Tk_SetClassProcs(3tk)

💖 Tk_SetClassProcs — register widget specific procedures 💖

okay bestie, gather round, because this is a Tk Library Procedure and it's genuinely iconic. It's called Tk_SetClassProcs and it lives in the 3tk manual section. Let's get into it 🫶

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✨ NAME ✨

Tk_SetClassProcs — register widget specific procedures

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🌸 SYNOPSIS 🌸

#include <tk.h>

Tk_SetClassProcs(tkwin, procs, instanceData)

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🎀 ARGUMENTS 🎀

• Tk_Window tkwin (in) — the token for the window you wanna modify, no cap.
• const Tk_ClassProcs *procs (in) — a pointer to the data structure holding your widget specific procedures. > ⚠️ okay listen, this one matters: the data structure that procs points at must be static. Tk keeps a reference to it for as long as the window exists, so if you let it go out of scope it's giving 💀. Don't do that to yourself.
• void *instanceData (in) — an arbitrary one-word value that gets passed along to your widget callbacks. It's your little care package, iykyk.

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🦋 DESCRIPTION 🦋

Tk_SetClassProcs is what you call to register a set of procedures that get used as callbacks in different places. Very main character energy of it.

The structure that procs points to contains the following:

typedef struct {
    Tcl_Size size;
    Tk_ClassWorldChangedProc *worldChangedProc;
    Tk_ClassCreateProc *createProc;
    Tk_ClassModalProc *modalProc;
} Tk_ClassProcs;

The size field exists to make future expansion of the structure easy — it's the lowkey genius move. It should always be set to (literally) sizeof(Tk_ClassProcs).

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💫 worldChangedProc 💫

worldChangedProc gets invoked when the system has altered in some way that requires some reaction from the widget. For example, when a font alias (peep the font manual entry) is reconfigured, widgets configured to use that font alias have to update their display accordingly. Slay, keep up 💅

worldChangedProc should have arguments and results that match the type Tk_ClassWorldChangedProc:

typedef void Tk_ClassWorldChangedProc(
        void *instanceData);

The instanceData parameter passed to the worldChangedProc will be identical to the instanceData parameter passed to Tk_SetClassProcs. Same one, fr fr.

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🌈 createProc 🌈

createProc is used to create platform-dependent windows. It gets invoked by Tk_MakeWindowExist. Obsessed with a handoff honestly.

createProc should have arguments and results that match the type Tk_ClassCreateProc:

typedef Window Tk_ClassCreateProc(
        Tk_Window tkwin,
        Window parent,
        void *instanceData);

The tkwin and instanceData parameters will be identical to the tkwin and instanceData parameters passed to Tk_SetClassProcs. The parent parameter will be the parent of the window to be created. And the createProc should return the created window — that's its whole job, periodt.

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⭐ modalProc ⭐

modalProc gets invoked after all bindings on a widget have been triggered, in order to handle a modal loop. It's the cleanup-bestie of the group.

modalProc should have arguments and results that match the type Tk_ClassModalProc:

typedef void Tk_ClassModalProc(
        Tk_Window tkwin,
        XEvent *eventPtr);

The tkwin parameter to modalProc will be identical to the tkwin parameter passed to Tk_SetClassProcs. The eventPtr parameter will be a pointer to an XEvent structure describing the event being processed. 🌸

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👑 KEYWORDS 👑

callback, class

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and that's the whole page, bestie — you ate it 💖

this was pulled straight from Tk 8.4, and the page itself is Tk_SetClassProcs(3tk). mwah, go forth and register your procs 🎀✨🦋