+
+
+# Layer Change Code
+
+Thir runs code every time that the layers get changed. This can be useful for layer indication, or custom layer handling.
+
+### Example `layer_state_set_*` Implementation
+
+This example shows how to set the [RGB Underglow](feature_rgblight.md) lights based on the layer, using the Planck as an example
+
+```
+uint32_t layer_state_set_user(uint32_t state) {
+ switch (biton32(state)) {
+ case _RAISE:
+ rgblight_setrgb (0x00, 0x00, 0xFF);
+ break;
+ case _LOWER:
+ rgblight_setrgb (0xFF, 0x00, 0x00);
+ break;
+ case _PLOVER:
+ rgblight_setrgb (0x00, 0xFF, 0x00);
+ break;
+ case _ADJUST:
+ rgblight_setrgb (0x7A, 0x00, 0xFF);
+ break;
+ default: // for any other layers, or the default layer
+ rgblight_setrgb (0x00, 0xFF, 0xFF);
+ break;
+ }
+ return state;
+}
+```
+### `layer_state_set_*` Function Documentation
+
+* Keyboard/Revision: `void uint32_t layer_state_set_kb(uint32_t state)`
+* Keymap: `uint32_t layer_state_set_user(uint32_t state)`
+
+The `state` is the bitmask of the active layers, as explained in the [Keymap Overview](keymap.md#keymap-layer-status)