Copying the Screen Using StretchBlt Function

Copy

#include <windows.h>

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);


int WINAPI WinMain(HINSTANCE hInstance,
                   HINSTANCE hPrevInstance,
                   LPSTR lpCmdLine,
                   int nCmdShow)
{
    MSG msg;
    WNDCLASS wc = {0};

    wc.style         = CS_HREDRAW | CS_VREDRAW;
    wc.lpszClassName = TEXT("Screen copy");
    wc.hInstance     = hInstance;
    wc.hbrBackground = GetSysColorBrush(COLOR_BTNFACE);
    wc.lpfnWndProc   = WndProc;
    wc.hCursor       = LoadCursor(NULL, IDC_ARROW);

    RegisterClass(&wc);


    CreateWindow(
        wc.lpszClassName,
        TEXT("Screen Copy using StretchBlt"),
        WS_OVERLAPPEDWINDOW | WS_VISIBLE,
        100,
        100,
        500,
        400,
        NULL,
        NULL,
        hInstance,
        NULL);


    while(GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return msg.wParam;
}



LRESULT CALLBACK WndProc(HWND hwnd,
                         UINT msg,
                         WPARAM wParam,
                         LPARAM lParam)
{
    switch(msg)
    {

    case WM_LBUTTONDOWN:
    {
        int screenWidth;
        int screenHeight;

        int windowWidth;
        int windowHeight;

        RECT rect;

        HDC screenDC;
        HDC windowDC;


        // Get screen dimensions

        screenWidth  = GetSystemMetrics(SM_CXSCREEN);
        screenHeight = GetSystemMetrics(SM_CYSCREEN);


        // Get application window client area size

        GetClientRect(hwnd, &rect);

        windowWidth  = rect.right - rect.left;
        windowHeight = rect.bottom - rect.top;



        // Get desktop device context

        screenDC = GetWindowDC(NULL);


        // Get application window device context

        windowDC = GetDC(hwnd);



        // Copy and resize desktop image into application window

        StretchBlt(
            windowDC,
            0,
            0,
            windowWidth,
            windowHeight,

            screenDC,
            0,
            0,
            screenWidth,
            screenHeight,

            SRCCOPY);



        // Release device contexts

        ReleaseDC(NULL, screenDC);
        ReleaseDC(hwnd, windowDC);


        break;
    }



    case WM_DESTROY:

        PostQuitMessage(0);
        return 0;

    }


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