C++ Splash screen create standart controls

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#include <windows.h>
#include <WindowsX.h>
#include <GdiPlus.h>
#include "resource.h"
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#pragma comment ( lib, "Gdiplus.lib" )

ULONG_PTR m_gdiplusToken;
HBITMAP hBmpSplash;

BOOL Blend(
    HWND hWnd,      // Must be a layered window
    HBITMAP hBmp,   // The image. Must be 32bpp ARGB format
    BYTE alpha )    // Overall opacity (0=transparent, 255=opaque)
{
    BLENDFUNCTION bf =
    {
        AC_SRC_OVER,    // BlendOp
        0,              // BlendFlags
        alpha,          // SourceConstantAlpha
        AC_SRC_ALPHA    // AlphaFormat
    };

    // Find the image's size in pixels
    BITMAP bm = {};
    if( sizeof(bm) != GetObject(hBmp, sizeof(bm), &bm) ) return FALSE;
    SIZE size = { bm.bmWidth, bm.bmHeight };

    // Create a screen device context and select the image into it.
    HDC hdc = CreateCompatibleDC(NULL);
    if( !hdc ) return FALSE;
    HBITMAP hBmpOld = SelectBitmap(hdc, hBmp);

    // Update the layered window
    POINT ptSrc = { 0, 0 };
    BOOL bRet = UpdateLayeredWindow(
        hWnd,
        NULL /*hdcDst NULL to use the default palette for the screen*/,
        NULL /*pptDst NULL because the removed isn't changing */,
        &size,
        hdc,
        &ptSrc,
        RGB(0,0,0),
        &bf,
        ULW_ALPHA );

    // Restore the device context and clean up
    SelectBitmap(hdc, hBmpOld);
    DeleteDC(hdc);

    return bRet;
}

LRESULT CALLBACK WndProc(HWND window, UINT uMsg, WPARAM wParam, LPARAM lParam) {
    switch (uMsg) {

    case WM_CREATE:
        break;

    case WM_MOUSEMOVE:
        break;

	case WM_LBUTTONDOWN:
	{
		PostMessage(window, WM_NCLBUTTONDOWN, HTCAPTION,NULL);
		break;
	}

    case WM_NCDESTROY:
        PostQuitMessage(0);
        break;
    }

    return DefWindowProc(window, uMsg, wParam, lParam);
}

int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE, LPTSTR,
   int nCmdShow)
{
	Gdiplus::GdiplusStartupInput gdiplusStartupInput;
	Gdiplus::GdiplusStartup(&m_gdiplusToken, &gdiplusStartupInput, NULL);
	hBmpSplash = LoadBitmap(hInstance, MAKEINTRESOURCE(IDB_SPLASH));
	
	WNDCLASSEX wcex;

	wcex.cbSize          = sizeof(WNDCLASSEX);
	wcex.style           = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
	wcex.lpfnWndProc     = WndProc;
	wcex.cbClsExtra      = 0;
	wcex.cbWndExtra      = 8; // 8 bytes, to allow for 64-bit architecture
	wcex.hInstance       = hInstance; // CHECK
	wcex.hIcon           = NULL;
	wcex.hCursor         = ::LoadCursor(NULL, IDC_ARROW);
	wcex.hbrBackground   = (HBRUSH)NULL_BRUSH; // CHECK
	wcex.lpszMenuName    = NULL;
	wcex.lpszClassName	 = "GDI_Window";
	wcex.hIconSm         = NULL;
	
	RegisterClassEx(&wcex);

	HWND wnd = CreateWindowEx(WS_EX_TOPMOST | WS_EX_LAYERED, "GDI_Window", "GDI Window", WS_POPUP , 0, 0, 700, 500, NULL, NULL, hInstance, NULL);
	
	Blend(wnd, hBmpSplash, 255);
	ShowWindow(wnd, nCmdShow);
	UpdateWindow(wnd);

	MSG msg = { 0 };

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

	Gdiplus::GdiplusShutdown(m_gdiplusToken);
   return 0;                                                              
}