Windows API学习之滚动条系列函数

技术2026-04-18 0

作者：朱金灿来源：http://blog.csdn.net/clever101

Windows API中滚动条相关函数有两个：int SetScrollInfo( HWND hwnd, int fnBar, LPSCROLLINFO lpsi, BOOL fRedraw );

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

见名知意，SetScrollInfo就是用来设置窗口的滚动信息，GetScrollInfo就是用来获取窗口的滚动信息。SetScrollInfo的参数含义如下：参数意义hwnd滚动条控件的句柄或带有标准滚动栏的窗口的句柄fnBar用于指定哪一种滚动条，只能是下面的值之一：SB_CTL ：滚动条控件SB_HORZ：水平滚动条SB_VERT：垂直滚动条lpsi滚动条信息结构体指针。下面作进一步详细介绍。fRedraw 值为TRUE表示要Windows重新绘制计算了新信息后的滚动条，FALSE表示不绘制。

GetScrollInfo的参数含义如下：

参数意义hwnd滚动条控件的句柄或带有标准滚动栏的窗口的句柄fnBar用于指定哪一种滚动条，只能是下面的值之一：SB_CTL ：滚动条控件SB_HORZ：水平滚动条SB_VERT：垂直滚动条lpsi滚动条信息结构体指针。下面作进一步详细介绍。

值得注意的是在调用GetScrollInfo函数时要获取相关滚动信息，需要指定SCROLLINFO结构体中的fMask成员的值。fMask取下面的值的组合值：值意义SIF_PAGE 获取SCROLLINFO中的nPage成员的值（即一页的大小）。SIF_POS 获取SCROLLINFO中的nPos成员的值。SIF_RANGE获取SCROLLINFO中的nPos成员的nMin 和 nMax的值。SIF_TRACKPOS获取SCROLLINFO中的nTrackPos成员的值。nTrackPosSIF_RANGE、SIF_POS、SIF_PAGE和SIF_TRACKPOS的组合。

使用例程（据petzod的《windows程序设计》第四章，仅列出主要代码片段，具体请下载源码）：

view plain copy to clipboard print ? case WM_SIZE: { // save the width and height of window when changed the size of window cxClient = LOWORD(lp); // the width cyClient = HIWORD(lp); // the height // set vertical scroll bar range and page size si.cbSize = sizeof(SCROLLBARINFO); 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 and page size si.cbSize = sizeof(SCROLLBARINFO); si.fMask = SIF_RANGE|SIF_PAGE; si.nMin = 0; si.nMax = 2 + nMaxWidth/cxChar; si.nPage = cxClient/cxChar; SetScrollInfo(hWnd,SB_HORZ,&si,TRUE); return 0; } case WM_VSCROLL: { // get all vertical scroll bar information si.cbSize = sizeof(SCROLLINFO); si.fMask = SIF_ALL; ::GetScrollInfo(hWnd,SB_VERT,&si); // save the position for comparison later on nVertPos = si.nPos; switch (LOWORD(wp)) { case SB_LINEUP: { si.nPos -=1;// the height decrease 1 unit break; } case SB_LINEDOWN: { si.nPos +=1;// the height increase 1 unit break; } case SB_PAGEUP: { // back to prev page, the cyClient/cyChar is the number of row in one page si.nPos -= cyClient/cyChar; break; } case SB_PAGEDOWN: { // back to next page si.nPos += cyClient/cyChar; break; } case SB_THUMBPOSITION: { si.nPos = HIWORD(wp); 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 update it if (si.nPos!=nVertPos) { ::ScrollWindow(hWnd,0,cyChar*(nVertPos-si.nPos),NULL,NULL); ::UpdateWindow(hWnd); } return 0; } case WM_HSCROLL: { // get all the vertical scroll bar information si.cbSize = sizeof(si); si.fMask = SIF_ALL; // save the position for comparison later on ::GetScrollInfo(hWnd,SB_HORZ,&si); nHorzPos = si.nPos; switch (LOWORD(wp)) { 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 postion has changed ,scroll the window if (si.nPos!=nHorzPos) { ::ScrollWindow(hWnd,cxChar*(nHorzPos-si.nPos),0,NULL,NULL); } return 0; } 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); nVertPos = si.nPos; // get horizontal scroll bar position GetScrollInfo(hWnd,SB_HORZ,&si); nHorzPos = si.nPos; // find painting limits int nPaintBeg = max(0,nVertPos+ps.rcPaint.top/cyChar); // the begin row int nPaintEnd = min(NUMLINES-1,nVertPos+ps.rcPaint.bottom/cyChar); // the end row for (int i =nPaintBeg;i<=nPaintEnd;i++) { // calculate the y position of draw region, when y position less 0,skip int x = cxChar*(1-nHorzPos); int y = cyChar*(i-nVertPos); ::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,_T("%5d"),::GetSystemMetrics(sysmetrics[i].Index))); ::SetTextAlign(hdc,TA_LEFT|TA_TOP); } ::EndPaint(hWnd,&ps); return 0; }