1 files changed, 102 insertions, 0 deletions
diff --git a/devtools/client/shared/theme.js b/devtools/client/shared/theme.js
new file mode 100644
index 0000000000..e3c3ff608d
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+++ b/devtools/client/shared/theme.js
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const variableFileContents = require("raw!chrome://devtools/skin/variables.css");
+
+const THEME_SELECTOR_STRINGS = {
+  light: ":root.theme-light {",
+  dark: ":root.theme-dark {",
+  root: ":root {",
+};
+const THEME_PREF = "devtools.theme";
+
+/**
+ * Takes a theme name and returns the contents of its variable rule block.
+ * The first time this runs fetches the variables CSS file and caches it.
+ */
+function getThemeFile(name) {
+  // If there's no theme expected for this name, use `light` as default.
+  const selector = THEME_SELECTOR_STRINGS[name] || THEME_SELECTOR_STRINGS.light;
+
+  // This is a pretty naive way to find the contents between:
+  // selector {
+  //   name: val;
+  // }
+  // There is test coverage for this feature (browser_theme.js)
+  // so if an } is introduced in the variables file it will catch that.
+  let theme = variableFileContents;
+  theme = theme.substring(theme.indexOf(selector));
+  theme = theme.substring(0, theme.indexOf("}"));
+
+  return theme;
+}
+
+/**
+ * Returns the "auto" theme.
+ */
+const getAutoTheme = (exports.getAutoTheme = () => {
+  return Services.appinfo.chromeColorSchemeIsDark ? "dark" : "light";
+});
+
+/**
+ * Returns the string value of the current theme,
+ * like "dark" or "light".
+ */
+const getTheme = (exports.getTheme = () => {
+  const theme = Services.prefs.getCharPref(THEME_PREF);
+  if (theme == "auto") {
+    return getAutoTheme();
+  }
+  return theme;
+});
+
+/**
+ * Returns a color indicated by `type` (like "toolbar-background", or
+ * "highlight-red"), with the ability to specify a theme, or use whatever the
+ * current theme is if left unset. If theme not found, falls back to "light"
+ * theme. Returns null if the type cannot be found for the theme given.
+ */
+/* eslint-disable no-unused-vars */
+const getColor = (exports.getColor = (type, theme) => {
+  const themeName = theme || getTheme();
+  let themeFile = getThemeFile(themeName);
+  let match = themeFile.match(new RegExp("--theme-" + type + ": (.*);"));
+  const variableMatch = match ? match[1].match(/var\((.*)\)/) : null;
+
+  // Check if the match is a color variable and retrieve the value of the color variable
+  // if needed
+  if (variableMatch) {
+    themeFile = getThemeFile("root");
+    match = themeFile.match(new RegExp(`${variableMatch[1]}: (.*);`));
+  }
+
+  // Return the appropriate variable in the theme, or otherwise, null.
+  return match ? match[1] : null;
+});
+
+/**
+ * Set the theme preference.
+ */
+const setTheme = (exports.setTheme = newTheme => {
+  Services.prefs.setCharPref(THEME_PREF, newTheme);
+});
+
+/**
+ * Add an observer for theme changes.
+ */
+const addThemeObserver = (exports.addThemeObserver = observer => {
+  Services.obs.addObserver(observer, "look-and-feel-changed");
+  Services.prefs.addObserver(THEME_PREF, observer);
+});
+
+/**
+ * Remove an observer for theme changes.
+ */
+const removeThemeObserver = (exports.removeThemeObserver = observer => {
+  Services.obs.removeObserver(observer, "look-and-feel-changed");
+  Services.prefs.removeObserver(THEME_PREF, observer);
+});
+/* eslint-enable */