AMP_Base_Sanitizer::has_light_shadow_dom()
Description #
Determine whether the resulting AMP element uses a "light" shadow DOM.
Sometimes AMP components serve as wrappers for native elements, like amp-img for img. When this is the case, authors sometimes will want to style the shadow element (such as to set object-fit). Normally if a selector contains img then the style sanitizer will always convert this to amp-img (and amp-anim), which may break the author's intended selector target. So when using a sanitizer's selector conversion mapping to rewrite non-AMP to AMP selectors, it will first check to see if the selector already mentions an AMP tag and if so it will skip the conversions for that selector. In this way, an amp-img img selector will not get converted into amp-img amp-img. The selector mapping also is involved when doing tree shaking. In the case of the selector amp-img img, the tree shaker would normally strip out this selector because no img may be present in the page as it is added by the AMP runtime (unless noscript fallbacks have been added, and this also disregards data-hero images which are added later by AMP Optimizer). So in order to prevent such selectors from being stripped out, it's important to include the amp-img selector among the dynamic_element_selectors so that the img in the amp-img img selector is ignored for the purposes of tree shaking. This method is used to indicate which sanitizers are involved in such element conversions. If this method returns true, then the keys in the selector conversion mapping should be used as dynamic_element_selectors.
In other words, this method indicates whether keys in the conversion mapping are ancestors of elements which are created at runtime. This method is only relevant when the get_selector_conversion_mapping() method returns a mapping.
See also
- {@see AMP_Style_Sanitizer::ampify_ruleset_selectors()}
- {@see AMP_Base_Sanitizer::get_selector_conversion_mapping()}