These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.02 s (backtrack: 0/20).

[ebuild  N     ] x11-libs/libXtst-1.2.5::gentoo  USE="-doc" 285 KiB
[ebuild  N     ] app-misc/joymouse-0.5-r2::gentoo  91 KiB

Total: 2 packages (2 new), Size of downloads: 376 KiB