src/material/slider/slider-input.ts - main - githubmirror/components

src/material/slider/slider-input.ts
826 строк24 KB
Kristiyan Kostadinov
fix(material/slider): thumb jumping on safari (#33619)
03 авг 2026, 21:26
03 авг 2026, 21:260071466
/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.dev/license
 */

import {
  booleanAttribute,
  ChangeDetectorRef,
  Directive,
  ElementRef,
  EventEmitter,
  forwardRef,
  inject,
  Input,
  NgZone,
  numberAttribute,
  OnDestroy,
  Output,
  Renderer2,
  signal,
} from '@angular/core';
import {ControlValueAccessor, FormControl, NG_VALUE_ACCESSOR} from '@angular/forms';
import {Subject} from 'rxjs';
import {
  _MatThumb,
  MatSliderDragEvent,
  _MatSlider,
  _MatSliderRangeThumb,
  _MatSliderThumb,
  MAT_SLIDER_RANGE_THUMB,
  MAT_SLIDER_THUMB,
  MAT_SLIDER,
} from './slider-interface';
import {Platform} from '@angular/cdk/platform';

/**
 * Provider that allows the slider thumb to register as a ControlValueAccessor.
 * @docs-private
 */
export const MAT_SLIDER_THUMB_VALUE_ACCESSOR: any = {
  provide: NG_VALUE_ACCESSOR,
  useExisting: forwardRef(() => MatSliderThumb),
  multi: true,
};

/**
 * Provider that allows the range slider thumb to register as a ControlValueAccessor.
 * @docs-private
 */
export const MAT_SLIDER_RANGE_THUMB_VALUE_ACCESSOR: any = {
  provide: NG_VALUE_ACCESSOR,
  useExisting: forwardRef(() => MatSliderRangeThumb),
  multi: true,
};

/**
 * Directive that adds slider-specific behaviors to an input element inside `<mat-slider>`.
 * Up to two may be placed inside of a `<mat-slider>`.
 *
 * If one is used, the selector `matSliderThumb` must be used, and the outcome will be a normal
 * slider. If two are used, the selectors `matSliderStartThumb` and `matSliderEndThumb` must be
 * used, and the outcome will be a range slider with two slider thumbs.
 */
@Directive({
  selector: 'input[matSliderThumb]',
  exportAs: 'matSliderThumb',
  host: {
    'class': 'mdc-slider__input',
    'type': 'range',
    '[attr.aria-valuetext]': '_valuetext()',
    '(change)': '_onChange()',
    '(input)': '_onInput()',
    // TODO(wagnermaciel): Consider using a global event listener instead.
    // Reason: I have found a semi-consistent way to mouse up without triggering this event.
    '(blur)': '_onBlur()',
    '(focus)': '_onFocus()',
  },
  providers: [
    MAT_SLIDER_THUMB_VALUE_ACCESSOR,
    {provide: MAT_SLIDER_THUMB, useExisting: MatSliderThumb},
  ],
})
export class MatSliderThumb implements _MatSliderThumb, OnDestroy, ControlValueAccessor {
  readonly _ngZone = inject(NgZone);
  readonly _elementRef = inject<ElementRef<HTMLInputElement>>(ElementRef);
  readonly _cdr = inject(ChangeDetectorRef);
  protected _slider = inject<_MatSlider>(MAT_SLIDER);
  private _platform = inject(Platform);
  private _listenerCleanups!: (() => void)[];

  @Input({transform: numberAttribute})
  get value(): number {
    return numberAttribute(this._hostElement.value, 0);
  }
  set value(value: number) {
    if (value === null) {
      value = this._getDefaultValue();
    }
    value = isNaN(value) ? 0 : value;
    const stringValue = value + '';
    if (!this._hasSetInitialValue) {
      this._initialValue = stringValue;
      return;
    }
    if (this._isActive) {
      return;
    }
    this._setValue(stringValue);
  }

  /**
   * Handles programmatic value setting. This has been split out to
   * allow the range thumb to override it and add additional necessary logic.
   */
  protected _setValue(value: string) {
    this._hostElement.value = value;
    this._updateThumbUIByValue();
    this._slider._onValueChange(this);
    this._cdr.detectChanges();
    this._slider._cdr.markForCheck();
  }

  /** Event emitted when the `value` is changed. */
  @Output() readonly valueChange: EventEmitter<number> = new EventEmitter<number>();

  /** Event emitted when the slider thumb starts being dragged. */
  @Output() readonly dragStart: EventEmitter<MatSliderDragEvent> =
    new EventEmitter<MatSliderDragEvent>();

  /** Event emitted when the slider thumb stops being dragged. */
  @Output() readonly dragEnd: EventEmitter<MatSliderDragEvent> =
    new EventEmitter<MatSliderDragEvent>();

  /**
   * The current translateX in px of the slider visual thumb.
   * @docs-private
   */
  get translateX(): number {
    if (this._slider.min >= this._slider.max) {
      this._translateX = this._tickMarkOffset;
      return this._translateX;
    }
    if (this._translateX === undefined) {
      this._translateX = this._calcTranslateXByValue();
    }
    return this._translateX;
  }
  set translateX(v: number) {
    this._translateX = v;
  }
  private _translateX: number | undefined;

  /**
   * Indicates whether this thumb is the start or end thumb.
   * @docs-private
   */
  thumbPosition: _MatThumb = _MatThumb.END;

  /** @docs-private */
  get min(): number {
    return numberAttribute(this._hostElement.min, 0);
  }
  set min(v: number) {
    this._hostElement.min = v + '';
    this._cdr.detectChanges();
  }

  /** @docs-private */
  get max(): number {
    return numberAttribute(this._hostElement.max, 0);
  }
  set max(v: number) {
    this._hostElement.max = v + '';
    this._cdr.detectChanges();
  }

  get step(): number {
    return numberAttribute(this._hostElement.step, 0);
  }
  set step(v: number) {
    this._hostElement.step = v + '';
    this._cdr.detectChanges();
  }

  /** @docs-private */
  get disabled(): boolean {
    return booleanAttribute(this._hostElement.disabled);
  }
  set disabled(v: boolean) {
    this._hostElement.disabled = v;
    this._cdr.detectChanges();

    if (this._slider.disabled !== this.disabled) {
      this._slider.disabled = this.disabled;
    }
  }

  /** The percentage of the slider that coincides with the value. */
  get percentage(): number {
    if (this._slider.min >= this._slider.max) {
      return this._slider._isRtl() ? 1 : 0;
    }
    return (this.value - this._slider.min) / (this._slider.max - this._slider.min);
  }

  /** @docs-private */
  get fillPercentage(): number {
    if (!this._slider._cachedWidth) {
      return this._slider._isRtl() ? 1 : 0;
    }
    if (this._translateX === 0) {
      return 0;
    }
    return this.translateX / this._slider._cachedWidth;
  }

  /** The host native HTML input element. */
  _hostElement = this._elementRef.nativeElement;

  /** The aria-valuetext string representation of the input's value. */
  _valuetext = signal('');

  /** The radius of a native html slider's knob. */
  _knobRadius: number = 8;

  /** The distance in px from the start of the slider track to the first tick mark. */
  _tickMarkOffset = 3;

  /** Whether user's cursor is currently in a mouse down state on the input. */
  _isActive: boolean = false;

  /** Whether the input is currently focused (either by tab or after clicking). */
  _isFocused: boolean = false;

  /** Used to relay updates to _isFocused to the slider visual thumbs. */
  private _setIsFocused(v: boolean): void {
    this._isFocused = v;
  }

  /**
   * Whether the initial value has been set.
   * This exists because the initial value cannot be immediately set because the min and max
   * must first be relayed from the parent MatSlider component, which can only happen later
   * in the component lifecycle.
   */
  private _hasSetInitialValue: boolean = false;

  /** The stored initial value. */
  _initialValue: string | undefined;

  /** Defined when a user is using a form control to manage slider value & validation. */
  private _formControl: FormControl | undefined;

  /** Emits when the component is destroyed. */
  protected readonly _destroyed = new Subject<void>();

  /**
   * Indicates whether UI updates should be skipped.
   *
   * This flag is used to avoid flickering
   * when correcting values on pointer up/down.
   */
  _skipUIUpdate: boolean = false;

  /** Callback called when the slider input value changes. */
  protected _onChangeFn: ((value: any) => void) | undefined;

  /** Callback called when the slider input has been touched. */
  private _onTouchedFn: () => void = () => {};

  /**
   * Whether the NgModel has been initialized.
   *
   * This flag is used to ignore ghost null calls to
   * writeValue which can break slider initialization.
   *
   * See https://github.com/angular/angular/issues/14988.
   */
  protected _isControlInitialized = false;

  constructor() {
    const renderer = inject(Renderer2);

    this._ngZone.runOutsideAngular(() => {
      this._listenerCleanups = [
        renderer.listen(this._hostElement, 'pointerdown', this._onPointerDown.bind(this)),
        renderer.listen(this._hostElement, 'pointermove', this._onPointerMove.bind(this)),
        renderer.listen(this._hostElement, 'pointerup', this._onPointerUp.bind(this)),
      ];
    });
  }

  ngOnDestroy(): void {
    this._listenerCleanups.forEach(cleanup => cleanup());
    this._destroyed.next();
    this._destroyed.complete();
    this.dragStart.complete();
    this.dragEnd.complete();
  }

  /** @docs-private */
  initProps(): void {
    this._updateWidthInactive();

    // If this or the parent slider is disabled, just make everything disabled.
    if (this.disabled !== this._slider.disabled) {
      // The MatSlider setter for disabled will relay this and disable both inputs.
      this._slider.disabled = true;
    }

    this.step = this._slider.step;
    this.min = this._slider.min;
    this.max = this._slider.max;
    this._initValue();
  }

  /** @docs-private */
  initUI(): void {
    this._updateThumbUIByValue();
  }

  _initValue(): void {
    this._hasSetInitialValue = true;
    if (this._initialValue === undefined) {
      this.value = this._getDefaultValue();
    } else {
      this._hostElement.value = this._initialValue;
      this._updateThumbUIByValue();
      this._slider._onValueChange(this);
      this._cdr.detectChanges();
    }
  }

  _getDefaultValue(): number {
    return this.min;
  }

  _onBlur(): void {
    this._setIsFocused(false);
    this._onTouchedFn();
  }

  _onFocus(): void {
    this._slider._setTransition(false);
    this._slider._updateTrackUI(this);
    this._setIsFocused(true);
  }

  _onChange(): void {
    this.valueChange.emit(this.value);
    // only used to handle the edge case where user
    // mousedown on the slider then uses arrow keys.
    if (this._isActive) {
      this._updateThumbUIByValue({withAnimation: true});
    }
  }

  _onInput(): void {
    this._onChangeFn?.(this.value);
    // handles arrowing and updating the value when
    // a step is defined.
    if (this._slider.step || !this._isActive) {
      this._updateThumbUIByValue({withAnimation: !this._isActive});
    }
    this._slider._onValueChange(this);
  }

  _onNgControlValueChange(): void {
    // only used to handle when the value change
    // originates outside of the slider.
    if (!this._isActive || !this._isFocused) {
      this._slider._onValueChange(this);
      this._updateThumbUIByValue();
    }
    this._slider.disabled = this._formControl!.disabled;
  }

  _onPointerDown(event: PointerEvent): void {
    if (this.disabled || event.button !== 0) {
      return;
    }

    // On IOS, dragging only works if the pointer down happens on the
    // slider thumb and the slider does not receive focus from pointer events.
    if (this._platform.IOS) {
      const isCursorOnSliderThumb = this._slider._isCursorOnSliderThumb(
        event,
        this._slider._getThumb(this.thumbPosition)._hostElement.getBoundingClientRect(),
      );

      this._isActive = isCursorOnSliderThumb;
      this._updateWidthActive();
      this._slider._updateDimensions();
      return;
    }

    this._isActive = true;
    this._setIsFocused(true);
    this._updateWidthActive();
    this._slider._updateDimensions();

    // Does nothing if a step is defined because we
    // want the value to snap to the values on input.
    if (!this._slider.step) {
      this._updateThumbUIByPointerEvent(event, {withAnimation: true});
    }

    if (!this.disabled) {
      this._handleValueCorrection(event);
      this.dragStart.emit({source: this, parent: this._slider, value: this.value});
    }
  }

  /**
   * Corrects the value of the slider on pointer up/down.
   *
   * Called on pointer down and up because the value is set based
   * on the inactive width instead of the active width.
   */
  private _handleValueCorrection(event: PointerEvent): void {
    // Don't update the UI with the current value! The value on pointerdown
    // and pointerup is calculated in the split second before the input(s)
    // resize. See _updateWidthInactive() and _updateWidthActive() for more
    // details.
    this._skipUIUpdate = true;

    // Note that this function gets triggered before the actual value of the
    // slider is updated. This means if we were to set the value here, it
    // would immediately be overwritten. Using setTimeout ensures the setting
    // of the value happens after the value has been updated by the
    // pointerdown event.
    setTimeout(() => {
      this._skipUIUpdate = false;
      this._fixValue(event);
    }, 0);
  }

  /** Corrects the value of the slider based on the pointer event's position. */
  _fixValue(event: PointerEvent): void {
    const xPos = event.clientX - this._slider._cachedLeft;
    const width = this._slider._cachedWidth;
    const step = this._slider.step === 0 ? 1 : this._slider.step;
    const numSteps = Math.floor((this._slider.max - this._slider.min) / step);
    const percentage = this._slider._isRtl() ? 1 - xPos / width : xPos / width;

    // To ensure the percentage is rounded to the necessary number of decimals.
    const fixedPercentage = Math.round(percentage * numSteps) / numSteps;

    const impreciseValue =
      fixedPercentage * (this._slider.max - this._slider.min) + this._slider.min;
    const value = Math.round(impreciseValue / step) * step;
    const prevValue = this.value;

    if (value === prevValue) {
      // Because we prevented UI updates, if it turns out that the race
      // condition didn't happen and the value is already correct, we
      // have to apply the ui updates now.
      this._slider._onValueChange(this);
      this._slider.step > 0
        ? this._updateThumbUIByValue()
        : this._updateThumbUIByPointerEvent(event, {withAnimation: this._slider._hasAnimation});
      return;
    }

    this.value = value;
    this.valueChange.emit(this.value);
    this._onChangeFn?.(this.value);
    this._slider._onValueChange(this);
    this._slider.step > 0
      ? this._updateThumbUIByValue()
      : this._updateThumbUIByPointerEvent(event, {withAnimation: this._slider._hasAnimation});
  }

  _onPointerMove(event: PointerEvent): void {
    // Again, does nothing if a step is defined because
    // we want the value to snap to the values on input.
    if (!this._slider.step && this._isActive) {
      this._updateThumbUIByPointerEvent(event);
    }
  }

  _onPointerUp(): void {
    if (this._isActive) {
      this._isActive = false;
      if (this._platform.SAFARI) {
        this._setIsFocused(false);
      }
      this.dragEnd.emit({source: this, parent: this._slider, value: this.value});

      // This setTimeout is to prevent the pointerup from triggering a value
      // change on the input based on the inactive width. It's not clear why
      // but for some reason on IOS this race condition is even more common so
      // the timeout needs to be increased.
      setTimeout(() => this._updateWidthInactive(), this._platform.IOS ? 10 : 0);
    }
  }

  _clamp(v: number): number {
    const min = this._tickMarkOffset;
    const max = this._slider._cachedWidth - this._tickMarkOffset;
    return Math.max(Math.min(v, max), min);
  }

  _calcTranslateXByValue(): number {
    if (this._slider._isRtl()) {
      return (
        (1 - this.percentage) * (this._slider._cachedWidth - this._tickMarkOffset * 2) +
        this._tickMarkOffset
      );
    }
    return (
      this.percentage * (this._slider._cachedWidth - this._tickMarkOffset * 2) +
      this._tickMarkOffset
    );
  }

  _calcTranslateXByPointerEvent(event: PointerEvent): number {
    return event.clientX - this._slider._cachedLeft;
  }

  /**
   * Used to set the slider width to the correct
   * dimensions while the user is dragging.
   */
  _updateWidthActive(): void {}

  /**
   * Sets the slider input to disproportionate dimensions to allow for touch
   * events to be captured on touch devices.
   */
  _updateWidthInactive(): void {
    this._hostElement.style.padding = `0 ${this._slider._inputPadding}px`;
    this._hostElement.style.width = `calc(100% + ${
      this._slider._inputPadding - this._tickMarkOffset * 2
    }px)`;
    this._hostElement.style.left = `-${this._slider._rippleRadius - this._tickMarkOffset}px`;
  }

  _updateThumbUIByValue(options?: {withAnimation: boolean}): void {
    this.translateX = this._clamp(this._calcTranslateXByValue());
    this._updateThumbUI(options);
  }

  _updateThumbUIByPointerEvent(event: PointerEvent, options?: {withAnimation: boolean}): void {
    this.translateX = this._clamp(this._calcTranslateXByPointerEvent(event));
    this._updateThumbUI(options);
  }

  _updateThumbUI(options?: {withAnimation: boolean}) {
    this._slider._setTransition(!!options?.withAnimation);
    this._slider._onTranslateXChange(this);
  }

  /**
   * Sets the input's value.
   * @param value The new value of the input
   * @docs-private
   */
  writeValue(value: any): void {
    if (this._isControlInitialized || value !== null) {
      this.value = value;
    }
  }

  /**
   * Registers a callback to be invoked when the input's value changes from user input.
   * @param fn The callback to register
   * @docs-private
   */
  registerOnChange(fn: any): void {
    this._onChangeFn = fn;
    this._isControlInitialized = true;
  }

  /**
   * Registers a callback to be invoked when the input is blurred by the user.
   * @param fn The callback to register
   * @docs-private
   */
  registerOnTouched(fn: any): void {
    this._onTouchedFn = fn;
  }

  /**
   * Sets the disabled state of the slider.
   * @param isDisabled The new disabled state
   * @docs-private
   */
  setDisabledState(isDisabled: boolean): void {
    this.disabled = isDisabled;
  }

  focus(): void {
    this._hostElement.focus();
  }

  blur(): void {
    this._hostElement.blur();
  }
}

@Directive({
  selector: 'input[matSliderStartThumb], input[matSliderEndThumb]',
  exportAs: 'matSliderRangeThumb',
  providers: [
    MAT_SLIDER_RANGE_THUMB_VALUE_ACCESSOR,
    {provide: MAT_SLIDER_RANGE_THUMB, useExisting: MatSliderRangeThumb},
  ],
})
export class MatSliderRangeThumb extends MatSliderThumb implements _MatSliderRangeThumb {
  override readonly _cdr = inject(ChangeDetectorRef);

  /** @docs-private */
  getSibling(): _MatSliderRangeThumb | undefined {
    if (!this._sibling) {
      this._sibling = this._slider._getInput(this._isEndThumb ? _MatThumb.START : _MatThumb.END) as
        MatSliderRangeThumb | undefined;
    }
    return this._sibling;
  }
  private _sibling: MatSliderRangeThumb | undefined;

  /**
   * Returns the minimum translateX position allowed for this slider input's visual thumb.
   * @docs-private
   */
  getMinPos(): number {
    const sibling = this.getSibling();
    if (!this._isLeftThumb && sibling) {
      return sibling.translateX;
    }
    return this._tickMarkOffset;
  }

  /**
   * Returns the maximum translateX position allowed for this slider input's visual thumb.
   * @docs-private
   */
  getMaxPos(): number {
    const sibling = this.getSibling();
    if (this._isLeftThumb && sibling) {
      return sibling.translateX;
    }
    return this._slider._cachedWidth - this._tickMarkOffset;
  }

  _setIsLeftThumb(): void {
    this._isLeftThumb =
      (this._isEndThumb && this._slider._isRtl()) || (!this._isEndThumb && !this._slider._isRtl());
  }

  /** Whether this slider corresponds to the input on the left hand side. */
  _isLeftThumb = false;

  /** Whether this slider corresponds to the input with greater value. */
  _isEndThumb = false;

  constructor() {
    super();

    this._isEndThumb = this._hostElement.hasAttribute('matSliderEndThumb');
    this._setIsLeftThumb();
    this.thumbPosition = this._isEndThumb ? _MatThumb.END : _MatThumb.START;
  }

  override _getDefaultValue(): number {
    return this._isEndThumb && this._slider._isRange ? this.max : this.min;
  }

  override _onInput(): void {
    super._onInput();
    this._updateSibling();
    if (!this._isActive) {
      this._updateWidthInactive();
    }
  }

  override _onNgControlValueChange(): void {
    super._onNgControlValueChange();
    this.getSibling()?._updateMinMax();
  }

  override _onPointerDown(event: PointerEvent): void {
    if (this.disabled || event.button !== 0) {
      return;
    }
    if (this._sibling) {
      this._sibling._updateWidthActive();
      this._sibling._hostElement.classList.add('mat-mdc-slider-input-no-pointer-events');
    }
    super._onPointerDown(event);
  }

  override _onPointerUp(): void {
    super._onPointerUp();
    if (this._sibling) {
      setTimeout(() => {
        this._sibling!._updateWidthInactive();
        this._sibling!._hostElement.classList.remove('mat-mdc-slider-input-no-pointer-events');
      });
    }
  }

  override _onPointerMove(event: PointerEvent): void {
    super._onPointerMove(event);
    if (!this._slider.step && this._isActive) {
      this._updateSibling();
    }
  }

  override _fixValue(event: PointerEvent): void {
    super._fixValue(event);
    this._sibling?._updateMinMax();
  }

  override _clamp(v: number): number {
    return Math.max(Math.min(v, this.getMaxPos()), this.getMinPos());
  }

  _updateMinMax(): void {
    const sibling = this.getSibling();
    if (!sibling) {
      return;
    }
    if (this._isEndThumb) {
      this.min = Math.max(this._slider.min, sibling.value);
      this.max = this._slider.max;
    } else {
      this.min = this._slider.min;
      this.max = Math.min(this._slider.max, sibling.value);
    }
  }

  override _updateWidthActive(): void {
    const minWidth = this._slider._rippleRadius * 2 - this._slider._inputPadding * 2;
    const maxWidth =
      this._slider._cachedWidth + this._slider._inputPadding - minWidth - this._tickMarkOffset * 2;
    const percentage =
      this._slider.min < this._slider.max
        ? (this.max - this.min) / (this._slider.max - this._slider.min)
        : 1;
    const width = maxWidth * percentage + minWidth;
    this._hostElement.style.width = `${width}px`;
    this._hostElement.style.padding = `0 ${this._slider._inputPadding}px`;
  }

  override _updateWidthInactive(): void {
    const sibling = this.getSibling();
    if (!sibling) {
      return;
    }
    const maxWidth = this._slider._cachedWidth - this._tickMarkOffset * 2;
    const midValue = this._isEndThumb
      ? this.value - (this.value - sibling.value) / 2
      : this.value + (sibling.value - this.value) / 2;

    const _percentage = this._isEndThumb
      ? (this.max - midValue) / (this._slider.max - this._slider.min)
      : (midValue - this.min) / (this._slider.max - this._slider.min);

    const percentage = this._slider.min < this._slider.max ? _percentage : 1;

    // Extend the native input width by the radius of the ripple
    let ripplePadding = this._slider._rippleRadius;

    // If one of the inputs is maximally sized (the value of both thumbs is
    // equal to the min or max), make that input take up all of the width and
    // make the other unselectable.
    if (percentage === 1) {
      ripplePadding = 48;
    } else if (percentage === 0) {
      ripplePadding = 0;
    }

    const width = maxWidth * percentage + ripplePadding;
    this._hostElement.style.width = `${width}px`;
    this._hostElement.style.padding = '0px';

    if (this._isLeftThumb) {
      this._hostElement.style.left = `-${this._slider._rippleRadius - this._tickMarkOffset}px`;
      this._hostElement.style.right = 'auto';
    } else {
      this._hostElement.style.left = 'auto';
      this._hostElement.style.right = `-${this._slider._rippleRadius - this._tickMarkOffset}px`;
    }
  }

  _updateStaticStyles(): void {
    this._hostElement.classList.toggle('mat-slider__right-input', !this._isLeftThumb);
  }

  private _updateSibling(): void {
    const sibling = this.getSibling();
    if (!sibling) {
      return;
    }
    sibling._updateMinMax();
    if (this._isActive) {
      sibling._updateWidthActive();
    } else {
      sibling._updateWidthInactive();
    }
  }

  /**
   * Sets the input's value.
   * @param value The new value of the input
   * @docs-private
   */
  override writeValue(value: any): void {
    if (this._isControlInitialized || value !== null) {
      this.value = value;
      this._updateWidthInactive();
      this._updateSibling();
    }
  }

  override _setValue(value: string) {
    super._setValue(value);
    this._updateWidthInactive();
    this._updateSibling();
  }
}