Gimp doesn't start

[Vincent Habchi]

> Christophs-MBP:MacOS kuku$ pwd
> /Applications/MacPorts/GIMP.app/Contents/MacOS
> Christophs-MBP:MacOS kuku$ ls
> GIMP
> Christophs-MBP:MacOS kuku$ file GIMP
> GIMP: Mach-O 64-bit executable x86_64
> Christophs-MBP:MacOS kuku$ ./GIMP
> 2018-11-28 08:23:18.176 GIMP[86714:1924234] Failed to connect (cancelButton) outlet from (ScriptExecController) to (NSButton): missing setter or instance variable
> 2018-11-28 08:23:18.176 GIMP[86714:1924234] Failed to connect (messageTextField) outlet from (ScriptExecController) to (NSTextField): missing setter or instance variable
> Anzeige kann nicht geöffnet werden: 

Nah. This is not X11 related but Cocoa-. It means the underlying handling code for some UI elements is missing, which is rather strange. 
When you launch GIMP, do you (briefly) see the X11 icon popping up?

Did you installed GTK3 with the +quartz variant too?

Viel Glück :/

V.