feat(behaviors): Add caps word (&caps_word).

* Add new `&caps_word` behavior that acts like caps lock, but
  releases automatically when any "break" keycode is pressed.

app/CMakeLists.txt

@@ -47,6 +47,7 @@ if ((NOT CONFIG_ZMK_SPLIT) OR CONFIG_ZMK_SPLIT_BLE_ROLE_CENTRAL)
   target_sources(app PRIVATE src/behaviors/behavior_reset.c)
   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_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

@@ -14,3 +14,4 @@
 #include <behaviors/bluetooth.dtsi>
 #include <behaviors/ext_power.dtsi>
 #include <behaviors/outputs.dtsi>
+#include <behaviors/caps_word.dtsi>

app/dts/behaviors/caps_word.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/ caps_word: behavior_caps_word {
+			compatible = "zmk,behavior-caps-word";
+			label = "CAPS_WORD";
+			#binding-cells = <0>;
+			continue-list = <UNDERSCORE>;
+		};
+	};
+};
+

app/dts/bindings/behaviors/zmk,behavior-caps-word.yaml

@@ -0,0 +1,15 @@
+# Copyright (c) 2021 The ZMK Contributors
+# SPDX-License-Identifier: MIT
+
+description: Caps word behavior
+
+compatible: "zmk,behavior-caps-word"
+
+include: zero_param.yaml
+
+properties:
+  continue-list:
+    type: array
+    required: true
+  mods:
+    type: int

app/src/behaviors/behavior_caps_word.c

@@ -0,0 +1,186 @@
+/*
+ * Copyright (c) 2021 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#define DT_DRV_COMPAT zmk_behavior_caps_word
+
+#include <device.h>
+#include <drivers/behavior.h>
+#include <logging/log.h>
+#include <zmk/behavior.h>
+
+#include <zmk/endpoints.h>
+#include <zmk/event_manager.h>
+#include <zmk/events/position_state_changed.h>
+#include <zmk/events/keycode_state_changed.h>
+#include <zmk/events/modifiers_state_changed.h>
+#include <zmk/hid.h>
+#include <zmk/keymap.h>
+
+LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
+
+#if DT_HAS_COMPAT_STATUS_OKAY(DT_DRV_COMPAT)
+
+struct caps_word_continue_item {
+    uint16_t page;
+    uint32_t id;
+    uint8_t implicit_modifiers;
+};
+
+struct behavior_caps_word_config {
+    zmk_mod_flags_t mods;
+    uint8_t index;
+    uint8_t continuations_count;
+    struct caps_word_continue_item continuations[];
+};
+
+struct behavior_caps_word_data {
+    bool active;
+};
+
+static void activate_caps_word(const struct device *dev) {
+    struct behavior_caps_word_data *data = dev->data;
+
+    data->active = true;
+}
+
+static void deactivate_caps_word(const struct device *dev) {
+    struct behavior_caps_word_data *data = dev->data;
+
+    data->active = false;
+}
+
+static int on_caps_word_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_caps_word_data *data = dev->data;
+
+    if (data->active) {
+        deactivate_caps_word(dev);
+    } else {
+        activate_caps_word(dev);
+    }
+
+    return ZMK_BEHAVIOR_OPAQUE;
+}
+
+static int on_caps_word_binding_released(struct zmk_behavior_binding *binding,
+                                         struct zmk_behavior_binding_event event) {
+    return ZMK_BEHAVIOR_OPAQUE;
+}
+
+static const struct behavior_driver_api behavior_caps_word_driver_api = {
+    .binding_pressed = on_caps_word_binding_pressed,
+    .binding_released = on_caps_word_binding_released,
+};
+
+static int caps_word_keycode_state_changed_listener(const zmk_event_t *eh);
+
+ZMK_LISTENER(behavior_caps_word, caps_word_keycode_state_changed_listener);
+ZMK_SUBSCRIPTION(behavior_caps_word, zmk_keycode_state_changed);
+
+static const struct device *devs[DT_NUM_INST_STATUS_OKAY(DT_DRV_COMPAT)];
+
+static bool caps_word_is_caps_includelist(const struct behavior_caps_word_config *config,
+                                          uint16_t usage_page, uint8_t usage_id,
+                                          uint8_t implicit_modifiers) {
+    for (int i = 0; i < config->continuations_count; i++) {
+        const struct caps_word_continue_item *continuation = &config->continuations[i];
+        LOG_DBG("Comparing with 0x%02X - 0x%02X (with implicit mods: 0x%02X)", continuation->page,
+                continuation->id, continuation->implicit_modifiers);
+
+        if (continuation->page == usage_page && continuation->id == usage_id &&
+            continuation->implicit_modifiers == implicit_modifiers) {
+            LOG_DBG("Continuing capsword, found included usage: 0x%02X - 0x%02X", usage_page,
+                    usage_id);
+            return true;
+        }
+    }
+
+    return false;
+}
+
+static bool caps_word_is_alpha(uint8_t usage_id) {
+    return (usage_id >= HID_USAGE_KEY_KEYBOARD_A && usage_id <= HID_USAGE_KEY_KEYBOARD_Z);
+}
+
+static bool caps_word_is_numeric(uint8_t usage_id) {
+    return (usage_id >= HID_USAGE_KEY_KEYBOARD_1_AND_EXCLAMATION &&
+            usage_id <= HID_USAGE_KEY_KEYBOARD_0_AND_RIGHT_PARENTHESIS);
+}
+
+static void caps_word_enhance_usage(const struct behavior_caps_word_config *config,
+                                    struct zmk_keycode_state_changed *ev) {
+    if (ev->usage_page != HID_USAGE_KEY || !caps_word_is_alpha(ev->keycode)) {
+        return;
+    }
+
+    LOG_DBG("Enhancing usage 0x%02X with modifiers: 0x%02X", ev->keycode, config->mods);
+    ev->implicit_modifiers |= config->mods;
+}
+
+static int caps_word_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_caps_word_data *data = dev->data;
+        if (!data->active) {
+            continue;
+        }
+
+        const struct behavior_caps_word_config *config = dev->config;
+
+        caps_word_enhance_usage(config, ev);
+
+        if (!caps_word_is_alpha(ev->keycode) && !caps_word_is_numeric(ev->keycode) &&
+            !caps_word_is_caps_includelist(config, ev->usage_page, ev->keycode,
+                                           ev->implicit_modifiers)) {
+            LOG_DBG("Deactivating caps_word for 0x%02X - 0x%02X", ev->usage_page, ev->keycode);
+            deactivate_caps_word(dev);
+        }
+    }
+
+    return ZMK_EV_EVENT_BUBBLE;
+}
+
+static int behavior_caps_word_init(const struct device *dev) {
+    const struct behavior_caps_word_config *config = dev->config;
+    devs[config->index] = dev;
+    return 0;
+}
+
+#define CAPS_WORD_LABEL(i, _n) DT_INST_LABEL(i)
+
+#define PARSE_BREAK(i)                                                                             \
+    {.page = (HID_USAGE_PAGE(i) & 0xFF),                                                           \
+     .id = HID_USAGE_ID(i),                                                                        \
+     .implicit_modifiers = SELECT_MODS(i)},
+
+#define BREAK_ITEM(i, n) PARSE_BREAK(DT_INST_PROP_BY_IDX(n, continue_list, i))
+
+#define KP_INST(n)                                                                                 \
+    static struct behavior_caps_word_data behavior_caps_word_data_##n = {.active = false};         \
+    static struct behavior_caps_word_config behavior_caps_word_config_##n = {                      \
+        .index = n,                                                                                \
+        .mods = DT_INST_PROP_OR(n, mods, MOD_LSFT),                                                \
+        .continuations = {UTIL_LISTIFY(DT_INST_PROP_LEN(n, continue_list), BREAK_ITEM, n)},        \
+        .continuations_count = DT_INST_PROP_LEN(n, continue_list),                                 \
+    };                                                                                             \
+    DEVICE_DT_INST_DEFINE(n, behavior_caps_word_init, device_pm_control_nop,                       \
+                          &behavior_caps_word_data_##n, &behavior_caps_word_config_##n,            \
+                          APPLICATION, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT,                        \
+                          &behavior_caps_word_driver_api);
+
+DT_INST_FOREACH_STATUS_OKAY(KP_INST)
+
+#endif

app/tests/caps-word/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 = <
+				&caps_word &kp A
+				&kp N6 &kp MINUS
+			>;
+		};
+	};
+};

app/tests/caps-word/continue-with-non-alpha-continue-list-item/events.patterns

@@ -0,0 +1,4 @@
+s/.*hid_listener_keycode_//p
+s/.*hid_implicit_modifiers_//p
+s/.*caps_word_enhance_usage/enhance_usage/p
+s/.*caps_word_is_caps_includelist/caps_includelist/p

app/tests/caps-word/continue-with-non-alpha-continue-list-item/keycode_events.snapshot

@@ -0,0 +1,17 @@
+enhance_usage: Enhancing usage 0x04 with modifiers: 0x02
+pressed: usage_page 0x07 keycode 0x04 implicit_mods 0x02 explicit_mods 0x00
+press: Modifiers set to 0x02
+released: usage_page 0x07 keycode 0x04 implicit_mods 0x00 explicit_mods 0x00
+release: Modifiers set to 0x00
+caps_includelist: Comparing with 0x07 - 0x2d (with implicit mods: 0x02)
+caps_includelist: Comparing with 0x07 - 0x2d (with implicit mods: 0x00)
+caps_includelist: Continuing capsword, found included usage: 0x07 - 0x2d
+pressed: usage_page 0x07 keycode 0x2d implicit_mods 0x00 explicit_mods 0x00
+press: Modifiers set to 0x00
+released: usage_page 0x07 keycode 0x2d implicit_mods 0x00 explicit_mods 0x00
+release: Modifiers set to 0x00
+enhance_usage: Enhancing usage 0x04 with modifiers: 0x02
+pressed: usage_page 0x07 keycode 0x04 implicit_mods 0x02 explicit_mods 0x00
+press: Modifiers set to 0x02
+released: usage_page 0x07 keycode 0x04 implicit_mods 0x00 explicit_mods 0x00
+release: Modifiers set to 0x00

app/tests/caps-word/continue-with-non-alpha-continue-list-item/native_posix.keymap

@@ -0,0 +1,21 @@
+#include <dt-bindings/zmk/keys.h>
+#include <behaviors.dtsi>
+#include <dt-bindings/zmk/kscan_mock.h>
+#include "../behavior_keymap.dtsi"
+
+&caps_word {
+	continue-list = <UNDERSCORE MINUS>;
+};
+
+&kscan {
+	events = <
+	ZMK_MOCK_PRESS(0,0,10)
+	ZMK_MOCK_RELEASE(0,0,10)
+	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(0,1,10)
+	ZMK_MOCK_RELEASE(0,1,10)
+	>;
+};

app/tests/caps-word/continue-with-non-modified-numeric-usage-id/events.patterns

@@ -0,0 +1,4 @@
+s/.*hid_listener_keycode_//p
+s/.*hid_implicit_modifiers_//p
+s/.*caps_word_enhance_usage/enhance_usage/p
+s/.*caps_word_is_caps_includelist/caps_includelist/p

app/tests/caps-word/continue-with-non-modified-numeric-usage-id/keycode_events.snapshot

@@ -0,0 +1,14 @@
+enhance_usage: Enhancing usage 0x04 with modifiers: 0x02
+pressed: usage_page 0x07 keycode 0x04 implicit_mods 0x02 explicit_mods 0x00
+press: Modifiers set to 0x02
+released: usage_page 0x07 keycode 0x04 implicit_mods 0x00 explicit_mods 0x00
+release: Modifiers set to 0x00
+pressed: usage_page 0x07 keycode 0x23 implicit_mods 0x00 explicit_mods 0x00
+press: Modifiers set to 0x00
+released: usage_page 0x07 keycode 0x23 implicit_mods 0x00 explicit_mods 0x00
+release: Modifiers set to 0x00
+enhance_usage: Enhancing usage 0x04 with modifiers: 0x02
+pressed: usage_page 0x07 keycode 0x04 implicit_mods 0x02 explicit_mods 0x00
+press: Modifiers set to 0x02
+released: usage_page 0x07 keycode 0x04 implicit_mods 0x00 explicit_mods 0x00
+release: Modifiers set to 0x00

app/tests/caps-word/continue-with-non-modified-numeric-usage-id/native_posix.keymap

@@ -0,0 +1,21 @@
+#include <dt-bindings/zmk/keys.h>
+#include <behaviors.dtsi>
+#include <dt-bindings/zmk/kscan_mock.h>
+#include "../behavior_keymap.dtsi"
+
+&caps_word {
+	continue-list = <UNDERSCORE MINUS>;
+};
+
+&kscan {
+	events = <
+	ZMK_MOCK_PRESS(0,0,10)
+	ZMK_MOCK_RELEASE(0,0,10)
+	ZMK_MOCK_PRESS(0,1,10)
+	ZMK_MOCK_RELEASE(0,1,10)
+	ZMK_MOCK_PRESS(1,0,10)
+	ZMK_MOCK_RELEASE(1,0,10)
+	ZMK_MOCK_PRESS(0,1,10)
+	ZMK_MOCK_RELEASE(0,1,10)
+	>;
+};

app/tests/caps-word/deactivate-by-non-alpha-non-continuation/events.patterns

@@ -0,0 +1,3 @@
+s/.*hid_listener_keycode_//p
+s/.*hid_implicit_modifiers_//p
+s/.*caps_word_enhance_usage/enhance_usage/p

app/tests/caps-word/deactivate-by-non-alpha-non-continuation/keycode_events.snapshot

@@ -0,0 +1,13 @@
+enhance_usage: Enhancing usage 0x04 with modifiers: 0x02
+pressed: usage_page 0x07 keycode 0x04 implicit_mods 0x02 explicit_mods 0x00
+press: Modifiers set to 0x02
+released: usage_page 0x07 keycode 0x04 implicit_mods 0x00 explicit_mods 0x00
+release: Modifiers set to 0x00
+pressed: usage_page 0x07 keycode 0x2d implicit_mods 0x00 explicit_mods 0x00
+press: Modifiers set to 0x00
+released: usage_page 0x07 keycode 0x2d 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/caps-word/deactivate-by-non-alpha-non-continuation/native_posix.keymap

@@ -0,0 +1,17 @@
+#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)
+	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(0,1,10)
+	ZMK_MOCK_RELEASE(0,1,10)
+	>;
+};

app/tests/caps-word/deactivate-by-second-press/events.patterns

@@ -0,0 +1,3 @@
+s/.*hid_listener_keycode_//p
+s/.*hid_implicit_modifiers_//p
+s/.*caps_word_enhance_usage/enhance_usage/p

app/tests/caps-word/deactivate-by-second-press/keycode_events.snapshot

@@ -0,0 +1,9 @@
+enhance_usage: Enhancing usage 0x04 with modifiers: 0x02
+pressed: usage_page 0x07 keycode 0x04 implicit_mods 0x02 explicit_mods 0x00
+press: Modifiers set to 0x02
+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/caps-word/deactivate-by-second-press/native_posix.keymap

@@ -0,0 +1,17 @@
+#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)
+	ZMK_MOCK_PRESS(0,1,10)
+	ZMK_MOCK_RELEASE(0,1,10)
+	ZMK_MOCK_PRESS(0,0,10)
+	ZMK_MOCK_RELEASE(0,0,10)
+	ZMK_MOCK_PRESS(0,1,10)
+	ZMK_MOCK_RELEASE(0,1,10)
+	>;
+};

docs/docs/behaviors/caps-word.md

@@ -0,0 +1,74 @@
+---
+title: Caps Word Behavior
+sidebar_label: Caps Word
+---
+
+## Summary
+
+The caps word behavior behaves similar to a caps lock, but will automatically deactivate when one of the configured "break keycodes" is pressed, or if the caps word key is pressed again. For smaller keyboards, using [mod-taps](/docs/behaviors/mod-tap), this can help avoid repeated alternating holds when typing words in all caps.
+
+The modifiers are applied only to to the alphabetic (`A` to `Z`) keycodes, to avoid automatically appliying them to numeric values, etc.
+
+### Behavior Binding
+
+- Reference: `&caps_word`
+
+Example:
+
+```
+&caps_word
+```
+
+### Configuration
+
+#### Continue List
+
+By default, the caps word will remain active when any alphanumeric character or the underscore (`UNDERSCORE`) characters are pressed. Any other keycode sent,
+will turn off caps word. If you would like to override this, you can set a new array of keys in the `continue-list` property in your keymap:
+
+```
+&caps_word {
+    continue-list = <UNDERSCORE MINUS>;
+};
+
+/ {
+    keymap {
+        ...
+    };
+};
+```
+
+#### Applied Modifier(s)
+
+In addition, if you would like _multiple_ modifiers, instead of just `MOD_LSFT`, you can override the `mods` property:
+
+```
+&caps_word {
+    mods = <MOD_LSFT | MOD_LALT>;
+};
+
+/ {
+    keymap {
+        ...
+    };
+};
+```
+
+### Multiple Caps Breaks
+
+If you want to use multiple caps breaks with different codes to break the caps, you can add additional caps words instances to use in your keymap:
+
+```
+/ {
+    prog_caps: behavior_prog_caps_word {
+        compatible = "zmk,behavior-caps-word";
+        label = "PROG_CAPS";
+        #binding-cells = <0>;
+        continue-list = <UNDERSCORE>;
+    };
+
+    keymap {
+        ...
+    };
+};
+```

docs/sidebars.js

@@ -27,6 +27,7 @@ module.exports = {
       "behaviors/mod-morph",
       "behaviors/sticky-key",
       "behaviors/sticky-layer",
+      "behaviors/caps-word",
       "behaviors/reset",
       "behaviors/bluetooth",
       "behaviors/outputs",