学习windows编程 day3 之滚动条完善

#include <windows.h>
#include "Sysmet.h"
#include <strsafe.h>


LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)
{
    //声明全局数据：类名
    static TCHAR szClassName[] = TEXT("MyWindows");
    HWND hwnd;
    MSG msg;

    //注册窗口类
    WNDCLASS wndclass;

    wndclass.hInstance = hInstance;
    wndclass.lpszClassName = szClassName;
    wndclass.cbClsExtra = 0;
    wndclass.cbWndExtra = 0;
    wndclass.lpfnWndProc = WndProc;
    wndclass.lpszMenuName = NULL;
    wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wndclass.style = CS_HREDRAW;

    if (!RegisterClass(&wndclass))
    {
        MessageBox(NULL, TEXT("this program must run in Windows NT!"), szClassName, MB_ICONERROR);
        return 0;
    }

    hwnd = CreateWindow(
        szClassName,
        TEXT("MyFirstPractice"),
        WS_OVERLAPPEDWINDOW|WS_VSCROLL,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        NULL,
        NULL,
        hInstance,
        NULL
        );

    ShowWindow(hwnd, nShowCmd);
    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)
{
    HDC hdc;
    PAINTSTRUCT ps;
    RECT rect;
    //获取字体大小，初始化数据
    static int cxChar, cyChar, cxCaps;
    //获取每次重绘窗口后的大小尺寸
    static int cxClient, cyClient;
    //获取总行数和当前行数
    static numCount, curCount;

    static int y;
    int FirstLine, LastLine;

    TEXTMETRIC tm;
    TCHAR szBuffer[100];
    size_t st;
    SCROLLINFO si;

    switch (message)
    {
    case WM_CREATE:
        hdc = GetDC(hwnd);
        //获取字体大小，初始化数据
        GetTextMetrics(hdc, &tm);
        cxChar = tm.tmAveCharWidth;
        cyChar = tm.tmHeight + tm.tmExternalLeading;
        cxCaps = (tm.tmPitchAndFamily & 1 ? 3 : 2)*cxChar / 2;

        //初始化总行数和当前行数
        numCount = NUMLINES;
        curCount = 0;

        //初始化滚动条位置
        SetScrollRange(hwnd, SB_VERT, 0, numCount, FALSE);
        SetScrollPos(hwnd, SB_VERT, 0, TRUE);

        ReleaseDC(hwnd, &hdc);

        break;
    case WM_SIZE:
        //获取每次重绘后的屏幕大小
        cxClient = LOWORD(lParam);    //这是获取当前窗口的大小
        cyClient = HIWORD(lParam);

        //设置垂直滚动条的范围和页面大小
        si.cbSize = sizeof(si);    //为了更好的兼容版本
        si.fMask = SIF_RANGE | SIF_PAGE;
        si.nMin = 0;
        si.nMax = numCount - 1;
        si.nPage = cyClient / cyChar;    //页面的大小设置

        SetScrollInfo(hwnd, SB_VERT, &si, TRUE);
        break;
    case WM_VSCROLL:
        //获得垂直滚动条的信息
        si.cbSize = sizeof(si);
        si.fMask = SIF_ALL;
        GetScrollInfo(hwnd, SB_VERT, &si);

        //保存当前滑块的位置
        curCount = si.nPos;


        switch (LOWORD(wParam))
        {
        case SB_LINEUP:
            si.nPos -= 1;
            break;
        case SB_LINEDOWN:
            si.nPos += 1;
            break;
        case SB_PAGEUP:
            //先获取当前页面有几行
            si.nPos -= si.nPage;
            break;
        case SB_PAGEDOWN:
            //先获取当前页面的行数
            si.nPos += si.nPage;
            break;

        case SB_THUMBTRACK:
            si.nPos = si.nTrackPos;
            break;
            //在si.nTrackPos中存放着SB_THUMBTRACK和SB_THUMBPOSITION的位置信息
        case SB_THUMBPOSITION:
            si.nPos = si.nTrackPos;
            break;
        default:
            break;
        }

        //设置滚动滑块的新位置
        si.fMask = SIF_POS;
        SetScrollInfo(hwnd, SB_VERT, &si, TRUE);

        //再次获得滚动滑块的位置，由于窗口调整，他可能不是同一个值
        GetScrollInfo(hwnd, SB_VERT, &si);
        //curCount是前面未滚动的数据，si.nPos是刚刚滚动后的数据（除非是在顶部或者底部，不然由于窗口调整，两种一定不是同一个值）
        if (si.nPos != curCount)
        {
            ScrollWindow(hwnd, 0, cyChar*(curCount-si.nPos), NULL, NULL);
            /*
                hwnd                     :窗口句柄
                0                         :水平滚动的数量
                cyChar*(curCount-si.nPos):垂直滚动的距离
                NULL（lpRect）             :为NULL时，当前整个客户区将被滚动
                NULL（lpClipRect）         :与上一个参数有关，当上一个设置区域后，该参数在其区域中裁剪区域进行滚动
            */
            UpdateWindow(hwnd);
            //不进入消息队列，直接发送WM_PAINT消息进行处理
        }
        break;
    case WM_PAINT:
        hdc = BeginPaint(hwnd, &ps);
        
        //获取垂直滚动条的位置
        si.cbSize = sizeof(si);
        si.fMask = SIF_POS;
        GetScrollInfo(hwnd,SB_VERT, &si);
        curCount = si.nPos;

        //计算需要重绘的区域
        FirstLine = max(0, curCount + ps.rcPaint.top / cyChar);
        LastLine = min(numCount - 1, curCount + ps.rcPaint.bottom / cyChar);
        /*
            ps是结构体，ps.rcPaint是指需要重绘的部分窗口矩形，ps.rcPaint.top是该矩形的上部
        */


        for (int i = FirstLine; i < LastLine;i++)
        {
            y = cyChar*(i - curCount);    //相当于将这个重绘区域看着新窗口，重这个区域的顶部开始重新绘制

            StringCchLength(sysmetrics[i].szLabel, 100, &st);
            TextOut(hdc, 0, y, sysmetrics[i].szLabel, st);

            StringCchLength(sysmetrics[i].szDesc, 100, &st);
            TextOut(hdc, 40 * cxChar, y, sysmetrics[i].szDesc, st);

            SetTextAlign(hdc, TA_RIGHT | TA_TOP);

            StringCchPrintf(szBuffer, 100, L"%5d", GetSystemMetrics(sysmetrics[i].iIndex));
            StringCchLength(szBuffer, 100, &st);
            TextOut(hdc, 40 * cxChar + 40 * cxCaps, y, szBuffer, st);

            SetTextAlign(hdc, TA_LEFT);
        }

        EndPaint(hwnd, &ps);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }


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