学步园

#pragma comment(linker, "/subsystem:windows")

#include <windows.h>

// ----------------------------------------------------------------------------

static HDC g_hDC       = NULL;
static HDC g_memDC     = NULL;
static HBITMAP g_memBM = NULL;

static POINTS g_cPointsBegin = {0};
static BOOL g_bDrawEnable = FALSE;

// ----------------------------------------------------------------------------

static void GetCurClientSize(HWND hWnd, int& nWidth, int& nHeight)
{
    RECT rc = {0};
    GetClientRect(hWnd, &rc);
    nWidth = rc.right - rc.left;
    nHeight = rc.bottom - rc.top;
}

static void ChangeMemDCSize(HWND hWnd, HDC hDC, HDC& memDC, HBITMAP& memBM)
{
    if ( hWnd && hDC && memDC && memBM )
    {
        int nWidth = 0;
        int nHeight = 0;
        GetCurClientSize(hWnd, nWidth, nHeight);

        HDC memDCNew = CreateCompatibleDC(hDC);

        HBITMAP memBMNew = CreateCompatibleBitmap(hDC, nWidth, nHeight);
        HBITMAP memBMOld = (HBITMAP)SelectObject(memDCNew, memBMNew);
        DeleteObject(memBMOld);

        HPEN hPen = CreatePen(PS_SOLID, 0, RGB(255,255,255));
        HPEN hPenOld = (HPEN)SelectObject(memDCNew, hPen);
        DeleteObject(hPenOld);

        HBRUSH hBrush = CreateSolidBrush(RGB(255,255,255));
        HBRUSH hBrushOld = (HBRUSH)SelectObject(memDCNew, hBrush);
        DeleteObject(hBrushOld);

        Rectangle(memDCNew, 0, 0, nWidth, nHeight);

        BitBlt(
            memDCNew, 0, 0, nWidth, nHeight,
            memDC, 0, 0,
            SRCCOPY
        );

        DeleteObject(memBM);
        memBM = memBMNew;

        DeleteDC(memDC);
        memDC = memDCNew;
    }
}

// ----------------------------------------------------------------------------

LRESULT MyInit(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    LRESULT ret = FALSE;

    g_hDC = GetDC(hWnd);
    if ( g_hDC != NULL )
    {
        g_memDC = CreateCompatibleDC(g_hDC);
        if ( g_memDC != NULL )
        {
            int nWidth = 0;
            int nHeight = 0;
            GetCurClientSize(hWnd, nWidth, nHeight);
            g_memBM = CreateCompatibleBitmap(g_hDC, nWidth, nHeight);
            if ( g_memBM != NULL )
            {
                HBITMAP memBMOld = (HBITMAP)SelectObject(g_memDC, g_memBM);
                DeleteObject(memBMOld);

                SendMessage(hWnd, WM_KEYDOWN, VK_F1, 0);
                ret = TRUE;
            }
        }
    }

    return ret;
}

LRESULT UnInit(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    if ( g_memBM != NULL )
    {
        DeleteObject(g_memBM);
        g_memBM = NULL;
    }

    if ( g_memDC != NULL )
    {
        DeleteDC(g_memDC);
        g_memDC = NULL;
    }

    if ( g_hDC != NULL )
    {
        ReleaseDC(hWnd, g_hDC);
        g_hDC = NULL;
    }

    return TRUE;
}

// ----------------------------------------------------------------------------

LRESULT OnLButtonDown(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    g_cPointsBegin = MAKEPOINTS(lParam);
    g_bDrawEnable = TRUE;
    SetCapture(hWnd);
    return TRUE;
}

LRESULT OnMouseMove(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    if ( MK_LBUTTON == wParam )
    {
        if ( g_bDrawEnable )
        {
            POINTS pt = {0};
            pt = MAKEPOINTS(lParam);

            SendMessage(hWnd, WM_PAINT, 0, 0);

            MoveToEx(g_hDC, g_cPointsBegin.x, g_cPointsBegin.y, NULL);
            LineTo(g_hDC, pt.x, pt.y);
        }
    }

    return TRUE;
}

LRESULT OnLButtonUp(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    if ( TRUE == g_bDrawEnable )
    {
        g_bDrawEnable = FALSE;

        POINTS pt = {0};
        pt = MAKEPOINTS(lParam);

        HPEN hPen = CreatePen(PS_SOLID, 0, RGB(0,255,0));
        HPEN hPenOld = (HPEN)SelectObject(g_memDC, hPen);

        MoveToEx(g_memDC, g_cPointsBegin.x, g_cPointsBegin.y, NULL);
        LineTo(g_memDC, pt.x, pt.y);

        SelectObject(g_memDC, hPenOld);
        DeleteObject(hPen);

        SendMessage(hWnd, WM_PAINT, 0, 0);
    }

    ReleaseCapture();
    return TRUE;
}

// ----------------------------------------------------------------------------

LRESULT OnKeyDown(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    if ( VK_F1 == wParam )
    {
        if ( g_memDC != NULL )
        {
            int nWidth = 0;
            int nHeight = 0;
            GetCurClientSize(hWnd, nWidth, nHeight);

            HPEN hPen = CreatePen(PS_SOLID, 0, RGB(255,255,255));
            HPEN hPenOld = (HPEN)SelectObject(g_memDC, hPen);
            HBRUSH hBrush = CreateSolidBrush(RGB(255,255,255));
            HBRUSH hBrushOld = (HBRUSH)SelectObject(g_memDC, hBrush);

            Rectangle(g_memDC, 0, 0, nWidth, nHeight);

            SelectObject(g_memDC, hPenOld);
            DeleteObject(hPen);
            SelectObject(g_memDC, hBrushOld);
            DeleteObject(hBrush);

            InvalidateRect(hWnd, NULL, TRUE);
        }
    }
    else if ( VK_ESCAPE == wParam )
    {
        SendMessage(hWnd, WM_CLOSE, 0, 0);
    }

    return TRUE;
}

// ----------------------------------------------------------------------------

LRESULT OnCreate(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    return MyInit(hWnd, message, wParam, lParam);
}

LRESULT OnClose(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    UnInit(hWnd, message, wParam, lParam);
    DestroyWindow(hWnd);
    return TRUE;
}

LRESULT OnSize(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    if ( SIZE_MINIMIZED != wParam )
    {
        ChangeMemDCSize(hWnd, g_hDC, g_memDC, g_memBM);
    }

    return TRUE;
}

LRESULT OnPaint(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    if ( g_hDC != NULL && g_memDC != NULL )
    {
        int nWidth = 0;
        int nHeight = 0;
        GetCurClientSize(hWnd, nWidth, nHeight);

        BitBlt(
            g_hDC, 0, 0, nWidth, nHeight,
            g_memDC, 0, 0,
            SRCCOPY
        );
    }

    return TRUE;
}

LRESULT OnOtherMessage(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_LBUTTONDOWN:
        OnLButtonDown(hWnd, message, wParam, lParam);
        break;

    case WM_MOUSEMOVE:
        OnMouseMove(hWnd, message, wParam, lParam);
        break;

    case WM_LBUTTONUP:
        OnLButtonUp(hWnd, message, wParam, lParam);
        break;

    case WM_KEYDOWN:
        OnKeyDown(hWnd, message, wParam, lParam);
        break;
    }

    return TRUE;
}

// ----------------------------------------------------------------------------

LRESULT CALLBACK MainWndProc(
    HWND hWnd,
    UINT message,
    WPARAM wParam,
    LPARAM lParam
)
{
    switch (message)
    {
    case WM_CREATE:
        if ( TRUE != OnCreate(hWnd, message, wParam, lParam) )
        {
            SendMessage(hWnd, WM_CLOSE, 0, 0);
        }
        break;

    case WM_CLOSE:
        OnClose(hWnd, message, wParam, lParam);
        break;

    case WM_SIZE:
        OnSize(hWnd, message, wParam, lParam);
        break;

    case WM_PAINT:
        OnPaint(hWnd, message, wParam, lParam);
        break;

    case WM_DESTROY:
        PostQuitMessage(0);
        break;

    default:
        OnOtherMessage(hWnd, message, wParam, lParam);
        break;
    }

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

// ----------------------------------------------------------------------------

int WINAPI WinMain(
    HINSTANCE hInstance,
    HINSTANCE hPrevInstance,
    LPSTR lpCmdLine,
    int nCmdShow
)
{
    MSG msg;
    BOOL bRet;
    WNDCLASS wc;
    UNREFERENCED_PARAMETER(lpCmdLine);

    // Register the main window class.
    wc.style = CS_HREDRAW | CS_VREDRAW;
    wc.lpfnWndProc = (WNDPROC)MainWndProc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = hInstance;
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wc.lpszMenuName =  NULL;
    wc.lpszClassName = "MyDraw";

    if ( !RegisterClass(&wc) )
    {
        return FALSE;
    }

    HWND hWnd = CreateWindow(
                    wc.lpszClassName,
                    "画图板",
                    WS_OVERLAPPEDWINDOW,
                    CW_USEDEFAULT, CW_USEDEFAULT,
                    CW_USEDEFAULT, CW_USEDEFAULT,
                    NULL, NULL, hInstance, NULL
                );

    if ( NULL == hWnd )
    {
        return FALSE;
    }

    ShowWindow(hWnd, nCmdShow);
    UpdateWindow(hWnd);

    while ( (bRet = GetMessage(&msg, NULL, 0, 0)) != 0 )
    {
        if ( -1 == bRet )
        {
            // handle the error and possibly exit
            return FALSE;
        }
        else
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    }

    // Return the exit code to the system.
    return msg.wParam;
}