C# [Win32] [API] Layered Windows

         static void* WndProc(void* hwnd, uint uMsg, void* wParam, void* lParam)
         {
             switch (uMsg)
             {
                 case WM_PAINT:
                 case WM_CTLCOLORMSGBOX:
                 case WM_CTLCOLOREDIT:
                 case WM_CTLCOLORLISTBOX:
                 case WM_CTLCOLORBTN:
                 case WM_CTLCOLORDLG:
                 case WM_CTLCOLORSCROLLBAR:
                 case WM_CTLCOLORSTATIC:
                 case WM_CAPTURECHANGED:
                     {
                         if (_pimg != null)
                         {
                             void* _hwnd = GetAncestor(hwnd, GA_ROOT);

                             uint uw, uh;
                             GdipGetImageWidth(_pimg, &uw); GdipGetImageHeight(_pimg, &uh);

                             RECT rcc, rcs;
                             GetClientRect(_hwnd, &rcc);
                             GetWindowRect(_hwnd, &rcs);

                             PAINTSTRUCT ps;
                             void* hdc = BeginPaint(_hwnd, &ps); //GetDC(hwnd);
                             void* hdcmem = CreateCompatibleDC(hdc);                            

                             BITMAPINFO bi;
                             bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
                             bi.bmiHeader.biWidth = (int)uw;
                             bi.bmiHeader.biHeight = (int)uh;
                             bi.bmiHeader.biPlanes = ;
                             bi.bmiHeader.biBitCount = ;
                             bi.bmiHeader.biCompression = BI_RGB;
                             bi.bmiHeader.biClrUsed = ;
                             bi.bmiHeader.biSizeImage = ;

                             void* pvbits;
                             void* hbmpmem = CreateDIBSection(hdc, &bi, DIB_RGB_COLORS, &pvbits, null, 0u);

                             if (hbmpmem != null)
                             {
                                 SelectObject(hdcmem, hbmpmem);

                                 GpGraphics* g;
                                 if (GdipCreateFromHDC(hdcmem, &g) == )
                                 {
                                     GdipDrawImageRectI(g, _pimg, , , (int)uw, (int)uh);

 #if true
                                     RECT rc;
                                     for (int i = ; i < ; i++)
                                     {
                                         void* h = GetDlgItem(_hwnd, i);
                                         if (IsWindowVisible(h) == )
                                         {
                                             GetWindowRect(h, &rc);
                                             MapWindowPoints(null, _hwnd, (POINT*)&rc, );
                                             GpBitmap* gpbmp;
                                             GdipCreateBitmapFromScan0(rc.right - rc.left, rc.bottom - rc.top, , PixelFormat32bppARGB, null, &gpbmp);
                                             GpGraphics* gpg;
                                             if (GdipGetImageGraphicsContext((GpImage*)gpbmp, &gpg) == )
                                             {
                                                 void* hdc2;
                                                 GdipGetDC(gpg, &hdc2);
                                                 SendMessageW(h, WM_PRINT, hdc2, (void*)(PRF_NONCLIENT | PRF_CLIENT | PRF_ERASEBKGND | PRF_CHILDREN));
                                                 GdipReleaseDC(gpg, hdc2);
                                                 GdipDeleteGraphics(gpg);
                                             }
                                             GdipDrawImageRectI(g, (GpImage*)gpbmp, rc.left, rc.top, rc.right - rc.left, rc.bottom - rc.top);
                                             GdipDisposeImage((GpImage*)gpbmp);
                                         }
                                     }
 #endif

                                     POINT ptscr;

                                     POINT ptdst;
                                     ptdst.x = rcs.left;
                                     ptdst.y = rcs.top;

                                     SIZE szwnd;
                                     szwnd.cx = (int)uw;
                                     szwnd.cy = (int)uh;

                                     BLENDFUNCTION bf;
                                     bf.BlendOp = AC_SRC_OVER;
                                     bf.BlendFlags = 0x0;
                                     bf.SourceConstantAlpha = 0xff;
                                     bf.AlphaFormat = AC_SRC_ALPHA;

                                     UPDATELAYEREDWINDOWINFO ulwi;
                                     ulwi.cbSize = sizeof(UPDATELAYEREDWINDOWINFO);
                                     ulwi.hdcDst = hdc;
                                     ulwi.pptDst = &ptdst;
                                     ulwi.psize = &szwnd;
                                     ulwi.hdcSrc = hdcmem;
                                     ulwi.pptSrc = &ptscr;
                                     ulwi.crKey = (COLORREF)0u;
                                     ulwi.pblend = &bf;
                                     ulwi.dwFlags = ULW_ALPHA;
                                     ulwi.prcDirty = null;

                                     //UpdateLayeredWindow(_hWnd, hdc, &ptdst, &szwnd, hdcmem, &ptscr, (COLORREF)0u, &bf, ULW_ALPHA);
                                     UpdateLayeredWindowIndirect(_hwnd, &ulwi);

                                     GdipDeleteGraphics(g);
                                 }
                                 DeleteObject(hbmpmem);
                             }

                             DeleteDC(hdcmem);
                             //ReleaseDC(hwnd, hdc);
                             EndPaint(_hwnd, &ps);
                         }
                     }
                     break;
             }
             return DefWindowProcW(hwnd, uMsg, wParam, lParam);
         }