Method SetLayeredWindowBitmap

Rtxpt/SampleCommon/SplashScreen.cpp:396–434

}

void SplashScreen::SetLayeredWindowBitmap(HWND hwnd, const uint8_t* bgraPremul, UINT w, UINT h)
{
    HDC screenDC = GetDC(nullptr);
    HDC memDC = CreateCompatibleDC(screenDC);

    BITMAPINFO bmi = {};
    bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
    bmi.bmiHeader.biWidth = (LONG)w;
    bmi.bmiHeader.biHeight = -(LONG)h; // top-down
    bmi.bmiHeader.biPlanes = 1;
    bmi.bmiHeader.biBitCount = 32;
    bmi.bmiHeader.biCompression = BI_RGB;

    void* dibBits = nullptr;
    HBITMAP dib = CreateDIBSection(screenDC, &bmi, DIB_RGB_COLORS, &dibBits, nullptr, 0);
    memcpy(dibBits, bgraPremul, (size_t)w * (size_t)h * 4);

    HGDIOBJ oldObj = SelectObject(memDC, dib);

    int x = 0;
    int y = 0;
    CenterOnPrimaryMonitorPx(w, h, x, y);

    POINT ptDst = { x, y };
    SIZE  szDst = { (LONG)w, (LONG)h };
    POINT ptSrc = { 0, 0 };

    BLENDFUNCTION bf = {};
    bf.BlendOp = AC_SRC_OVER;
    bf.SourceConstantAlpha = 255;
    bf.AlphaFormat = AC_SRC_ALPHA;

    UpdateLayeredWindow(hwnd, screenDC, &ptDst, &szDst, memDC, &ptSrc, 0, &bf, ULW_ALPHA);

    SelectObject(memDC, oldObj);
    DeleteObject(dib);
    DeleteDC(memDC);
    ReleaseDC(nullptr, screenDC);
}