"Stephen J. Turnbull" <turnbull(a)sk.tsukuba.ac.jp&gt; writes: Which is exactly the problem I encountered -- the custom [note the pun] tagset functions get a DEVICE argument, whereas Custom would need a FRAME argument. This was the killer problem against porting Custom to use specifiers. I also couldn't fathom a way to extend custom tagsets without breaking backward compatibility (and NO, we can't know that there is no code using that stuff.) But read on. [Imagine Hrvoje with a lamp lit above his head] A way to fix it in a backward-compatible way has popped into my head! Just add another optional argument to `define-specifier-tag' that determines how PREDICATE will be called: (define-specifier-tag TAG &optional PREDICATE HOW-TO-CALL) Documentation: Define a new specifier tag. If PREDICATE is specified, it should be a function of one argument (by default a device) that specifies whether the tag matches that particular device. If PREDICATE is omitted, the tag matches all devices. With HOW-TO-CALL you can specify the argument that will be provided to PREDICATE; legal values are `device' for a device argument, `frame' for a frame argument, and `locale' for a generalized locale argument (window, buffer, frame, or device.) For backward compatibility, nil is the same as `device'. You can redefine an existing user-defined specifier tag. However, you cannot redefine the built-in specifier tags (the device types and classes) or the symbols nil, t, 'all, or 'global. Custom would set up its specifier tag for the background-mode property of the locale, or frame (but NOT device!) Note that only the interface light-bulb is lit -- implementation might still be hard, especially if we did it right. In this case, "do it right" means that a statement like automagically changes face instances in the selected window: (set-face-background 'default "black" (selected-window)) See above, and sorry for the time it took me to respond. RL is a bitch. -- Hrvoje Niksic <hniksic(a)srce.hr&gt; | Student at FER Zagreb, Croatia --------------------------------+-------------------------------- aibohphobia (ay' bo fo beeya): n. The fear of palindromes.