feat(behaviors): `&key_repeat` behavior + tests.

* Add new `&key_repeat` behavior that captures and re-sends
  the most recently triggered keycode.

Closes: #853

app/CMakeLists.txt

@@ -48,6 +48,7 @@ if ((NOT CONFIG_ZMK_SPLIT) OR CONFIG_ZMK_SPLIT_BLE_ROLE_CENTRAL)
   target_sources(app PRIVATE src/behaviors/behavior_hold_tap.c)
   target_sources(app PRIVATE src/behaviors/behavior_sticky_key.c)
   target_sources(app PRIVATE src/behaviors/behavior_caps_word.c)
+  target_sources(app PRIVATE src/behaviors/behavior_key_repeat.c)
   target_sources(app PRIVATE src/behaviors/behavior_momentary_layer.c)
   target_sources(app PRIVATE src/behaviors/behavior_mod_morph.c)
   target_sources(app PRIVATE src/behaviors/behavior_outputs.c)

app/dts/behaviors.dtsi

@@ -15,3 +15,4 @@
 #include <behaviors/ext_power.dtsi>
 #include <behaviors/outputs.dtsi>
 #include <behaviors/caps_word.dtsi>
+#include <behaviors/key_repeat.dtsi>

app/dts/behaviors/key_repeat.dtsi

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2021 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <dt-bindings/zmk/keys.h>
+
+/ {
+	behaviors {
+		/omit-if-no-ref/ key_repeat: behavior_key_repeat {
+			compatible = "zmk,behavior-key-repeat";
+			label = "KEY_REPEAT";
+			#binding-cells = <0>;
+			usage-pages = <HID_USAGE_KEY>;
+		};
+	};
+};
+

app/dts/bindings/behaviors/zmk,behavior-key-repeat.yaml

@@ -0,0 +1,13 @@
+# Copyright (c) 2021 The ZMK Contributors
+# SPDX-License-Identifier: MIT
+
+description: Key repeat behavior
+
+compatible: "zmk,behavior-key-repeat"
+
+include: zero_param.yaml
+
+properties:
+  usage-pages:
+    type: array
+    required: true

app/src/behaviors/behavior_key_repeat.c

@@ -0,0 +1,124 @@
+/*
+ * Copyright (c) 2021 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#define DT_DRV_COMPAT zmk_behavior_key_repeat
+
+#include <device.h>
+#include <drivers/behavior.h>
+#include <logging/log.h>
+#include <zmk/behavior.h>
+
+#include <zmk/event_manager.h>
+#include <zmk/events/keycode_state_changed.h>
+
+LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
+
+#if DT_HAS_COMPAT_STATUS_OKAY(DT_DRV_COMPAT)
+
+struct behavior_key_repeat_config {
+    uint8_t index;
+    uint8_t usage_pages_count;
+    uint16_t usage_pages[];
+};
+
+struct behavior_key_repeat_data {
+    struct zmk_keycode_state_changed last_keycode_pressed;
+    struct zmk_keycode_state_changed current_keycode_pressed;
+};
+
+static int on_key_repeat_binding_pressed(struct zmk_behavior_binding *binding,
+                                         struct zmk_behavior_binding_event event) {
+    const struct device *dev = device_get_binding(binding->behavior_dev);
+    struct behavior_key_repeat_data *data = dev->data;
+
+    if (data->last_keycode_pressed.usage_page == 0) {
+        return ZMK_BEHAVIOR_OPAQUE;
+    }
+
+    memcpy(&data->current_keycode_pressed, &data->last_keycode_pressed,
+           sizeof(struct zmk_keycode_state_changed));
+    data->current_keycode_pressed.timestamp = k_uptime_get();
+
+    ZMK_EVENT_RAISE(new_zmk_keycode_state_changed(data->current_keycode_pressed));
+
+    return ZMK_BEHAVIOR_OPAQUE;
+}
+
+static int on_key_repeat_binding_released(struct zmk_behavior_binding *binding,
+                                          struct zmk_behavior_binding_event event) {
+    const struct device *dev = device_get_binding(binding->behavior_dev);
+    struct behavior_key_repeat_data *data = dev->data;
+
+    if (data->current_keycode_pressed.usage_page == 0) {
+        return ZMK_BEHAVIOR_OPAQUE;
+    }
+
+    data->current_keycode_pressed.timestamp = k_uptime_get();
+    data->current_keycode_pressed.state = false;
+
+    ZMK_EVENT_RAISE(new_zmk_keycode_state_changed(data->current_keycode_pressed));
+    return ZMK_BEHAVIOR_OPAQUE;
+}
+
+static const struct behavior_driver_api behavior_key_repeat_driver_api = {
+    .binding_pressed = on_key_repeat_binding_pressed,
+    .binding_released = on_key_repeat_binding_released,
+};
+
+static int key_repeat_keycode_state_changed_listener(const zmk_event_t *eh);
+
+ZMK_LISTENER(behavior_key_repeat, key_repeat_keycode_state_changed_listener);
+ZMK_SUBSCRIPTION(behavior_key_repeat, zmk_keycode_state_changed);
+
+static const struct device *devs[DT_NUM_INST_STATUS_OKAY(DT_DRV_COMPAT)];
+
+static int key_repeat_keycode_state_changed_listener(const zmk_event_t *eh) {
+    struct zmk_keycode_state_changed *ev = as_zmk_keycode_state_changed(eh);
+    if (ev == NULL || !ev->state) {
+        return ZMK_EV_EVENT_BUBBLE;
+    }
+
+    for (int i = 0; i < DT_NUM_INST_STATUS_OKAY(DT_DRV_COMPAT); i++) {
+        const struct device *dev = devs[i];
+        if (dev == NULL) {
+            continue;
+        }
+
+        struct behavior_key_repeat_data *data = dev->data;
+        const struct behavior_key_repeat_config *config = dev->config;
+
+        for (int u = 0; u < config->usage_pages_count; u++) {
+            if (config->usage_pages[u] == ev->usage_page) {
+                memcpy(&data->last_keycode_pressed, ev, sizeof(struct zmk_keycode_state_changed));
+                break;
+            }
+        }
+    }
+
+    return ZMK_EV_EVENT_BUBBLE;
+}
+
+static int behavior_key_repeat_init(const struct device *dev) {
+    const struct behavior_key_repeat_config *config = dev->config;
+    devs[config->index] = dev;
+    return 0;
+}
+
+#define KR_INST(n)                                                                                 \
+    static struct behavior_key_repeat_data behavior_key_repeat_data_##n = {};                      \
+    static struct behavior_key_repeat_config behavior_key_repeat_config_##n = {                    \
+        .index = n,                                                                                \
+        .usage_pages = DT_INST_PROP(n, usage_pages),                                               \
+        .usage_pages_count = DT_INST_PROP_LEN(n, usage_pages),                                     \
+    };                                                                                             \
+    DEVICE_DT_INST_DEFINE(n, behavior_key_repeat_init, device_pm_control_nop,                      \
+                          &behavior_key_repeat_data_##n, &behavior_key_repeat_config_##n,          \
+                          APPLICATION, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT,                        \
+                          &behavior_key_repeat_driver_api);
+
+DT_INST_FOREACH_STATUS_OKAY(KR_INST)
+
+#endif

app/tests/key-repeat/behavior_keymap.dtsi

@@ -0,0 +1,17 @@
+#include <dt-bindings/zmk/keys.h>
+#include <behaviors.dtsi>
+#include <dt-bindings/zmk/kscan_mock.h>
+
+/ {
+	keymap {
+		compatible = "zmk,keymap";
+		label = "Default keymap";
+
+		default_layer {
+			bindings = <
+			&key_repeat &kp A
+			&kp B &kp C_VOL_UP
+			>;
+		};
+	};
+};

app/tests/key-repeat/ignore-other-usage-page-events/events.patterns

@@ -0,0 +1,2 @@
+s/.*hid_listener_keycode_//p
+s/.*hid_implicit_modifiers_//p

app/tests/key-repeat/ignore-other-usage-page-events/keycode_events.snapshot

@@ -0,0 +1,12 @@
+pressed: usage_page 0x07 keycode 0x04 implicit_mods 0x00 explicit_mods 0x00
+press: Modifiers set to 0x00
+released: usage_page 0x07 keycode 0x04 implicit_mods 0x00 explicit_mods 0x00
+release: Modifiers set to 0x00
+pressed: usage_page 0x0c keycode 0xe9 implicit_mods 0x00 explicit_mods 0x00
+press: Modifiers set to 0x00
+released: usage_page 0x0c keycode 0xe9 implicit_mods 0x00 explicit_mods 0x00
+release: Modifiers set to 0x00
+pressed: usage_page 0x07 keycode 0x04 implicit_mods 0x00 explicit_mods 0x00
+press: Modifiers set to 0x00
+released: usage_page 0x07 keycode 0x04 implicit_mods 0x00 explicit_mods 0x00
+release: Modifiers set to 0x00

app/tests/key-repeat/ignore-other-usage-page-events/native_posix.keymap

@@ -0,0 +1,15 @@
+#include <dt-bindings/zmk/keys.h>
+#include <behaviors.dtsi>
+#include <dt-bindings/zmk/kscan_mock.h>
+#include "../behavior_keymap.dtsi"
+
+&kscan {
+	events = <
+	ZMK_MOCK_PRESS(0,1,10)
+	ZMK_MOCK_RELEASE(0,1,10)
+	ZMK_MOCK_PRESS(1,1,10)
+	ZMK_MOCK_RELEASE(1,1,10)
+	ZMK_MOCK_PRESS(0,0,10)
+	ZMK_MOCK_RELEASE(0,0,10)
+	>;
+};

app/tests/key-repeat/press-and-release-after-key-usage/events.patterns

@@ -0,0 +1,2 @@
+s/.*hid_listener_keycode_//p
+s/.*hid_implicit_modifiers_//p

app/tests/key-repeat/press-and-release-after-key-usage/keycode_events.snapshot

@@ -0,0 +1,8 @@
+pressed: usage_page 0x07 keycode 0x04 implicit_mods 0x00 explicit_mods 0x00
+press: Modifiers set to 0x00
+released: usage_page 0x07 keycode 0x04 implicit_mods 0x00 explicit_mods 0x00
+release: Modifiers set to 0x00
+pressed: usage_page 0x07 keycode 0x04 implicit_mods 0x00 explicit_mods 0x00
+press: Modifiers set to 0x00
+released: usage_page 0x07 keycode 0x04 implicit_mods 0x00 explicit_mods 0x00
+release: Modifiers set to 0x00

app/tests/key-repeat/press-and-release-after-key-usage/native_posix.keymap

@@ -0,0 +1,13 @@
+#include <dt-bindings/zmk/keys.h>
+#include <behaviors.dtsi>
+#include <dt-bindings/zmk/kscan_mock.h>
+#include "../behavior_keymap.dtsi"
+
+&kscan {
+	events = <
+	ZMK_MOCK_PRESS(0,1,10)
+	ZMK_MOCK_RELEASE(0,1,10)
+	ZMK_MOCK_PRESS(0,0,10)
+	ZMK_MOCK_RELEASE(0,0,10)
+	>;
+};

app/tests/key-repeat/send-nothing-if-no-keys-pressed-yet/events.patterns

@@ -0,0 +1,2 @@
+s/.*hid_listener_keycode_//p
+s/.*hid_implicit_modifiers_//p

app/tests/key-repeat/send-nothing-if-no-keys-pressed-yet/native_posix.keymap

@@ -0,0 +1,11 @@
+#include <dt-bindings/zmk/keys.h>
+#include <behaviors.dtsi>
+#include <dt-bindings/zmk/kscan_mock.h>
+#include "../behavior_keymap.dtsi"
+
+&kscan {
+	events = <
+	ZMK_MOCK_PRESS(0,0,10)
+	ZMK_MOCK_RELEASE(0,0,10)
+	>;
+};

docs/docs/behaviors/key-repeat.md

@@ -0,0 +1,38 @@
+---
+title: Key Repeat Behavior
+sidebar_label: Key Repeat
+---
+
+## Summary
+
+The key repeat behavior when triggered will send whatever keycode was last sent/triggered.
+
+### Behavior Binding
+
+- Reference: `&key_repeat`
+
+Example:
+
+```
+&key_repeat
+```
+
+### Configuration
+
+#### Usage Pages
+
+By default, the key repeat will only track the last pressed key from the HID "Key" usage page, and ignore events from other usages, e.g. Consumer page.
+
+If you'd rather have the repeat also capture and send Consumer page usages, you can update the existing behavior:
+
+```
+&key_repeat {
+    usage-pages = <HID_USAGE_KEY HID_USAGE_CONSUMER>;
+};
+
+/ {
+    keymap {
+        ...
+    };
+};
+```