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fix cursor offset inside CSS zoom containers, add syncZoom() API and demo #1131

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fix cursor offset inside CSS zoom containers, add syncZoom() API and demo #1131

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65 changes: 65 additions & 0 deletions demos/inside-css-zoom.html
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Original file line number Diff line number Diff line change
@@ -0,0 +1,65 @@
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Inside CSS Zoom</title>
<meta name="viewport" content="width=device-width, initial-scale=1">

<link rel="stylesheet" href="../dist/uPlot.min.css">
</head>
<body>
<script src="../dist/uPlot.iife.js"></script>

<div id="chart-wrap" style="zoom: 1.5; border: 2px dashed #ccc; padding: 10px; display: inline-block;">
<div id="chart"></div>
</div>

<br><br>

<label>CSS Zoom: <input id="zoomInput" type="number" value="1.5" step="0.25" min="0.25" max="5" style="width: 60px;"></label>
<button id="applyZoom">Apply Zoom</button>

<br><br>

<label><input id="autoDetect" type="checkbox"> Auto-detect (u.syncZoom() with no args)</label>

<script>
var n = 100, xs = [], ys = [], ys2 = [];
for (var i = 0; i < n; i++) {
xs[i] = i;
ys[i] = 50 + 30 * Math.sin(i * 0.1);
ys2[i] = 40 + 20 * Math.cos(i * 0.08);
}

var wrap = document.getElementById("chart-wrap");
var el = document.getElementById("chart");

var u = new uPlot({
width: 600,
height: 300,
title: "Inside CSS Zoom",
scales: {
x: { time: false },
},
series: [
{},
{ label: "Series A", stroke: "blue", width: 2 },
{ label: "Series B", stroke: "orange", width: 2 },
],
cursor: { show: true },
}, [xs, ys, ys2], el);

document.getElementById("applyZoom").onclick = function() {
var z = parseFloat(document.getElementById("zoomInput").value) || 1;
var auto = document.getElementById("autoDetect").checked;

wrap.style.zoom = z;

if (auto)
u.syncZoom(); // auto-detect from DOM
else
u.syncZoom(z); // explicit value, no DOM traversal
};
</script>
</body>
</html>
21 changes: 19 additions & 2 deletions src/uPlot.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3093,6 +3093,17 @@ export default function uPlot(opts, data, then) {
}

let rect = null;
let cssZoom = 1;

function getEffectiveZoom(el) {
let z = 1;
while (el) {
let s = getComputedStyle(el).zoom;
if (s && s !== 'normal') z *= parseFloat(s);
el = el.parentElement;
}
return z;
}

Object.defineProperty(self, 'rect', {
get() {
Expand All @@ -3108,6 +3119,7 @@ export default function uPlot(opts, data, then) {
rect = null;
else {
rect = over.getBoundingClientRect();
cssZoom = getEffectiveZoom(over);
fire("syncRect", rect);
}
}
Expand Down Expand Up @@ -3139,8 +3151,8 @@ export default function uPlot(opts, data, then) {
setCursorEvent(e);

if (e != null) {
_l = e.clientX - rect.left;
_t = e.clientY - rect.top;
_l = (e.clientX - rect.left) / cssZoom;
_t = (e.clientY - rect.top) / cssZoom;
}
else {
if (_l < 0 || _t < 0) {
Expand Down Expand Up @@ -3408,6 +3420,11 @@ export default function uPlot(opts, data, then) {
cursorPlots.add(self);

self.syncRect = syncRect;

// allows external code to notify uPlot when container CSS zoom changes,
// e.g. u.syncZoom() to auto-detect, or u.syncZoom(1.5) to set explicitly.
// avoids the performance cost of recalculating on every mousemove.
self.syncZoom = (z) => { cssZoom = z ?? getEffectiveZoom(over); };
}

// external on/off
Expand Down