1 files changed, 149 insertions, 50 deletions

diff --git a/quantum/process_keycode/process_auto_shift.c b/quantum/process_keycode/process_auto_shift.c
index b1267922c..a2d315408 100644
--- a/quantum/process_keycode/process_auto_shift.c
+++ b/quantum/process_keycode/process_auto_shift.c
@@ -16,48 +16,149 @@
 
 #ifdef AUTO_SHIFT_ENABLE
 
+#    include <stdbool.h>
 #    include <stdio.h>
 
 #    include "process_auto_shift.h"
 
-static bool     autoshift_enabled = true;
 static uint16_t autoshift_time    = 0;
 static uint16_t autoshift_timeout = AUTO_SHIFT_TIMEOUT;
 static uint16_t autoshift_lastkey = KC_NO;
+static struct {
+    // Whether autoshift is enabled.
+    bool enabled : 1;
+    // Whether the last auto-shifted key was released after the timeout.  This
+    // is used to replicate the last key for a tap-then-hold.
+    bool lastshifted : 1;
+    // Whether an auto-shiftable key has been pressed but not processed.
+    bool in_progress : 1;
+    // Whether the auto-shifted keypress has been registered.
+    bool holding_shift : 1;
+} autoshift_flags = {true, false, false, false};
+
+/** \brief Record the press of an autoshiftable key
+ *
+ *  \return Whether the record should be further processed.
+ */
+static bool autoshift_press(uint16_t keycode, uint16_t now, keyrecord_t *record) {
+    if (!autoshift_flags.enabled) {
+        return true;
+    }
+
+#    ifndef AUTO_SHIFT_MODIFIERS
+    if (get_mods() & (~MOD_BIT(KC_LSFT))) {
+        return true;
+    }
+#    endif
+#    ifdef AUTO_SHIFT_REPEAT
+    const uint16_t elapsed = TIMER_DIFF_16(now, autoshift_time);
+#        ifndef AUTO_SHIFT_NO_AUTO_REPEAT
+    if (!autoshift_flags.lastshifted) {
+#        endif
+        if (elapsed < TAPPING_TERM && keycode == autoshift_lastkey) {
+            // Allow a tap-then-hold for keyrepeat.
+            if (!autoshift_flags.lastshifted) {
+                register_code(autoshift_lastkey);
+            } else {
+                // Simulate pressing the shift key.
+                add_weak_mods(MOD_BIT(KC_LSFT));
+                register_code(autoshift_lastkey);
+            }
+            return false;
+        }
+#        ifndef AUTO_SHIFT_NO_AUTO_REPEAT
+    }
+#        endif
+#    endif
 
-void autoshift_flush(void) {
-    if (autoshift_lastkey != KC_NO) {
-        uint16_t elapsed = timer_elapsed(autoshift_time);
+    // Record the keycode so we can simulate it later.
+    autoshift_lastkey           = keycode;
+    autoshift_time              = now;
+    autoshift_flags.in_progress = true;
 
-        if (elapsed > autoshift_timeout) {
-            tap_code16(LSFT(autoshift_lastkey));
+#    if !defined(NO_ACTION_ONESHOT) && !defined(NO_ACTION_TAPPING)
+    clear_oneshot_layer_state(ONESHOT_OTHER_KEY_PRESSED);
+#    endif
+    return false;
+}
+
+/** \brief Registers an autoshiftable key under the right conditions
+ *
+ * If the autoshift delay has elapsed, register a shift and the key.
+ *
+ * If the autoshift key is released before the delay has elapsed, register the
+ * key without a shift.
+ */
+static void autoshift_end(uint16_t keycode, uint16_t now, bool matrix_trigger) {
+    // Called on key down with KC_NO, auto-shifted key up, and timeout.
+    if (autoshift_flags.in_progress) {
+        // Process the auto-shiftable key.
+        autoshift_flags.in_progress = false;
+
+        // Time since the initial press was recorded.
+        const uint16_t elapsed = TIMER_DIFF_16(now, autoshift_time);
+        if (elapsed < autoshift_timeout) {
+            register_code(autoshift_lastkey);
+            autoshift_flags.lastshifted = false;
         } else {
-            tap_code(autoshift_lastkey);
+            // Simulate pressing the shift key.
+            add_weak_mods(MOD_BIT(KC_LSFT));
+            register_code(autoshift_lastkey);
+            autoshift_flags.lastshifted = true;
+#    if defined(AUTO_SHIFT_REPEAT) && !defined(AUTO_SHIFT_NO_AUTO_REPEAT)
+            if (matrix_trigger) {
+                // Prevents release.
+                return;
+            }
+#    endif
         }
 
-        autoshift_time    = 0;
-        autoshift_lastkey = KC_NO;
+#    if TAP_CODE_DELAY > 0
+        wait_ms(TAP_CODE_DELAY);
+#    endif
+        unregister_code(autoshift_lastkey);
+        del_weak_mods(MOD_BIT(KC_LSFT));
+    } else {
+        // Release after keyrepeat.
+        unregister_code(keycode);
+        if (keycode == autoshift_lastkey) {
+            // This will only fire when the key was the last auto-shiftable
+            // pressed. That prevents aaaaBBBB then releasing a from unshifting
+            // later Bs (if B wasn't auto-shiftable).
+            del_weak_mods(MOD_BIT(KC_LSFT));
+        }
     }
+    send_keyboard_report();  // del_weak_mods doesn't send one.
+    // Roll the autoshift_time forward for detecting tap-and-hold.
+    autoshift_time = now;
 }
 
-void autoshift_on(uint16_t keycode) {
-    autoshift_time    = timer_read();
-    autoshift_lastkey = keycode;
+/** \brief Simulates auto-shifted key releases when timeout is hit
+ *
+ *  Can be called from \c matrix_scan_user so that auto-shifted keys are sent
+ *  immediately after the timeout has expired, rather than waiting for the key
+ *  to be released.
+ */
+void autoshift_matrix_scan(void) {
+    if (autoshift_flags.in_progress) {
+        const uint16_t now     = timer_read();
+        const uint16_t elapsed = TIMER_DIFF_16(now, autoshift_time);
+        if (elapsed >= autoshift_timeout) {
+            autoshift_end(autoshift_lastkey, now, true);
+        }
+    }
 }
 
 void autoshift_toggle(void) {
-    if (autoshift_enabled) {
-        autoshift_enabled = false;
-        autoshift_flush();
-    } else {
-        autoshift_enabled = true;
-    }
+    autoshift_flags.enabled = !autoshift_flags.enabled;
+    del_weak_mods(MOD_BIT(KC_LSFT));
 }
 
-void autoshift_enable(void) { autoshift_enabled = true; }
+void autoshift_enable(void) { autoshift_flags.enabled = true; }
+
 void autoshift_disable(void) {
-    autoshift_enabled = false;
-    autoshift_flush();
+    autoshift_flags.enabled = false;
+    del_weak_mods(MOD_BIT(KC_LSFT));
 }
 
 #    ifndef AUTO_SHIFT_NO_SETUP
@@ -70,19 +171,30 @@ void autoshift_timer_report(void) {
 }
 #    endif
 
-bool get_autoshift_state(void) { return autoshift_enabled; }
+bool get_autoshift_state(void) { return autoshift_flags.enabled; }
 
 uint16_t get_autoshift_timeout(void) { return autoshift_timeout; }
 
 void set_autoshift_timeout(uint16_t timeout) { autoshift_timeout = timeout; }
 
 bool process_auto_shift(uint16_t keycode, keyrecord_t *record) {
+    // Note that record->event.time isn't reliable, see:
+    // https://github.com/qmk/qmk_firmware/pull/9826#issuecomment-733559550
+    const uint16_t now = timer_read();
+
     if (record->event.pressed) {
+        if (autoshift_flags.in_progress) {
+            // Evaluate previous key if there is one. Doing this elsewhere is
+            // more complicated and easier to break.
+            autoshift_end(KC_NO, now, false);
+        }
+        // For pressing another key while keyrepeating shifted autoshift.
+        del_weak_mods(MOD_BIT(KC_LSFT));
+
         switch (keycode) {
             case KC_ASTG:
                 autoshift_toggle();
                 return true;
-
             case KC_ASON:
                 autoshift_enable();
                 return true;
@@ -102,41 +214,28 @@ bool process_auto_shift(uint16_t keycode, keyrecord_t *record) {
                 autoshift_timer_report();
                 return true;
 #    endif
+        }
+    }
+
+    switch (keycode) {
 #    ifndef NO_AUTO_SHIFT_ALPHA
-            case KC_A ... KC_Z:
+        case KC_A ... KC_Z:
 #    endif
 #    ifndef NO_AUTO_SHIFT_NUMERIC
-            case KC_1 ... KC_0:
+        case KC_1 ... KC_0:
 #    endif
 #    ifndef NO_AUTO_SHIFT_SPECIAL
-            case KC_TAB:
-            case KC_MINUS ... KC_SLASH:
-            case KC_NONUS_BSLASH:
-#    endif
-                autoshift_flush();
-                if (!autoshift_enabled) return true;
-
-#    ifndef AUTO_SHIFT_MODIFIERS
-                if (get_mods()) {
-                    return true;
-                }
-#    endif
-                autoshift_on(keycode);
-
-                // We need some extra handling here for OSL edge cases
-#    if !defined(NO_ACTION_ONESHOT) && !defined(NO_ACTION_TAPPING)
-                clear_oneshot_layer_state(ONESHOT_OTHER_KEY_PRESSED);
+        case KC_TAB:
+        case KC_MINUS ... KC_SLASH:
+        case KC_NONUS_BSLASH:
 #    endif
+            if (record->event.pressed) {
+                return autoshift_press(keycode, now, record);
+            } else {
+                autoshift_end(keycode, now, false);
                 return false;
-
-            default:
-                autoshift_flush();
-                return true;
-        }
-    } else {
-        autoshift_flush();
+            }
     }
-
     return true;
 }