对话框滚动条

// 初始化

BOOL SD_OnInitDialog(HWND hwnd, HWND /*hwndFocus*/, LPARAM /*lParam*/){    RECT rc = {};    GetClientRect(hwnd, &rc);    const SIZE sz = { rc.right - rc.left, rc.bottom - rc.top };    SCROLLINFO si = {};    si.cbSize = sizeof(SCROLLINFO);    si.fMask = SIF_PAGE | SIF_POS | SIF_RANGE;    si.nPos = si.nMin = 1;    si.nMax = sz.cx;    si.nPage = sz.cx;    SetScrollInfo(hwnd, SB_HORZ, &si, FALSE);    si.nMax = sz.cy;    si.nPage = sz.cy;    SetScrollInfo(hwnd, SB_VERT, &si, FALSE);   return FALSE;}

// handle WM_SIZE

void SD_OnSize(HWND hwnd, UINT state, int cx, int cy){    if(state != SIZE_RESTORED && state != SIZE_MAXIMIZED)        return;    SCROLLINFO si = {};    si.cbSize = sizeof(SCROLLINFO);    const int bar[] = { SB_HORZ, SB_VERT };    const int page[] = { cx, cy };    for(size_t i = 0; i < ARRAYSIZE(bar); ++i)    {        si.fMask = SIF_PAGE;        si.nPage = page[i];        SetScrollInfo(hwnd, bar[i], &si, TRUE);        si.fMask = SIF_RANGE | SIF_POS;        GetScrollInfo(hwnd, bar[i], &si);        const int maxScrollPos = si.nMax - (page[i] - 1);        // Scroll client only if scroll bar is visible and window's        // content is fully scrolled toward right and/or bottom side.        // Also, update window's content on maximize.        const bool needToScroll =            (si.nPos != si.nMin && si.nPos == maxScrollPos) ||            (state == SIZE_MAXIMIZED);        if(needToScroll)        {            SD_ScrollClient(hwnd, bar[i], si.nPos);        }    }}

void SD_OnHScroll(HWND hwnd, HWND /*hwndCtl*/, UINT code, int /*pos*/){    SD_OnHVScroll(hwnd, SB_HORZ, code);}void SD_OnVScroll(HWND hwnd, HWND /*hwndCtl*/, UINT code, int /*pos*/){    SD_OnHVScroll(hwnd, SB_VERT, code);}void SD_OnHVScroll(HWND hwnd, int bar, UINT code){    const int scrollPos = SD_GetScrollPos(hwnd, bar, code);    if(scrollPos == -1)        return;    SetScrollPos(hwnd, bar, scrollPos, TRUE);    SD_ScrollClient(hwnd, bar, scrollPos);}void SD_ScrollClient(HWND hwnd, int bar, int pos){    static int s_prevx = 1;    static int s_prevy = 1;    int cx = 0;    int cy = 0;    int& delta = (bar == SB_HORZ ? cx : cy);    int& prev = (bar == SB_HORZ ? s_prevx : s_prevy);    delta = prev - pos;    prev = pos;    if(cx || cy)    {        ScrollWindow(hwnd, cx, cy, NULL, NULL);    }}int SD_GetScrollPos(HWND hwnd, int bar, UINT code){    SCROLLINFO si = {};    si.cbSize = sizeof(SCROLLINFO);    si.fMask = SIF_PAGE | SIF_POS | SIF_RANGE | SIF_TRACKPOS;    GetScrollInfo(hwnd, bar, &si);    const int minPos = si.nMin;    const int maxPos = si.nMax - (si.nPage - 1);    int result = -1;    switch(code)    {    case SB_LINEUP /*SB_LINELEFT*/:        result = max(si.nPos - 1, minPos);        break;    case SB_LINEDOWN /*SB_LINERIGHT*/:        result = min(si.nPos + 1, maxPos);        break;    case SB_PAGEUP /*SB_PAGELEFT*/:        result = max(si.nPos - (int)si.nPage, minPos);        break;    case SB_PAGEDOWN /*SB_PAGERIGHT*/:        result = min(si.nPos + (int)si.nPage, maxPos);        break;    case SB_THUMBPOSITION:        // do nothing        break;    case SB_THUMBTRACK:        result = si.nTrackPos;        break;    case SB_TOP /*SB_LEFT*/:        result = minPos;        break;    case SB_BOTTOM /*SB_RIGHT*/:        result = maxPos;        break;    case SB_ENDSCROLL:        // do nothing        break;    }    return result;}

成员说明：
cbSize: SCROLLINFO结构长度字节数，该值在设置和查询参数时都必须填写。
fMask: 指定结构中的哪些成员是有效，该值共有如下5种选择，可以选择多种用“OR”组合起来，该值在

设置和查询参数时都必须填写。
SIF_ALL　　　　　　:整个结构都有效
SIF_DISABLENOSCROLL:该值仅在设定参数时使用，视控件参数设定的需要来对本结构的成员进行取舍。
SIF_PAGE　　　　　 :nPage成员有效
SIF_POS　　　　　　:nPos成员有效
SIF_RANGE　　　　　:nMin和nMax成员有效
nMin:滚动范围最小值
nMax:滚动范围最大值
nPage:页尺寸，用来确定比例滚动框的大小
nPos:滚动框的位置
nTrackPos:拖动时滚动框的位置，该参数只能查询，不能设置。