In the middle of adding Windows Aero DWM support to HTMLayout and Sciter:

This is standard sample htmlayoutsdk/html_samples/border-radius/rounded-tabs.htm from the SDK

Seems like I need to add “aero” as an additional value to CSS @media selector in order to support such screens. This document is using simple html { background-color:transparent; } declaration to make it transparent.

And w7aero sample application is calling this function

void ExtendFrameIntoClient(HWND hwnd)
{
   // Negative margins have special meaning to DwmExtendFrameIntoClientArea.
   // Negative margins create the "sheet of glass" effect, where the client area
   //  is rendered as a solid surface with no window border.
   MARGINS margins = {-1};
   HRESULT hr = S_OK;
   // Extend frame across entire window.
   hr = DwmExtendFrameIntoClientArea(hwnd,&margins);
   assert (SUCCEEDED(hr)); hr;
}

Pretty easy I would say…