Swing/DarkMode の変更点

---
category: swing
folder: DarkMode
title: JEditorPaneのStyleSheetをLight・Darkテーマに合わせて切り替える
tags: [JEditorPane, StyleSheet, LookAndFeel, Toolkit, PropertyChangeListener]
author: aterai
pubdate: 2025-04-07T09:41:23+09:00
description: JEditorPaneのStyleSheetを起動時のシステムテーマがLightかDarkかなどに応じて切り替えるよう設定します。
image: https://drive.google.com/uc?id=1rNhaj-mqEkjn2ntU4yNaMPj-DJOdzBfW
---
* Summary [#summary]
`JEditorPane`の`StyleSheet`を起動時のシステムテーマが`Light`か`Dark`かなどに応じて切り替えるよう設定します。

#download(https://drive.google.com/uc?id=1rNhaj-mqEkjn2ntU4yNaMPj-DJOdzBfW)

* Source Code Examples [#sourcecode]
#code(link){{
public static void updateTheme(JEditorPane editor) {
  updateTheme(editor, isDarkMode());
}

public static void updateTheme(JEditorPane editor, boolean isDark) {
  EditorKit kit = editor.getEditorKit();
  HTMLEditorKit htmlEditorKit;
  if (kit instanceof HTMLEditorKit) {
    htmlEditorKit = (HTMLEditorKit) kit;
  } else {
    htmlEditorKit = new HTMLEditorKit();
  }
  if (isDark) {
    htmlEditorKit.setStyleSheet(makeDarkStyleSheet());
    editor.setBackground(new Color(0x1E_1F_22));
  } else {
    htmlEditorKit.setStyleSheet(makeLightStyleSheet());
    editor.setBackground(new Color(0xEE_EE_EE));
  }
  editor.setEditorKit(htmlEditorKit);
}

public static boolean isDarkMode() {
  boolean isDark;
  String os = System.getProperty("os.name").toLowerCase(Locale.ENGLISH);
  if (os.contains("windows")) {
    isDark = isWindowsDarkMode();
  } else if (os.contains("linux")) {
    isDark = isLinuxDarkMode();
  } else if (os.contains("mac")) {
    isDark = isMackDarkMode();
  } else {
    isDark = false;
  }
  return isDark;
}

public static String getProcessOutput(String... cmd)
      throws IOException, InterruptedException {
  ProcessBuilder builder = new ProcessBuilder(cmd);
  builder.redirectErrorStream(true);
  Process p = builder.start();
  String str;
  try (BufferedReader pr = new BufferedReader(
            new InputStreamReader(p.getInputStream()))) {
    str = pr.lines().collect(Collectors.joining(System.lineSeparator()));
  }
  return str;
}

public static boolean isWindowsDarkMode() {
  String[] cmd = {
      "powershell.exe",
      "Get-ItemPropertyValue",
      "-Path",
      "HKCU:\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize",
      "-Name",
      "AppsUseLightTheme;"
  };
  boolean isDarkMode;
  try {
    String str = getProcessOutput(cmd).trim();
    isDarkMode = Objects.equals("0", str);
  } catch (IOException | InterruptedException ex) {
    Logger.getGlobal().severe(ex::getMessage);
    isDarkMode = false;
  }
  return isDarkMode;
}

public static boolean isLinuxDarkMode() {
  Toolkit tk = Toolkit.getDefaultToolkit();
  Object theme = tk.getDesktopProperty("gnome.Net/ThemeName");
  return Objects.toString(theme).contains("dark");
}

public static boolean isMackDarkMode() {
  return false;
}

// https://raw.githack.com/google/code-prettify/master/styles/index.html
// Prettify Themes Gallery
public static StyleSheet makeLightStyleSheet() {
  StyleSheet styleSheet = new StyleSheet();
  styleSheet.addRule("pre{background:#eeeeee}");
  styleSheet.addRule(".str{color:#008800}");
  styleSheet.addRule(".kwd{color:#000088}");
  styleSheet.addRule(".com{color:#880000}");
  styleSheet.addRule(".typ{color:#660066}");
  styleSheet.addRule(".lit{color:#006666}");
  styleSheet.addRule(".pun{color:#666600}");
  styleSheet.addRule(".pln{color:#000000}");
  styleSheet.addRule(".tag{color:#000088}");
  styleSheet.addRule(".atn{color:#660066}");
  styleSheet.addRule(".atv{color:#008800}");
  styleSheet.addRule(".dec{color:#660066}");
  return styleSheet;
}

public static StyleSheet makeDarkStyleSheet() {
  StyleSheet styleSheet = new StyleSheet();
  styleSheet.addRule("pre{background:#1e1f22}");
  styleSheet.addRule(".str{color:#ffa0a0}");
  styleSheet.addRule(".kwd{color:#f0e68c;font-weight:bold}");
  styleSheet.addRule(".com{color:#87ceeb}");
  styleSheet.addRule(".typ{color:#98fb98}");
  styleSheet.addRule(".lit{color:#cd5c5c}");
  styleSheet.addRule(".pun{color:#ffffff}");
  styleSheet.addRule(".pln{color:#ffffff}");
  styleSheet.addRule(".tag{color:#f0e68c;font-weight:bold}");
  styleSheet.addRule(".atn{color:#bdb76b;font-weight:bold}");
  styleSheet.addRule(".atv{color:#ffa0a0}");
  styleSheet.addRule(".dec{color:#98fb98}");
  return styleSheet;
}
}}

* Explanation [#explanation]
- `OS`が`Windows`の場合、個人用設定の色をライト、ダークで切り替えても`Swing`アプリ側でそのイベントを取得できない
-- `Windows 7`などでは[[DesktopPropertyの変更を監視する>Swing/DesktopProperty]]のように`Toolkit`に`PropertyChangeListener`を追加することで画面の配色変更を取得可能だったが、`Windows 10`や`Windows 11`では動作しない？
-- このサンプルでは、起動時や`JRadioButtonMenuItem`でテーマを手動切り替えしたときに、レジストリから`HKCU:\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize`の値を取得して`0`の場合は`Dark`テーマと判断し、`StyleSheet`の切り替えを実行
-- [https://gist.github.com/HanSolo/7cf10b86efff8ca2845bf5ec2dd0fe1d Detector: A plain Java class that offers some utility methods to detect dark theme on MacOS and Windows · GitHub]

- `OS`が`Linux(Ubuntu+gnome)`の場合、設定の外観、スタイルをデフォルト(ライト)、ダークで切り替えると、`Swing`アプリ側でもそのイベントを取得可能
-- `GTKLookAndFeel`はデフォルトでスタイル切り替えが発生すると`SynthTheme`を切り替えて各コンポーネントの配色を変更している
-- 以下のように、`Toolkit`にデスクトッププロパティを`gnome.Net/ThemeName`として`PropertyChangeListener`を追加すればスタイル切り替えイベントを取得可能なので、テーマ名に`dark`が含まれる場合は`Dark`テーマと判断し、`StyleSheet`の切り替えを実行
#code{{
String key = "gnome.Net/ThemeName";
Toolkit.getDefaultToolkit().addPropertyChangeListener(key, e -> {
  if (sys.isSelected()) {
    boolean isDark = Objects.toString(e.getNewValue()).contains("dark");
    ThemeUtils.updateTheme(editor, isDark);
    loadHtml(editor);
  }
});
}}

- `OS`が`Mac`の場合、このサンプルでは未対応
- `OS`が`Mac`の場合には、このサンプルは未対応だが、以下のサイトの方法で対応可能
-- [https://github.com/Dansoftowner/jSystemThemeDetector Dansoftowner/jSystemThemeDetector: Java library for detecting that the (desktop) operating system uses dark UI theme or not]
-- [https://gist.github.com/HanSolo/7cf10b86efff8ca2845bf5ec2dd0fe1d Detector: A plain Java class that offers some utility methods to detect dark theme on MacOS and Windows · GitHub]

* Reference [#reference]
- [https://github.com/Dansoftowner/jSystemThemeDetector Dansoftowner/jSystemThemeDetector: Java library for detecting that the (desktop) operating system uses dark UI theme or not]
- [https://gist.github.com/HanSolo/7cf10b86efff8ca2845bf5ec2dd0fe1d Detector: A plain Java class that offers some utility methods to detect dark theme on MacOS and Windows · GitHub]
-- via: [https://harmoniccode.blogspot.com/2021/02/poor-mans-dark-mode-detection.html Harmonic Code: "Poor man's" dark mode detection]
- [https://raw.githack.com/google/code-prettify/master/styles/index.html Prettify Themes Gallery]
- [[DesktopPropertyの変更を監視する>Swing/DesktopProperty]]

* Comment [#comment]
#comment
#comment