ColorSlider.ts

/*
Copyright 2020 Adobe. All rights reserved.
This file is licensed to you under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License. You may obtain a copy
of the License at http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under
the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
OF ANY KIND, either express or implied. See the License for the specific language
governing permissions and limitations under the License.
*/

import {
    CSSResultArray,
    html,
    PropertyValues,
    TemplateResult,
} from '@spectrum-web-components/base';
import { ifDefined } from '@spectrum-web-components/base/src/directives.js';
import {
    property,
    query,
} from '@spectrum-web-components/base/src/decorators.js';
import { streamingListener } from '@spectrum-web-components/base/src/streaming-listener.js';
import { Focusable } from '@spectrum-web-components/shared/src/focusable.js';
import type { ColorHandle } from '@spectrum-web-components/color-handle';
import '@spectrum-web-components/color-handle/sp-color-handle.js';
import {
    ColorController,
    ColorValue,
    HSL,
} from '@spectrum-web-components/reactive-controllers/src/Color.js';

import styles from './color-slider.css.js';

/**
 * @element sp-color-slider
 * @slot gradient - a custom gradient visually outlining the available color values
 * @fires input - The value of the Color Slider has changed.
 * @fires change - An alteration to the value of the Color Slider has been committed by the user.
 */
export class ColorSlider extends Focusable {
    public static override get styles(): CSSResultArray {
        return [styles];
    }

    @property({ type: Boolean, reflect: true })
    public override disabled = false;

    @property({ type: Boolean, reflect: true })
    public focused = false;

    @query('.handle')
    private handle!: ColorHandle;

    @property({ type: String })
    public label = 'hue';

    @property({ type: Boolean, reflect: true })
    public vertical = false;

    private colorController = new ColorController(this, {
        /* c8 ignore next 3 */
        applyColorToState: () => {
            this.sliderHandlePosition = 100 * (this.colorController.hue / 360);
        },
        extractColorFromState: (controller) => ({
            ...(controller.getColor('hsl') as HSL),
            h: this.value,
        }),
        maintains: 'saturation',
    });

    @property({ type: Number })
    public get value(): number {
        return this.colorController.hue;
    }

    public set value(hue: number) {
        this.colorController.hue = hue;
    }

    @property({ type: Number, reflect: true })
    public sliderHandlePosition = 0;

    @property({ type: String })
    public get color(): ColorValue {
        return this.colorController.color;
    }

    public set color(color: ColorValue) {
        this.colorController.color = color;
    }

    @property({ type: Number })
    public step = 1;

    private get altered(): number {
        return this._altered;
    }

    private set altered(altered: number) {
        this._altered = altered;
        this.step = Math.max(1, this.altered * 10);
    }

    private _altered = 0;

    @query('input')
    public input!: HTMLInputElement;

    public override get focusElement(): HTMLInputElement {
        return this.input;
    }

    private handleKeydown(event: KeyboardEvent): void {
        const { key } = event;
        this.focused = true;
        this.altered = [event.shiftKey, event.ctrlKey, event.altKey].filter(
            (key) => !!key
        ).length;
        let delta = 0;
        switch (key) {
            case 'ArrowUp':
                delta = this.step;
                break;
            case 'ArrowDown':
                delta = -this.step;
                break;
            case 'ArrowLeft':
                delta = this.step * (this.isLTR ? -1 : 1);
                break;
            case 'ArrowRight':
                delta = this.step * (this.isLTR ? 1 : -1);
                break;
            default:
                return;
        }
        event.preventDefault();

        this.sliderHandlePosition = Math.min(
            100,
            Math.max(0, this.sliderHandlePosition + delta)
        );
        this.value = 360 * (this.sliderHandlePosition / 100);
        this.colorController.applyColorFromState();

        if (delta != 0) {
            this.dispatchEvent(
                new Event('input', {
                    bubbles: true,
                    composed: true,
                })
            );
            this.dispatchEvent(
                new Event('change', {
                    bubbles: true,
                    composed: true,
                })
            );
        }
    }

    private handleInput(event: Event & { target: HTMLInputElement }): void {
        const { valueAsNumber } = event.target;

        this.value = valueAsNumber;
        this.sliderHandlePosition = 100 * (this.value / 360);
        this.colorController.applyColorFromState();
    }

    private handleChange(event: Event & { target: HTMLInputElement }): void {
        this.handleInput(event);
        this.dispatchEvent(
            new Event('change', {
                bubbles: true,
                composed: true,
            })
        );
    }

    public override focus(focusOptions: FocusOptions = {}): void {
        super.focus(focusOptions);
        this.forwardFocus();
    }

    private forwardFocus(): void {
        this.focused = this.hasVisibleFocusInTree();
        this.input.focus();
    }

    private handleFocusin(): void {
        this.focused = true;
    }

    private handleFocusout(): void {
        if (this._pointerDown) {
            return;
        }
        this.altered = 0;
        this.focused = false;
    }

    private boundingClientRect!: DOMRect;
    private _pointerDown = false;

    private handlePointerdown(event: PointerEvent): void {
        if (event.button !== 0) {
            event.preventDefault();
            return;
        }
        this._pointerDown = true;
        this.colorController.savePreviousColor();
        this.boundingClientRect = this.getBoundingClientRect();
        (event.target as HTMLElement).setPointerCapture(event.pointerId);
        if (event.pointerType === 'mouse') {
            this.focused = true;
        }
    }

    private handlePointermove(event: PointerEvent): void {
        this.sliderHandlePosition = this.calculateHandlePosition(event);
        this.value = 360 * (this.sliderHandlePosition / 100);

        this.colorController.applyColorFromState();

        this.dispatchEvent(
            new Event('input', {
                bubbles: true,
                composed: true,
                cancelable: true,
            })
        );
    }

    private handlePointerup(event: PointerEvent): void {
        this._pointerDown = false;
        (event.target as HTMLElement).releasePointerCapture(event.pointerId);

        const applyDefault = this.dispatchEvent(
            new Event('change', {
                bubbles: true,
                composed: true,
                cancelable: true,
            })
        );
        if (!applyDefault) {
            this.colorController.restorePreviousColor();
        }
        // Retain focus on input element after mouse up to enable keyboard interactions
        this.focus();
        if (event.pointerType === 'mouse') {
            this.focused = false;
        }
    }

    /**
     * Returns the value under the cursor
     * @param: PointerEvent on slider
     * @return: Slider value that correlates to the position under the pointer
     */
    private calculateHandlePosition(event: PointerEvent): number {
        /* c8 ignore next 3 */
        if (!this.boundingClientRect) {
            return this.sliderHandlePosition;
        }
        const rect = this.boundingClientRect;
        const minOffset = this.vertical ? rect.top : rect.left;
        const offset = this.vertical ? event.clientY : event.clientX;
        const size = this.vertical ? rect.height : rect.width;

        const percent = Math.max(0, Math.min(1, (offset - minOffset) / size));
        const sliderHandlePosition =
            this.vertical || !this.isLTR ? 100 - 100 * percent : 100 * percent;

        return sliderHandlePosition;
    }

    private handleGradientPointerdown(event: PointerEvent): void {
        if (event.button !== 0) {
            return;
        }
        event.stopPropagation();
        event.preventDefault();
        this.handle.dispatchEvent(new PointerEvent('pointerdown', event));
        this.handlePointermove(event);
    }

    private get handlePositionStyles(): string {
        return `${this.vertical ? 'inset-block-end' : 'inset-inline-start'}: ${
            this.sliderHandlePosition
        }%`;
    }

    protected override render(): TemplateResult {
        return html`
            <div
                class="checkerboard"
                role="presentation"
                @pointerdown=${this.handleGradientPointerdown}
            >
                <div
                    class="gradient"
                    role="presentation"
                    style="background: linear-gradient(to ${this.vertical
                        ? 'top'
                        : 'right'}, var(--sp-color-slider-gradient, var(--sp-color-slider-gradient-fallback)));"
                >
                    <slot name="gradient"></slot>
                </div>
            </div>
            <sp-color-handle
                tabindex=${ifDefined(this.focused ? undefined : '0')}
                @focus=${this.forwardFocus}
                ?focused=${this.focused}
                class="handle"
                color="hsl(${this.value}, 100%, 50%)"
                ?disabled=${this.disabled}
                style=${this.handlePositionStyles}
                ${streamingListener({
                    start: ['pointerdown', this.handlePointerdown],
                    streamInside: ['pointermove', this.handlePointermove],
                    end: [
                        ['pointerup', 'pointercancel', 'pointerleave'],
                        this.handlePointerup,
                    ],
                })}
            ></sp-color-handle>
            <input
                type="range"
                class="slider"
                min="0"
                max="360"
                step=${this.step}
                aria-label=${this.label}
                .value=${String(this.value)}
                @input=${this.handleInput}
                @change=${this.handleChange}
                @keydown=${this.handleKeydown}
            />
        `;
    }

    protected override firstUpdated(changed: PropertyValues): void {
        super.firstUpdated(changed);
        this.boundingClientRect = this.getBoundingClientRect();
        this.addEventListener('focusin', this.handleFocusin);
        this.addEventListener('focusout', this.handleFocusout);
    }
}