NativeScript/nativescript-core/utils/layout-helper/index.ios.ts

import { round, MODE_MASK } from "./layout-helper-common";

export * from "./layout-helper-common";

let mainScreenScale;

export function makeMeasureSpec(size: number, mode: number): number {
	return (Math.round(Math.max(0, size)) & ~MODE_MASK) | (mode & MODE_MASK);
}

export function getDisplayDensity(): number {
	return mainScreenScale;
}

export function toDevicePixels(value: number): number {
	return value * mainScreenScale;
}

export function toDeviceIndependentPixels(value: number): number {
	return value / mainScreenScale;
}

export function measureNativeView(
	nativeView: any /* UIView */,
	width: number,
	widthMode: number,
	height: number,
	heightMode: number
): { width: number; height: number } {
	const view = <UIView>nativeView;
	const nativeSize = view.sizeThatFits({
		width:
			widthMode === 0 /* layout.UNSPECIFIED */
				? Number.POSITIVE_INFINITY
				: toDeviceIndependentPixels(width),
		height:
			heightMode === 0 /* layout.UNSPECIFIED */
				? Number.POSITIVE_INFINITY
				: toDeviceIndependentPixels(height),
	});

	nativeSize.width = round(toDevicePixels(nativeSize.width));
	nativeSize.height = round(toDevicePixels(nativeSize.height));

	return nativeSize;
}

mainScreenScale = UIScreen.mainScreen.scale;