When running rawtherapee under xfce4 in a minimal configuration, the x11-themes/gtk-engines2 port is not installed. However, rawtherapee installs a default .config/Rawtherapee4.1/options file which sets a theme of "25-Gray-Gray.gtkrc" "/usr/local/share/rawtherapee/themes/25-Gray-Gray.gtkrc" This causes numerous warnings on startup and at other points about the missing theme "clearlooks" The rawtherapee port should either have x11-themes/gtk-engines2 as a dependency, or better, suppress the warnings if no theme is explicitly expressed by the user or the installation; it seems to run just fine without gtk-engines2 installed. This may be a situation which exists with other gtk based apps. All of this happens fairly early on in rawtherapee's main() method, line 143. I am extracting this as a separate piece of bug 214509, as it is mainly cosmetic and it is unrelated to the core dump which is the main focus of 214509.
add cross reference to 214509
Getting rid of the warnings without gtk-engines2 installed is fairly simple -- set the option "UseSystemTheme" to true. That seems to override the specific theme set in the "Theme" option. This may or may not be a desirable default behaviour, depending on your perspective. When no system theme is installed, you get "normal" backgrounds, generally white with grey headers. While fine for many applications, it is not generally desirable for photo-editing apps. What I don't understand is why I see the 25-Gray-Gray theme when I don't have gtk-engines2 installed. If that happens because the total absense of a theme (no user specific, system use set to false) results in hard-coded values corresponding to 25-Gray-Gray, then having the default for the "Theme" option set to something like "none", leaving the use system theme set to false, and setting an error handler to trap and discard the warning messages might be appropriate. I suspect that's not a high priority ;-), so forcing a dependency is probably the prudent path to take.
Do you have a desktop environment installed via one of the master/meta ports? If yes, which one? gnome and -lite and mate already list gtk-engines2 as requisite.
(my question meaning: which is the all-encompassing xfce* port that you install)
I have no all-encompassing desktop port installed. Essentially, all I have installed is a window manager, xfce4. Something not uncommon among hardened criminals ;-) but in any case a reasonable choice. For example, consider the X minimalist who installs twm and nothing.
rawtherapee-5.0-gtk3 now uses Gtk+3 and should not require the gtk-engines2 port any more. Please reopen this bug if it does counter to what I'm writing.