fable/val Public Public: anyone can read this; nobody can change it.

/**

 * How big the world is drawn, before it is scaled onto the screen.

 *

 * A raycaster does not need device pixels. Every column is a ray marched

 * through the grid, so the cost of the frame is the width of the canvas, and

 * a retina window asks for three thousand of them — 1512 rays and as many

 * fills at every frame, sixty times a second, for a picture made of flat

 * shaded columns that upscales almost invisibly.

 *

 * So the world is drawn into an offscreen canvas 960 columns wide however

 * big the window is, and blitted up; the HUD, the crosshair and the minimap

 * stay on the visible canvas at full resolution, where sharpness actually

 * shows. Fidelity is cheap here and frame rate is not: this game can be

 * stick figures if that is what runs.

 *

 * The ladder is the knob the frame governor turns: a rung coarser is about a

 * fifth fewer rays, and the rungs are in order of what they cost, so going

 * down one can never cost more. Nothing here touches what is sent, predicted

 * or simulated — it is a count of columns out of a canvas size and a level.

 */

/** Internal widths, finest first. The first rung is what every window gets. */

export const WIDTHS = [960, 800, 672, 544, 448];

const clamp = (n, low, high) => (n < low ? low : n > high ? high : n);

/**

 * The size to draw the world at: never wider than the canvas actually has

 * pixels for — upscaling a 448px render onto a 360px phone would be paying

 * for columns nobody can see — and never so small it stops being a picture.

 * The aspect is the canvas's own, so the blit only ever scales.

 */

export function renderSize(deviceWidth, deviceHeight, level) {

  const want = WIDTHS[clamp(level | 0, 0, WIDTHS.length - 1)];

  const width = Math.max(240, Math.min(want, Math.round(deviceWidth) || 240));

  const height = Math.max(

    1,

    Math.round(width * (deviceHeight > 0 && deviceWidth > 0 ? deviceHeight / deviceWidth : 0.6)),

  );

  return { width, height };

}