Module: Daisy::ThemeHelper

Defined in:
app/helpers/daisy/theme_helper.rb

Instance Method Summary collapse

Instance Method Details

#theme_preload_script ⇒ String

Returns an inline script that preloads the saved theme from localStorage to prevent a flash of content when the page loads.

This script runs synchronously in the head section before the page renders. It resolves the saved theme mode (light / dark pin that scheme; system follows the OS preference) and the matching per-scheme theme preference, then sets the data-theme, data-color-scheme, and data-theme-mode attributes on the html element. The legacy single savedTheme key is still honored until the ThemeController migrates it.

Examples:

In a layout file

head
  = theme_preload_script
  = stylesheet_link_tag "application"

Returns:

  • (String) —

    The inline script as a string



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# File 'app/helpers/daisy/theme_helper.rb', line 27

def theme_preload_script
  "    <script>\n      (function() {\n        try {\n          var mode = localStorage.getItem('savedThemeMode');\n          var theme = null;\n          var slot = null;\n          var colorScheme = null;\n\n          if (mode) {\n            slot = mode === 'system'\n              ? (window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light')\n              : mode;\n            theme = localStorage.getItem(slot === 'dark' ? 'savedDarkTheme' : 'savedLightTheme') || slot;\n\n            // A slot may hold a theme of the OTHER scheme (a dark theme\n            // as the daytime choice); its actual scheme was cached at\n            // save time since CSS isn't loaded yet to compute it.\n            colorScheme = localStorage.getItem(slot === 'dark' ? 'savedDarkScheme' : 'savedLightScheme') || slot;\n          } else {\n            // Legacy single-theme key; the ThemeController migrates it to\n            // the per-slot model on connect.\n            theme = localStorage.getItem('savedTheme');\n          }\n\n          if (theme) {\n            document.documentElement.setAttribute('data-theme', theme);\n          }\n          if (colorScheme) {\n            document.documentElement.setAttribute('data-color-scheme', colorScheme);\n          }\n          if (mode) {\n            document.documentElement.setAttribute('data-theme-mode', mode);\n          }\n        } catch (e) {\n          // localStorage not available (e.g., private browsing mode)\n        }\n      })();\n    </script>\n  SCRIPT\nend\n".html_safe