DateBox: fix mask behavior with Chinese MS IME backspace and refocus (T1331089)

packages/devextreme/js/__internal/ui/date_box/date_box.mask.ts

@@ -4,6 +4,7 @@ import { getFormat } from '@js/common/core/localization/ldml/date.format';
 import { getRegExpInfo } from '@js/common/core/localization/ldml/date.parser';
 import numberLocalization from '@js/common/core/localization/number';
 import devices from '@js/core/devices';
+import type { dxElementWrapper } from '@js/core/renderer';
 import browser from '@js/core/utils/browser';
 import { clipboardText } from '@js/core/utils/dom';
 import { fitIntoRange, inRange, sign } from '@js/core/utils/math';
@@ -15,6 +16,7 @@ import type { DateLike, Properties } from '@js/ui/date_box';
 import dateLocalization from '@ts/core/localization/date';
 import type { OptionChanged } from '@ts/core/widget/types';
 import type { KeyboardKeyDownEvent } from '@ts/events/core/m_keyboard_processor';
+import type { ValueChangedEvent } from '@ts/ui/editor/editor';
 
 import type { DxMouseWheelEvent } from '../scroll_view/types';
 import type { DateBoxBaseProperties } from './date_box.base';
@@ -25,6 +27,7 @@ const MASK_EVENT_NAMESPACE = 'dateBoxMask';
 const FORWARD = 1;
 const BACKWARD = -1;
 const IME_DIGIT_CODE_REGEXP = /^(?:Digit|Numpad)(\d)$/;
+const IME_BACKSPACE_INPUT_TYPE = 'deleteContentBackward';
 
 export interface DateBoxMaskProperties extends Properties {
   emptyDateValue?: Date;
@@ -52,6 +55,8 @@ class DateBoxMask extends DateBoxBase {
 
   _isIMECommitPending?: boolean;
 
+  _isClearingValue?: boolean;
+
   _supportedKeys(): Record<string, (e: KeyboardEvent) => boolean | undefined> {
     const originalHandlers = super._supportedKeys();
     const callOriginalHandler = (e: KeyboardEvent): boolean | undefined => {
@@ -307,6 +312,17 @@ class DateBoxMask extends DateBoxBase {
 
       return;
     }
+
+    if (this._useMaskBehavior() && event?.inputType === IME_BACKSPACE_INPUT_TYPE) {
+      if (this._isAllSelected()) {
+        this._selectFirstPart();
+      }
+      this._revertPart(BACKWARD);
+      this._syncInputWithMask();
+
+      return;
+    }
+
     super._keyPressHandler(e);
 
     if (this._maskInputHandler) {
@@ -792,6 +808,20 @@ class DateBoxMask extends DateBoxBase {
     }
   }
 
+  _clearValueHandler(e: ValueChangedEvent & DxEvent): void {
+    this._isClearingValue = true;
+    super._clearValueHandler(e);
+    this._isClearingValue = false;
+  }
+
+  _focusInHandler(e: DxEvent & { relatedTarget: Element | dxElementWrapper }): void {
+    super._focusInHandler(e);
+
+    if (this._useMaskBehavior() && !e.isDefaultPrevented() && !this._isClearingValue) {
+      this._selectFirstPart();
+    }
+  }
+
   _focusOutHandler(e: DxEvent): void {
     const shouldFireChangeEvent = this._useMaskBehavior() && !e.isDefaultPrevented();
 

packages/devextreme/testing/tests/DevExpress.ui.widgets.editors/datebox.mask.tests.js

@@ -787,6 +787,26 @@ module('Keyboard navigation', setupModule, () => {
         assert.strictEqual(this.instance.option('value'), null, 'value has been cleared');
     });
 
+    test('deleteContentBackward input event should revert the active date part to its minimum value without clearing the value (Chinese MS IME composition backspace) (T1331089)', function(assert) {
+        this.instance.option({
+            displayFormat: 'MM/dd/yyyy',
+            value: new Date(2025, 9, 16), // Oct 16, 2025; text = '10/16/2025'
+        });
+
+        this.$input.get(0).focus();
+
+        this.$input.trigger($.Event('input', {
+            type: 'input',
+            originalEvent: $.Event('input', {
+                inputType: 'deleteContentBackward',
+            })
+        }));
+
+        assert.ok(this.instance.option('text').length > 0, 'text is not cleared after IME composition backspace');
+        assert.deepEqual(this.keyboard.caret(), { start: 0, end: 2 }, 'first date part (month) is still active');
+        assert.strictEqual(this.instance.option('text'), '01/16/2025', 'month part is reset to minimum value, other parts unchanged');
+    });
+
     QUnit.testInActiveWindow('focusout should clear search value', function(assert) {
         this.keyboard.type('1');
         assert.strictEqual(this.instance.option('text'), 'January 10 2012', 'text has been changed');
@@ -798,6 +818,20 @@ module('Keyboard navigation', setupModule, () => {
         assert.deepEqual(this.keyboard.caret(), { start: 9, end: 11 }, 'first group has been filled again');
     });
 
+    QUnit.testInActiveWindow('first part should be active when re-focusing after all parts are completed (T1331089)', function(assert) {
+        this.instance.option({
+            displayFormat: 'MM/dd/yyyy',
+            value: new Date(2025, 0, 1),
+        });
+
+        this.keyboard.type('10162025'); // Oct 16, 2025
+
+        this.$input.focusout();
+        this.$input.get(0).focus();
+
+        assert.deepEqual(this.keyboard.caret(), { start: 0, end: 2 }, 'month part is selected after re-focusing');
+    });
+
     test('enter should clear search value', function(assert) {
         this.keyboard.type('1');