windows程序设计第四章 system2.c 新增滚动条功能

新添加的滚动条功能，首先就是要在createWindow的时候，修改参数风格模式

     hwnd = CreateWindow (szAppName, TEXT ("Get System Metrics No. 2"),
                          WS_OVERLAPPEDWINDOW | WS_VSCROLL,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          NULL, NULL, hInstance, NULL) ;

然后再winproc，窗口过程 中的WM_CREATE消息中设定滚动条的初始位置：

 SetScrollRange (hwnd, SB_VERT, 0, NUMLINES - 1,FALSE) ;
 SetScrollPos   (hwnd, SB_VERT, iVscrollPos, TRUE) ;

添加WM_SIZE消息，获取客户区大小

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

添加相应动作的 消息：

     case WM_VSCROLL:
          switch (LOWORD (wParam))
          {
          case SB_LINEUP:
               iVscrollPos -= 1 ;
               break ;
     
          case SB_LINEDOWN:
               iVscrollPos += 1 ;
               break ;
     
          case SB_PAGEUP:
               iVscrollPos -= cyClient / cyChar ;
               break ;
     
          case SB_PAGEDOWN:
               iVscrollPos += cyClient / cyChar ;
               break ;
     
          case SB_THUMBPOSITION:
               iVscrollPos = HIWORD (wParam) ;
               break ;
     
          default :
               break ;
          }

          iVscrollPos = max (0, min (iVscrollPos, NUMLINES - 1)) ;

          if (iVscrollPos != GetScrollPos (hwnd, SB_VERT))
          {
               SetScrollPos (hwnd, SB_VERT, iVscrollPos, TRUE) ;
               InvalidateRect (hwnd, NULL, TRUE) ;
          }
          return 0 ;

完整源代码：system2.c

/*----------------------------------------------------
   SYSMETS2.C -- System Metrics Display Program No. 2
                 (c) Charles Petzold, 1998
  ----------------------------------------------------*/

#define WINVER 0x0500
#include <windows.h>
#include "sysmets.h"
 
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     static TCHAR szAppName[] = TEXT ("SysMets2") ;
     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 ("Get System Metrics No. 2"),
                          WS_OVERLAPPEDWINDOW | WS_VSCROLL,
                          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, cyClient, iVscrollPos ;
     HDC         hdc ;
     int         i, y ;
     PAINTSTRUCT ps ;
     TCHAR       szBuffer[10] ;
     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) ;

          SetScrollRange (hwnd, SB_VERT, 0, NUMLINES - 1, FALSE) ;
          SetScrollPos   (hwnd, SB_VERT, iVscrollPos, TRUE) ;
          return 0 ;

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

     case WM_VSCROLL:
          switch (LOWORD (wParam))
          {
          case SB_LINEUP:
               iVscrollPos -= 1 ;
               break ;
     
          case SB_LINEDOWN:
               iVscrollPos += 1 ;
               break ;
     
          case SB_PAGEUP:
               iVscrollPos -= cyClient / cyChar ;
               break ;
     
          case SB_PAGEDOWN:
               iVscrollPos += cyClient / cyChar ;
               break ;
     
          case SB_THUMBPOSITION:
               iVscrollPos = HIWORD (wParam) ;
               break ;
     
          default :
               break ;
          }

          iVscrollPos = max (0, min (iVscrollPos, NUMLINES - 1)) ;

          if (iVscrollPos != GetScrollPos (hwnd, SB_VERT))
          {
               SetScrollPos (hwnd, SB_VERT, iVscrollPos, TRUE) ;
               InvalidateRect (hwnd, NULL, TRUE) ;
          }
          return 0 ;

     case WM_PAINT:
          hdc = BeginPaint (hwnd, &ps) ;
     
          for (i = 0 ; i < NUMLINES ; i++)
          {
               y = cyChar * (i - iVscrollPos) ;
     
               TextOut (hdc, 0, y,
                        sysmetrics[i].szLabel,
                        lstrlen (sysmetrics[i].szLabel)) ;
     
               TextOut (hdc, 22 * cxCaps, y,
                        sysmetrics[i].szDesc,
                        lstrlen (sysmetrics[i].szDesc)) ;
     
               SetTextAlign (hdc, TA_RIGHT | TA_TOP) ;
     
               TextOut (hdc, 22 * cxCaps + 40 * cxChar, y, szBuffer,
                        wsprintf (szBuffer, TEXT ("%5d"),
                             GetSystemMetrics (sysmetrics[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) ;
}

运行结果：