feature(hold-tap): no-hold-flash for retro taps

This is an improvement on retro-tap, solving the 'flashing hold' issue
users people experience.

When the tapping-term expires, the hold key is normally pressed. When
retro-tap is enabled, this is undesirable; only an interrupted hold-tap
should trigger the hold behavior.

This change disables the hold behavior for the 'STATUS_HOLD_TIMER'
state when retro-tap is enabled, and makes sure the
'STATUS_HOLD_INTERRUPT' state will be triggered when appropriate.

app/src/behaviors/behavior_hold_tap.c

@@ -317,6 +317,10 @@ static inline const char *decision_moment_str(enum decision_moment decision_mome
 }
 
 static int press_binding(struct active_hold_tap *hold_tap) {
+    if (hold_tap->config->retro_tap && hold_tap->status == STATUS_HOLD_TIMER) {
+        return 0;
+    }
+
     struct zmk_behavior_binding_event event = {
         .position = hold_tap->position,
         .timestamp = hold_tap->timestamp,
@@ -335,6 +339,10 @@ static int press_binding(struct active_hold_tap *hold_tap) {
 }
 
 static int release_binding(struct active_hold_tap *hold_tap) {
+    if (hold_tap->config->retro_tap && hold_tap->status == STATUS_HOLD_TIMER) {
+        return 0;
+    }
+
     struct zmk_behavior_binding_event event = {
         .position = hold_tap->position,
         .timestamp = hold_tap->timestamp,
@@ -396,12 +404,18 @@ static void decide_retro_tap(struct active_hold_tap *hold_tap) {
     }
 }
 
-static void update_hold_status_for_retro_tap(uint32_t position) {
+static void update_hold_status_for_retro_tap(uint32_t ignore_position) {
     for (int i = 0; i < ZMK_BHV_HOLD_TAP_MAX_HELD; i++) {
         struct active_hold_tap *hold_tap = &active_hold_taps[i];
-        if (hold_tap->position != position && hold_tap->status == STATUS_HOLD_TIMER) {
+        if (hold_tap->position == ignore_position ||
+            hold_tap->position == ZMK_BHV_HOLD_TAP_POSITION_NOT_USED ||
+            hold_tap->config->retro_tap == false) {
+            continue;
+        }
+        if (hold_tap->status == STATUS_HOLD_TIMER) {
             LOG_DBG("Update hold tap %d status to hold-interrupt", hold_tap->position);
             hold_tap->status = STATUS_HOLD_INTERRUPT;
+            press_binding(hold_tap);
         }
     }
 }

app/tests/hold-tap/balanced/6-retro-tap/keycode_events.snapshot

@@ -5,16 +5,14 @@ kp_released: usage_page 0x07 keycode 0x09 implicit_mods 0x00 explicit_mods 0x00
 ht_binding_released: 0 cleaning up hold-tap
 ht_binding_pressed: 0 new undecided hold_tap
 ht_decide: 0 decided hold-timer (balanced decision moment timer)
-kp_pressed: usage_page 0x07 keycode 0xe1 implicit_mods 0x00 explicit_mods 0x00
-kp_released: usage_page 0x07 keycode 0xe1 implicit_mods 0x00 explicit_mods 0x00
 decide_retro_tap: 0 retro tap
 kp_pressed: usage_page 0x07 keycode 0x09 implicit_mods 0x00 explicit_mods 0x00
 kp_released: usage_page 0x07 keycode 0x09 implicit_mods 0x00 explicit_mods 0x00
 ht_binding_released: 0 cleaning up hold-tap
 ht_binding_pressed: 0 new undecided hold_tap
 ht_decide: 0 decided hold-timer (balanced decision moment timer)
-kp_pressed: usage_page 0x07 keycode 0xe1 implicit_mods 0x00 explicit_mods 0x00
 update_hold_status_for_retro_tap: Update hold tap 0 status to hold-interrupt
+kp_pressed: usage_page 0x07 keycode 0xe1 implicit_mods 0x00 explicit_mods 0x00
 kp_pressed: usage_page 0x07 keycode 0x07 implicit_mods 0x00 explicit_mods 0x00
 kp_released: usage_page 0x07 keycode 0x07 implicit_mods 0x00 explicit_mods 0x00
 kp_released: usage_page 0x07 keycode 0xe1 implicit_mods 0x00 explicit_mods 0x00

app/tests/hold-tap/hold-preferred/6-retro-tap/keycode_events.snapshot

@@ -5,16 +5,14 @@ kp_released: usage_page 0x07 keycode 0x09 implicit_mods 0x00 explicit_mods 0x00
 ht_binding_released: 0 cleaning up hold-tap
 ht_binding_pressed: 0 new undecided hold_tap
 ht_decide: 0 decided hold-timer (hold-preferred decision moment timer)
-kp_pressed: usage_page 0x07 keycode 0xe1 implicit_mods 0x00 explicit_mods 0x00
-kp_released: usage_page 0x07 keycode 0xe1 implicit_mods 0x00 explicit_mods 0x00
 decide_retro_tap: 0 retro tap
 kp_pressed: usage_page 0x07 keycode 0x09 implicit_mods 0x00 explicit_mods 0x00
 kp_released: usage_page 0x07 keycode 0x09 implicit_mods 0x00 explicit_mods 0x00
 ht_binding_released: 0 cleaning up hold-tap
 ht_binding_pressed: 0 new undecided hold_tap
 ht_decide: 0 decided hold-timer (hold-preferred decision moment timer)
-kp_pressed: usage_page 0x07 keycode 0xe1 implicit_mods 0x00 explicit_mods 0x00
 update_hold_status_for_retro_tap: Update hold tap 0 status to hold-interrupt
+kp_pressed: usage_page 0x07 keycode 0xe1 implicit_mods 0x00 explicit_mods 0x00
 kp_pressed: usage_page 0x07 keycode 0x07 implicit_mods 0x00 explicit_mods 0x00
 kp_released: usage_page 0x07 keycode 0x07 implicit_mods 0x00 explicit_mods 0x00
 kp_released: usage_page 0x07 keycode 0xe1 implicit_mods 0x00 explicit_mods 0x00

app/tests/hold-tap/tap-preferred/6-retro-tap/events.patterns

@@ -1,6 +0,0 @@
-s/.*hid_listener_keycode/kp/p
-s/.*mo_keymap_binding/mo/p
-s/.*on_hold_tap_binding/ht_binding/p
-s/.*decide_hold_tap/ht_decide/p
-s/.*update_hold_status_for_retro_tap/update_hold_status_for_retro_tap/p
-s/.*decide_retro_tap/decide_retro_tap/p

app/tests/hold-tap/tap-preferred/6-retro-tap/keycode_events.snapshot

@@ -1,21 +0,0 @@
-ht_binding_pressed: 0 new undecided hold_tap
-ht_decide: 0 decided tap (tap-preferred decision moment key-up)
-kp_pressed: usage_page 0x07 keycode 0x09 implicit_mods 0x00 explicit_mods 0x00
-kp_released: usage_page 0x07 keycode 0x09 implicit_mods 0x00 explicit_mods 0x00
-ht_binding_released: 0 cleaning up hold-tap
-ht_binding_pressed: 0 new undecided hold_tap
-ht_decide: 0 decided hold-timer (tap-preferred decision moment timer)
-kp_pressed: usage_page 0x07 keycode 0xe1 implicit_mods 0x00 explicit_mods 0x00
-kp_released: usage_page 0x07 keycode 0xe1 implicit_mods 0x00 explicit_mods 0x00
-decide_retro_tap: 0 retro tap
-kp_pressed: usage_page 0x07 keycode 0x09 implicit_mods 0x00 explicit_mods 0x00
-kp_released: usage_page 0x07 keycode 0x09 implicit_mods 0x00 explicit_mods 0x00
-ht_binding_released: 0 cleaning up hold-tap
-ht_binding_pressed: 0 new undecided hold_tap
-ht_decide: 0 decided hold-timer (tap-preferred decision moment timer)
-kp_pressed: usage_page 0x07 keycode 0xe1 implicit_mods 0x00 explicit_mods 0x00
-update_hold_status_for_retro_tap: Update hold tap 0 status to hold-interrupt
-kp_pressed: usage_page 0x07 keycode 0x07 implicit_mods 0x00 explicit_mods 0x00
-kp_released: usage_page 0x07 keycode 0x07 implicit_mods 0x00 explicit_mods 0x00
-kp_released: usage_page 0x07 keycode 0xe1 implicit_mods 0x00 explicit_mods 0x00
-ht_binding_released: 0 cleaning up hold-tap

app/tests/hold-tap/tap-preferred/6-retro-tap/native_posix.keymap

@@ -1,45 +0,0 @@
-#include <dt-bindings/zmk/keys.h>
-#include <behaviors.dtsi>
-#include <dt-bindings/zmk/kscan_mock.h>
-
-/ {
-	behaviors {
-		tp: behavior_tap_preferred {
-			compatible = "zmk,behavior-hold-tap";
-			label = "MOD_TAP";
-			#binding-cells = <2>;
-			flavor = "tap-preferred";
-			tapping_term_ms = <300>;
-			bindings = <&kp>, <&kp>;
-			retro-tap;
-		};
-	};
-
-	keymap {
-		compatible = "zmk,keymap";
-		label ="Default keymap";
-
-		default_layer {
-			bindings = <
-				&tp LEFT_SHIFT F &none
-				&kp D &none>;
-		};
-	};
-};
-
-
-&kscan {
-	events = <
-		/* tap */
-		ZMK_MOCK_PRESS(0,0,10) 
-		ZMK_MOCK_RELEASE(0,0,10) 
-		/* retro tap */
-		ZMK_MOCK_PRESS(0,0,400)
-		ZMK_MOCK_RELEASE(0,0,10) 
-		/* hold  */
-		ZMK_MOCK_PRESS(0,0,400)
-		ZMK_MOCK_PRESS(1,0,10)
-		ZMK_MOCK_RELEASE(1,0,10)
-		ZMK_MOCK_RELEASE(0,0,10) 
-	>;
-};

docs/docs/behaviors/hold-tap.md

@@ -51,7 +51,7 @@ In QMK, unlike ZMK, this functionality is enabled by default, and you turn it of
 
 If retro tap is enabled, the tap behavior is triggered when releasing the hold-tap key if no other key was pressed in the meantime.
 
-For example, if you press `&mt LEFT_SHIFT A` for a long time and then release it without pressing another key in the meantime, it will output `a`. (Actually, `LEFT_SHIFT` will be pressed when the tapping term expires, which is released just before the `a` is tapped.
+For example, if you press `&mt LEFT_SHIFT A` and then release it without pressing another key, it will output `a`.
 
 ```
 &mt {