学习windows编程 day4 之 绘制随机矩形和peekMessage

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

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

int cxClient, cyClient;

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,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        NULL,
        NULL,
        hInstance,
        NULL
        );

    ShowWindow(hwnd, nShowCmd);
    UpdateWindow(hwnd);

//     while (GetMessage(&msg, NULL, 0, 0))    阻塞函数    这个NULL是指接收当前窗口，包括非客户区的信息，如果设为hwnd则（指的是当前客户区）处理非客户区时，不会响应去退出程序，所以会在后台存在  ？？？
//     {
//         TranslateMessage(&msg);
//         DispatchMessage(&msg);
//     }


// #define PM_NOREMOVE         0x0000
// #define PM_REMOVE           0x0001
// #define PM_NOYIELD          0x0002
// #if(WINVER >= 0x0500)
// #define PM_QS_INPUT         (QS_INPUT << 16)
// #define PM_QS_POSTMESSAGE   ((QS_POSTMESSAGE | QS_HOTKEY | QS_TIMER) << 16)
// #define PM_QS_PAINT         (QS_PAINT << 16)
// #define PM_QS_SENDMESSAGE   (QS_SENDMESSAGE << 16)

    while (TRUE)
    {
        if (PeekMessage(&msg,NULL,0,0,PM_REMOVE))//PM_REMOVE接收后删除 PM_NOREMOVE获取后不删除（偷窥）
        {
            if (msg.message==WM_QUIT)
            {
                break;
            }
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
        else
        {
            //rand()    //0~MAX_RAND 0-32767
            //绘制矩形，用到消息处理中的数据（全局）
            DrawRectangle(hwnd);
        }
    }

    return msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    HDC hdc;
    PAINTSTRUCT ps;
    RECT rect;
//    static int cxClient, cyClient;    //static是指数据在这个函数中为全局，不是在程序中

    switch (message)
    {
    case WM_SIZE:
        cxClient = LOWORD(lParam);
        cyClient = HIWORD(lParam);
        break;
    case WM_PAINT:
        hdc = BeginPaint(hwnd, &ps);
        GetClientRect(hwnd, &rect);


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


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


void DrawRectangle(HWND hwnd)
{
//     TCHAR szBuffer[100];
//     StringCchPrintf(szBuffer, 100, L"%d %d", cxClient, cyClient);
//     MessageBox(NULL, szBuffer, L"Info", NULL);
    HBRUSH hBrush;
    HDC hdc;
    RECT rect;

    if (cxClient == 0 || cyClient == 0)
        return;
    hdc = GetDC(hwnd);
    SetRect(&rect, rand() % cxClient, rand() % cyClient, rand() % cxClient, rand() % cyClient);
    hBrush = CreateSolidBrush(RGB(rand() % 256, rand() % 256, rand() % 256));
    FillRect(hdc, &rect, hBrush);
    DeleteObject(hBrush);
    ReleaseDC(hwnd, hdc);
}