Groups provide a facility for grouping related rules, similar to functions in other programming languages. When used effectively, groups can reduce the size and complexity of your keyboards significantly.
Groups can match on context only, or on context and keystroke. The context-only groups can be very useful for pre- and post-processing rules, such as reordering stacked diacritics.
Only the first rule in the group that matches will be fired. There are two special rules,
will then fire if a rule is either matched or not matched, respectively. The criteria for not matching is a little more nuanced, however, as a keystroke
is deemed to have not matched only if it would have generated a character anyway, so F1 would not fire the
rule, unlike a character key.
Rules in a group have a special order. They are ordered first by length of context, with longest context first, and then by line order in the file. This slightly non-intuitive ordering makes it much simpler to group rules according to their function, rather than necessarily by their priority.
The examples below show the two types of groups.
group(mygroup) c context only 'a' > 'b' group(mygroup) using keys c context and keystroke 'a' + 'a' > 'c'
use() statement allows you move into another group when a rule
is matched. All output from the current group preceding the
use() statement is processed into the context
before the subsequent group is entered (although it is not sent to the application until processing finishes for the current
keystroke). For example:
c This example prohibits two vowels in a row store(vowel) 'aeiouAEIOU' begin Unicode > use(precheck) group(precheck) any(vowel) > context use(precedingVowel) nomatch > use(main) c Preceding character is not a vowel. Do normal processing. group(precedingVowel) using keys + any(vowel) > beep nomatch > use(main) c This key is not a vowel. Do normal processing. group(main) using keys c Main processing goes here
Some important things to note from this example:
The first rule (
any(vowel) > context use(precedingVowel)) uses the
context statement to copy the matched context to the output, so that Keyman can move it back into the context for
use with the
precedingVowel group. If you do not do this, the context will be dropped before
used, and the character will be deleted from the screen.
If the final group processed is a context and keystroke group (
using keys), and there is no
nomatch rule, and the
keystroke is not matched in the group, the keystroke will be output to the screen, regardless of whether or not it was matched in
The following statements and special rules are used with groups:
- Defines the starting group for the keyboard layout
- Starts a new group of rules
- A system rule that is fired when another rule in the group is matched
- A system rule that is fired when no rule is matched
- Stops processing of the current keystroke
- Starts processing in another group