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calligraphy.html
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calligraphy.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Calligraphy Pad</title>
<style>
html,
body,
#pad {
width: 100%;
height: 100%;
margin: 0;
padding: 0;
overflow: hidden;
}
#controls {
position: absolute;
top: 0.5em;
right: 0.5em;
opacity: 0.33;
text-align: right;
}
#controls:hover {
opacity: 1.0;
}
#nib_display {
margin: 0 auto;
width: 6em;
height: 6em;
border: 1px solid black;
}
button {
width: 2.5em;
height: 2.5em;
}
</style>
</head>
<body>
<canvas id="pad"></canvas>
<div id="controls">
<canvas id="nib_display"></canvas>
<div>
Size
<button onclick="window.button_events.increaseSize()">+</button>
<button onclick="window.button_events.decreaseSize()">-</button>
</div>
<div>
Angle
<button onclick="window.button_events.rotateLeft()">⤿</button>
<button onclick="window.button_events.rotateRight()">⤾</button>
</div>
</div>
<script>
window.modules = {}
</script>
<script>
window.modules.drawing = ({ padScale, ctx }, state) => {
const drawNib = (context, start, end) => {
const nibXOffset = state.nibWidth * Math.cos(Math.PI * 2 * state.nibAngle / 360) / 2
const nibYOffset = -state.nibWidth * Math.sin(Math.PI * 2 * state.nibAngle / 360) / 2
context.beginPath()
context.moveTo(start.x - nibXOffset, start.y - nibYOffset)
context.lineTo(start.x + nibXOffset, start.y + nibYOffset)
context.lineTo(end.x + nibXOffset, end.y + nibYOffset)
context.lineTo(end.x - nibXOffset, end.y - nibYOffset)
context.closePath()
context.fill()
}
const render = () => {
if (!state.drawing) {
return
}
drawNib(ctx, state.lastPos, state.mousePos)
state.lastPos = state.mousePos
}
const loop = () => {
requestAnimationFrame(loop)
render()
}
const updateNib = (nibDisplay) => {
const nibCtx = nibDisplay.getContext('2d');
const { width, height } = nibDisplay
nibCtx.clearRect(0, 0, width, height);
nibCtx.font = '36px serif'
nibCtx.fillText(`${state.nibWidth}px, ${state.nibAngle}°`, 4, height - 6)
drawNib(
nibCtx,
{ x: width / 2 - padScale, y: height / 2 - padScale },
{ x: width / 2 + padScale, y: height / 2 + padScale },
)
}
return { loop, updateNib }
}
</script>
<script>
window.modules.events = ({ pad, updateNib }, state) => {
const calculateMousePos = ({ clientX, clientY }) => {
const { left, top } = pad.getBoundingClientRect()
return {
x: padScale * (clientX - left),
y: padScale * (clientY - top),
}
}
const mousedown = (e) => {
state.drawing = true
state.lastPos = calculateMousePos(e)
}
const mouseup = () => {
state.drawing = false
}
const mousemove = (e) => {
state.mousePos = calculateMousePos(e)
}
const touchstart = (e) => {
const { clientX, clientY } = e.touches[0]
state.mousePos = calculateMousePos({ clientX, clientY })
mousedown({ clientX, clientY })
}
const touchend = (e) => {
mouseup()
}
const touchmove = (e) => {
const { clientX, clientY } = e.touches[0]
mousemove({ clientX, clientY })
}
const preventCanvasEvent = (e) => {
if (e.target === pad) {
e.preventDefault()
}
}
const increaseSize = () => {
state.nibWidth += 5;
updateNib()
}
const decreaseSize = () => {
state.nibWidth -= 5;
updateNib()
}
const rotateLeft = () => {
state.nibAngle += 5;
updateNib()
}
const rotateRight = () => {
state.nibAngle -= 5;
updateNib()
}
return {
apply: (el, ev) => {
Object.entries(ev).forEach(([event, handler]) => {
el.addEventListener(event, handler)
})
},
pad: { mousedown, mouseup, mousemove, touchstart, touchend, touchmove },
body: {
touchstart: preventCanvasEvent,
touchend: preventCanvasEvent,
touchmove: preventCanvasEvent
},
button: {
increaseSize,
decreaseSize,
rotateLeft,
rotateRight,
}
}
}
</script>
<script>
const padScale = 2
const pad = document.getElementById('pad')
const nibDisplay = document.getElementById('nib_display')
const setCanvasSize = (canvas) =>
createImageBitmap(canvas).then(bitmap => {
canvas.width = canvas.offsetWidth * padScale
canvas.height = canvas.offsetHeight * padScale
canvas.getContext('2d').drawImage(bitmap, 0, 0)
})
setCanvasSize(pad)
setCanvasSize(nibDisplay).then(() => {
drawing.updateNib(nibDisplay)
})
window.addEventListener('resize', () => { setCanvasSize(pad) })
const state = {
drawing: false,
mousePos: { x: 0, y: 0 },
lastPos: this.mousePos,
nibAngle: 30,
nibWidth: 20,
}
const ctx = pad.getContext('2d')
ctx.fillStyle = 'black'
ctx.lineWidth = padScale * 4
const drawing = window.modules.drawing(
{ ctx, padScale },
state,
)
drawing.loop()
const events = window.modules.events(
{ pad, updateNib: () => { drawing.updateNib(nibDisplay) } },
state,
)
events.apply(pad, events.pad)
events.apply(document.body, events.body)
window.button_events = events.button
</script>
</body>
</html>