cache timezone calculation

packages/devextreme/js/__internal/scheduler/appointment_popup/m_form.ts

@@ -11,12 +11,10 @@ import $ from '@js/core/renderer';
 import dateUtils from '@js/core/utils/date';
 import dateSerialization from '@js/core/utils/date_serialization';
 import { extend } from '@js/core/utils/extend';
-import type AbstractStore from '@js/data/abstract_store';
 import Form from '@js/ui/form';
 import { current, isFluent } from '@js/ui/themes';
 
 import { createAppointmentAdapter } from '../m_appointment_adapter';
-import type { TimezoneLabel } from '../m_utils_time_zone';
 import timeZoneUtils from '../m_utils_time_zone';
 
 const SCREEN_SIZE_OF_SINGLE_COLUMN = 600;
@@ -41,10 +39,11 @@ const E2E_TEST_CLASSES = {
   recurrenceSwitch: 'e2e-dx-scheduler-form-recurrence-switch',
 };
 
-const DEFAULT_TIMEZONE_EDITOR_DATA_SOURCE_OPTIONS = {
+const createTimeZoneDataSource = () => new DataSource({
+  store: timeZoneUtils.getTimeZonesCache(),
   paginate: true,
   pageSize: 10,
-};
+});
 
 const getStylingModeFunc = (): string | undefined => (isFluent(current()) ? 'filled' : undefined);
 
@@ -193,6 +192,7 @@ export class AppointmentForm {
         valueExpr: 'id',
         placeholder: noTzTitle,
         searchEnabled: true,
+        dataSource: createTimeZoneDataSource(),
         onValueChanged: (args) => {
           const { form } = this;
           const secondTimezoneEditor = form.getEditor(secondTimeZoneExpr);
@@ -428,59 +428,6 @@ export class AppointmentForm {
     editor && this.form.itemOption(editorPath, 'editorOptions', extend({}, editor.editorOptions, options));
   }
 
-  private scheduleTimezoneEditorDataSourceUpdate(
-    editorName: string,
-    dataSource: { store: () => AbstractStore; reload: () => void },
-    selectedTimezoneLabel: TimezoneLabel | null,
-    date: Date,
-  ): void {
-    timeZoneUtils.getTimeZoneLabelsAsyncBatch(date)
-      .catch(() => [] as TimezoneLabel[])
-      .then(async (timezones) => {
-        const store = dataSource.store();
-
-        await store.remove(selectedTimezoneLabel?.id);
-
-        // NOTE: Unfortunately, our store not support bulk operations
-        // So, we update it record-by-record
-        const insertPromises = timezones.reduce<Promise<void>[]>((result, timezone) => {
-          result.push(store.insert(timezone));
-          return result;
-        }, []);
-
-        // NOTE: We should wait for all insertions before reload
-        await Promise.all(insertPromises);
-
-        dataSource.reload();
-        // NOTE: We should re-assign dataSource to the editor
-        // to repaint this editor after dataSource update
-        this.setEditorOptions(editorName, 'Main', { dataSource });
-      }).catch(() => {});
-  }
-
-  private setupTimezoneEditorDataSource(
-    editorName: string,
-    selectedTimezoneId: string | null,
-    date: Date,
-  ): void {
-    const selectedTimezoneLabel = selectedTimezoneId
-      ? timeZoneUtils.getTimeZoneLabel(selectedTimezoneId, date)
-      : null;
-
-    const dataSource = new DataSource({
-      ...DEFAULT_TIMEZONE_EDITOR_DATA_SOURCE_OPTIONS,
-      store: selectedTimezoneLabel ? [selectedTimezoneLabel] : [],
-    });
-
-    this.setEditorOptions(editorName, 'Main', { dataSource });
-    this.scheduleTimezoneEditorDataSourceUpdate(
-      editorName,
-      dataSource,
-      selectedTimezoneLabel,
-      date,
-    );
-  }
-
   updateFormData(formData: Record<string, any>): void {
     this.isFormUpdating = true;
     this.form.option('formData', formData);
@@ -489,16 +436,9 @@ export class AppointmentForm {
     const { expr } = dataAccessors;
 
     const rawStartDate = dataAccessors.get('startDate', formData);
-    const rawEndDate = dataAccessors.get('endDate', formData);
-    const startDateTimezone = dataAccessors.get('startDateTimeZone', formData) ?? null;
-    const endDateTimezone = dataAccessors.get('endDateTimeZone', formData) ?? null;
 
     const allDay = dataAccessors.get('allDay', formData);
     const startDate = new Date(rawStartDate);
-    const endDate = new Date(rawEndDate);
-
-    this.setupTimezoneEditorDataSource(expr.startDateTimeZoneExpr, startDateTimezone, startDate);
-    this.setupTimezoneEditorDataSource(expr.endDateTimeZoneExpr, endDateTimezone, endDate);
 
     this.updateRecurrenceEditorStartDate(startDate, expr.recurrenceRuleExpr);
 

packages/devextreme/js/__internal/scheduler/header/types.ts

@@ -1,5 +1,3 @@
 import type { Properties } from '@js/ui/scheduler';
 
-import type { ArrayElement } from '../utils/types';
-
-export type RawViewType = ArrayElement<Required<Properties>['views']>;
+export type RawViewType = Required<Properties>['views'][number];

packages/devextreme/js/__internal/scheduler/m_scheduler.ts

@@ -66,7 +66,7 @@ import { hide as hideLoading, show as showLoading } from './m_loading';
 import { getRecurrenceProcessor } from './m_recurrence';
 import subscribes from './m_subscribes';
 import { utils } from './m_utils';
-import timeZoneUtils from './m_utils_time_zone';
+import timeZoneUtils, { type TimezoneLabel } from './m_utils_time_zone';
 import { SchedulerOptionsValidator, SchedulerOptionsValidatorErrorsHandler } from './options_validator/index';
 import { AgendaResourceProcessor } from './resources/m_agenda_resource_processor';
 import {
@@ -229,6 +229,8 @@ class Scheduler extends Widget<any> {
 
   _editAppointmentData: any;
 
+  _timeZonesPromise!: Promise<TimezoneLabel[]>;
+
   private _optionsValidator!: SchedulerOptionsValidator;
 
   private _optionsValidatorErrorHandler!: SchedulerOptionsValidatorErrorsHandler;
@@ -1002,6 +1004,7 @@ class Scheduler extends Widget<any> {
   }
 
   _init() {
+    this._timeZonesPromise = timeZoneUtils.cacheTimeZones();
     this._initExpressions({
       startDateExpr: this.option('startDateExpr'),
       endDateExpr: this.option('endDateExpr'),

packages/devextreme/js/__internal/scheduler/m_utils_time_zone.test.ts

@@ -0,0 +1,62 @@
+import {
+  afterAll, beforeAll, describe, expect, it, jest,
+} from '@jest/globals';
+import { macroTaskArray } from '@ts/scheduler/utils/index';
+
+import timeZoneUtils from './m_utils_time_zone';
+import timeZoneList from './timezones/timezone_list';
+
+const defaultTimeZones = timeZoneList.value;
+
+describe('timezone utils', () => {
+  describe('cacheTimeZones / getTimeZonesCache', () => {
+    beforeAll(() => {
+      timeZoneList.value = [
+        'Etc/GMT+12',
+        'Etc/GMT+11',
+      ];
+    });
+    afterAll(() => {
+      timeZoneList.value = defaultTimeZones;
+    });
+
+    it('should cache timezones only once and save into global variable', async () => {
+      const mock = jest.spyOn(macroTaskArray, 'map');
+
+      expect(timeZoneUtils.getTimeZonesCache()).toEqual([]);
+      await timeZoneUtils.cacheTimeZones();
+      expect(timeZoneUtils.getTimeZonesCache()).toEqual([
+        { id: 'Etc/GMT+12', title: '(GMT -12:00) Etc - GMT+12' },
+        { id: 'Etc/GMT+11', title: '(GMT -11:00) Etc - GMT+11' },
+      ]);
+      await timeZoneUtils.cacheTimeZones();
+      await timeZoneUtils.cacheTimeZones();
+      expect(mock).toHaveBeenCalledTimes(1);
+    });
+  });
+
+  describe('getTimeZones', () => {
+    it('should return timezones with offsets of default timezones list', () => {
+      timeZoneList.value = [
+        'Etc/GMT+12',
+        'Etc/GMT+11',
+      ];
+      expect(timeZoneUtils.getTimeZones(
+        new Date('2025-04-23T10:00:00Z'),
+      )).toEqual([
+        { id: 'Etc/GMT+12', title: '(GMT -12:00) Etc - GMT+12', offset: -12 },
+        { id: 'Etc/GMT+11', title: '(GMT -11:00) Etc - GMT+11', offset: -11 },
+      ]);
+      timeZoneList.value = defaultTimeZones;
+    });
+
+    it('should return timezones with offsets of custom timezones list', () => {
+      expect(timeZoneUtils.getTimeZones(
+        new Date('2025-04-23T10:00:00Z'),
+        ['Canada/Pacific'],
+      )).toEqual([
+        { id: 'Canada/Pacific', title: '(GMT -07:00) Canada - Pacific', offset: -7 },
+      ]);
+    });
+  });
+});

packages/devextreme/js/__internal/scheduler/m_utils_time_zone.ts

@@ -23,7 +23,6 @@ export interface TimezoneData extends TimezoneLabel {
 const toMs = dateUtils.dateToMilliseconds;
 const MINUTES_IN_HOUR = 60;
 const MS_IN_MINUTE = 60000;
-const GET_TIMEZONES_BATCH_SIZE = 20;
 const GMT = 'GMT';
 const offsetFormatRegexp = /^GMT(?:[+-]\d{2}:\d{2})?$/;
 
@@ -333,33 +332,40 @@ const addOffsetsWithoutDST = (date: Date, ...offsets: number[]): Date => {
     : newDate;
 };
 
-const getTimeZoneLabelsAsyncBatch = (
-  date = new Date(),
-): Promise<TimezoneLabel[]> => macroTaskArray.map(
-  timeZoneList.value,
-  (timezoneId) => ({
-    id: timezoneId,
-    title: getTimezoneTitle(timezoneId, date),
-  }),
-  GET_TIMEZONES_BATCH_SIZE,
-);
-
-const getTimeZoneLabel = (
-  timezoneId: string,
-  date = new Date(),
-): TimezoneLabel => ({
-  id: timezoneId,
-  title: getTimezoneTitle(timezoneId, date),
-});
-
 const getTimeZones = (
   date = new Date(),
-): TimezoneData[] => timeZoneList.value.map((timezoneId) => ({
+  timeZones = timeZoneList.value,
+): TimezoneData[] => timeZones.map((timezoneId) => ({
   id: timezoneId,
   title: getTimezoneTitle(timezoneId, date),
   offset: calculateTimezoneByValue(timezoneId, date),
 }));
 
+const GET_TIMEZONES_BATCH_SIZE = 10;
+let timeZoneDataCache: TimezoneLabel[] = [];
+let timeZoneDataCachePromise: Promise<TimezoneLabel[]> | undefined;
+const cacheTimeZones = async (
+  date = new Date(),
+): Promise<TimezoneLabel[]> => {
+  if (timeZoneDataCachePromise) {
+    return timeZoneDataCachePromise;
+  }
+
+  timeZoneDataCachePromise = macroTaskArray.map(
+    timeZoneList.value,
+    (timezoneId) => ({
+      id: timezoneId,
+      title: getTimezoneTitle(timezoneId, date),
+    }),
+    GET_TIMEZONES_BATCH_SIZE,
+  );
+  timeZoneDataCache = await timeZoneDataCachePromise;
+
+  return timeZoneDataCache;
+};
+
+const getTimeZonesCache = (): TimezoneLabel[] => timeZoneDataCache;
+
 const utils = {
   getDaylightOffset,
   getDaylightOffsetInMs,
@@ -385,9 +391,9 @@ const utils = {
   setOffsetsToDate,
   addOffsetsWithoutDST,
 
-  getTimeZoneLabelsAsyncBatch,
-  getTimeZoneLabel,
   getTimeZones,
+  getTimeZonesCache,
+  cacheTimeZones,
 };
 
 export default utils;

packages/devextreme/js/common/core/environment.d.ts

@@ -92,10 +92,11 @@ export type SchedulerTimeZone = {
 
 /**
 * @docid utils.getTimeZones
-* @publicName getTimeZones(date)
+* @publicName getTimeZones(date, timeZones)
 * @param1 date:Date|undefined
+* @param2 timeZones:Array<string>|undefined
 * @namespace DevExpress.common.core.environment
 * @static
 * @public
 */
-export function getTimeZones(date?: Date): Array<SchedulerTimeZone>;
+export function getTimeZones(date?: Date, timeZones?: string[]): Array<SchedulerTimeZone>;

packages/devextreme/ts/dx.all.d.ts

@@ -2652,9 +2652,12 @@ declare module DevExpress.common.core.environment {
     */
    export const devices: DevExpress.core.DevicesObject;
   /**
-   * [descr:utils.getTimeZones(date)]
+   * [descr:utils.getTimeZones(date, timeZones)]
    */
-  export function getTimeZones(date?: Date): Array<SchedulerTimeZone>;
+  export function getTimeZones(
+    date?: Date,
+    timeZones?: string[]
+  ): Array<SchedulerTimeZone>;
   /**
    * [descr:hideTopOverlay()]
    */