[scheduler] Improve timeline event layout performance

packages/x-scheduler-internals/package.json

@@ -57,8 +57,9 @@
   ],
   "scripts": {
     "typescript": "tsgo -p tsconfig.json",
-    "build": "code-infra build --tsgo --copy \"src/**/*.css\" --copy \"src/**/*.css:esm\"",
-    "prebuild": "rimraf build tsconfig.build.tsbuildinfo"
+    "build": "code-infra build --tsgo --copy \"src/**/*.css\" --copy \"src/**/*.css:esm\" --ignore 'src/**/*.bench.ts'",
+    "prebuild": "rimraf build tsconfig.build.tsbuildinfo",
+    "bench:jsdom": "pnpm vitest bench -c ./vitest.config.jsdom.mts"
   },
   "repository": {
     "type": "git",

packages/x-scheduler-internals/src/use-event-occurrences-with-timeline-position/useEventOccurrencesWithTimelinePosition.bench.ts

@@ -0,0 +1,33 @@
+import { bench, describe } from 'vitest';
+import type { SchedulerEventOccurrence } from '../models';
+import { computeOccurrencesWithTimelinePosition } from './useEventOccurrencesWithTimelinePosition';
+
+const denseOccurrences = createOccurrences(2_000, () => [0, 60]);
+const rollingOccurrences = createOccurrences(10_000, (index) => [index, index + 100]);
+
+describe('timeline occurrence positioning', () => {
+  bench('2,000 fully overlapping occurrences', () => {
+    computeOccurrencesWithTimelinePosition(denseOccurrences, Infinity);
+  });
+
+  bench('10,000 rolling occurrences with 100 concurrent events', () => {
+    computeOccurrencesWithTimelinePosition(rollingOccurrences, 1);
+  });
+});
+
+function createOccurrences(
+  count: number,
+  getRange: (index: number) => [start: number, end: number],
+) {
+  return Array.from({ length: count }, (_, index) => {
+    const [start, end] = getRange(index);
+    return {
+      id: index,
+      key: String(index),
+      displayTimezone: {
+        start: { timestamp: start },
+        end: { timestamp: end },
+      },
+    } as SchedulerEventOccurrence;
+  });
+}

packages/x-scheduler-internals/src/use-event-occurrences-with-timeline-position/useEventOccurrencesWithTimelinePosition.test.ts

@@ -2,7 +2,9 @@ import { adapter, EventBuilder } from 'test/utils/scheduler';
 import { renderHook } from '@mui/internal-test-utils';
 import type { SchedulerProcessedEvent } from '@mui/x-scheduler-internals/models';
 import { getOccurrencesFromEvents } from '@mui/x-scheduler-internals/internals';
+import { sortEventOccurrences } from '@mui/x-scheduler-internals/sort-event-occurrences';
 import {
+  computeOccurrencesWithTimelinePosition,
   computeOccurrencesFirstIndexLookup,
   useEventOccurrencesWithTimelinePosition,
 } from './useEventOccurrencesWithTimelinePosition';
@@ -237,12 +239,145 @@ describe('useDayListEventOccurrencesWithPosition', () => {
         visibleResources: {},
         recurringEventsPlugin: null,
       });
-      const lookup = computeOccurrencesFirstIndexLookup(adapter, occurrences);
+      const lookup = computeOccurrencesFirstIndexLookup(occurrences);
 
       expect(Object.keys(lookup)).to.have.length(result.occurrences.length);
       for (const occurrence of result.occurrences) {
         expect(lookup[occurrence.key]).to.equal(occurrence.position.firstIndex);
       }
     });
   });
+
+  it('should update the available span when a freed lane is reused', () => {
+    const occurrences = [
+      EventBuilder.new().id('A').singleDay('2024-01-15T10:00:00Z', 30).toOccurrence(),
+      EventBuilder.new().id('B').singleDay('2024-01-15T10:01:00Z', 39).toOccurrence(),
+      EventBuilder.new().id('C').singleDay('2024-01-15T10:10:00Z', 120).toOccurrence(),
+      EventBuilder.new().id('D').singleDay('2024-01-15T10:50:00Z', 60).toOccurrence(),
+      EventBuilder.new().id('E').singleDay('2024-01-15T11:00:00Z', 30).toOccurrence(),
+    ];
+
+    const resultBeforeReuse = computeOccurrencesWithTimelinePosition(
+      occurrences.slice(0, -1),
+      Infinity,
+    );
+    const result = computeOccurrencesWithTimelinePosition(occurrences, Infinity);
+
+    expect(resultBeforeReuse.occurrences[3].position).to.deep.equal({
+      firstIndex: 1,
+      lastIndex: 2,
+    });
+    expect(result.maxIndex).to.equal(3);
+    expect(result.occurrences.map(({ id, position }) => ({ id, ...position }))).to.deep.equal([
+      { id: 'A', firstIndex: 1, lastIndex: 1 },
+      { id: 'B', firstIndex: 2, lastIndex: 2 },
+      { id: 'C', firstIndex: 3, lastIndex: 3 },
+      { id: 'D', firstIndex: 1, lastIndex: 1 },
+      { id: 'E', firstIndex: 2, lastIndex: 2 },
+    ]);
+  });
+
+  it('should match the quadratic layout for varied event distributions', () => {
+    let seed = 239;
+    const random = () => {
+      seed = (seed * 16807) % 2147483647;
+      return (seed - 1) / 2147483646;
+    };
+
+    for (let iteration = 0; iteration < 100; iteration += 1) {
+      const occurrenceCount = 1 + Math.floor(random() * 40);
+      const occurrences = Array.from({ length: occurrenceCount }, (_, index) => {
+        const startMinutes = Math.floor(random() * 12) * 30;
+        const durationMinutes = Math.floor(random() * 9) * 15;
+        const start = adapter.addMinutes(collectionStart, startMinutes).toISOString();
+        return EventBuilder.new()
+          .id(`${iteration}-${index}`)
+          .singleDay(start, durationMinutes)
+          .toOccurrence();
+      });
+      const maxSpan = [1, 2, 4, Infinity][iteration % 4];
+
+      const result = computeOccurrencesWithTimelinePosition(occurrences, maxSpan);
+      const expected = computeLayoutQuadratically(occurrences, maxSpan);
+
+      expect(result.occurrences.map(({ id, position }) => ({ id, ...position }))).to.deep.equal(
+        expected.occurrences,
+      );
+      expect(result.maxIndex).to.equal(expected.maxIndex);
+    }
+  });
+
+  it('should position a dense set of occurrences', () => {
+    const occurrences = Array.from({ length: 1_000 }, (_, index) =>
+      EventBuilder.new().id(index).singleDay('2024-01-15T10:00:00Z', 120).toOccurrence(),
+    );
+
+    const result = computeOccurrencesWithTimelinePosition(occurrences, Infinity);
+
+    expect(result.maxIndex).to.equal(1_000);
+    expect(result.occurrences[0].position).to.deep.equal({ firstIndex: 1, lastIndex: 1 });
+    expect(result.occurrences[999].position).to.deep.equal({
+      firstIndex: 1_000,
+      lastIndex: 1_000,
+    });
+  });
 });
+
+function computeLayoutQuadratically(
+  occurrences: ReturnType<EventBuilder['toOccurrence']>[],
+  maxSpan: number,
+) {
+  const sortedOccurrences = sortEventOccurrences(occurrences);
+  const firstIndexLookup: Record<string, number> = {};
+  let maxIndex = 1;
+
+  for (let index = 0; index < sortedOccurrences.length; index += 1) {
+    const occurrence = sortedOccurrences[index];
+    const usedIndexes = new Set<number>();
+    for (let previousIndex = 0; previousIndex < index; previousIndex += 1) {
+      const previousOccurrence = sortedOccurrences[previousIndex];
+      if (
+        previousOccurrence.displayTimezone.end.timestamp >
+        occurrence.displayTimezone.start.timestamp
+      ) {
+        usedIndexes.add(firstIndexLookup[previousOccurrence.key]);
+      }
+    }
+
+    let firstIndex = 1;
+    while (usedIndexes.has(firstIndex)) {
+      firstIndex += 1;
+    }
+    firstIndexLookup[occurrence.key] = firstIndex;
+    maxIndex = Math.max(maxIndex, firstIndex);
+  }
+
+  return {
+    occurrences: sortedOccurrences.map((occurrence, index) => {
+      const firstIndex = firstIndexLookup[occurrence.key];
+      const usedIndexes = new Set(
+        sortedOccurrences
+          .filter((otherOccurrence, otherIndex) =>
+            otherIndex < index
+              ? otherOccurrence.displayTimezone.end.timestamp >
+                occurrence.displayTimezone.start.timestamp
+              : otherIndex > index &&
+                otherOccurrence.displayTimezone.start.timestamp <
+                  occurrence.displayTimezone.end.timestamp,
+          )
+          .map((otherOccurrence) => firstIndexLookup[otherOccurrence.key]),
+      );
+      let lastIndex = firstIndex;
+      while (
+        !usedIndexes.has(lastIndex + 1) &&
+        lastIndex < maxIndex &&
+        lastIndex - firstIndex < maxSpan - 1
+      ) {
+        lastIndex += 1;
+      }
+
+      return { id: occurrence.id, firstIndex, lastIndex };
+    }),
+    maxIndex,
+  };
+}