RGB Underglow improvements

[Nicell]

Here are a list of improvements still to be made to RGB underglow:

• Add Kconfig options for underglow state defaults
• Add settings support for underglow state to persist between resets
• Add Kconfig options to enable/disable each effect to save on storage space
• Work towards split support of syncing RGB effects and animations
• Add support for a "layer" effect that can trigger a underglow color if a specific layer is active
• Add support for using RGB underglow behavior actions through rotary encoders
• Convert hsb_to_rgb to use integers instead of floats to improve performance(?)

[coltontcrowe]

Are any of these tasks currently being worked on?

[Nicell]

Are any of these tasks currently being worked on?

The only one currently being worked on is Work towards split support of syncing RGB effects and animations with #547

[coltontcrowe]

Cool! I want to try to implement the layer functionality, but I’ll probably convert hsb_to_rgb to integers first since that looks like an easy one.

[coltontcrowe]

I've been working on converting hsb_to_rgb using integers. How worried are we if the conversion means numbers may round differently during the conversion process? I'm noticing a few of the rgb values produced with the function I'm working on are off by 1 compared to the old function.

[idesignstuff]

How complex would it be to support pwm RGB with this underglow behavior?
I have one RGB led per board on a split (Xiao BLE built-in) and would like to use it to show modes/layers/ble/battery etc.
Currently, because it has a common anode, and each color has its own cathode, they are sort of supported in the backlight, but that can't specify relative brightness, only all of them as a group.

Currently in my .conf file, I have this:

# Uncomment for backlight
CONFIG_ZMK_BACKLIGHT=y

CONFIG_ZMK_BACKLIGHT_AUTO_OFF_IDLE=y
CONFIG_ZMK_BACKLIGHT_BRT_START=50
CONFIG_ZMK_BACKLIGHT_BRT_STEP=10

In the keyboard.dtsi file:

/ {
    chosen {
        zmk,backlight = &backlight;
    };
};

In kconfig.defconfig I have:

if ZMK_BACKLIGHT

config PWM
    default y

config LED_PWM
    default y

endif # ZMK_BACKLIGHT

In keyboard_left.overlay I have:

&pwm0 {
    status = "okay";
    /* Red LED P0_26 or D11, Green LED P0_30 or D12, Blue LED P0_6 or D13 */
    ch0-pin = <26>; /* LED RED */
    ch1-pin = <30>; /* LED GRN */
    ch2-pin = <6>;  /* LED BLU */
}; 
/ {
    backlight: pwmleds {
        compatible = "pwm-leds";
        label = "Backlight LEDs";
        pwm_led_0 {
            pwms = <&pwm0 26>; label = "Backlight LED RED";
        };
        pwm_led_1 {
            pwms = <&pwm0 30>; label = "Backlight LED GRN";
        };
        pwm_led_2 {
            pwms = <&pwm0 6>; label = "Backlight LED BLU";
        };
    };
};  

Is it possible to assign separate values for each color with the current state of ZMK?