uno-toolkit-system-theme-helper

name	uno-toolkit-system-theme-helper
description	Use SystemThemeHelper to detect system theme (light/dark), check if dark mode is active, and set application theme. Provides static methods for theme retrieval and management.
when_to_use	Use when reading or programmatically switching dark / light mode from C# (not the XAML `ThemeResource` lookup path) — detecting the current system theme, setting the application theme at runtime, or toggling between modes.
metadata	{"author":"uno-platform","version":"2.4","category":"toolkit"}

Uno Toolkit SystemThemeHelper — Agent Skill

Workflow

Docs lookup: call uno_platform_docs_search(...) first, then uno_platform_docs_fetch(sourcePath="…") using the sourcePath field from a result (a relative .md path; add the result's anchor for a section). Never pass a URL, a .html link, or a hand-built path.

Step 1: Fetch the SystemThemeHelper Documentation

uno_platform_docs_search("Uno Toolkit SystemThemeHelper theme light dark mode detect")

Primary documentation page:

• SystemThemeHelper: external/uno.toolkit.ui/doc/helpers/SystemThemeHelper.md

Fetch the page:

uno_platform_docs_fetch(sourcePath="external/uno.toolkit.ui/doc/helpers/SystemThemeHelper.md")

Key Principles (Stable)

• SystemThemeHelper.GetCurrentOsTheme() — returns ApplicationTheme.Light or ApplicationTheme.Dark
• SystemThemeHelper.GetRootTheme(XamlRoot?) — gets the app theme for a given XamlRoot
• SystemThemeHelper.IsRootInDarkMode(XamlRoot?) — quick check if dark mode is active
• SystemThemeHelper.SetRootTheme(XamlRoot?, bool) — set theme (true = dark)
• SystemThemeHelper.SetApplicationTheme(XamlRoot?, ElementTheme) — set theme using ElementTheme enum
• No ThemeChanged event exists — there is no event to subscribe to for theme changes
• Namespace: using Uno.Toolkit.UI;

Related Skills

• [[uno-themes-semantic-colors-brushes]] — Semantic color palette and brush system