滚动条二

//此程序不知道什么问题横滚动条没有实现
#include<windows.h>
#include"framework.h"

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT("SysMets3");
    MSG msg;
    HWND hwnd;
    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("This program requires Windows NT!"), szAppName, MB_ICONERROR);
        return 0;
    }

    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, 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, cyClient, cxClient, iMaxWidth;
    HDC hdc;
    PAINTSTRUCT ps;
    TEXTMETRIC tm;
    SCROLLINFO si;
    int i, y, x, iVertPos, iHorzPos, iPaintBeg, iPaintEnd;
    TCHAR szBuffer[10];

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

        GetTextMetrics(hdc, &tm);
        cxChar = tm.tmAveCharWidth;
        cyChar = tm.tmHeight + tm.tmExternalLeading;
        cxCaps = (tm.tmPitchAndFamily & 1 ? 3 : 2) * cxChar / 2;

        ReleaseDC(hwnd, hdc);
        iMaxWidth = 40 * cxChar + 22 * cxCaps;
        return 0;
    case WM_SIZE:
        cyClient = HIWORD(lParam);
        cxClient = LOWORD(lParam);

        si.cbSize = sizeof(si);
        si.fMask = SIF_RANGE | SIF_PAGE;
        si.nPage = cyClient / cyChar;
        si.nMin = 0;
        si.nMax = NUMLINES - 1;

        SetScrollInfo(hwnd, SB_VERT, &si, TRUE);

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

        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;
        }

        si.fMask = SIF_POS;
        SetScrollInfo(hwnd, SB_VERT, &si, TRUE);
        GetScrollInfo(hwnd, SB_VERT, &si);

        if (iVertPos != si.nPos)
        {
            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;
        }
        si.fMask = SIF_POS;
        SetScrollInfo(hwnd, SB_HORZ, &si, TRUE);
        GetScrollInfo(hwnd, SB_HORZ, &si);

        if (iHorzPos != si.nPos)
        {
            ScrollWindow(hwnd, cxChar * (iHorzPos - si.nPos), 0, NULL, NULL);
    
        }
        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 + ps.rcPaint.top / cyChar);
        iPaintEnd = min(NUMLINES - 1, iVertPos + ps.rcPaint.bottom / cyChar);
        for (i = iPaintBeg; i <= iPaintEnd; i++)
        {
            y = cyChar * (i - iVertPos);
            x = cxChar * (1 - iHorzPos);

            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].Index)));
            SetTextAlign(hdc, TA_LEFT | TA_TOP);
        }
        EndPaint(hwnd, &ps);
        return 0;
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }

    return DefWindowProc(hwnd, message, wParam, lParam);
}