How to set the light theme as the default theme?

Question

Eclipse RCP 2022-06

After exporting the product, I found that if the current theme of win10 is dark, RCP also uses the dark theme

In other words, eclipse will now decide which theme to choose at startup based on the theme of the operating system

How do disable this feature?? I don't want to use it until the dark theme is complete

Updated as recommended by greg-449

Possibly set system property org.eclipse.swt.internal.win32.useDarkModeExplorerTheme to false. Look at the source of Display to see all the properties that can be set on Windows

This is my exported product profile

-startup
plugins/org.eclipse.equinox.launcher_1.6.400.v20210924-0641.jar
--launcher.library
plugins/org.eclipse.equinox.launcher.win32.win32.x86_64_1.2.500.v20220509-0833
-clearPersistedState
--launcher.appendVmargs
--launcher.defaultAction
openFile
-vmargs
-Dosgi.requiredJavaVersion=17
-Dorg.eclipse.swt.internal.win32.useDarkModeExplorerTheme=false
-Xms1024m
-Xmx2048m
-XX:+UseG1GC
--add-modules=ALL-SYSTEM

Still unsolvable

Reply to howlger

The exported product is the most basic product

This is a particularly simple test for the new version of RCP export products

Other settings are based on platform feature

plugin.xml

<plugin>
   <extension
         id="product"
         point="org.eclipse.core.runtime.products">
      <product
            application="org.eclipse.ui.ide.workbench"
            name="BitFan">
         <property
               name="appName"
               value="BitFan">
         </property>
         <property
               name="windowImages"
               value="logo16.png,logo32.png,logo48.png,logo64.png,logo128.png,logo256.png">
         </property>
         <property
               name="startupForegroundColor"
               value="FFFFFF">
         </property>
         <property
               name="startupMessageRect"
               value="30,272,445,20">
         </property>
         <property
               name="startupProgressRect"
               value="28,295,445,15">
         </property>
         <property
               name="applicationCSSResources"
               value="platform:/plugin/org.eclipse.ui.themes/images/">
         </property>
         <property
               name="applicationXMI"
               value="org.eclipse.platform/LegacyIDE.e4xmi">
         </property>
         <property
               name="cssTheme"
               value="org.eclipse.e4.ui.css.theme.e4_default">
         </property>
         <property
               name="buildIdLocation"
               value="0,220">
         </property>
         <property
               name="buildIdSize"
               value="293,40">
         </property>
         <property
               name="preferenceCustomization"
               value="plugin_customization.ini">
         </property>
      </product>
   </extension>

</plugin>

Reply to howlger again

boolean hasDarkTheme = getThemes().stream().anyMatch(t -> t.getId().startsWith(E4_DARK_THEME_ID));
String themeToRestore = Display.isSystemDarkTheme() && hasDarkTheme ? E4_DARK_THEME_ID : alternateTheme;
if (themeToRestore != null && flag) {
    setTheme(themeToRestore, false);
}

I tracked that "Display.isSystemDarkTheme()" is true, so the dark theme is set

Then I set -Dorg.eclipse.swt.internal.win32.useDarkModeExplorerTheme=false in the Run Configurations VM Arguments

clear run, still the dark theme

This parameter has no effect

It judges by reading the registry

public static boolean isSystemDarkTheme () {
    boolean isDarkTheme = false;
    /*
     * The registry settings, and Dark Theme itself, is present since Win10 1809
     */
    if (OS.WIN32_BUILD >= OS.WIN32_BUILD_WIN10_1809) {
        int[] result = OS.readRegistryDwords(OS.HKEY_CURRENT_USER,
                "Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize", "AppsUseLightTheme");
        if (result!=null) {
            isDarkTheme = (result[0] == 0);
        }
    }
    return isDarkTheme;
}

I think this problem can only be solved by deleting the dark theme , But how to delete it? It seems that the "org.eclipse.ui.activities" extension point cannot disable themes

Maybe I can remove it through removeExtension, but this needs to be done before the workbench starts. At present, I only know that the splashHandlers extension point can be implemented. Should I do this?

Answer 1

Under normal circumstances, there is no way to solve this problem, because the restore method of ThemeEngine determines whether to use dark theme according to the Display

@Override
public void restore(String alternateTheme) {
    String prefThemeId = getPreferenceThemeId();

    // Bug 562794, 563601: Eclipse once contained two identical themes named
    // "Classic" and "Windows Classic" and the second was removed with bug 562794.
    // An old workspace using the removed "Windows Classic" theme would be reseted
    // to the default theme on update. Since both themes are identical we silently
    // change the theme to the remaining "Classic" theme and don't disturb the user.
    if ("org.eclipse.e4.ui.css.theme.e4_classic6.0,6.1,6.2,6.3".equals(prefThemeId)) { //$NON-NLS-1$
        prefThemeId = "org.eclipse.e4.ui.css.theme.e4_classic"; //$NON-NLS-1$
    }

    boolean flag = true;
    if (prefThemeId != null) {
        for (ITheme t : getThemes()) {
            if (prefThemeId.equals(t.getId())) {
                setTheme(t, false);
                flag = false;
                break;
            }
        }
    }

    /*
     * Any Platform: if the system has Dark appearance set and Eclipse is using the
     * default settings, then start Eclipse in Dark theme. Check that there is a
     * dark theme present.
     */
    boolean hasDarkTheme = getThemes().stream().anyMatch(t -> t.getId().startsWith(E4_DARK_THEME_ID));
    String themeToRestore = Display.isSystemDarkTheme() && hasDarkTheme ? E4_DARK_THEME_ID : alternateTheme;
    if (themeToRestore != null && flag) {
        setTheme(themeToRestore, false);
    }
}

But "Display.isSystemDarkTheme" is determined based on the operating system registry

public static boolean isSystemDarkTheme () {
    boolean isDarkTheme = false;
    /*
     * The registry settings, and Dark Theme itself, is present since Win10 1809
     */
    if (OS.WIN32_BUILD >= OS.WIN32_BUILD_WIN10_1809) {
        int[] result = OS.readRegistryDwords(OS.HKEY_CURRENT_USER,
                "Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize", "AppsUseLightTheme");
        if (result!=null) {
            isDarkTheme = (result[0] == 0);
        }
    }
    return isDarkTheme;
}

Solution

Remove all themes first

private void removeThemes()throws Exception {
    ExtensionRegistry registry = (ExtensionRegistry)Platform.getExtensionRegistry() ;
    Field field = ExtensionRegistry.class.getDeclaredField("masterToken") ; //$NON-NLS-1$
    field.setAccessible( true ) ;
    Object masterToken = field.get(registry) ;
    IExtensionPoint extPoint = registry.getExtensionPoint(ThemeEngine.THEME_PLUGIN_ID);
    IExtension extensions[] = extPoint.getExtensions() ;
    for (IExtension e : extensions ) {
        if( "org.eclipse.ui.themes".equals( e.getContributor().getName() ) ) { //$NON-NLS-1$
            registry.removeExtension( e , masterToken ) ;
            return ;
        }
    }
}

Then add extension points in the appropriate plug-ins (I defined in the product plug-ins)

   <extension
         point="org.eclipse.e4.ui.css.swt.theme">
      <theme
            basestylesheeturi="platform:/plugin/org.eclipse.ui.themes/css/e4_default_win.css"
            id="org.eclipse.e4.ui.css.theme.e4_default"
            label="Light"
            os="win32">
      </theme>
   </extension>

Finally, modify the start method of the application

@Override
public Object start(IApplicationContext appContext) throws Exception {
    removeThemes();
    ...
    ...
}