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diff --git a/quantum/repeat_key.h b/quantum/repeat_key.h
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+// Copyright 2022-2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include "quantum.h"
+
+uint16_t get_last_keycode(void);             /**< Keycode of the last key. */
+uint8_t  get_last_mods(void);                /**< Mods active with the last key. */
+void     set_last_keycode(uint16_t keycode); /**< Sets the last key. */
+void     set_last_mods(uint8_t mods);        /**< Sets the last mods. */
+
+/** @brief Gets the record for the last key. */
+keyrecord_t* get_last_record(void);
+
+/** @brief Sets keycode and record info for the last key. */
+void set_last_record(uint16_t keycode, keyrecord_t* record);
+
+/**
+ * @brief Signed count of times the key has been repeated or alternate repeated.
+ *
+ * @note The count is nonzero only while a repeated or alternate-repeated key is
+ *       being processed.
+ *
+ * When a key is pressed normally, the count is 0. When the Repeat Key is used
+ * to repeat a key, the count is 1 on the first repeat, 2 on the second repeat,
+ * and continuing up to 127.
+ *
+ * Negative counts are used similarly for alternate repeating. When the
+ * Alternate Repeat Key is used, the count is -1 on the first alternate repeat,
+ * -2 on the second, continuing down to -127.
+ */
+int8_t get_repeat_key_count(void);
+
+/**
+ * @brief Calls `process_record()` on a generated record repeating the last key.
+ * @param event Event information in the generated record.
+ */
+void repeat_key_invoke(const keyevent_t* event);
+
+#ifndef NO_ALT_REPEAT_KEY
+
+/**
+ * @brief Keycode to be used for alternate repeating.
+ *
+ * Alternate Repeat performs this keycode based on the last eligible pressed key
+ * and mods, get_last_keycode() and get_last_mods(). For example, when the last
+ * key was KC_UP, this function returns KC_DOWN. The function returns KC_NO if
+ * the last key doesn't have a defined alternate.
+ */
+uint16_t get_alt_repeat_key_keycode(void);
+
+/**
+ * @brief Calls `process_record()` to alternate repeat the last key.
+ * @param event Event information in the generated record.
+ */
+void alt_repeat_key_invoke(const keyevent_t* event);
+
+/**
+ * @brief Optional user callback to define additional alternate keys.
+ *
+ * When `get_alt_repeat_key_keycode()` is called, it first calls this callback.
+ * It should return a keycode representing the "alternate" of the given keycode
+ * and mods. Returning KC_NO defers to the default definitions in
+ * `get_alt_repeat_key_keycode()`.
+ */
+uint16_t get_alt_repeat_key_keycode_user(uint16_t keycode, uint8_t mods);
+
+#endif // NO_ALT_REPEAT_KEY