tkinter façade: item specs, StringVar traces, and what settings.py still needs

Two gaps the façade hit the moment songformatter's settings.py RAN (both fixed, recorded here for the next pass over the surface):

• StringVar had no trace_add. BooleanVar did. An Entry's textvariable is a StringVar, so the trace an editable field uses was the missing one — and an unresolved method compiles clean and jumps to 0 ([[bug-nilpy-unknown-method-segfaults]]), so it was a segfault, not a diagnostic.
• A canvas item is named by its id OR by a TAG. bbox/itemconfigure took an Integer, so canvas.bbox("all") — the commonest call in the widget — raised TypeError: expected a number, got str from inside the callback. TkiItemSpec now takes either.

Still missing for songformatter

Menu, ttk.Notebook/Button/Separator/Frame/PanedWindow, Text, Toplevel, PhotoImage, filedialog, messagebox, the constants (LEFT/END/BOTH/…), event_generate, and the remaining geometry-manager options. See [[feature-nilpy-tkinter-facade-widening]].

Rule the two gaps illustrate

Every parameter of this façade that Python spells with more than one type must be a Variant (an item id or a tag, a number or a pair, a name or a font tuple). An Integer parameter is a bet that the application never writes the other spelling, and settings.py lost that bet twice in one file.

RESOLVED 2026-07-31 — the "still missing" list is empty

Both gaps this ticket was filed for (StringVar.trace_add, a canvas item named by a TAG) were already fixed when it was written. The list it left behind has since landed too, and was re-checked one name at a time against lib/pcl/tkinter.pas:

Menu, Text, Toplevel, PhotoImage, filedialog (askopenfilename / asksaveasfilename / askdirectory), messagebox (showinfo / showwarning / showerror / askyesno / askokcancel / askyesnocancel), the module constants, event_generate, and the geometry-manager options are all present. ttk is not a separate unit: ttk resolves onto tkinter and the ttk widgets sit beside the classic ones using the ttk:: command prefix, so ttk.Button / Notebook / Separator / Frame / PanedWindow all work.

The measured proof is not the census but the corpus: all five of songformatter's modules — settings.py, convertrawtext.py, key_analysis.py, render_backend.py and SongFormatter.py — now COMPILE unmodified.

The rule this ticket ends on ("every parameter Python spells with more than one type must be a Variant") is the part worth keeping, and it held up: nothing in this pass had to widen an Integer again.

Log

• 2026-07-31 — resolved, commit bc2a960ce.