#include <windows.h>
#include <commctrl.h>


LRESULT __stdcall WindowProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
HBRUSH CreateTransparentBrush(HWND hwndParent, HWND hwndStatic);
BOOL __stdcall KillBrush(HWND hwnd, LPARAM lParam);

int main()
{
	HINSTANCE _hInstance = GetModuleHandle(0);
	WNDCLASSEX winClass; 
	MSG        uMsg;

    ZeroMemory(&winClass, sizeof(WNDCLASSEX));
    
	winClass.lpszClassName = "MY_WINDOWS_CLASS";
	winClass.cbSize        = sizeof(WNDCLASSEX);
	winClass.lpfnWndProc   = (WNDPROC)WindowProc;
	winClass.hInstance     = _hInstance;
	winClass.hIcon	       = LoadIcon(0, IDI_APPLICATION);
	winClass.hCursor       = LoadCursor(NULL, IDC_ARROW);

	// bitmapa 1024*1 zrobiona z samej góry twojego screena (obszar klienta)
	HBITMAP bm = (HBITMAP)LoadImage(0, "c:\\brush.bmp", IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE);
	winClass.hbrBackground = CreatePatternBrush(bm);

	RegisterClassEx(&winClass);
	DeleteObject(bm);

	HWND hwnd = CreateWindowEx( NULL, "MY_WINDOWS_CLASS", "Transparent Trackbar", WS_OVERLAPPEDWINDOW | WS_VISIBLE, 200, 200, 830, 70, NULL, NULL, _hInstance, NULL );

    UpdateWindow( hwnd );

	HWND hwnd2 = CreateWindowEx( NULL, TRACKBAR_CLASS, NULL, WS_CHILD | WS_VISIBLE,  10, 10, 380, 30, hwnd, (HMENU)1005, _hInstance, NULL );
	HWND hwnd3 = CreateWindowEx( NULL, TRACKBAR_CLASS, NULL, WS_CHILD | WS_VISIBLE, 390, 10, 380, 30, hwnd, (HMENU)1000, _hInstance, NULL );


	while (GetMessage(&uMsg,0,0,0))
	{
		TranslateMessage( &uMsg );
		DispatchMessage( &uMsg );
	}
    return UnregisterClass( "MY_WINDOWS_CLASS", _hInstance );
}



LRESULT __stdcall WindowProc( HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
	LRESULT result = 0;
	switch( msg )
	{
		case WM_CLOSE:
			EnumChildWindows(hwnd, KillBrush, 0);
			DestroyWindow(hwnd);
			PostQuitMessage(0);
			break;

		case WM_CTLCOLORSTATIC:
			result = (LRESULT)CreateTransparentBrush(hwnd, (HWND)lParam);
			break;

		default:
			result = DefWindowProc( hwnd, msg, wParam, lParam );
	}
	return result;
}


// stwórz bitmap&#281; o wielko&#347;ci hwndStatic.szeroko&#347;&#263; * 1
// skopiuj do niej obraz okna hwndParent o 1 pixel wy&#380;ej ni&#380; hwndStatic
// zrób brush z bitmapy
HBRUSH CreateTransparentBrush(HWND hwndParent, HWND hwndStatic)
{
	HBRUSH hbr = (HBRUSH)GetProp(hwndStatic, "BRUSH");
	if (!hbr)
	{
		RECT rc;
		GetWindowRect(hwndStatic, &rc);
		ScreenToClient(hwndParent, (POINT*)&rc);
		HDC dcParent = GetDC(hwndParent);
		int w = rc.right - rc.left;

		HDC dcMemory = CreateCompatibleDC(dcParent);
		HBITMAP hbm = (HBITMAP)SelectObject(dcMemory, (HGDIOBJ)CreateCompatibleBitmap(dcParent, w, 1));
		BitBlt(dcMemory, 0,0,w,2, dcParent, rc.left, rc.top-1, SRCCOPY);
		hbm = (HBITMAP)SelectObject(dcMemory, hbm);
		ReleaseDC(hwndParent, dcParent);
		DeleteDC(dcMemory);
		hbr = CreatePatternBrush(hbm);
		SetProp(hwndStatic, "BRUSH", (HANDLE)hbr);
	}
	return hbr;
}


BOOL __stdcall KillBrush(HWND hwnd, LPARAM lParam)
{
	HBRUSH hbr = (HBRUSH)GetProp(hwnd, "BRUSH");
	if (hbr) DeleteObject(hbr);
	return true;
}