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/*
* Copyright (C) 2022 Yomichan Authors
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
/**
* This class is used to control theme attributes on DOM elements.
*/
class ThemeController {
/**
* Creates a new instance of the class.
* @param {?Element} element A DOM element which theme properties are applied to.
*/
constructor(element) {
this._element = element;
this._theme = 'default';
this._outerTheme = 'default';
this._siteTheme = null;
this._browserTheme = 'light';
}
/**
* Gets the DOM element which theme properties are applied to.
* @type {?Element}
*/
get element() {
return this._element;
}
/**
* Sets the DOM element which theme properties are applied to.
* @param {?Element} value The DOM element to assign.
*/
set element(value) {
this._element = value;
}
/**
* Gets the main theme for the content.
* @type {string}
*/
get theme() {
return this._theme;
}
/**
* Sets the main theme for the content.
* @param {string} value The theme value to assign.
*/
set theme(value) {
this._theme = value;
}
/**
* Gets the outer theme for the content.
* @type {string}
*/
get outerTheme() {
return this._outerTheme;
}
/**
* Sets the outer theme for the content.
* @param {string} value The outer theme value to assign.
*/
set outerTheme(value) {
this._outerTheme = value;
}
/**
* Gets the override value for the site theme.
* If this value is `null`, the computed value will be used.
* @type {?string}
*/
get siteTheme() {
return this._siteTheme;
}
/**
* Sets the override value for the site theme.
* If this value is `null`, the computed value will be used.
* @param {?string} value The site theme value to assign.
*/
set siteTheme(value) {
this._siteTheme = value;
}
/**
* Gets the browser's preferred color theme.
* The value can be either 'light' or 'dark'.
* @type {?string}
*/
get browserTheme() {
return this._browserTheme;
}
/**
* Prepares the instance for use and applies the theme settings.
*/
prepare() {
const mediaQueryList = window.matchMedia('(prefers-color-scheme: dark)');
mediaQueryList.addEventListener('change', this._onPrefersColorSchemeDarkChange.bind(this));
this._onPrefersColorSchemeDarkChange(mediaQueryList);
}
/**
* Updates the theme attributes on the target element.
* If the site theme value isn't overridden, the current site theme is recomputed.
*/
updateTheme() {
if (this._element === null) { return; }
const computedSiteTheme = this._siteTheme !== null ? this._siteTheme : this.computeSiteTheme();
const data = this._element.dataset;
data.theme = this._resolveThemeValue(this._theme, computedSiteTheme);
data.outerTheme = this._resolveThemeValue(this._outerTheme, computedSiteTheme);
data.siteTheme = computedSiteTheme;
data.browserTheme = this._browserTheme;
data.themeRaw = this._theme;
data.outerThemeRaw = this._outerTheme;
}
/**
* Computes the current site theme based on the background color.
* @returns {'light'|'dark'} The theme of the site.
*/
computeSiteTheme() {
const color = [255, 255, 255];
const {documentElement, body} = document;
if (documentElement !== null) {
this._addColor(color, window.getComputedStyle(documentElement).backgroundColor);
}
if (body !== null) {
this._addColor(color, window.getComputedStyle(body).backgroundColor);
}
const dark = (color[0] < 128 && color[1] < 128 && color[2] < 128);
return dark ? 'dark' : 'light';
}
/**
* Event handler for when the preferred browser theme changes.
* @param {MediaQueryList|MediaQueryListEvent} detail The object containing event details.
* @param {boolean} detail.matches The object containing event details.
*/
_onPrefersColorSchemeDarkChange({matches}) {
this._browserTheme = (matches ? 'dark' : 'light');
this.updateTheme();
}
/**
* Resolves a settings theme value to the actual value which should be used.
* @param {string} theme The theme value to resolve.
* @param {string} computedSiteTheme The computed site theme value to use for when the theme value is `'auto'`.
* @returns {string} The resolved theme value.
*/
_resolveThemeValue(theme, computedSiteTheme) {
switch (theme) {
case 'auto': return computedSiteTheme;
case 'browser': return this._browserTheme;
default: return theme;
}
}
/**
* Adds the value of a CSS color to an accumulation target.
* @param {number[]} target The target color buffer to accumulate into, as an array of [r, g, b].
* @param {string|*} cssColor The CSS color value to add to the target. If this value is not a string,
* the target will not be modified.
*/
_addColor(target, cssColor) {
if (typeof cssColor !== 'string') { return; }
const color = this._getColorInfo(cssColor);
if (color === null) { return; }
const a = color[3];
if (a <= 0.0) { return; }
const aInv = 1.0 - a;
for (let i = 0; i < 3; ++i) {
target[i] = target[i] * aInv + color[i] * a;
}
}
/**
* Decomposes a CSS color string into its RGBA values.
* @param {string} cssColor The color value to decompose. This value is expected to be in the form RGB(r, g, b) or RGBA(r, g, b, a).
* @returns {?number[]} The color and alpha values as [r, g, b, a]. The color component values range from [0, 255], and the alpha ranges from [0, 1].
*/
_getColorInfo(cssColor) {
const m = /^\s*rgba?\s*\(\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*(?:,\s*([\d.]+)\s*)?\)\s*$/.exec(cssColor);
if (m === null) { return null; }
const m4 = m[4];
return [
Number.parseInt(m[1], 10),
Number.parseInt(m[2], 10),
Number.parseInt(m[3], 10),
m4 ? Math.max(0.0, Math.min(1.0, Number.parseFloat(m4))) : 1.0
];
}
}
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