I experience the same issue as OP on Ubuntu 18.04: WM_WINDOW_ROLE is respected, while WM_CLASS set via `--classname` is ignored.
While I understand the dev's comment referring to gtk3 non-support of WM_CLASS, I also agree with OP that this function, although for limited use cases, is very useful when customizing .desktop files.
Example use case: I want to use `terminator -c ncmpcpp` ncmpcpp` for the `exec` field of a FreeDesktop file, in order to set StartupWM_CLASS and display a custom icon an name in the Ubuntu dock (or any app launcher).
I experience the same issue as OP on Ubuntu 18.04: WM_WINDOW_ROLE is respected, while WM_CLASS set via `--classname` is ignored.
While I understand the dev's comment referring to gtk3 non-support of WM_CLASS, I also agree with OP that this function, although for limited use cases, is very useful when customizing .desktop files.
Example use case: I want to use `terminator -c ncmpcpp` ncmpcpp` for the `exec` field of a FreeDesktop file, in order to set StartupWM_CLASS and display a custom icon an name in the Ubuntu dock (or any app launcher).