Kaleidoscope/doc/plugin/Syster.md

# Kaleidoscope-Syster

Syster is a way to input symbols in a different way: instead of macros, Leader
sequences or the like, we trigger the special input mode, and enter the symbol's
name. Once finished, we hit `Space`, and this plugin will do the rest: delete
everything we typed, look up an action for the entered symbol, and execute that.

There are a number of ways this can be useful, but the easiest showcase is
symbolic Unicode input: `SYSTER coffee SPACE` turns into `☕`, with just a
little code.

## Using the plugin

To use the plugin, one needs to include the header and set up a function that
will handle the symbol actions:

```c++
#include <Kaleidoscope.h>
#include <Kaleidoscope-EEPROM-Settings.h>
#include <Kaleidoscope-HostOS.h>
#include <Kaleidoscope-Syster.h>
#include <Kaleidoscope-Unicode.h>
#include <kaleidoscope/hid.h>

void systerAction(kaleidoscope::plugin::Syster::action_t action, const char *symbol) {
  switch (action) {
  case kaleidoscope::plugin::Syster::StartAction:
    Unicode.type (0x2328);
    break;
  case kaleidoscope::plugin::Syster::EndAction:
    handleKeyswitchEvent (Key_Backspace, UNKNOWN_KEYSWITCH_LOCATION, IS_PRESSED | INJECTED);
    kaleidoscope::hid::sendKeyboardReport ();
    handleKeyswitchEvent (Key_Backspace, UNKNOWN_KEYSWITCH_LOCATION, WAS_PRESSED | INJECTED);
    kaleidoscope::hid::sendKeyboardReport ();
    break;
  case kaleidoscope::plugin::Syster::SymbolAction:
    Serial.print ("systerAction: symbol=");
    Serial.println (symbol);
    if (strcmp (symbol, "coffee") == 0) {
      Unicode.type (0x2615);
    }
    break;
  }
}

KALEIDOSCOPE_INIT_PLUGINS(EEPROMSettings, HostOS, Unicode, Syster);

void setup() {
  Serial.begin(9600);
  Kaleidoscope.setup ();
}
```

**Note** that we need to use the `Syster` object before any other that adds or
changes key behaviour! Failing to do so may result in unpredictable behaviour.

## Plugin methods

The plugin provides the `Syster` object, with no public methods. There are two
methods outside of the object, however, that can be overridden:

### `systerAction(action, symbol)`

> Called whenever an action needs to be taken, which can happen in three cases:

> First, when the `Syster` key is pressed and the alternate processing starts.
> In this case, `action` will be set to
> `kaleidoscope::plugin::Syster::StartAction`, and `symbol` will be `NULL`. This
> function can be used to do some setup to make it more obvious that the Syster
> input mode is active, such as sending a Unicode symbol to the host, or
> lighting up LEDs, or anything else we'd like.
>
> Second, when the sequence is finished with a `Space`. In this case, `action`
> will be set to `kaleidoscope::plugin::Syster::EndAction` and `symbol` will be
> `NULL`. This can be used to undo anything that the start action did, if need
> be.
>
> Third, when the action for the symbol should be made. In this case, `action`
> is set to `kaleidoscope::plugin::Syster::SymbolAction`, and `symbol` will be a
> C string. It is up to us, what we do with this information, how we handle it.

### `keyToChar(key)`

> A function that turns a keycode into a character. If using QWERTY on the host,
> the default implementation is sufficient. When using something else, you may
> have to reimplement this function.

## Dependencies

* [Kaleidoscope-Ranges](Ranges.md)

## Further reading

Starting from the [example][plugin:example] is the recommended way of getting
started with the plugin.

 [plugin:example]: ../../examples/Syster/Syster.ino

## Upgrading

Previous versions of `Syster` used `kaleidoscope::Syster::action_t` as the type
of Syster actions. In newer versions, this is
`kaleidoscope::plugin::Syster::action_t`. The old name still works, but will be
removed by 2019-01-14.