There are now at least two tools with dmenu functionality. One of them is dmenu itself. Second - dmenu > rofi symlink runs rofi in dmenu mode.
Steps to Reproduce:
1. ln -s /usr/bin/rofi /usr/local/bin/dmenu
2. Try something
I did not check all apps, using dmenu, with rofi, For now all I tried is i3-hud-menu (unpackaged), but it's not working correctly (doesn't activate acions).
Neither of dmenu and rofi are developed to mirror each other's features, so this would probably fail with many combinations of either one and their prospective users.
dmenu is probably unaware of rofi, because it's origin of its class.
Rofi's menu mode, however, is right for this purpose. At least this example passes:
ls | rofi -dmenu
With 'dmenu' > 'rofi' symlink compatibility should be enough.
could be a reason to add USE=dmenu to rofi (meaning dmenu compat), which would imply "!x11-misc/dmenu" in deps.
To be more exact, from rofi man:
The idea is that the basic usage command-line flags are obeyed, theme-related flags are not. Besides, rofi offers some extended features (like multi-select, highlighting, message bar, extra key bindings).
I tried to compare for what dmenu switches are supported in rofi:
-f (grab input until ready)
I can confirm, tabbed and surf are ok wiht rofi. With only exception - rofi doesn't truly embed itself as requests new tabbed from git, just matches parent's position.