README: clarify v1.0 vs v1.1 API for separate module repos

- ZMK_RGB_EFFECT_PERSISTENT flag: layer effect survives RGB toggle
- on_idle callback: wake re-renders layer, sleep turns off without
  clearing layer_effect_active
- is_active callback: ext power stays on for layer RGB
- Wakeup filtering: battery events (wakeup=false) don't wake sleeping
  RGB, layer changes (wakeup=true) do
- Layer filtering: only refresh when changed layer matches active top
  layer, skip unnecessary re-renders
- Fade delay: calls zmk_rgb_set_tick_delay() with per-layer DT
  fade-delay prop after rendering static pixels

Requires: zmk fork rgb-modular-v1.1 branch

README.md

@@ -0,0 +1,205 @@
+# zmk-rgb-effects
+
+Modular RGB effects for ZMK keyboards. Provides per-key per-layer RGB indicators and a framework for adding custom effects without forking ZMK.
+
+Requires: [ZMK fork](https://github.com/afiqzudinhadi/zmk) branch `rgb-modular-v1.1` (modular effect registration API).
+
+## Setup
+
+Add to your `west.yml`:
+
+```yaml
+manifest:
+  remotes:
+    - name: afiqzudinhadi
+      url-base: https://github.com/afiqzudinhadi
+  projects:
+    - name: zmk
+      remote: afiqzudinhadi
+      revision: rgb-modular-v1.1
+      import: app/west.yml
+    - name: zmk-rgb-effects
+      remote: afiqzudinhadi
+      revision: v1.1.1
+```
+
+Enable in your `.conf`:
+
+```
+CONFIG_ZMK_RGB_UNDERGLOW=y
+CONFIG_ZMK_RGB_EFFECT_LAYER=y
+```
+
+## Per-key layer effect
+
+Define per-key colors in your keymap/overlay using devicetree:
+
+```dts
+#include <dt-bindings/zmk/rgb_colors.h>
+
+/ {
+    underglow-layer {
+        compatible = "zmk,underglow-layer";
+        pixel-lookup = <
+            5  4  3  2  1  0
+            6  7  8  9  10 11
+            17 16 15 14 13 12
+        >;
+
+        layer0 {
+            layer-id = <0>;
+            bindings = <
+                &ugc RGB_RED  &ugc RGB_RED  &ugc RGB_OFF ...
+            >;
+        };
+
+        layer1 {
+            layer-id = <1>;
+            fade-delay = <15>;
+            bindings = <
+                &ugc RGB_BLUE &ugc RGB_BLUE &ugc RGB_OFF ...
+            >;
+        };
+    };
+};
+```
+
+### Properties
+
+- `pixel-lookup` — maps LED chain index to key position
+- `layer-id` — which keymap layer this color map applies to
+- `fade-delay` — seconds before reverting to animated effect (-1 = never)
+- `bindings` — color per key using behaviors below
+
+### Behaviors
+
+| Behavior | Description | Params |
+|----------|-------------|--------|
+| `&ugc` | Static color | `param1` = RGB hex color |
+| `&ubi` | Battery indicator | `param1` = low color, `param2` = ok color, `threshold` DT prop |
+| `&ugi` | HID indicator (caps/num/scroll lock) | `param1` = off color, `param2` = on color, `indicator` DT prop |
+
+## Adding custom effects
+
+Create a `.c` file with `ZMK_RGB_EFFECT_DEFINE`:
+
+```c
+#include <zmk/rgb_effect.h>
+
+static void my_render(struct zmk_rgb_effect_ctx *ctx) {
+    for (int i = 0; i < ctx->num_pixels; i++) {
+        struct zmk_led_hsb hsb = ctx->base_color;
+        hsb.h = (*ctx->animation_step + i * 30) % 360;
+        ctx->pixels[i] = zmk_rgb_hsb_to_rgb(zmk_rgb_hsb_scale_min_max(hsb));
+    }
+    *ctx->animation_step += ctx->animation_speed;
+}
+
+ZMK_RGB_EFFECT_DEFINE(my_effect, "My Effect",
+    my_render, 0, NULL, NULL, NULL, NULL);
+```
+
+Add to `CMakeLists.txt`:
+
+```cmake
+target_sources(app PRIVATE src/effects/my_effect.c)
+```
+
+The effect auto-registers via linker section. Accessible by cycling with `RGB_EFF`.
+
+### As a separate module repo
+
+You can also create effects in their own repo without modifying this module:
+
+```
+my-zmk-rgb-rainbow/
+├── zephyr/
+│   └── module.yml
+├── CMakeLists.txt
+├── Kconfig
+└── src/
+    └── rainbow.c
+```
+
+`zephyr/module.yml`:
+```yaml
+build:
+  cmake: .
+  kconfig: Kconfig
+```
+
+`Kconfig`:
+```
+config ZMK_RGB_EFFECT_RAINBOW
+    bool "Rainbow RGB effect"
+    depends on ZMK_RGB_UNDERGLOW
+    default y
+```
+
+`CMakeLists.txt`:
+```cmake
+if(CONFIG_ZMK_RGB_EFFECT_RAINBOW)
+  target_sources(app PRIVATE src/rainbow.c)
+endif()
+```
+
+`src/rainbow.c` uses `ZMK_RGB_EFFECT_DEFINE` exactly as above.
+
+Add to your `west.yml`:
+```yaml
+- name: my-zmk-rgb-rainbow
+  remote: your-github-remote
+  revision: main
+```
+
+Requires the ZMK fork with the modular effect API. No dependency on this module — the linker section collects effect registrations across all modules.
+
+- `rgb-modular-v1.0` — basic effect API (`ZMK_RGB_EFFECT_DEFINE` with 6 params: render, flags, on_select, on_deselect). Sufficient for simple animated or static effects.
+- `rgb-modular-v1.1` — extended API (adds `on_idle`, `is_active` callbacks, `ZMK_RGB_EFFECT_PERSISTENT` flag, `zmk_rgb_request_refresh_wakeup()`, `zmk_rgb_set_tick_delay()`, `zmk_rgb_is_on()`). Needed for effects that persist across RGB toggle/idle or use fade-delay.
+
+Start with `rgb-modular-v1.0` if you want to explore the API from scratch.
+
+### Effect flags
+
+| Flag | Description |
+|------|-------------|
+| `0` | Animated — core runs render at 25ms tick |
+| `ZMK_RGB_EFFECT_STATIC` | No periodic tick — render called on demand via `zmk_rgb_request_refresh()` |
+| `ZMK_RGB_EFFECT_PERSISTENT` | Survives RGB toggle and idle sleep |
+
+### Effect callbacks
+
+| Callback | When called |
+|----------|-------------|
+| `render` | Each tick (animated) or on refresh (static) |
+| `on_select` | Effect becomes active |
+| `on_deselect` | User cycles to different effect |
+| `on_idle(bool awake)` | Keyboard sleeps/wakes (persistent effects only) |
+| `is_active()` | Queried for ext power gating — return `true` to keep LEDs powered |
+
+### Render context
+
+| Field | Type | Description |
+|-------|------|-------------|
+| `pixels` | `struct led_rgb *` | LED buffer to write |
+| `num_pixels` | `uint16_t` | Strip length |
+| `base_color` | `struct zmk_led_hsb` | User-configured HSB color |
+| `animation_step` | `uint16_t *` | Read/write animation counter |
+| `animation_speed` | `uint8_t` | User-configured speed (1-5) |
+
+### Utility functions
+
+- `zmk_rgb_hsb_to_rgb(hsb)` — HSB to RGB conversion
+- `zmk_rgb_hsb_scale_min_max(hsb)` — scale brightness to configured min/max
+- `zmk_rgb_hsb_scale_zero_max(hsb)` — scale brightness from 0 to max
+- `zmk_rgb_request_refresh()` — trigger re-render for static effects
+- `zmk_rgb_request_refresh_wakeup(bool)` — refresh with conditional wake from sleep
+- `zmk_rgb_set_tick_delay(int seconds)` — delayed tick restart (for fade effects)
+- `zmk_rgb_is_on()` — query RGB on/off state
+
+## Versioning
+
+`vX.Y.Z` where:
+- **X** — major version (breaking API changes)
+- **Y** — ZMK core dependency version (matches `rgb-modular-vX.Y`)
+- **Z** — custom effects (0 = defaults only, 1+ = custom effects included)

src/effects/layer_effect.c

@@ -90,11 +90,16 @@ static void layer_effect_render(struct zmk_rgb_effect_ctx *ctx) {
     uint8_t layer = rgb_underglow_top_layer();
     const struct zmk_behavior_binding *rgbmap = rgb_underglow_get_bindings(layer);
     if (rgbmap != NULL) {
-        apply_rgbmap(ctx->pixels, ctx->num_pixels, rgbmap, ZMK_KEYMAP_LEN,
+        if (apply_rgbmap(ctx->pixels, ctx->num_pixels, rgbmap, ZMK_KEYMAP_LEN,
-                     layer, ctx->base_color.b);
+                         layer, ctx->base_color.b)) {
+            int fade_delay = zmk_rgbmap_fade_delay(layer);
+            if (fade_delay >= 0) {
+                zmk_rgb_set_tick_delay(fade_delay);
+            }
+        }
     } else {
-        for (int i = 0; i < ctx->num_pixels; i++) {
+        if (zmk_rgb_is_on()) {
-            ctx->pixels[i] = (struct led_rgb){r : 0, g : 0, b : 0};
+            zmk_rgb_underglow_transient_off();
         }
     }
 }
@@ -107,11 +112,27 @@ static void layer_effect_on_deselect(void) {
     layer_effect_active = false;
 }
 
-ZMK_RGB_EFFECT_DEFINE(effect_layer, "Layer Indicators",
+static void layer_effect_on_idle(bool awake) {
-                      layer_effect_render, ZMK_RGB_EFFECT_STATIC,
+    if (awake) {
-                      layer_effect_on_select, layer_effect_on_deselect);
+        if (layer_effect_active) {
+            zmk_rgb_request_refresh_wakeup(true);
+        }
+    } else {
+        zmk_rgb_underglow_transient_off();
+    }
+}
 
-/* Event listeners — refresh pixels on layer/color change */
+static bool layer_effect_is_active(void) {
+    return layer_effect_active;
+}
+
+ZMK_RGB_EFFECT_DEFINE(effect_layer, "Layer Indicators",
+                      layer_effect_render,
+                      ZMK_RGB_EFFECT_STATIC | ZMK_RGB_EFFECT_PERSISTENT,
+                      layer_effect_on_select, layer_effect_on_deselect,
+                      layer_effect_on_idle, layer_effect_is_active);
+
+/* Event listeners */
 
 static int layer_effect_event_listener(const zmk_event_t *eh) {
     if (!layer_effect_active) {
@@ -126,13 +147,17 @@ static int layer_effect_event_listener(const zmk_event_t *eh) {
 #if !IS_ENABLED(CONFIG_ZMK_SPLIT_ROLE_CENTRAL)
         set_peripheral_layers_state(ev->layers);
 #endif
-        zmk_rgb_request_refresh();
+        zmk_rgb_request_refresh_wakeup(true);
         return 0;
     }
 #endif
 
     if (as_zmk_underglow_color_changed(eh)) {
-        zmk_rgb_request_refresh();
+        const struct zmk_underglow_color_changed *ev = as_zmk_underglow_color_changed(eh);
+        uint8_t layer = rgb_underglow_top_layer();
+        if ((ev->layers & BIT(layer)) == BIT(layer)) {
+            zmk_rgb_request_refresh_wakeup(ev->wakeup);
+        }
         return 0;
     }