--- /dev/null
+<?php
+
+namespace Drupal\Core\Theme;
+
+/**
+ * Provides a high level access to the active theme and methods to use it.
+ *
+ * Beside the active theme it provides a wrapper around _theme as well as the
+ * alter functionality for themes.
+ */
+interface ThemeManagerInterface {
+
+ /**
+ * Generates themed output.
+ *
+ * See the @link themeable Default theme implementations topic @endlink for
+ * details.
+ *
+ * @param string $hook
+ * The name of the theme hook to call.
+ * @param array $variables
+ * An associative array of theme variables.
+ *
+ * @return string|\Drupal\Component\Render\MarkupInterface
+ * The rendered output, or a Markup object.
+ */
+ public function render($hook, array $variables);
+
+ /**
+ * Returns the active theme object.
+ *
+ * @return \Drupal\Core\Theme\ActiveTheme
+ */
+ public function getActiveTheme();
+
+ /**
+ * Determines whether there is an active theme.
+ *
+ * @return bool
+ */
+ public function hasActiveTheme();
+
+ /**
+ * Resets the current active theme.
+ *
+ * Note: This method should not be used in common cases, just in special cases
+ * like tests.
+ *
+ * @return $this
+ */
+ public function resetActiveTheme();
+
+ /**
+ * Sets the current active theme manually.
+ *
+ * Note: This method should not be used in common cases, just in special cases
+ * like tests.
+ *
+ * @param \Drupal\Core\Theme\ActiveTheme $active_theme
+ * The new active theme.
+ * @return $this
+ */
+ public function setActiveTheme(ActiveTheme $active_theme);
+
+ /**
+ * Passes alterable variables to specific $theme_TYPE_alter() implementations.
+ *
+ * Executes an alter hook on the current theme. It also invokes alter hooks
+ * for all base themes.
+ *
+ * $theme specifies the theme name of the active theme and all its base
+ * themes.
+ *
+ * This dispatch function hands off the passed-in variables to type-specific
+ * $theme_TYPE_alter() implementations in the active theme. It ensures a
+ * consistent interface for all altering operations.
+ *
+ * A maximum of 2 alterable arguments is supported. In case more arguments
+ * need to be passed and alterable, modules provide additional variables
+ * assigned by reference in the last $context argument:
+ * @code
+ * $context = array(
+ * 'alterable' => &$alterable,
+ * 'unalterable' => $unalterable,
+ * 'foo' => 'bar',
+ * );
+ * $this->alter('mymodule_data', $alterable1, $alterable2, $context);
+ * @endcode
+ *
+ * Note that objects are always passed by reference in PHP5. If it is
+ * absolutely required that no implementation alters a passed object in
+ * $context, then an object needs to be cloned:
+ * @code
+ * $context = array(
+ * 'unalterable_object' => clone $object,
+ * );
+ * $this->alter('mymodule_data', $data, $context);
+ * @endcode
+ *
+ * @param string|array $type
+ * A string describing the type of the alterable $data. 'form', 'links',
+ * 'node_content', and so on are several examples. Alternatively can be an
+ * array, in which case $theme_TYPE_alter() is invoked for each value in the
+ * array. When Form API is using $this->alter() to
+ * execute both $theme_form_alter() and $theme_form_FORM_ID_alter()
+ * implementations, it passes array('form', 'form_' . $form_id) for $type.
+ * @param mixed $data
+ * The variable that will be passed to $theme_TYPE_alter() implementations
+ * to be altered. The type of this variable depends on the value of the
+ * $type argument. For example, when altering a 'form', $data will be a
+ * structured array. When altering a 'profile', $data will be an object.
+ * @param mixed $context1
+ * (optional) An additional variable that is passed by reference.
+ * @param mixed $context2
+ * (optional) An additional variable that is passed by reference. If more
+ * context needs to be provided to implementations, then this should be an
+ * associative array as described above.
+ *
+ * @see \Drupal\Core\Extension\ModuleHandlerInterface
+ */
+ public function alter($type, &$data, &$context1 = NULL, &$context2 = NULL);
+
+ /**
+ * Provides an alter hook for a specific theme.
+ *
+ * Similar to ::alter, it also invokes the alter hooks for the base themes.
+ *
+ * @param \Drupal\Core\Theme\ActiveTheme $theme
+ * A manually specified theme.
+ * @param string|array $type
+ * A string describing the type of the alterable $data.
+ * @param mixed $data
+ * The variable that will be passed to $theme_TYPE_alter() implementations
+ * @param mixed $context1
+ * (optional) An additional variable that is passed by reference.
+ * @param mixed $context2
+ * (optional) An additional variable that is passed by reference.
+ *
+ * @see ::alter
+ */
+ public function alterForTheme(ActiveTheme $theme, $type, &$data, &$context1 = NULL, &$context2 = NULL);
+
+}