Disclaimer: this bug has been filed in a semi-automated manner.
When emerging the package x11-libs/gtk+-2.24.12, the following elog messages are displayed:
* Please install app-text/evince for print preview functionality.
* Alternatively, check "gtk-print-preview-command" documentation and
* add it to your gtkrc.
Such messages should only be displayed when the package is a new install.
These situations can be checked in the ebuild as follows:
if ! has_version 'x11-libs/gtk+'; then
See the tracker bug 440214 for more details.
There is already a check on evince iirc.
if ! has_version "app-text/evince"; then
elog "Please install app-text/evince for print preview functionality."
elog "Alternatively, check \"gtk-print-preview-command\" documentation and"
elog "add it to your gtkrc."