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import { clamp } from './modules/Util.js';
class Canvas {
constructor(rootId) {
const root = document.getElementById(rootId);
this.element = document.createElement('canvas');
this.context = this.element.getContext('2d');
/* state variables */
this.scale = 1;
this.zoom = 1;
const ZOOM_SPEED = 1.2;
this.mouse = {
screenPos: { x: 0, y: 0 },
drawingPos: { x: 0, y: 0 },
};
this.pan = { x: 0, y: 0 };
this.panning = false;
/* callbacks */
this.onDraw = null;
this.onMouseMove = null;
/* register event listeners */
/* mouse movement */
this.element.addEventListener('mousemove', e => {
this.mouse.screenPos.x = e.offsetX;
this.mouse.screenPos.y = e.offsetY;
const [xd, yd] = this.screenToDrawingPos(e.offsetX, e.offsetY);
/* compute movement */
const dx = e.movementX / (this.zoom * this.scale);
const dy = e.movementY / (this.zoom * this.scale);
/* pan? */
if (this.panning) {
this.pan.x += dx;
this.pan.y += dy;
this.setTransform();
}
this.mouse.drawingPos.x = xd;
this.mouse.drawingPos.y = yd;
if (this.onMouseMove) this.onMouseMove(this.mousePos);
});
/* clicking */
this.element.addEventListener('mousedown', e => {
e.preventDefault();
if (e.button === 1) this.panning = true;
});
this.element.addEventListener('mouseup', e => {
if (e.button === 1) this.panning = false;
});
/* mouse leave */
this.element.addEventListener('mouseleave', e => {
this.panning = false;
});
/* mouse wheel */
this.element.addEventListener('wheel', e => {
if (this.panning) return; // don't zoom and pan simultaneously
const delta = e.deltaY < 0 ? ZOOM_SPEED : 1/ZOOM_SPEED;
const alpha = (1/delta) - 1;
/* zoom in */
this.zoom *= delta;
this.zoom = clamp(this.zoom, 1, 1000);
this.setTransform();
/* pan to keep mouse in the same place */
const [mouseX, mouseY] = this.screenToDrawingPos(this.mouse.screenPos.x, this.mouse.screenPos.y);
this.pan.x += mouseX - this.mouse.drawingPos.x;
this.pan.y += mouseY - this.mouse.drawingPos.y;
this.setTransform();
this.draw();
});
/* finalize setup */
this.fillWindow();
window.addEventListener('resize', () => this.fillWindow());
root.appendChild(this.element);
}
setTransform() {
/* clamp pan */
const xMax = this.pixelsToUnits(this.element.width) - 1;
const yMax = this.pixelsToUnits(this.element.height) - 1;
this.pan.x = clamp(this.pan.x, xMax, 0);
this.pan.y = clamp(this.pan.y, yMax, 0);
this.context.setTransform(1, 0, 0, 1, 0, 0);
this.context.scale(this.zoom * this.scale, this.zoom * this.scale);
this.context.translate(this.pan.x, this.pan.y);
}
fillWindow() {
const width = window.innerWidth;
const height = window.innerHeight;
this.scale = Math.max(width, height);
this.element.width = width; this.element.height = height;
this.setTransform();
this.draw();
}
pixelsToUnits(value) {
return value / this.zoom / this.scale;
}
unitsToPixels(value) {
return value * this.zoom * this.scale;
}
screenToDrawingPos(xs, ys) {
const matrix = this.context.getTransform();
matrix.invertSelf();
/* compute drawing-space position */
const x = matrix.a*xs + matrix.b*ys + matrix.e;
const y = matrix.c*xs + matrix.d*ys + matrix.f;
return [ x, y ];
}
draw() {
this.context.clearRect(0, 0, 1, 1);
if (this.onDraw) this.onDraw(this.context);
}
}
export default Canvas;
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