windows程序设计 例题解析 SYSMETS3

//头文件未给出

/*----------------------------------------------------
   SYSMETS3.C -- System Metrics Display Program No. 3
                 (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 ("SysMets3") ;
     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 ("Get System Metrics No. 3"),
                          WS_OVERLAPPEDWINDOW | WS_VSCROLL | WS_HSCROLL,//水平和垂直滚动条
                          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, cxClient, cyClient, iMaxWidth ;
     HDC         hdc ;
     int         i, x, y, iVertPos, iHorzPos, iPaintBeg, iPaintEnd ;
     PAINTSTRUCT ps ;
     SCROLLINFO  si ;
     TCHAR       szBuffer[10] ;
     TEXTMETRIC  tm ;
    
     switch (message)
     {
     case WM_CREATE:

//字体初始化和滚动条初始化
          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) ;

               // Save the width of the three columns
         
          iMaxWidth = 40 * cxChar + 22 * cxCaps ; //水平滚动的最大范围
          return 0 ;
         
     case WM_SIZE:

//获取客户区大小
          cxClient = LOWORD (lParam) ;
          cyClient = HIWORD (lParam) ;

// 设置垂直滚动条的范围和每页的大小

//注意要使用setscrollinfo和getscrollinfo函数，则必须在使用之前初始化SI结构体中cbsize和fmask成员

//同时还得初始化根据fmask指定的成员，

          si.cbSize = sizeof (si) ;                      //结构体大小
          si.fMask  = SIF_RANGE | SIF_PAGE ; //指定了要初始化滚动条范围和每页大小
          si.nMin   = 0 ;
          si.nMax   = NUMLINES - 1 ; //滚动条范围
          si.nPage  = cyClient / cyChar ;  /每页大小

//初始化后就可以使用这些函数了
          SetScrollInfo (hwnd, SB_VERT, &si, TRUE) ;

               // 水平滚动条范围和每页大小

          si.cbSize = sizeof (si) ;
          si.fMask  = SIF_RANGE | SIF_PAGE ;
          si.nMin   = 0 ;
          si.nMax   = 2 + iMaxWidth / cxChar ;
          si.nPage  = cxClient / cxChar ;
          SetScrollInfo (hwnd, SB_HORZ, &si, TRUE) ;
          return 0 ;
         
     case WM_VSCROLL:
               // Get all the vertial scroll bar information

          si.cbSize = sizeof (si) ;
          si.fMask  = SIF_ALL ;//获取结构体全部信息
          GetScrollInfo (hwnd, SB_VERT, &si) ;

               // Save the position for comparison later on

          iVertPos = si.nPos ;

          switch (LOWORD (wParam))
          {
          case SB_TOP:
               si.nPos = si.nMin ;
               break ;
              
          case SB_BOTTOM:
               si.nPos = si.nMax ;
               break ;
              
          case SB_LINEUP:
               si.nPos -= 1 ;
               break ;
              
          case SB_LINEDOWN:
               si.nPos += 1 ;
               break ;
              
          case SB_PAGEUP:
               si.nPos -= si.nPage ;
               break ;
              
          case SB_PAGEDOWN:
               si.nPos += si.nPage ;
               break ;
              
          case SB_THUMBTRACK:
               si.nPos = si.nTrackPos ;
               break ;
              
          default:
               break ;        
          }
               // Set the position and then retrieve it.  Due to adjustments
               //   by Windows it may not be the same as the value set.

          si.fMask = SIF_POS ;//这里没只指定结构体大小是因为在上面已经指定过了
          SetScrollInfo (hwnd, SB_VERT, &si, TRUE) ;
          GetScrollInfo (hwnd, SB_VERT, &si) ;

               // If the position has changed, scroll the window and update it

          if (si.nPos != iVertPos)  //判断滚动条的位置
          {                   
               ScrollWindow (hwnd, 0, cyChar * (iVertPos - si.nPos),
                                   NULL, NULL) ;//使得文本在垂直方向滚动

               UpdateWindow (hwnd) ;//立即更新，产生WM_PAINT消息（不进入队列）
          }
          return 0 ;
         
     case WM_HSCROLL:
               //水平滚动条相关信息，和垂直滚动条类似

          si.cbSize = sizeof (si) ;
          si.fMask  = SIF_ALL ;

               // Save the position for comparison later on

          GetScrollInfo (hwnd, SB_HORZ, &si) ;
          iHorzPos = si.nPos ;

          switch (LOWORD (wParam))
          {
          case SB_LINELEFT:
               si.nPos -= 1 ;
               break ;
              
          case SB_LINERIGHT:
               si.nPos += 1 ;
               break ;
              
          case SB_PAGELEFT:
               si.nPos -= si.nPage ;
               break ;
              
          case SB_PAGERIGHT:
               si.nPos += si.nPage ;
               break ;
              
          case SB_THUMBPOSITION:
               si.nPos = si.nTrackPos ;
               break ;
              
          default :
               break ;
          }
               // Set the position and then retrieve it.  Due to adjustments
               //   by Windows it may not be the same as the value set.

          si.fMask = SIF_POS ;
          SetScrollInfo (hwnd, SB_HORZ, &si, TRUE) ;
          GetScrollInfo (hwnd, SB_HORZ, &si) ;
         
               // If the position has changed, scroll the window

          if (si.nPos != iHorzPos)
          {
               ScrollWindow (hwnd, cxChar * (iHorzPos - si.nPos), 0,
                             NULL, NULL) ;
          }
          return 0 ;

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

               // 获取垂直滚动条位置

          si.cbSize = sizeof (si) ;
          si.fMask  = SIF_POS ;
          GetScrollInfo (hwnd, SB_VERT, &si) ;
          iVertPos = si.nPos ;

               // 获取水平滚动条位置

          GetScrollInfo (hwnd, SB_HORZ, &si) ;
          iHorzPos = si.nPos ;

               // 这句话不怎么好理解，体味流程就可以了，不要纠结细节，知道改变了水平或垂直滚动条位置，文本会跟着滚动就可以了

          iPaintBeg = max (0, iVertPos + ps.rcPaint.top / cyChar) ;
          iPaintEnd = min (NUMLINES - 1,
                           iVertPos + ps.rcPaint.bottom / cyChar) ;
         
          for (i = iPaintBeg ; i <= iPaintEnd ; i++)
          {
               x = cxChar * (1 - iHorzPos) ;
               y = cyChar * (i - iVertPos) ;
              
               TextOut (hdc, x, y,
                        sysmetrics[i].szLabel,
                        lstrlen (sysmetrics[i].szLabel)) ;
              
               TextOut (hdc, x + 22 * cxCaps, y,
                        sysmetrics[i].szDesc,
                        lstrlen (sysmetrics[i].szDesc)) ;
              
               SetTextAlign (hdc, TA_RIGHT | TA_TOP) ;
              
               TextOut (hdc, x + 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) ;
}