XkbKeyHasActions(3)

✨ NAME ✨

XkbKeyHasActions(3) is from the XKB FUNCTIONS manual, and it's here to answer one very specific question: does the key for a given keycode have any actions attached to it? 💖

🎀 SYNOPSIS 🎀

int XkbKeyHasActions (XkbDescPtr xkb, KeyCode keycode);

🫶 ARGUMENTS 🫶

• xkb — the Xkb description you're curious about.
• keycode — the keycode you're checking.

👑 DESCRIPTION 👑

Okay so, a key action is literally the thing that defines the effect key presses and releases have on the server's internal state. Example: the expected key action for pressing the Shift key is to set the Shift modifier. And for each keysym bound to each key, there is zero or one key action. Periodt. 💅

Think of it like this: just as the entire list of key symbols for the keyboard mapping is held in the syms field of the client map, the entire list of key actions for the keyboard mapping is held in the acts array of the server map. The total size of acts is specified by size_acts, and the number of entries is specified by num_acts. ✨

The key_acts array is indexed by keycode, and it describes the actions associated with a key. It has min_key_code unused entries at the start to allow direct indexing using a keycode. If a key_acts entry is zero, that means the key does not have any actions associated with it. If an entry is not zero, that entry represents an index into the acts field of the server map — much like how the offset field of a KeySymMapRec structure is an index into the syms field of the client map. 🦋

Why is the acts field a linear list of XkbActions? To reduce the memory consumption associated with a keymap. Because Xkb allows individual keys to have multiple shift levels and a different number of groups per key, a single two-dimensional array of KeySyms would potentially be very large and sparse. Instead, Xkb provides a small two-dimensional array of XkbActions for each key. To store all of these individual arrays, Xkb concatenates each array together in the acts field of the server map. 🎀

The key action structures consist only of fields of type char or unsigned char. This is done to optimize data transfer when the server sends bytes over the wire. If the fields are anything but bytes, the server has to sift through all of the actions and swap any nonbyte fields. Because they consist of nothing but bytes, it can just copy them out. 🔥

And finally: XkbKeyHasActions returns True if the key corresponding to keycode has any actions associated with it; otherwise, it returns False. 🌸

💅 RETURN VALUES 💅

• True — the XkbKeyHasActions function will return True if the key corresponding to keycode has any actions associated with it.
• False — the XkbKeyHasActions function will return False if the key corresponding to keycode does not have any actions associated with it.

🧚 STRUCTURES 🧚

The KeySymMapRec structure is defined as follows:

           #define XkbNumKbdGroups             4
           #define XkbMaxKbdGroup              (XkbNumKbdGroups-1)

           typedef struct {                    /* map to keysyms for a single keycode */
               unsigned char       kt_index[XkbNumKbdGroups];  /* key type index for each group */
               unsigned char       group_info; /* # of groups and out of range group handling */
               unsigned char       width;      /* max # of shift levels for key */
               unsigned short      offset;     /* index to keysym table in syms array */
       } XkbSymMapRec, *XkbSymMapPtr;

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That's the whole vibe check, bestie 🫶 This page comes from X Version 11, libX11 1.8.14, and it goes by XkbKeyHasActions(3) — mwah 💋✨