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Count chart redraws instead of timing the resize check (fix #495) #497

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Merged
stephaniehobson merged 1 commit into from
Nov 10, 2026
Merged

Count chart redraws instead of timing the resize check (fix #495) #497

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33 changes: 22 additions & 11 deletions tests/playwright/specs/fixtures/resize.spec.js
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Original file line number Diff line number Diff line change
Expand Up @@ -19,10 +19,13 @@ const dates = Array.from({ length: weekCount }, (unused, index) => (
new Date(newestDate - index * 7 * 24 * 60 * 60 * 1000).toISOString().slice(0, 10)
));

// On the dev server this resize sequence blocks the main thread for about
// 150 ms. Animating the lines on resize took it to about 6 s, and redrawing on
// every resize event to about 1.5 s.
const longTaskBudget = 1000;
// Each redraw writes every line's d attribute once, and animating a redraw adds
// more writes, so counting the writes catches both lines animating on resize
// and charts redrawing on every resize event, however fast the runner is.
//
// Tracing slows each viewport change past ChartContainer's resize debounce, so
// on a traced retry every chart would redraw at every width.
test.use({ trace: 'off' });

test.beforeEach(async ({ page }) => {
await page.route(
Expand All @@ -38,17 +41,21 @@ test.beforeEach(async ({ page }) => {
);
});

test('Hardware charts redraw to the new width after a resize without blocking the page', async ({ page }) => {
test('Hardware charts redraw once, without animating, after a series of resizes', async ({ page }) => {
await page.setViewportSize({ width: 1280, height: 900 });
await page.goto('/dashboard/hardware');
await expect(page.locator(chartSelector)).toHaveCount(dashboard.metrics.length);
await expect(page.locator(chartSelector).last()).toBeVisible();

await page.evaluate(() => {
window.longTaskTotal = 0;
new PerformanceObserver(list => {
for (const entry of list.getEntries()) window.longTaskTotal += entry.duration;
}).observe({ type: 'longtask' });
window.lineWrites = new Map();
new MutationObserver(records => {
for (const record of records) {
if (!record.target.classList.contains('mg-main-line')) continue;
const chart = record.target.closest('.metricsGraphicsCon');
window.lineWrites.set(chart, (window.lineWrites.get(chart) || 0) + 1);
}
}).observe(document.querySelector('#application'), { subtree: true, attributeFilter: ['d'] });
});

for (const width of [1180, 1080, 980, 880, 800, 880, 960]) {
Expand All @@ -61,7 +68,11 @@ test('Hardware charts redraw to the new width after a resize without blocking th
return [...document.querySelectorAll(selector)].every(svg => Number(svg.getAttribute('width')) === mainWidth);
}, chartSelector)).toBe(true);

// Long-task entries are reported after the task ends.
// Long enough for a trailing debounced redraw or a 1 s line animation.
await page.waitForTimeout(1000);
expect(await page.evaluate(() => window.longTaskTotal)).toBeLessThan(longTaskBudget);
const writes = await page.evaluate(() => [...document.querySelectorAll('.metricsGraphicsCon')].map(chart => ({
lines: chart.querySelectorAll('path.mg-main-line').length,
writes: window.lineWrites.get(chart) || 0,
})));
expect(writes).toEqual(writes.map(({ lines }) => ({ lines, writes: lines })));
});
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