//   异形窗口2  在WM_ERASEBKGND消息中自贴图
//By MoreWindows-(http://blog.csdn.net/MoreWindows)
#include <windows.h>
const char szAppName[] = "异形窗口2 MoreWindows-(http://blog.csdn.net/MoreWindows)";

/*
 * 函数名称: GetWindowSize
 * 函数功能: 得到窗口的宽高
 * hwnd      窗口句柄
 * pnWidth   窗口宽
 * pnHeight  窗口高
*/
void GetWindowSize(HWND hwnd, int *pnWidth, int *pnHeight);


/*
 * 函数名称: InitBitmapWindow
 * 函数功能: 位图窗口初始化
 * hinstance 进程实例
 * nWidth    窗口宽
 * nHeight   窗口高
 * nCmdshow  显示方式-与ShowWindow函数的第二个参数相同
*/
BOOL InitBitmapWindow(HINSTANCE hinstance, int nWidth, int nHeight, int nCmdshow);

// 位图窗口消息处理函数
LRESULT CALLBACK BitmapWindowWndPrco(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParm);

          
HBITMAP  g_hBitmap;
int APIENTRY WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR     lpCmdLine,
                     int       nCmdShow)
{
    //先创建一个无背影画刷窗口，
    //然后在WM_CREATE中并指定透明颜色, 缩放位图后加载至s_hdcMem中.
    //最后在WM_ERASEBKGND中用s_hdcMem贴图即可
    g_hBitmap = (HBITMAP)LoadImage(NULL, "Kitty.bmp", IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
    if (g_hBitmap == NULL)
    {
        MessageBox(NULL, "位图加载失败", "Error", MB_ICONERROR);
        return 0;
    }

    // 设置异形窗口大小
    BITMAP bm;
    GetObject(g_hBitmap, sizeof(bm), &bm);
    int nWindowWidth = bm.bmWidth;
    int nWindowHeight = bm.bmHeight + 100; //拉高100高度

    if (!InitBitmapWindow(hInstance, nWindowWidth, nWindowHeight, nCmdShow))
        return 0;

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

    return msg.wParam;
}


BOOL InitBitmapWindow(HINSTANCE hinstance, int nWidth, int nHeight, int nCmdshow)
{
    HWND hwnd;
    WNDCLASS wndclass;
    
    wndclass.style       = CS_VREDRAW | CS_HREDRAW;
    wndclass.lpfnWndProc = BitmapWindowWndPrco;    
    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(NULL_BRUSH);//窗口背影画刷为空
    wndclass.lpszMenuName  = NULL;
    wndclass.lpszClassName = szAppName;
    
    if (!RegisterClass(&wndclass))
    {
        MessageBox(NULL, "Program Need Windows NT!", "Error", MB_ICONERROR);
        return FALSE;
    }
    
    hwnd = CreateWindowEx(WS_EX_TOPMOST,
                        szAppName,
                        szAppName, 
                        WS_POPUP,
                        CW_USEDEFAULT, 
                        CW_USEDEFAULT, 
                        nWidth, 
                        nHeight,
                        NULL,
                        NULL,
                        hinstance,
                        NULL);
    if (hwnd == NULL)
        return FALSE;
    
    ShowWindow(hwnd, nCmdshow);
    UpdateWindow(hwnd);
    
    return TRUE;
}

LRESULT CALLBACK BitmapWindowWndPrco(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParm)
{
    static HDC s_hdcMem; //放置缩放后的位图
    
    switch (message)
    {
    case WM_CREATE:
        {
            // 设置分层属性
             SetWindowLong(hwnd, GWL_EXSTYLE, GetWindowLong(hwnd, GWL_EXSTYLE) | WS_EX_LAYERED);
            // 设置透明色
            COLORREF clTransparent = RGB(0, 0, 0);
             SetLayeredWindowAttributes(hwnd, clTransparent, 0, LWA_COLORKEY);
            
            //   缩放位图
            // 加载位图到hdcTemp中
            HDC hdc = GetDC(hwnd);
            HDC hdcTemp = CreateCompatibleDC(hdc);
            SelectObject(hdcTemp, g_hBitmap);

            // 得到窗口大小
            int nWidth, nHeight;
            GetWindowSize(hwnd, &nWidth, &nHeight);

            // 创建与窗口大小相等且能容纳位图的HDC - s_hdcMem
            s_hdcMem = CreateCompatibleDC(hdc);
            HBITMAP hbmp = CreateCompatibleBitmap(hdc, nWidth, nHeight);
            SelectObject(s_hdcMem, hbmp);

            // 将原位图缩放到窗口大小
            BITMAP bm;
            GetObject(g_hBitmap, sizeof(bm), &bm);
            StretchBlt(s_hdcMem, 0, 0, nWidth, nHeight, hdcTemp, 0, 0, bm.bmWidth, bm.bmHeight, SRCCOPY);
            
            // 释放资源
            DeleteDC(hdcTemp);
            ReleaseDC(hwnd, hdc);
        }
        return 0;

        
    case WM_KEYDOWN: 
        switch (wParam)
        {
        case VK_ESCAPE: //按下Esc键时退出
            SendMessage(hwnd, WM_DESTROY, 0, 0);
            return TRUE;
        }
        break;
    

    case WM_LBUTTONDOWN: //当鼠标左键点击时可以拖曳窗口
        PostMessage(hwnd, WM_SYSCOMMAND, SC_MOVE | HTCAPTION, 0); 
        return TRUE;
                
    case WM_ERASEBKGND: //在窗口背景中直接贴图
        {
            HDC hdc = (HDC)wParam;
            int nWidth, nHeight;
            GetWindowSize(hwnd, &nWidth, &nHeight);
            BitBlt(hdc, 0, 0, nWidth, nHeight, s_hdcMem, 0, 0, SRCCOPY);
            return TRUE;
        }

    case WM_DESTROY:
        DeleteDC(s_hdcMem);
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hwnd, message, wParam, lParm);
}


void GetWindowSize(HWND hwnd, int *pnWidth, int *pnHeight)
{
    RECT rc;
    GetWindowRect(hwnd, &rc);
    *pnWidth = rc.right - rc.left;
    *pnHeight = rc.bottom - rc.top;
}