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
Rather than drawing the window contents from the shadow framebuffer, use
Composite extension redirection to cause the server to maintain a bitmap
image of each top-level X window, and draw the window contents from
that, so that window contents which are occluded in the framebuffer show
correctly in the task bar and task switcher previews.
v2:
Fix incorrect use of memset() found by gcc5
hw/xwin/winshadgdi.c: In function ‘winBltExposedWindowRegionShadowGDI’:
hw/xwin/winshadgdi.c:861:9: warning: ‘memset’ used with constant zero length parameter; this could be due to transposed parameters [-Wmemset-transposed-args]
v3:
Turn on -compositewm by default
v4:
Ignore -swcursor if -compositewm
-swcursor is not compatible with -compositewm (because the window
contents are drawn from an off-screen pixmap, not from the screen
pixmap, where the software cursor will be drawn).
v5:
Update meson.build also
Add -compositewm option to help output
Update CI to install prerequisites
Promote the generated file containing the date & time build was
configured to top-level.
Rename it from xf86Build.h to buildDateTIme.h.
Use it as well in XQuartz, stringize BUILD_DATE when needed.
This needs a meson with PRs #1784, #1792 and #1794
Future work: remove conditionals which are always on, and simplify redundant
CYGDEBUG conditionals
Signed-off-by: Jon Turney <jon.turney@dronecode.org.uk>
Reviewed-by: Eric Anholt <eric@anholt.net>
