to get drop shadows working the style needs to be built with x11-xcb apparently. unfortunately it being missing during the cmake step is not reported in a suitable fashion. namely it does not show up in the cmake summary but rather the wall of random status output before the summary.

it would be very very very awesome if it could be made to show up in the summary as otherwise it goes unnoticed (as was the case in Kubuntu for example). also since the summary output is more or less a common format it's where one would apply computational parsing to throw warnings on missing dependencies, which is also bypassed by not having it listed in the summary.

example of current output:
[...]
-- Could NOT find KDE4Workspace (missing:  KDE4Workspace_CONFIG) (Required is at least version "4.9.80")
-- Found PkgConfig: /usr/bin/pkg-config (found version "0.28") 
-- checking for modules 'xcb;x11-xcb'
--   package 'x11-xcb' not found
-- Performing Test COMPILER_HAS_HIDDEN_VISIBILITY
-- Performing Test COMPILER_HAS_HIDDEN_VISIBILITY - Success
-- Performing Test COMPILER_HAS_HIDDEN_INLINE_VISIBILITY
-- Performing Test COMPILER_HAS_HIDDEN_INLINE_VISIBILITY - Success
-- Performing Test COMPILER_HAS_DEPRECATED_ATTR
-- Performing Test COMPILER_HAS_DEPRECATED_ATTR - Success
-- 
-- The following OPTIONAL packages have been found:

 * X11
 * Threads
 * Perl
 * PkgConfig

-- The following REQUIRED packages have been found:

 * Qt4
 * Automoc4
 * Phonon (required version >= 4.3.80)
 * KDE4Internal
 * KDE4

-- The following OPTIONAL packages have not been found:

 * KDE4Workspace (required version >= 4.9.80)
   Required to oxygen window decoration for kwin

-- Configuring done

Reproducible: Always