littlejsengine
Version:
LittleJS - Tiny and Fast HTML5 Game Engine
581 lines (507 loc) • 20.5 kB
JavaScript
/**
* LittleJS - The Tiny Fast JavaScript Game Engine
* MIT License - Copyright 2021 Frank Force
*
* Engine Features
* - Object oriented system with EngineObject base class
* - Automatic object lifecycle (update, physics, collision, rendering)
* - Engine helper classes: Vector2, Color, Timer, RandomGenerator
* - Hybrid rendering with WebGL batching and Canvas2D fallback
* - Audio system with wave, mp3, or ZzFX sound effects
* - Input system with keyboard, mouse, gamepad, and touch support
* - Tile layer rendering and collision detection
* - Particle effect system with emitters
* - Medal/achievement system with local storage
* - Comprehensive debug tools and visualizations
* - Fixed 60 FPS timestep with configurable time scale
* - Raycast and spatial query utilities
* - Plugin system for extending engine functionality
* - Start with engineInit() and provide your game callbacks
* @namespace Engine
*/
;
/** Name of engine
* @type {string}
* @default
* @memberof Engine */
const engineName = 'LittleJS';
/** Version of engine
* @type {string}
* @default
* @memberof Engine */
const engineVersion = '1.18.21';
/** Frames per second to update
* @type {number}
* @default
* @memberof Engine */
const frameRate = 60;
/** How many seconds each frame lasts, engine uses a fixed time step
* @type {number}
* @default 1/60
* @memberof Engine */
const timeDelta = 1/frameRate;
/** Array containing all engine objects
* @type {Array<EngineObject>}
* @memberof Engine */
let engineObjects = [];
/** Array with only objects set to collide with other objects this frame (for optimization)
* @type {Array<EngineObject>}
* @memberof Engine */
let engineObjectsCollide = [];
/** Current update frame, used to calculate time
* @type {number}
* @memberof Engine */
let frame = 0;
/** Current engine time since start in seconds
* @type {number}
* @memberof Engine */
let time = 0;
/** Actual clock time since start in seconds (not affected by pause, timescale, or frame rate clamping)
* @type {number}
* @memberof Engine */
let timeReal = 0;
/** Is the game paused? Causes time and objects to not be updated
* @type {boolean}
* @default false
* @memberof Engine */
let paused = false;
/** Get if game is paused
* @return {boolean}
* @memberof Engine */
function getPaused() { return paused; }
/** Set if game is paused
* @param {boolean} [isPaused]
* @memberof Engine */
function setPaused(isPaused=true) { paused = isPaused; }
// Engine internal variables
let frameTimeLastMS = 0, frameTimeBufferMS = 0, averageFPS = 0;
let showEngineVersion = true;
///////////////////////////////////////////////////////////////////////////////
// plugin hooks
const pluginList = [];
class EnginePlugin
{
constructor(update, render, glContextLost, glContextRestored)
{
this.update = update;
this.render = render;
this.glContextLost = glContextLost;
this.glContextRestored = glContextRestored;
}
}
/**
* @callback PluginCallback - Update or render function for a plugin
* @memberof Engine
*/
/** Add a new update function for a plugin
* @param {PluginCallback} [update]
* @param {PluginCallback} [render]
* @param {PluginCallback} [glContextLost]
* @param {PluginCallback} [glContextRestored]
* @memberof Engine */
function engineAddPlugin(update, render, glContextLost, glContextRestored)
{
// make sure plugin functions are unique
ASSERT(!pluginList.find(p=>
p.update === update && p.render === render &&
p.glContextLost === glContextLost &&
p.glContextRestored === glContextRestored));
const plugin = new EnginePlugin(update, render, glContextLost, glContextRestored);
pluginList.push(plugin);
}
///////////////////////////////////////////////////////////////////////////////
// Main Engine Functions
/**
* @callback GameInitCallback - Called after the engine starts, can be async
* @return {void|Promise<void>}
* @memberof Engine
*/
/**
* @callback GameCallback - Update or render function for the game
* @memberof Engine
*/
/** Startup LittleJS engine with your callback functions
* @param {GameInitCallback} gameInit - Called once after the engine starts up, can be async for loading
* @param {GameCallback} gameUpdate - Called every frame before objects are updated (60fps), use for game logic
* @param {GameCallback} gameUpdatePost - Called after physics and objects are updated, even when paused, use for UI updates
* @param {GameCallback} gameRender - Called before objects are rendered, use for drawing backgrounds/world elements
* @param {GameCallback} gameRenderPost - Called after objects are rendered, use for drawing UI/overlays
* @param {Array<string>} [imageSources=[]] - List of image file paths to preload (e.g., ['player.png', 'tiles.png'])
* @param {HTMLElement} [rootElement] - Root DOM element to attach canvas to, defaults to document.body
* @example
* // Basic engine startup
* engineInit(
* ()=> { LOG('Game initialized!'); }, // gameInit
* ()=> { updateGameLogic(); }, // gameUpdate
* ()=> { updateUI(); }, // gameUpdatePost
* ()=> { drawBackground(); }, // gameRender
* ()=> { drawHUD(); }, // gameRenderPost
* ['tiles.png', 'tilesLevel.png'] // images to load
* );
* @memberof Engine */
async function engineInit(gameInit, gameUpdate, gameUpdatePost, gameRender, gameRenderPost, imageSources=[], rootElement)
{
showEngineVersion && console.log(`${engineName} Engine v${engineVersion}`);
ASSERT(!mainContext, 'engine already initialized');
// runtime guard so release builds (where the assert is stripped) don't
// double-register listeners / double-add canvases on a second call
if (mainContext) return;
ASSERT(isArray(imageSources), 'pass in images as array');
// ensure body exists for minimal HTML where the script runs before <body> is parsed
if (!document.body)
document.documentElement.appendChild(document.createElement('body'));
rootElement ||= document.body;
// allow passing in empty functions
gameInit ||= ()=>{};
gameUpdate ||= ()=>{};
gameUpdatePost ||= ()=>{};
gameRender ||= ()=>{};
gameRenderPost ||= ()=>{};
// Called automatically by engine to setup render system
function enginePreRender()
{
// save canvas size
mainCanvasSize = vec2(mainCanvas.width, mainCanvas.height);
// disable smoothing for pixel art
mainContext.imageSmoothingEnabled = !tilesPixelated;
// setup gl rendering if enabled
glPreRender();
}
// internal update loop for engine
function engineUpdate(frameTimeMS=0)
{
// update time keeping
let frameTimeDeltaMS = frameTimeMS - frameTimeLastMS;
// skip delta on the very first frame so timeReal doesn't jump
// by ~page-load-time when RAF starts handing real timestamps
if (!frameTimeLastMS) frameTimeDeltaMS = 0;
frameTimeLastMS = frameTimeMS;
if (debug || debugWatermark)
averageFPS = lerp(averageFPS, 1e3/(frameTimeDeltaMS||1), .05);
const debugSpeedUp = debug && keyIsDown('Equal'); // +
const debugSpeedDown = debug && keyIsDown('Minus'); // -
const debugScale = debugSpeedUp ? 10 : debugSpeedDown ? .1 : 1;
// apply time deltas
timeReal += frameTimeDeltaMS * debugScale / 1e3;
const combinedScale = timeScale * debugScale;
frameTimeDeltaMS *= combinedScale;
frameTimeBufferMS += paused ? 0 : frameTimeDeltaMS;
if (combinedScale <= 1)
frameTimeBufferMS = min(frameTimeBufferMS, 50); // clamp min framerate
let wasUpdated = false;
if (paused)
{
// update everything except the game and objects
wasUpdated = true;
updateCanvas();
inputUpdate();
pluginList.forEach(plugin=>plugin.update?.());
// update object transforms even when paused
for (const o of engineObjects)
o.parent || o.updateTransforms();
// do post update
debugUpdate();
gameUpdatePost();
inputUpdatePost();
if (debugVideoCaptureIsActive())
renderFrame();
}
else
{
// apply time delta smoothing, improves smoothness of framerate in some browsers
let deltaSmooth = 0;
if (frameTimeBufferMS < 0 && frameTimeBufferMS > -9)
{
// force at least one update each frame since it is waiting for refresh
deltaSmooth = frameTimeBufferMS;
frameTimeBufferMS = 0;
}
// update multiple frames if necessary in case of slow framerate
for (; frameTimeBufferMS >= 0; frameTimeBufferMS -= 1e3 / frameRate)
{
// increment frame and update time
time = frame++ / frameRate;
// update game and objects
wasUpdated = true;
updateCanvas();
inputUpdate();
gameUpdate();
pluginList.forEach(plugin=>plugin.update?.());
engineObjectsUpdate();
// do post update
debugUpdate();
gameUpdatePost();
inputUpdatePost();
if (debugVideoCaptureIsActive())
renderFrame();
}
// add the time smoothing back in
frameTimeBufferMS += deltaSmooth;
}
if (!debugVideoCaptureIsActive())
renderFrame();
requestAnimationFrame(engineUpdate);
function renderFrame()
{
if (headlessMode) return;
// canvas must be updated before rendering
if (!wasUpdated)
updateCanvas();
// render the game and objects
enginePreRender();
gameRender();
engineObjects.sort((a,b)=> a.renderOrder - b.renderOrder);
for (const o of engineObjects)
o.destroyed || o.render();
// post rendering
gameRenderPost();
pluginList.forEach(plugin=>plugin.render?.());
inputRender();
debugRender();
glFlush();
debugRenderPost();
drawCount = 0;
primitiveCount = 0;
}
}
function updateCanvas()
{
if (headlessMode) return;
if (canvasFixedSize.x)
{
// set canvas fixed size
mainCanvasSize = canvasFixedSize.copy();
// fit to window using css width and height
const innerAspect = innerWidth / innerHeight;
const fixedAspect = canvasFixedSize.x / canvasFixedSize.y;
const w = innerAspect < fixedAspect ? '100%' : '';
const h = innerAspect < fixedAspect ? '' : '100%';
mainCanvas.style.width = w;
mainCanvas.style.height = h;
if (glCanvas)
{
glCanvas.style.width = w;
glCanvas.style.height = h;
}
}
else
{
// apply device pixel ratio for crisp rendering
const dpr = canvasPixelRatio ?? (devicePixelRatio || 1);
const viewWidth = innerWidth * dpr | 0;
const viewHeight = innerHeight * dpr | 0;
// get main canvas size based on window size
mainCanvasSize.x = min(viewWidth, canvasMaxSize.x);
mainCanvasSize.y = min(viewHeight, canvasMaxSize.y);
// responsive aspect ratio with native resolution
const innerAspect = viewWidth / viewHeight;
ASSERT(canvasMinAspect <= canvasMaxAspect);
if (canvasMaxAspect && innerAspect > canvasMaxAspect)
{
// full height
const w = mainCanvasSize.y * canvasMaxAspect | 0;
mainCanvasSize.x = min(w, canvasMaxSize.x);
}
else if (innerAspect < canvasMinAspect)
{
// full width
const h = mainCanvasSize.x / canvasMinAspect | 0;
mainCanvasSize.y = min(h, canvasMaxSize.y);
}
// set CSS display size so backing store renders at viewport size
const cssW = (mainCanvasSize.x / dpr | 0) + 'px';
const cssH = (mainCanvasSize.y / dpr | 0) + 'px';
mainCanvas.style.width = cssW;
mainCanvas.style.height = cssH;
if (glCanvas)
{
glCanvas.style.width = cssW;
glCanvas.style.height = cssH;
}
}
// clear main canvas and set size
mainCanvas.width = mainCanvasSize.x;
mainCanvas.height = mainCanvasSize.y;
// apply the clear color to main canvas
if (canvasClearColor.a > 0 && !glEnable)
{
mainContext.fillStyle = canvasClearColor.toString();
mainContext.fillRect(0, 0, mainCanvasSize.x, mainCanvasSize.y);
mainContext.fillStyle = BLACK.toString();
}
// set default line join and cap
mainContext.lineJoin = 'round';
mainContext.lineCap = 'round';
}
// skip setup if headless
if (headlessMode) return startEngine();
// setup webgl
glInit(rootElement);
// setup html
const styleRoot =
'margin:0;' + // fill the window
'overflow:hidden;' + // no scroll bars
'background:#000;' + // set background color
'user-select:none;' + // prevent hold to select
'-webkit-user-select:none;' + // compatibility for ios
'touch-action:none;' + // prevent mobile pinch to resize
'-webkit-touch-callout:none'; // compatibility for ios
rootElement.style.cssText = styleRoot;
mainCanvas = rootElement.appendChild(document.createElement('canvas'));
drawContext = mainContext = mainCanvas.getContext('2d');
// init stuff and start engine
inputInit();
audioInit();
debugInit();
// setup canvases
// transform way is still more reliable than flexbox or grid
const styleCanvas = 'position:absolute;'+ // allow canvases to overlap
'top:50%;left:50%;transform:translate(-50%,-50%)'; // center on screen
mainCanvas.style.cssText = styleCanvas;
if (glCanvas)
glCanvas.style.cssText = styleCanvas;
setCanvasPixelated(canvasPixelated);
updateCanvas();
glPreRender();
// create offscreen canvases for image processing
workCanvas = new OffscreenCanvas(64, 64);
workContext = workCanvas.getContext('2d');
workReadCanvas = new OffscreenCanvas(64, 64);
workReadContext = workReadCanvas.getContext('2d', { willReadFrequently: true });
// create promises for loading images
const promises = imageSources.map((src, i)=> loadTexture(i, src));
// no images to load
if (!imageSources.length)
promises.push(loadTexture(0));
// load engine font image
promises.push(imageFontInit());
if (showSplashScreen)
{
// draw splash screen
promises.push(new Promise(resolve =>
{
let t = 0;
updateSplash();
function updateSplash()
{
inputClear();
drawEngineLogo(t+=.01);
t>1 ? resolve() : setTimeout(updateSplash, 16);
}
}));
}
// wait for all the promises to finish
await Promise.all(promises);
return startEngine();
async function startEngine()
{
// wait for gameInit to load
await gameInit();
engineUpdate();
}
}
/** Update each engine object, remove destroyed objects, and update time
* can be called manually if objects need to be updated outside of main loop
* @memberof Engine */
function engineObjectsUpdate()
{
// get list of solid objects for physics optimization
engineObjectsCollide = engineObjects.filter(o=>o.collideSolidObjects);
// update physics before object update
for (const o of engineObjects)
if (!o.parent && !o.destroyed)
o.updatePhysics();
// recursive object update
function updateChildObject(o)
{
if (o.destroyed) return;
o.update();
for (const child of o.children)
updateChildObject(child);
}
for (const o of engineObjects)
{
if (o.parent || o.destroyed) continue;
// update top level objects
o.update();
for (const child of o.children)
updateChildObject(child);
o.updateTransforms();
}
// remove destroyed objects
engineObjects = engineObjects.filter(o=>!o.destroyed);
}
/** Destroy and remove all objects
* - This can be used to clear out all objects when restarting a level
* - Objects can override their destroy function to do cleanup or stick around
* @param {boolean} [immediate] - should attached effects be allowed to die off?
* @memberof Engine */
function engineObjectsDestroy(immediate=true)
{
for (const o of engineObjects)
o.parent || o.destroy(immediate);
engineObjects = engineObjects.filter(o=>!o.destroyed);
}
/** Collects all object within a given area
* @param {Vector2} [pos] - Center of test area, or undefined for all objects
* @param {Vector2|number} [size] - Radius of circle if float, rectangle size if Vector2
* @param {Array<EngineObject>} [objects=engineObjects] - List of objects to check
* @return {Array<EngineObject>} - List of collected objects
* @memberof Engine */
function engineObjectsCollect(pos, size, objects=engineObjects)
{
const collectedObjects = [];
if (!pos)
{
// all objects
for (const o of objects)
collectedObjects.push(o);
}
else if (size instanceof Vector2)
{
// bounding box test
for (const o of objects)
o.isOverlapping(pos, size) && collectedObjects.push(o);
}
else
{
// circle test
const sizeSquared = size*size;
for (const o of objects)
pos.distanceSquared(o.pos) < sizeSquared && collectedObjects.push(o);
}
return collectedObjects;
}
/**
* @callback ObjectCallbackFunction - Function that processes an object
* @param {EngineObject} object
* @memberof Engine
*/
/** Triggers a callback for each object within a given area
* @param {Vector2} [pos] - Center of test area, or undefined for all objects
* @param {Vector2|number} [size] - Radius of circle if float, rectangle size if Vector2
* @param {ObjectCallbackFunction} [callbackFunction] - Calls this function on every object that passes the test
* @param {Array<EngineObject>} [objects=engineObjects] - List of objects to check
* @memberof Engine */
function engineObjectsCallback(pos, size, callbackFunction, objects=engineObjects)
{ engineObjectsCollect(pos, size, objects).forEach(o => callbackFunction(o)); }
/** Return a list of objects intersecting a ray
* @param {Vector2} start
* @param {Vector2} end
* @param {Array<EngineObject>} [objects=engineObjects] - List of objects to check
* @return {Array<EngineObject>} - List of objects hit
* @memberof Engine */
function engineObjectsRaycast(start, end, objects=engineObjects)
{
const hitObjects = [];
for (const o of objects)
{
if (o.collideRaycast && isIntersecting(start, end, o.pos, o.size))
{
debugRaycast && debugRect(o.pos, o.size, '#f00');
hitObjects.push(o);
}
}
debugRaycast && debugLine(start, end, hitObjects.length ? '#f00' : '#00f', .02);
return hitObjects;
}