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scaling-text.js
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scaling-text.js
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function ScalingText (canvas) {
const ctx = canvas.getContext("2d")
let w = canvas.width
let h = canvas.height
let s = 1
let sW = w
let sH = h
let pL = 0
let pR = 0
let pT = 0
let pB = 0
let startOffset = 0
let sFontSize = 16
let fontFamily = 'Arial'
let fontColor = '#000'
let debugColor = '#f00'
let debug = false
let userText = ''
let userFontSize = 16
canvas.style.width = `${w}px`
canvas.style.height = `${h}px`
canvas.width = sW
canvas.height = sH
this.setDebug = (enabled) => {
debug = enabled
render()
}
this.setText = (text) => {
userText = text
render()
}
this.setFont = (size = 16, family = 'Arial', color = '#000', offset = 0) => {
fontColor = color
fontFamily = family
userFontSize = size
startOffset = offset * s
sFontSize = userFontSize * s
render()
}
this.setSize = (width, height, scale = 1, paddingTop = 10, paddingLeft = 10, paddingBottom = 10, paddingRight = 10) => {
w = width
h = height
s = scale
sW = w * s
sH = h * s
sFontSize = userFontSize * s
pT = paddingTop * s
pL = paddingLeft * s
pB = paddingBottom * s
pR = paddingRight * s
canvas.style.width = `${w}px`
canvas.style.height = `${h}px`
canvas.width = sW
canvas.height = sH
render()
}
function getLines (words) {
let lines = []
let currentLine = ''
let width = 0
const padding = pL + pR
words.forEach((word, idx) => {
const printWord = word + ' '
const { width: wordWidthSpace } = ctx.measureText(printWord)
const { width: wordWidthNoSpace } = ctx.measureText(word)
const isWider = (wordWidthNoSpace + width + padding) >= sW
if (isWider) {
// New line
lines.push(currentLine)
currentLine = ''
width = 0
}
width += wordWidthSpace
currentLine += printWord
})
if (currentLine.length > 0) {
lines.push(currentLine)
}
return lines
}
function render () {
// Set canvas properties
canvas.setAttribute('aria-label', userText)
// Clear canvas
ctx.clearRect(0, 0, sW, sH)
// Clean and split userText.
const words = userText.trim().replace(/\s+/gmi, ' ').split(/\s|\n/gi)
if (debug) {
ctx.fillStyle = debugColor
ctx.fillRect(0, 0, sW, pT)
ctx.fillRect(0, sH - pB, sW, sH)
ctx.fillRect(0, 0, pL, sH)
ctx.fillRect(sW - pR, 0, sW, sH)
}
let isWidthinBounds = false
let fontSize = sFontSize
let lines = []
// Test if text will fit. Reduce if it doesn't.
while (!isWidthinBounds) {
ctx.font = `${fontSize}px ${fontFamily}`;
lines = getLines(words)
const textHeightTest = lines.length * fontSize
if (textHeightTest < (sH - pT - pB)) {
isWidthinBounds = true
} else {
fontSize -= 2
}
if (fontSize <= 0) {
isWidthinBounds = false
}
}
// Center the text vertically.
const totalTextHeight = lines.length * fontSize
const startAt = (sH - totalTextHeight) / 2
if (debug) {
ctx.fillStyle = debugColor
ctx.fillRect(0, startAt, sW, 1) // Text start
ctx.fillRect(0, sH / 2, sW, 1) // Center
ctx.fillRect(0, startAt + totalTextHeight, sW, 1) // Text end
}
// Print out lines.
ctx.fillStyle = fontColor
lines.forEach((line, idx) => {
ctx.fillText(line, pL, startAt - startOffset + (fontSize * (idx + 1)))
})
}
}