home/.local/share/plasma/plasmoids/KdeControlStation/contents/ui/js/brightness.js

function updateBrightness(rootItem, source) {
	if (rootItem.updateScreenBrightnessJob) return;

	if (!source.data["PowerDevil"]) {
		return;
	}

	// we don't want passive brightness change send setBrightness call
	rootItem.disableBrightnessUpdate = true;

	if (typeof source.data["PowerDevil"]["Screen Brightness"] === "number") {
		rootItem.screenBrightness = source.data["PowerDevil"]["Screen Brightness"];
	}
	rootItem.disableBrightnessUpdate = false;
}