this is probably related to #352230, but a recent update to either qt-gui or cairo configures cairo to be built with -qt4 if the gtk use flag is set. Specifically it gives the following error: emerge: there are no ebuilds built with USE flags to satisfy ">=x11-libs/cairo-1.10.0[-qt4]". !!! One of the following packages is required to complete your request: - x11-libs/cairo-1.10.2-r1 (Change USE: -qt4) (dependency required by "x11-libs/qt-gui-4.6.3-r2" [ebuild]) (dependency required by "qt-gui" [argument])
I don't see how this is related to bug #352230 at all... Anyway, the dependency in qt-gui is correct afaik. To solve your issue you just have to rebuild cairo with USE="-qt4".
Actually it's both valid and invalid. Latest qt-gui ebuild (in unstable) don't have that block, but use x11-themes/qgtkstyle for bug bug 336801 - though it seems something got broken in revbumps: right now there's no way of using ~x11-themes/qgtkstyle-4.6.3 - every available qt-gui ebuild blocks it. Though there's another problem with cairo[qt4] - bug 351897.
qgtkstyle in Qt 4.6.3 is provided by the gtk USE flag in qt-gui-4.6.3. Unfortunately that requires cairo to be built with -qt4. There was an attempt to split the style into a separate ebuild, however due to the issues that came up we decided to revert 4.6.3 to its original, gtk USE state. We're still working on it for Qt 4.7. The qgtkstyle-4.6* ebuilds are masked, please don't try to use them :)
