 2） ;

}

// Get the new directory name and fill the list box.

GetCurrentDirectory (MAX_PATH + 1,szBuffer) ;

SetWindowText (hwndText,szBuffer) ;

SendMessage (hwndList,LB_RESETCONTENT,0,0) ;

SendMessage (hwndList,LB_DIR,DIRATTR,

（LPARAM) TEXT ("*.*")) ;

}

InvalidateRect (hwnd,NULL,TRUE) ;

}

return 0 ;

case WM_PAINT :

if (!bValidFile)

break ;

if (INVALID_HANDLE_VALUE == (hFile = CreateFile (szFile,

GENERIC_READ,FILE_SHARE_READ,NULL,OPEN_EⅪSTING,0,NULL)))

{

bValidFile = FALSE ;

break ;

}

ReadFile (hFile,buffer,MAXREAD,&i,NULL) ;

CloseHandle (hFile) ;

// i now equals the number of bytes in buffer.

// Commence getting a device context for displaying text.

hdc = BeginPaint (hwnd,&ps) ;

SelectObject (hdc,GetStockObject (SYSTEM_FⅨED_FONT)) ;

SetTextColor (hdc,GetSysColor (COLOR_BTNTEXT)) ;

SetBkColor (hdc,GetSysColor (COLOR_BTNFACE)) ;

// Assume the file is ASCⅡ

DrawTextA (hdc,buffer,i,&rect,DTFLAGS) ;

EndPaint (hwnd,&ps) ;

return 0 ;

case WM_DESTROY :

PostQuitMessage (0) ;

return 0 ;

}

return DefWindowProc (hwnd,message,wParam,lParam) ;

}

LRESULT CALLBACK ListProc (HWND hwnd,UINT message,

WPARAM wParam,LPARAM lParam)

{

if (message == WM_KEYDOWN && wParam == VK_RETURN)

SendMessage (GetParent (hwnd),WM_COMMAND,

MAKELONG （1,LBN_DBLCLK),(LPARAM) hwnd) ;

return CallWindowProc (OldList,hwnd,message,wParam,lParam) ;

}

在ENⅥRON中，當我們選擇一個環境變數時－無論是使用滑鼠還是鍵盤－程式都將顯示一個環境字串。但是，如果我們在HEAD中使用這種選擇顯示方法，那么程式回應會很慢，這是因為在清單方塊中移動選擇時，程式仍然要不斷地打開和關閉檔案。