Add an option to turn on the use of the X window's alpha channel in
multiwindow mode, i.e. this uses the X window's alpha channel for
compositing into the native desktop.
This works on W7/Vista (using DwmEnableBlurBehindWindow()), and Windows
10 (using the undocumented SetWindowCompositionAttribute()), but not on
Windows 8/8.1
-compositewm must be enabled for this to be useful, as we only have a
pixmap with an alpha channel for the X window in that case. The
framebuffer/root window doesn't have one (unless perhaps you are using
the rootless extension, maybe...).
v2:
Update meson.build
Future work:
A window property to control use of alpha?
Option to turn off blur on W7/Vista
Implement _NET_WM_WINDOW_OPACITY
Update what c-extensions says about Windows platforms support a bit:
- Document that MinGW Win32 gets let off being POSIX-compilant
- Document the minimum Windows version supported
Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>
Reviewed-by: Colin Harrison <colin.harrison@virgin.net>