滚动条处理的经典实例

来自于windows程序设计， 且看代码：

/*-----------------------------------------------
   SYSMETS.H -- System metrics display structure
  -----------------------------------------------*/


#define NUMLINES ((int) (sizeof sysmetrics / sizeof sysmetrics [0]))

struct
{
     int iIndex ;
     TCHAR * szLabel ;
     TCHAR * szDesc ;
}
sysmetrics [] =
{
     SM_CXSCREEN, TEXT ("SM_CXSCREEN"),
                              TEXT ("Screen width in pixels"),
     SM_CYSCREEN, TEXT ("SM_CYSCREEN"),
                              TEXT ("Screen height in pixels"),
     SM_CXVSCROLL, TEXT ("SM_CXVSCROLL"),
                              TEXT ("Vertical scroll width"),
     SM_CYHSCROLL, TEXT ("SM_CYHSCROLL"),
                              TEXT ("Horizontal scroll height"),
     SM_CYCAPTION, TEXT ("SM_CYCAPTION"),
                              TEXT ("Caption bar height"),
     SM_CXBORDER, TEXT ("SM_CXBORDER"),
                              TEXT ("Window border width"),
     SM_CYBORDER, TEXT ("SM_CYBORDER"),
                              TEXT ("Window border height"),
     SM_CXFIXEDFRAME, TEXT ("SM_CXFIXEDFRAME"),
                              TEXT ("Dialog window frame width"),
     SM_CYFIXEDFRAME, TEXT ("SM_CYFIXEDFRAME"),
                              TEXT ("Dialog window frame height"),
     SM_CYVTHUMB, TEXT ("SM_CYVTHUMB"),
                              TEXT ("Vertical scroll thumb height"),
     SM_CXHTHUMB, TEXT ("SM_CXHTHUMB"),
                              TEXT ("Horizontal scroll thumb width"),
     SM_CXICON, TEXT ("SM_CXICON"),
                              TEXT ("Icon width"),
     SM_CYICON, TEXT ("SM_CYICON"),
                              TEXT ("Icon height"),
     SM_CXCURSOR, TEXT ("SM_CXCURSOR"),
                              TEXT ("Cursor width"),
     SM_CYCURSOR, TEXT ("SM_CYCURSOR"),
                              TEXT ("Cursor height"),
     SM_CYMENU, TEXT ("SM_CYMENU"),
                              TEXT ("Menu bar height"),
     SM_CXFULLSCREEN, TEXT ("SM_CXFULLSCREEN"),
                              TEXT ("Full screen client area width"),
     SM_CYFULLSCREEN, TEXT ("SM_CYFULLSCREEN"),
                              TEXT ("Full screen client area height"),
     SM_CYKANJIWINDOW, TEXT ("SM_CYKANJIWINDOW"),
                              TEXT ("Kanji window height"),
     SM_MOUSEPRESENT, TEXT ("SM_MOUSEPRESENT"),
                              TEXT ("Mouse present flag"),
     SM_CYVSCROLL, TEXT ("SM_CYVSCROLL"),
                              TEXT ("Vertical scroll arrow height"),
     SM_CXHSCROLL, TEXT ("SM_CXHSCROLL"),
                              TEXT ("Horizontal scroll arrow width"),
     SM_DEBUG, TEXT ("SM_DEBUG"),
                              TEXT ("Debug version flag"),
     SM_SWAPBUTTON, TEXT ("SM_SWAPBUTTON"),
                              TEXT ("Mouse buttons swapped flag"),
     SM_CXMIN, TEXT ("SM_CXMIN"),
                              TEXT ("Minimum window width"),
     SM_CYMIN, TEXT ("SM_CYMIN"),
                              TEXT ("Minimum window height"),
     SM_CXSIZE, TEXT ("SM_CXSIZE"),
                              TEXT ("Min/Max/Close button width"),
     SM_CYSIZE, TEXT ("SM_CYSIZE"),
                              TEXT ("Min/Max/Close button height"),
     SM_CXSIZEFRAME, TEXT ("SM_CXSIZEFRAME"),
                              TEXT ("Window sizing frame width"),
     SM_CYSIZEFRAME, TEXT ("SM_CYSIZEFRAME"),
                              TEXT ("Window sizing frame height"),
     SM_CXMINTRACK, TEXT ("SM_CXMINTRACK"),
                              TEXT ("Minimum window tracking width"),
     SM_CYMINTRACK, TEXT ("SM_CYMINTRACK"),
                              TEXT ("Minimum window tracking height"),
     SM_CXDOUBLECLK, TEXT ("SM_CXDOUBLECLK"),
                              TEXT ("Double click x tolerance"),
     SM_CYDOUBLECLK, TEXT ("SM_CYDOUBLECLK"),
                              TEXT ("Double click y tolerance"),
     SM_CXICONSPACING, TEXT ("SM_CXICONSPACING"),
                              TEXT ("Horizontal icon spacing"),
     SM_CYICONSPACING, TEXT ("SM_CYICONSPACING"),
                              TEXT ("Vertical icon spacing"),
     SM_MENUDROPALIGNMENT, TEXT ("SM_MENUDROPALIGNMENT"),
                              TEXT ("Left or right menu drop"),
     SM_PENWINDOWS, TEXT ("SM_PENWINDOWS"),
                              TEXT ("Pen extensions installed"),
     SM_DBCSENABLED, TEXT ("SM_DBCSENABLED"),
                              TEXT ("Double-Byte Char Set enabled"),
     SM_CMOUSEBUTTONS, TEXT ("SM_CMOUSEBUTTONS"),
                              TEXT ("Number of mouse buttons"),
     SM_SECURE, TEXT ("SM_SECURE"),
                              TEXT ("Security present flag"),
     SM_CXEDGE, TEXT ("SM_CXEDGE"),
                              TEXT ("3-D border width"),
     SM_CYEDGE, TEXT ("SM_CYEDGE"),
                              TEXT ("3-D border height"),
     SM_CXMINSPACING, TEXT ("SM_CXMINSPACING"),
                              TEXT ("Minimized window spacing width"),
     SM_CYMINSPACING, TEXT ("SM_CYMINSPACING"),
                              TEXT ("Minimized window spacing height"),
     SM_CXSMICON, TEXT ("SM_CXSMICON"),
                              TEXT ("Small icon width"),
     SM_CYSMICON, TEXT ("SM_CYSMICON"),
                              TEXT ("Small icon height"),
     SM_CYSMCAPTION, TEXT ("SM_CYSMCAPTION"),
                              TEXT ("Small caption height"),
     SM_CXSMSIZE, TEXT ("SM_CXSMSIZE"),
                              TEXT ("Small caption button width"),
     SM_CYSMSIZE, TEXT ("SM_CYSMSIZE"),
                              TEXT ("Small caption button height"),
     SM_CXMENUSIZE, TEXT ("SM_CXMENUSIZE"),
                              TEXT ("Menu bar button width"),
     SM_CYMENUSIZE, TEXT ("SM_CYMENUSIZE"),
                              TEXT ("Menu bar button height"),
     SM_ARRANGE, TEXT ("SM_ARRANGE"),
                              TEXT ("How minimized windows arranged"),
     SM_CXMINIMIZED, TEXT ("SM_CXMINIMIZED"),
                              TEXT ("Minimized window width"),
     SM_CYMINIMIZED, TEXT ("SM_CYMINIMIZED"),
                              TEXT ("Minimized window height"),
     SM_CXMAXTRACK, TEXT ("SM_CXMAXTRACK"),
                              TEXT ("Maximum dragable width"),
     SM_CYMAXTRACK, TEXT ("SM_CYMAXTRACK"),
                              TEXT ("Maximum dragable height"),
     SM_CXMAXIMIZED, TEXT ("SM_CXMAXIMIZED"),
                              TEXT ("Width of maximized window"),
     SM_CYMAXIMIZED, TEXT ("SM_CYMAXIMIZED"),
                              TEXT ("Height of maximized window"),
     SM_NETWORK, TEXT ("SM_NETWORK"),
                              TEXT ("Network present flag"),
     SM_CLEANBOOT, TEXT ("SM_CLEANBOOT"),
                              TEXT ("How system was booted"),
     SM_CXDRAG, TEXT ("SM_CXDRAG"),
                              TEXT ("Avoid drag x tolerance"),
     SM_CYDRAG, TEXT ("SM_CYDRAG"),
                              TEXT ("Avoid drag y tolerance"),
     SM_SHOWSOUNDS, TEXT ("SM_SHOWSOUNDS"),
                              TEXT ("Present sounds visually"),
     SM_CXMENUCHECK, TEXT ("SM_CXMENUCHECK"),
                              TEXT ("Menu check-mark width"),
     SM_CYMENUCHECK, TEXT ("SM_CYMENUCHECK"),
                              TEXT ("Menu check-mark height"),
     SM_SLOWMACHINE, TEXT ("SM_SLOWMACHINE"),
                              TEXT ("Slow processor flag"),
     SM_MIDEASTENABLED, TEXT ("SM_MIDEASTENABLED"),
                              TEXT ("Hebrew and Arabic enabled flag"),
     SM_MOUSEWHEELPRESENT, TEXT ("SM_MOUSEWHEELPRESENT"),
                              TEXT ("Mouse wheel present flag"),
     SM_XVIRTUALSCREEN, TEXT ("SM_XVIRTUALSCREEN"),
                              TEXT ("Virtual screen x origin"),
     SM_YVIRTUALSCREEN, TEXT ("SM_YVIRTUALSCREEN"),
                              TEXT ("Virtual screen y origin"),
     SM_CXVIRTUALSCREEN, TEXT ("SM_CXVIRTUALSCREEN"),
                              TEXT ("Virtual screen width"),
     SM_CYVIRTUALSCREEN, TEXT ("SM_CYVIRTUALSCREEN"),
                              TEXT ("Virtual screen height"),
     SM_CMONITORS, TEXT ("SM_CMONITORS"),
                              TEXT ("Number of monitors"),
     SM_SAMEDISPLAYFORMAT, TEXT ("SM_SAMEDISPLAYFORMAT"),
                              TEXT ("Same color format flag")
} ;


mets.c

#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("Sysmets4");
  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"),
         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, 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:
    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 columes

    iMaxWidth = 40 * cxChar + 22 * cxCaps;
    return 0;

  case WM_SIZE:
    cxClient = LOWORD(lParam);
    cyClient = HIWORD(lParam);
    // set the vertical scroll bar range and page size

    si.cbSize = sizeof(si);
    si.fMask = SIF_RANGE | SIF_PAGE;
    si.nMin = 0;
    si.nMax = NUMLINES - 1;
    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 = 0;
    si.nMax = 2 + iMaxWidth / cxChar;
    si.nPage = cxClient / cxChar;
    SetScrollInfo(hwnd, SB_HORZ, &si, TRUE);
    return 0;

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

    si.cbSize = sizeof(si);
    si.fMask = SIF_ALL;
    GetScrollInfo(hwnd, SB_VERT, &si);
    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;
    }

    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, 0, cyChar * (iVertPos - si.nPos),
         NULL, NULL);
      UpdateWindow(hwnd);
    }
    return 0;

  case WM_HSCROLL:
    si.cbSize = sizeof(si);
    si.fMask = SIF_ALL;
    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;
    deafult:
      break;
    }

    si.fMask = SIF_POS;
    SetScrollInfo(hwnd, SB_HORZ, &si, TRUE);
    GetScrollInfo(hwnd, SB_HORZ, &si);
    if(si.nPos != iHorzPos) {
      ScrollWindow(hwnd, cxChar * (iHorzPos - si.nPos),
         0, NULL, NULL);
    }
    return 0;

  case WM_KEYDOWN:
    switch(wParam) {
    case VK_HOME:
      SendMessage(hwnd, WM_VSCROLL, SB_TOP, 0);
      break;
    case VK_END:
      SendMessage(hwnd, WM_VSCROLL, SB_BOTTOM, 0);
      break;
    case VK_PRIOR:
      SendMessage(hwnd, WM_VSCROLL, SB_PAGEUP, 0);
      break;
    case VK_NEXT:
      SendMessage(hwnd, WM_VSCROLL, SB_PAGEDOWN, 0);
      break;
    case VK_UP:
      SendMessage(hwnd, WM_VSCROLL, SB_LINEUP, 0);
      break;
    case VK_DOWN:
      SendMessage(hwnd, WM_VSCROLL, SB_LINEDOWN, 0);
      break;
    case VK_LEFT:
      SendMessage(hwnd, WM_HSCROLL, SB_PAGEUP, 0);
      break;
    case VK_RIGHT:
      SendMessage(hwnd, WM_HSCROLL, SB_PAGEDOWN, 0);
      break;
    }
    return 0;

  case WM_PAINT:
    hdc = BeginPaint(hwnd, &ps);
    si.cbSize = sizeof(si);
    si.fMask = SIF_POS;
    GetScrollInfo(hwnd, SB_VERT, &si);
    iVertPos = si.nPos;

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

    iPaintBeg = max(0, iVertPos);
    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);
}