Install this version:
emerge -a =media-gfx/slideshow-9999
If this version is masked, you can unmask it using the autounmask tool or standard emerge options:
autounmask =media-gfx/slideshow-9999
Or alternatively:
emerge --autounmask-write -a =media-gfx/slideshow-9999
EAPI=4 DESCRIPTION="Slideshow is a kiosk-style application for showing text, image and video in a loop on monitors and projectors" HOMEPAGE="" SRC_URI="" LICENSE="" SLOT="0" KEYWORDS="amd64 x86" IUSE="" RDEPEND=">=media-gfx/slideshow-daemon-9999 >=media-gfx/slideshow-frontend-9999" DEPEND=""
>=media-gfx/slideshow-daemon-9999 >=media-gfx/slideshow-frontend-9999