1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
|
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;
this.onMouseDown = null;
this.onMouseUp = 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;
if (this.onMouseDown) this.onMouseDown(e);
});
this.element.addEventListener('mouseup', e => {
if (e.button === 1) this.panning = false;
if (this.onMouseUp) this.onMouseUp(e);
});
/* 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;
|
