# Keystrokes/LeaderPrefix/LeaderPrefix.ino
``` c++
,/* -*- mode: c++ -*-
* Kaleidoscope-LeaderPrefix -- Prefix arg for Leader plugin
* Copyright (C) 2021 Keyboard.io, Inc
*
* This program is free software: you can redistribute it and/or modify it under
* the terms of the GNU General Public License as published by the Free Software
* Foundation, version 3.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License along with
* this program. If not, see .
*/
#include
#include
#include
#include
#include "kaleidoscope/KeyEventTracker.h"
#include "kaleidoscope/LiveKeys.h"
#include "kaleidoscope/plugin.h"
// clang-format off
KEYMAPS(
[0] = KEYMAP_STACKED
(Key_NoKey, Key_1, Key_2, Key_3, Key_4, Key_5, Key_NoKey,
Key_Backtick, Key_Q, Key_W, Key_E, Key_R, Key_T, Key_Tab,
Key_PageUp, Key_A, Key_S, Key_D, Key_F, Key_G,
Key_PageDown, Key_Z, Key_X, Key_C, Key_V, Key_B, Key_Escape,
Key_LeftControl, Key_Backspace, Key_LeftGui, Key_LeftShift,
LEAD(0),
Key_skip, Key_6, Key_7, Key_8, Key_9, Key_0, Key_skip,
Key_Enter, Key_Y, Key_U, Key_I, Key_O, Key_P, Key_Equals,
Key_H, Key_J, Key_K, Key_L, Key_Semicolon, Key_Quote,
Key_skip, Key_N, Key_M, Key_Comma, Key_Period, Key_Slash, Key_Minus,
Key_RightShift, Key_RightAlt, Key_Spacebar, Key_RightControl,
LEAD(0)),
)
// clang-format on
namespace kaleidoscope {
namespace plugin {
// =============================================================================
/// Plugin to supply a numeric prefix argument to Leader key functions
///
/// This plugin lets the user type a numeric prefix after a Leader key is
/// pressed, but before the rest of the Leader sequence is begun, storing the
/// "prefix argument" and making it available to functions called from the
/// leader dictionary. LeaderPrefix allows us to define keys other than the
/// ones on the number row to be interpreted as the "digit" keys, because
/// whatever we use will need to be accessed without a layer change.
class LeaderPrefix : public Plugin {
public:
// We need to define `onKeyswitchEvent()` instead of `onKeyEvent()` because we
// need to intercept events before Leader sees them, and the Leader plugin
// uses the former.
EventHandlerResult onKeyswitchEvent(KeyEvent &event) {
// Every `onKeyswitchEvent()` function should begin with this to prevent
// re-processing events that it has already seen.
if (event_tracker_.shouldIgnore(event))
return EventHandlerResult::OK;
// `Active` means that we're actively building the prefix argument. If the
// plugin is not active, we're looking for a Leader key toggling on.
if (!active_) {
if (keyToggledOn(event.state) && isLeaderKey(event.key)) {
// A Leader key toggled on, so we set our state to "active", and set the
// arg value to zero.
active_ = true;
leader_arg_ = 0;
}
// Whether or not the plugin just became active, there's nothing more to
// do for this event.
return EventHandlerResult::OK;
}
// The plugin is "active", so we're looking for a "digit" key that just
// toggled on.
if (keyToggledOn(event.state)) {
// We search our array of digit keys to find one that matches the event.
// These "digit keys" are defined by their `KeyAddr` because they're
// probably independent of keymap and layer, and because a `KeyAddr` only
// takes one byte, whereas a `Key` takes two.
for (uint8_t i{0}; i < 10; ++i) {
if (digit_addrs_[i] == event.addr) {
// We found a match, which means that one of our "digit keys" toggled
// on. If this happens more than once, the user is typing a number
// with multiple digits, so we multiply the current value by ten
// before adding the new digit to the total.
leader_arg_ *= 10;
leader_arg_ += i;
// Next, we mask the key that was just pressed, so that nothing will
// happen when it is released.
live_keys.mask(event.addr);
// We return `ABORT` so that no other plugins (i.e. Leader) will see
// this keypress event.
return EventHandlerResult::ABORT;
}
}
}
// No match was found, so the key that toggled on was not one of our "digit
// keys". Presumably, this is the first key in the Leader sequence that is
// being typed. We leave the prefix argument at its current value so that
// it will still be set when the sequence is finished, and allow the event
// to pass through to the next plugin (i.e. Leader).
active_ = false;
return EventHandlerResult::OK;
}
uint16_t arg() const {
return leader_arg_;
}
private:
// The "digit keys": these are the keys on the number row of the Model01.
KeyAddr digit_addrs_[10] = {
KeyAddr(0, 14),
KeyAddr(0, 1),
KeyAddr(0, 2),
KeyAddr(0, 3),
KeyAddr(0, 4),
KeyAddr(0, 5),
KeyAddr(0, 10),
KeyAddr(0, 11),
KeyAddr(0, 12),
KeyAddr(0, 13),
};
// This event tracker is necessary to prevent re-processing events. Any
// plugin that defines `onKeyswitchEvent()` should use one.
KeyEventTracker event_tracker_;
// The current state of the plugin. It determines whether we're looking for a
// Leader keypress or building a prefix argument.
bool active_{false};
// The prefix argument itself.
uint16_t leader_arg_{0};
// Leader should probably provide this test, but since it doesn't, we add it
// here to determine if a key is a Leader key.
bool isLeaderKey(Key key) {
return (key >= ranges::LEAD_FIRST && key <= ranges::LEAD_LAST);
}
};
} // namespace plugin
} // namespace kaleidoscope
// This creates our plugin object.
kaleidoscope::plugin::LeaderPrefix LeaderPrefix;
auto &serial_port = Kaleidoscope.serialPort();
static void leaderTestX(uint8_t seq_index) {
serial_port.println(F("leaderTestX"));
}
static void leaderTestXX(uint8_t seq_index) {
serial_port.println(F("leaderTestXX"));
}
// This demonstrates how to use the prefix argument in a Leader function. In
// this case, our function just types as many `x` characters as specified by the
// prefix arg.
void leaderTestPrefix(uint8_t seq_index) {
// Read the prefix argument into a temporary variable:
uint8_t prefix_arg = LeaderPrefix.arg();
// Use a Macros helper function to tap the `X` key repeatedly.
while (prefix_arg-- > 0)
MacroSupport.tap(Key_X);
}
static const kaleidoscope::plugin::Leader::dictionary_t leader_dictionary[] PROGMEM =
LEADER_DICT({LEADER_SEQ(LEAD(0), Key_X), leaderTestX},
{LEADER_SEQ(LEAD(0), Key_X, Key_X), leaderTestXX},
{LEADER_SEQ(LEAD(0), Key_Z), leaderTestPrefix});
// The order matters here; LeaderPrefix won't work unless it precedes Leader in
// this list. If there are other plugins in the list, these two should ideally
// be next to each other, but that's not necessary.
KALEIDOSCOPE_INIT_PLUGINS(LeaderPrefix, Leader);
void setup() {
Kaleidoscope.setup();
Leader.dictionary = leader_dictionary;
}
void loop() {
Kaleidoscope.loop();
}
```