Adds conditional code paths to GdkCssShadowValue for painting outset
shadows, and allows shadows to be applied in two passes (first outset
then inset). This can be used to draw csd shadows in outer window
borders.
https://bugzilla.gnome.org/show_bug.cgi?id=695998
Signed-off-by: Rob Bradford <rob@linux.intel.com>
This commit is essentially a large reorganization. Instead of all value
subtypes having their own compute function, there is the general
_gtk_css_value_compute() function that then calls a vfunc on the
subtype.
