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Chart remembers initial value on left

This commit is contained in:
Neale Pickett 2022-04-24 13:28:20 -07:00
parent 54668eb0f1
commit 2290c2ff02
1 changed files with 5 additions and 5 deletions
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10
static/chart.mjs
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@ -20,8 +20,6 @@ class HistoryChart {
this.duration = duration this.duration = duration
this.data = [] this.data = []
this.max = 1
this.min = 0
// One canvas pixel = 20ms // One canvas pixel = 20ms
canvas.width = duration / (20 * Millisecond) canvas.width = duration / (20 * Millisecond)
@ -52,7 +50,8 @@ class HistoryChart {
let earliest = now - this.duration let earliest = now - this.duration
this.data.push([when, value]) this.data.push([when, value])
while (this.data[0][0] < earliest) { // Leave one old datapoint so we know the value when the window opens
while ((this.data.length > 1) && (this.data[1][0] < earliest)) {
this.data.shift() this.data.shift()
} }
@ -63,16 +62,17 @@ class HistoryChart {
let now = Date.now() let now = Date.now()
let earliest = now - this.duration let earliest = now - this.duration
let xScale = this.canvas.width / this.duration let xScale = this.canvas.width / this.duration
let yScale = this.canvas.height * 0.95
let y = 0 let y = 0
this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height) this.ctx.clearRect(0, 0, this.canvas.width, this.canvas.height)
this.ctx.moveTo(0, y) this.ctx.moveTo(0, 0)
this.ctx.beginPath() this.ctx.beginPath()
for (let point of this.data) { for (let point of this.data) {
let x = (point[0] - earliest) * xScale let x = (point[0] - earliest) * xScale
this.ctx.lineTo(x, y) this.ctx.lineTo(x, y)
y = point[1] * this.canvas.height y = point[1] * yScale
this.ctx.lineTo(x, y) this.ctx.lineTo(x, y)
} }
this.ctx.lineTo(this.canvas.width, y) this.ctx.lineTo(this.canvas.width, y)