[libxkbcommon] Question about how to get xkb_keycode_t from xkb_keysym_t.

[Daniel Stone]

Hi,

On 1 June 2015 at 12:22, 박성진 <sj76.park at samsung.com> wrote:

>  Actually, we'd like to provide a key grab protocol to wayland client(s)
>
> with which each client can make request to grab a key to wayland
> compositor.
>
> To use the protocol, we need to provide one or more keycodes associated
> with a given keysym to the compositor as an argument.
>
> At this moment we would like to call the following API to get keycode(s)
> from a keysym if exist.
>
> Could you share your opinion ?
>

You might be better off asking to grab on a particular keysym instead,
since the compositor always needs to track the current state so can
trivially extract the keysym.


> /**
>
>  @param[in] keymap : xkb_keymap pointer
>
>  @param[in] keysym : xkb_keysym_t keysym
>
>  @param[out] keycodes array : xkb_keycode_t pointer
>
>  @return number of keycodes found on success, otherwise -1
>
> */
>
> XKB_EXPORT int xkb_keycodes_from_keysym(struct xkb_keymap *keymap,
> xkb_keysym_t keysym, xkb_keycode_t *keycodes);
>
> or XKB_EXPORT int xkb_keymap_keycodes_from_keysym(struct xkb_keymap
> *keymap, xkb_keysym_t keysym, xkb_keycode_t *keycodes);
>
On the face of it, this seems okay, except you might want to document that
0 is a valid, non-error, return code; presumably in order to deal with
keycode allocation, you would have to do something like:
xkb_keycode_t *keycodes;
int num_keycodes;

num_keycodes = xkb_keymap_keycodes_from_keysym(keymap, keysym, NULL);
if (num_keycodes == -1)
    return -1;
else if (num_keycodes == 0)
    return 1; /* still succeeded, just don't have any keycodes */

keycodes = malloc(num_keycodes * sizeof(*keycodes));
num_keycodes = xkb_keymap_keycodes_from_keysym(keymap, keysym, keycodes);

Cheers,
Daniel


> Thanks and regards,
>
> Sung-Jin Park
>
>
>
> ------- *Original Message* -------
>
> *Sender* : Daniel Stone<daniel at fooishbar.org>
>
> *Date* : 2015-06-01 18:57 (GMT+09:00)
>
> *Title* : Re: [libxkbcommon] Question about how to get xkb_keycode_t from
> xkb_keysym_t.
>
>
> Hi Sung-Jin,
>
> On 1 June 2015 at 07:16, Sung-Jin Park <sj76.park at samsung.com> wrote:
>
>>  I'd like to ask how to get keycode(s) from keysym using libxkbcommon
>> API.
>> Is there any API in libxkbcommon ?
>>
>
> The short answer is, no.
>
> The long answer is, look through the keymap and find every keycode which
> produces that keysym, which may be on various layouts (groups) or shift
> levels.
>
> If you can share more details of what you actually want to achieve, that
> might be helpful.
>
> Cheers,
> Daniel
>
>
>
>
>
>
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