In LightningChartJS, is there a way to do a drag zoom where the zoom for X and Y is always equal? - lightningchart

Question

My problem is when I drag rectangle zoom for example (gyazo gif), the X axis is wider than the Y. In effect, the X axis is zoomed in more details than the Y and the visual of the graph looks different from the original graph.
https://gyazo.com/749db917465a8037b7c5f21792f572ce
I am looking for a way where if i zoom rectangle drag, the function is similar to zooming via mousewheel where x and y zoom feels equal.

Answer 1

here you will find an example how you can perform custom zoom rect instead of default and keep the ratio of the axes.
// Extract required parts from LightningChartJS.
const {
ColorRGBA,
ColorHEX,
emptyFill,
SolidFill,
SolidLine,
translatePoint,
_point,
lightningChart
} = lcjs;
// Import data-generator from 'xydata'-library.
const {
createProgressiveTraceGenerator
} = xydata
const chart = lightningChart()
.ChartXY()
// Disable default chart interactions with left mouse button.
// .setMouseInteractionRectangleFit(false)
.setMouseInteractionRectangleZoom(false)
.setTitleFillStyle(emptyFill)
// generate data and creating the series
const series = chart.addLineSeries().setStrokeStyle(
new SolidLine({
fillStyle: new SolidFill({ color: ColorHEX('#fff') }),
thickness: 2,
}),
)
// generate data and create series
createProgressiveTraceGenerator()
.setNumberOfPoints(200)
.generate()
.toPromise()
.then((data) => {
return series.add(data)
})
// create zooming rect and dispose it
const rect = chart
.addRectangleSeries()
.add({
x: 0,
y: 0,
width: 0,
height: 0,
})
.setFillStyle(new SolidFill({ color: ColorRGBA(255, 255, 255, 30) }))
.setStrokeStyle(
new SolidLine({
thickness: 2,
fillStyle: new SolidFill({ color: ColorRGBA(255, 255, 255, 255) }),
}),
)
.dispose()
// om Mouse drag restor rectange and set position and coordinates
chart.onSeriesBackgroundMouseDrag((obj, event, button, startLocation, delta) => {
if (button !== 0) return
const startLocationOnScale = translatePoint(
chart.engine.clientLocation2Engine(startLocation.x, startLocation.y),
chart.engine.scale,
series.scale,
)
const curLocationOnScale = translatePoint(chart.engine.clientLocation2Engine(event.x, event.y), chart.engine.scale, series.scale)
const x = Math.abs(series.getBoundaries().min.x) + Math.abs(series.getBoundaries().max.x)
const y = Math.abs(series.getBoundaries().min.y) + Math.abs(series.getBoundaries().max.y)
const ratio = x / y
const width = Math.abs(curLocationOnScale.x - startLocationOnScale.x)
const height = Math.abs(curLocationOnScale.y - startLocationOnScale.y)
const heightDirection = curLocationOnScale.y - startLocationOnScale.y // check direction of rect
// check for mouse direction to prevet fit and zoom conflict
if (curLocationOnScale.x > startLocationOnScale.x) {
rect.setDimensions({
x: startLocationOnScale.x,
y: startLocationOnScale.y,
width: width > height * ratio ? width : height * ratio,
height: width > height * ratio ? (heightDirection > 0 ? width : -width) / ratio : heightDirection,
}).restore()
} else {
// prevent phantom rectangle if you change zoom to fit during the dragging
rect.setDimensions({
x: 0,
y: 0,
width: 0,
height: 0,
}).dispose()
}
})
// on mouse drag stop dispose rect and zoom relative to its dimensions
chart.onSeriesBackgroundMouseDragStop((_, event, button, startLocation) => {
if (button !== 0) return
const rectZooom = rect.getDimensionsPositionAndSize()
if (rectZooom.width !== 0) {
chart.getDefaultAxisX().setInterval(rectZooom.x, (rectZooom.x + rectZooom.width), true, true)
if(rectZooom.height > 0){
chart.getDefaultAxisY().setInterval(rectZooom.y, (rectZooom.y + Math.abs(rectZooom.height)), true, true)
}else{
chart.getDefaultAxisY().setInterval((rectZooom.y - Math.abs(rectZooom.height)),rectZooom.y, true, true)
}
}
rect.setDimensions({
x: 0,
y: 0,
width: 0,
height: 0,
}).dispose()
})
<script src="https://unpkg.com/#arction/xydata#1.4.0/dist/xydata.iife.js"></script>
<script src="https://unpkg.com/#arction/lcjs#3.0.0/dist/lcjs.iife.js"></script>