2 files changed, 148 insertions, 124 deletions

diff --git a/quantum/process_keycode/process_combo.c b/quantum/process_keycode/process_combo.c
index 13f8bbb33..a157ed48b 100644
--- a/quantum/process_keycode/process_combo.c
+++ b/quantum/process_keycode/process_combo.c
@@ -14,141 +14,164 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "process_combo.h"
 #include "print.h"
+#include "process_combo.h"
 
-
-__attribute__ ((weak))
-combo_t key_combos[COMBO_COUNT] = {
+__attribute__((weak)) combo_t key_combos[COMBO_COUNT] = {
 
 };
 
-__attribute__ ((weak))
-void process_combo_event(uint8_t combo_index, bool pressed) {
-
-}
+__attribute__((weak)) void process_combo_event(uint8_t combo_index,
+                                               bool pressed) {}
 
+static uint16_t timer = 0;
 static uint8_t current_combo_index = 0;
+static bool drop_buffer = false;
+static bool is_active = false;
 
-static inline void send_combo(uint16_t action, bool pressed)
-{
-    if (action) {
-        if (pressed) {
-            register_code16(action);
-        } else {
-            unregister_code16(action);
-        }
-    } else {
-        process_combo_event(current_combo_index, pressed);
-    }
-}
-
-#define ALL_COMBO_KEYS_ARE_DOWN     (((1<<count)-1) == combo->state)
-#define NO_COMBO_KEYS_ARE_DOWN      (0 == combo->state)
-#define KEY_STATE_DOWN(key)         do{ combo->state |= (1<<key); } while(0)
-#define KEY_STATE_UP(key)           do{ combo->state &= ~(1<<key); } while(0)
-static bool process_single_combo(combo_t *combo, uint16_t keycode, keyrecord_t *record) 
-{
-    uint8_t count = 0;
-    uint8_t index = -1;
-    /* Find index of keycode and number of combo keys */
-    for (const uint16_t *keys = combo->keys; ;++count) {
-        uint16_t key = pgm_read_word(&keys[count]);
-        if (keycode == key) index = count;
-        if (COMBO_END == key) break;
-    }
-
-    /* Return if not a combo key */
-    if (-1 == (int8_t)index) return false;
-
-    /* The combos timer is used to signal whether the combo is active */
-    bool is_combo_active = combo->is_active;
-
-    if (record->event.pressed) {
-        KEY_STATE_DOWN(index);
-
-        if (is_combo_active) {
-            if (ALL_COMBO_KEYS_ARE_DOWN) { /* Combo was pressed */
-                send_combo(combo->keycode, true);
-                combo->is_active = false;
-            } else { /* Combo key was pressed */
-                combo->timer = timer_read();
-                combo->is_active = true;
+static uint8_t buffer_size = 0;
 #ifdef COMBO_ALLOW_ACTION_KEYS
-                combo->prev_record = *record;
+static keyrecord_t key_buffer[MAX_COMBO_LENGTH];
 #else
-                combo->prev_key = keycode;
+static uint16_t key_buffer[MAX_COMBO_LENGTH];
 #endif
-            }
-        }
+
+static inline void send_combo(uint16_t action, bool pressed) {
+  if (action) {
+    if (pressed) {
+      register_code16(action);
     } else {
-        if (ALL_COMBO_KEYS_ARE_DOWN) { /* Combo was released */
-            send_combo(combo->keycode, false);
-        }
+      unregister_code16(action);
+    }
+  } else {
+    process_combo_event(current_combo_index, pressed);
+  }
+}
 
-        if (is_combo_active) { /* Combo key was tapped */
+static inline void dump_key_buffer(bool emit) {
+  if (buffer_size == 0) {
+    return;
+  }
+
+  if (emit) {
+    for (uint8_t i = 0; i < buffer_size; i++) {
 #ifdef COMBO_ALLOW_ACTION_KEYS
-            record->event.pressed = true;
-            process_action(record, store_or_get_action(record->event.pressed, record->event.key));
-            record->event.pressed = false;
-            process_action(record, store_or_get_action(record->event.pressed, record->event.key));
+      const action_t action = store_or_get_action(key_buffer[i].event.pressed,
+                                                  key_buffer[i].event.key);
+      process_action(&(key_buffer[i]), action);
 #else
-            register_code16(keycode);
-            send_keyboard_report();
-            unregister_code16(keycode);
+      register_code16(key_buffer[i]);
+      send_keyboard_report();
 #endif
-            combo->is_active = false;
-            combo->timer = 0;            
-        }
-
-        KEY_STATE_UP(index);        
     }
+  }
 
-    if (NO_COMBO_KEYS_ARE_DOWN) {
-        combo->is_active = true;
-        combo->timer = 0;
-    }
-
-    return is_combo_active;
+  buffer_size = 0;
 }
 
-bool process_combo(uint16_t keycode, keyrecord_t *record)
-{
-    bool is_combo_key = false;
+#define ALL_COMBO_KEYS_ARE_DOWN (((1 << count) - 1) == combo->state)
+#define KEY_STATE_DOWN(key)                                                    \
+  do {                                                                         \
+    combo->state |= (1 << key);                                                \
+  } while (0)
+#define KEY_STATE_UP(key)                                                      \
+  do {                                                                         \
+    combo->state &= ~(1 << key);                                               \
+  } while (0)
+
+static bool process_single_combo(combo_t *combo, uint16_t keycode,
+                                 keyrecord_t *record) {
+  uint8_t count = 0;
+  uint8_t index = -1;
+  /* Find index of keycode and number of combo keys */
+  for (const uint16_t *keys = combo->keys;; ++count) {
+    uint16_t key = pgm_read_word(&keys[count]);
+    if (keycode == key)
+      index = count;
+    if (COMBO_END == key)
+      break;
+  }
+
+  /* Continue processing if not a combo key */
+  if (-1 == (int8_t)index)
+    return false;
+
+  bool is_combo_active = is_active;
+
+  if (record->event.pressed) {
+    KEY_STATE_DOWN(index);
+
+    if (is_combo_active) {
+      if (ALL_COMBO_KEYS_ARE_DOWN) { /* Combo was pressed */
+        send_combo(combo->keycode, true);
+        drop_buffer = true;
+      }
+    }
+  } else {
+    if (ALL_COMBO_KEYS_ARE_DOWN) { /* Combo was released */
+      send_combo(combo->keycode, false);
+    } else {
+      /* continue processing without immediately returning */
+      is_combo_active = false;
+    }
 
-    for (current_combo_index = 0; current_combo_index < COMBO_COUNT; ++current_combo_index) {
-        combo_t *combo = &key_combos[current_combo_index];
-        is_combo_key |= process_single_combo(combo, keycode, record);
-    }    
+    KEY_STATE_UP(index);
+  }
 
-    return !is_combo_key;
+  return is_combo_active;
 }
 
-void matrix_scan_combo(void)
-{
-    for (int i = 0; i < COMBO_COUNT; ++i) {
-        // Do not treat the (weak) key_combos too strict.
-        #pragma GCC diagnostic push
-        #pragma GCC diagnostic ignored "-Warray-bounds"
-        combo_t *combo = &key_combos[i];
-        #pragma GCC diagnostic pop
-        if (combo->is_active &&
-            combo->timer &&
-            timer_elapsed(combo->timer) > COMBO_TERM) {
-
-            /* This disables the combo, meaning key events for this
-             * combo will be handled by the next processors in the chain 
-             */
-            combo->is_active = false;
+#define NO_COMBO_KEYS_ARE_DOWN (0 == combo->state)
+
+bool process_combo(uint16_t keycode, keyrecord_t *record) {
+  bool is_combo_key = false;
+  drop_buffer = false;
+  bool no_combo_keys_pressed = false;
+
+  for (current_combo_index = 0; current_combo_index < COMBO_COUNT;
+       ++current_combo_index) {
+    combo_t *combo = &key_combos[current_combo_index];
+    is_combo_key |= process_single_combo(combo, keycode, record);
+    no_combo_keys_pressed |= NO_COMBO_KEYS_ARE_DOWN;
+  }
+
+  if (drop_buffer) {
+    /* buffer is only dropped when we complete a combo, so we refresh the timer
+     * here */
+    timer = timer_read();
+    dump_key_buffer(false);
+  } else if (!is_combo_key) {
+    /* if no combos claim the key we need to emit the keybuffer */
+    dump_key_buffer(true);
+
+    // reset state if there are no combo keys pressed at all
+    if (no_combo_keys_pressed) {
+      timer = 0;
+      is_active = true;
+    }
+  } else if (record->event.pressed && is_active) {
+    /* otherwise the key is consumed and placed in the buffer */
+    timer = timer_read();
 
+    if (buffer_size < MAX_COMBO_LENGTH) {
 #ifdef COMBO_ALLOW_ACTION_KEYS
-            process_action(&combo->prev_record, 
-                store_or_get_action(combo->prev_record.event.pressed, 
-                                    combo->prev_record.event.key));
+      key_buffer[buffer_size++] = *record;
 #else
-            unregister_code16(combo->prev_key);
-            register_code16(combo->prev_key);
+      key_buffer[buffer_size++] = keycode;
 #endif
-        }
     }
+  }
+
+  return !is_combo_key;
+}
+
+void matrix_scan_combo(void) {
+  if (is_active && timer && timer_elapsed(timer) > COMBO_TERM) {
+
+    /* This disables the combo, meaning key events for this
+     * combo will be handled by the next processors in the chain
+     */
+    is_active = false;
+    dump_key_buffer(true);
+  }
 }
diff --git a/quantum/process_keycode/process_combo.h b/quantum/process_keycode/process_combo.h
index a5787c9ed..f06d2d345 100644
--- a/quantum/process_keycode/process_combo.h
+++ b/quantum/process_keycode/process_combo.h
@@ -17,33 +17,34 @@
 #ifndef PROCESS_COMBO_H
 #define PROCESS_COMBO_H
 
-#include <stdint.h>
 #include "progmem.h"
 #include "quantum.h"
+#include <stdint.h>
 
-typedef struct
-{
-    const uint16_t *keys;
-    uint16_t keycode;        
 #ifdef EXTRA_EXTRA_LONG_COMBOS
-    uint32_t state;
+#define MAX_COMBO_LENGTH 32
 #elif EXTRA_LONG_COMBOS
-    uint16_t state;
+#define MAX_COMBO_LENGTH 16
 #else
-    uint8_t state;
+#define MAX_COMBO_LENGTH 8
 #endif
-    uint16_t timer;
-    bool is_active;
-#ifdef COMBO_ALLOW_ACTION_KEYS
-    keyrecord_t prev_record;
+
+typedef struct {
+  const uint16_t *keys;
+  uint16_t keycode;
+#ifdef EXTRA_EXTRA_LONG_COMBOS
+  uint32_t state;
+#elif EXTRA_LONG_COMBOS
+  uint16_t state;
 #else
-    uint16_t prev_key;
+  uint8_t state;
 #endif
 } combo_t;
 
-
-#define COMBO(ck, ca)       {.keys = &(ck)[0], .keycode = (ca)}
-#define COMBO_ACTION(ck)    {.keys = &(ck)[0]}
+#define COMBO(ck, ca)                                                          \
+  { .keys = &(ck)[0], .keycode = (ca) }
+#define COMBO_ACTION(ck)                                                       \
+  { .keys = &(ck)[0] }
 
 #define COMBO_END 0
 #ifndef COMBO_COUNT