windows程序设计读书笔记4——字符显示3

在之前的一章里我们使用InvalidateRect函数，生成窗口重绘消息进行重绘，但是并没有在处理滚动条消息时直接绘制，这样的代码效率并不高。

这里作者使用了UpdateWindow函数，直接进行窗口的重绘。同时使用新的滚动条函数 SetScrollInfo 和 GetScrollInfo。

这两个函数不仅包括上一篇中使用的四个函数，而且还增加了两个新功能：调整滑块大小、指定滑块位置。

int SetScrollInfo(
  __in  HWND hwnd,
  __in  int fnBar,
  __in  LPCSCROLLINFO lpsi,
  __in  BOOL fRedraw
);

BOOL GetScrollInfo(
  __in     HWND hwnd,
  __in     int fnBar,
  __inout  LPSCROLLINFO lpsi
);

第二个参数是指定类型的滚动条，可以是下面的值：

Value	Meaning
SB_CTL	Retrieves the parameters for a scroll bar control. The hwnd parameter must be the handle to the scroll bar control.
SB_HORZ	Retrieves the parameters for the window's standard horizontal scroll bar.
SB_VERT	Retrieves the parameters for the window's standard vertical scroll bar.

第三个参数是一个结构体

typedef struct tagSCROLLINFO {
  UINT cbSize;
  UINT fMask;
  int  nMin;
  int  nMax;
  UINT nPage;
  int  nPos;
  int  nTrackPos;
} SCROLLINFO, **LPCSCROLLINFO;

第四个参数是bool型，表示是否需要根据新的信息重绘滚动条。

下面是代码：

#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    =  ;
     wndclass.cbWndExtra    =  ;
     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  ;
     }

     hwnd = CreateWindow (szAppName, TEXT ("Get System Metrics No. 3"),
                          WS_OVERLAPPEDWINDOW | WS_VSCROLL | WS_HSCROLL,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          CW_USEDEFAULT, CW_USEDEFAULT,
                          NULL, NULL, hInstance, NULL) ;

     ShowWindow (hwnd, iCmdShow) ;
     UpdateWindow (hwnd) ;

     while (GetMessage (&msg, NULL, , ))
     {
          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[] ;
     TEXTMETRIC  tm ;

     switch (message)
     {
     case WM_CREATE:
          hdc = GetDC (hwnd) ;

          GetTextMetrics (hdc, &tm) ;
          cxChar = tm.tmAveCharWidth ;
          cxCaps = (tm.tmPitchAndFamily &  ?  : ) * cxChar /  ;
          cyChar = tm.tmHeight + tm.tmExternalLeading ;

          ReleaseDC (hwnd, hdc) ;

               // Save the width of the three columns

          iMaxWidth =  * cxChar +  * cxCaps ;
          return  ;

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

               // Set vertical scroll bar range and page size

          si.cbSize = sizeof (si) ;
          si.fMask  = SIF_RANGE | SIF_PAGE ;
          si.nMin   =  ;
          si.nMax   = NUMLINES -  ;
          si.nPage  = cyClient / cyChar ;
          SetScrollInfo (hwnd, SB_VERT, &si, TRUE) ;

               // Set horizontal scroll bar range and page size

          si.cbSize = sizeof (si) ;
          si.fMask  = SIF_RANGE | SIF_PAGE ;
          si.nMin   =  ;
          si.nMax   =  + iMaxWidth / cxChar ;
          si.nPage  = cxClient / cxChar ;
          SetScrollInfo (hwnd, SB_HORZ, &si, TRUE) ;
          return  ;

     case WM_VSCROLL:
               // Get all the vertial scroll bar information

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

          case SB_LINEDOWN:
               si.nPos +=  ;
               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 ;
          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)
          {
               ScrollWindow (hwnd, , cyChar * (iVertPos - si.nPos),
                                   NULL, NULL) ;
               UpdateWindow (hwnd) ;
          }
          return  ;

     case WM_HSCROLL:
               // Get all the vertial scroll bar information

          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 -=  ;
               break ;

          case SB_LINERIGHT:
               si.nPos +=  ;
               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), ,
                             NULL, NULL) ;
          }
          return  ;

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

               // Get vertical scroll bar position

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

               // Get horizontal scroll bar position

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

               // Find painting limits

          iPaintBeg = max (, iVertPos + ps.rcPaint.top / cyChar) ;
          iPaintEnd = min (NUMLINES - ,
                           iVertPos + ps.rcPaint.bottom / cyChar) ;

          for (i = iPaintBeg ; i <= iPaintEnd ; i++)
          {
               x = cxChar * ( - iHorzPos) ;
               y = cyChar * (i - iVertPos) ;

               TextOut (hdc, x, y,
                        sysmetrics[i].szLabel,
                        lstrlen (sysmetrics[i].szLabel)) ;

               TextOut (hdc, x +  * cxCaps, y,
                        sysmetrics[i].szDesc,
                        lstrlen (sysmetrics[i].szDesc)) ;

               SetTextAlign (hdc, TA_RIGHT | TA_TOP) ;

               TextOut (hdc, x +  * cxCaps +  * cxChar, y, szBuffer,
                        wsprintf (szBuffer, TEXT ("%5d"),
                             GetSystemMetrics (sysmetrics[i].iIndex))) ;

               SetTextAlign (hdc, TA_LEFT | TA_TOP) ;
          }

          EndPaint (hwnd, &ps) ;
          return  ;

     case WM_DESTROY :
          PostQuitMessage () ;
          return  ;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}