Trait LayoutNode 

pub trait LayoutNode<'dom>:
    Copy
    + Debug
    + NodeInfo
    + Send
    + Sync {
    type ConcreteDangerousStyleNode: DangerousStyleNode<'dom>;
    type ConcreteDangerousStyleElement: DangerousStyleElement<'dom>;
    type ConcreteLayoutElement: LayoutElement<'dom>;
    type ChildIterator: Iterator<Item = Self> + Sized;

    // Required methods
    fn with_pseudo(&self, pseudo_element_type: PseudoElement) -> Option<Self>;
    fn pseudo_element_chain(&self) -> PseudoElementChain;
    unsafe fn dangerous_style_node(self) -> Self::ConcreteDangerousStyleNode;
    unsafe fn dangerous_dom_parent(self) -> Option<Self>;
    unsafe fn dangerous_flat_tree_parent(self) -> Option<Self>;
    fn layout_data(&self) -> Option<&'dom GenericLayoutData>;
    fn is_connected(&self) -> bool;
    fn opaque(&self) -> OpaqueNode;
    fn type_id(&self) -> Option<LayoutNodeType>;
    fn initialize_layout_data<RequestedLayoutDataType: LayoutDataTrait>(&self);
    fn flat_tree_children(&self) -> LayoutIterator<Self::ChildIterator>;
    fn dom_children(&self) -> LayoutIterator<Self::ChildIterator>;
    fn as_html_element(&self) -> Option<Self::ConcreteLayoutElement>;
    fn as_element(&self) -> Option<Self::ConcreteLayoutElement>;
    fn style(&self, context: &SharedStyleContext<'_>) -> Arc<ComputedValues>;
    fn parent_style(
        &self,
        context: &SharedStyleContext<'_>,
    ) -> Arc<ComputedValues>;
    fn selected_style(
        &self,
        context: &SharedStyleContext<'_>,
    ) -> Arc<ComputedValues>;
    fn text_content(self) -> Cow<'dom, str>;
    fn selection(&self) -> Option<SharedSelection>;
    fn image_url(&self) -> Option<ServoUrl>;
    fn image_density(&self) -> Option<f64>;
    fn image_data(&self) -> Option<(Option<Image>, Option<ImageMetadata>)>;
    fn showing_broken_image_icon(&self) -> bool;
    fn canvas_data(&self) -> Option<HTMLCanvasData>;
    fn svg_data(&self) -> Option<SVGElementData<'dom>>;
    fn media_data(&self) -> Option<HTMLMediaData>;
    fn iframe_browsing_context_id(&self) -> Option<BrowsingContextId>;
    fn iframe_pipeline_id(&self) -> Option<PipelineId>;
    fn table_span(&self) -> Option<u32>;
    fn table_colspan(&self) -> Option<u32>;
    fn table_rowspan(&self) -> Option<u32>;
    fn is_single_line_text_input(&self) -> bool;
    fn is_root_of_user_agent_widget(&self) -> bool;
    fn set_uses_content_attribute_with_attr(
        &self,
        _uses_content_attribute_with_attr: bool,
    );
}

A trait that exposes a DOM nodes to layout. Implementors of this trait must abide by certain safety requirements. Layout will only ever access and mutate each node from a single thread at a time, though children may be used in parallel from other threads. That is why this trait does not allow access to parent nodes, as it would make it easy to cause race conditions and memory errors.

Note that the related DangerousStyleNode trait may access parent nodes, which is why that API is marked as unsafe here. In general DangerousStyleNode should only be used when interfacing with the stylo and selectors.

Required Associated Types

type ConcreteDangerousStyleNode: DangerousStyleNode<'dom>

The concrete implementation of DangerousStyleNode implemented in script.

type ConcreteDangerousStyleElement: DangerousStyleElement<'dom>

The concrete implementation of DangerousStyleElement implemented in script.

type ConcreteLayoutElement: LayoutElement<'dom>

The concrete implementation of [ConcreteLayoutElement] implemented in script.

type ChildIterator: Iterator<Item = Self> + Sized

The concrete implementation of [ChildIterator] implemented in script.

Required Methods

fn with_pseudo(&self, pseudo_element_type: PseudoElement) -> Option<Self>

Creates a new LayoutNode for the same LayoutNode with a different pseudo-element type.

Returns None if this pseudo doesn’t apply to the given element for one of the following reasons:

1. This node is not an element.
2. pseudo is eager and is not defined in the stylesheet. In this case, there is not reason to process the pseudo element at all.
3. pseudo is for ::servo-details-content and it doesn’t apply to this element, either because it isn’t a details or is in the wrong state.

fn pseudo_element_chain(&self) -> PseudoElementChain

Returns the PseudoElementChain for this LayoutElement.

unsafe fn dangerous_style_node(self) -> Self::ConcreteDangerousStyleNode

Returns access to a version of this LayoutNode that can be used by stylo and selectors. This is dangerous as it allows more access to ancestors nodes than LayoutNode. This should only be used when handing a node to stylo or selectors.

Safety

This should only ever be called from the main script thread. It is never okay to explicitly create a node for style while any layout worker threads are running.

unsafe fn dangerous_dom_parent(self) -> Option<Self>

Returns access to the DOM parent node of this node. This does not take into account shadow tree children and slottables. For that use Self::dangerous_flat_tree_parent.

Safety

This should only ever be called from the main script thread. It is never okay to explicitly access the parent node while any layout worker threads are running.

unsafe fn dangerous_flat_tree_parent(self) -> Option<Self>

Returns access to the flat tree parent node of this node. This takes into account shadow tree children and slottables. For that use Self::dangerous_flat_tree_parent.

Safety

This should only ever be called from the main script thread. It is never okay to explicitly access the parent node while any layout worker threads are running.

fn layout_data(&self) -> Option<&'dom GenericLayoutData>

Get the layout data of this node, attempting to downcast it to the desired type. Returns None if there is no layout data or it isn’t of the desired type.

fn is_connected(&self) -> bool

Returns whether the node is connected.

fn opaque(&self) -> OpaqueNode

Converts self into an OpaqueNode.

fn type_id(&self) -> Option<LayoutNodeType>

Returns the type ID of this node. Returns None if this is a pseudo-element; otherwise, returns Some.

fn initialize_layout_data<RequestedLayoutDataType: LayoutDataTrait>(&self)

Initialize this node with empty opaque layout data.

fn flat_tree_children(&self) -> LayoutIterator<Self::ChildIterator>

Returns an iterator over this node’s children in the flat tree. This takes into account shadow tree children and slottables.

fn dom_children(&self) -> LayoutIterator<Self::ChildIterator>

Returns an iterator over this node’s children in the DOM. This does not take shadow roots and assigned slottables into account. For that use Self::flat_tree_children.

fn as_html_element(&self) -> Option<Self::ConcreteLayoutElement>

Returns a LayoutElement if this is an element in the HTML namespace, None otherwise.

fn as_element(&self) -> Option<Self::ConcreteLayoutElement>

Returns a LayoutElement if this is an element.

fn style(&self, context: &SharedStyleContext<'_>) -> Arc<ComputedValues>

Returns the computed style for the given node, properly handling pseudo-elements. For elements this returns their style and for other nodes, this returns the style of the parent element, if one exists.

Panics

• Calling this method will panic it is an element has no style data, whether because styling has not run yet or was not run for this element.
• Calling this method will panic if it is a non-element node without a parent element.

fn parent_style(&self, context: &SharedStyleContext<'_>) -> Arc<ComputedValues>

Returns the style for a text node. This is computed on the fly from the parent style to avoid traversing text nodes in the style system.

Safety

Note that this does require accessing the parent, which this interface technically forbids. But accessing the parent is only unsafe insofar as it can be used to reach siblings and cousins. A simple immutable borrow of the parent data is fine, since the bottom-up traversal will not process the parent until all the children have been processed.

Panics

• Calling this method will panic if the parent element has no style data, whether because styling has not run yet or was not run for this element.
• Calling this method will panic if it is a non-element node without a parent element.

fn selected_style( &self, context: &SharedStyleContext<'_>, ) -> Arc<ComputedValues>

Returns the computed :selected style for the given node, properly handling pseudo-elements. For elements this returns their style and for other nodes, this returns the style of the parent element, if one exists.

Panics

• Calling this method will panic it is an element has no style data, whether because styling has not run yet or was not run for this element.
• Calling this method will panic if it is a non-element node without a parent element.

fn text_content(self) -> Cow<'dom, str>

Get the text content of this node, if it is a text node.

Panics

This method will panic if called on a node that is not a DOM text node.

fn selection(&self) -> Option<SharedSelection>

If this node manages a selection, this returns the shared selection for the node.

fn image_url(&self) -> Option<ServoUrl>

If this is an image element, returns its URL. If this is not an image element, fails.

fn image_density(&self) -> Option<f64>

If this is an image element, returns its current-pixel-density. If this is not an image element, fails.

fn image_data(&self) -> Option<(Option<Image>, Option<ImageMetadata>)>

If this is an image element, returns its image data. Otherwise, returns None.

fn showing_broken_image_icon(&self) -> bool

Whether or not this is an image element that is showing a broken image icon.

fn canvas_data(&self) -> Option<HTMLCanvasData>

Return the [HTMLCanvas] data for this node, if it is a canvas.

fn svg_data(&self) -> Option<SVGElementData<'dom>>

Return the SVGElementData for this node, if it is an SVG subtree.

fn media_data(&self) -> Option<HTMLMediaData>

Return the HTMLMediaData for this node, if it is a media element.

fn iframe_browsing_context_id(&self) -> Option<BrowsingContextId>

If this node is an iframe element, returns its browsing context ID. If this node is not an iframe element, fails. Returns None if there is no nested browsing context.

fn iframe_pipeline_id(&self) -> Option<PipelineId>

If this node is an iframe element, returns its pipeline ID. If this node is not an iframe element, fails. Returns None if there is no nested browsing context.

fn table_span(&self) -> Option<u32>

Return the table span property if it is an element that supports it.

fn table_colspan(&self) -> Option<u32>

Return the table colspan property if it is an element that supports it.

fn table_rowspan(&self) -> Option<u32>

Return the table rowspan property if it is an element that supports it.

fn is_single_line_text_input(&self) -> bool

Whether this is a container for the text within a single-line text input. This is used to solve the special case of line height for a text entry widget. https://html.spec.whatwg.org/multipage/#the-input-element-as-a-text-entry-widget

fn is_root_of_user_agent_widget(&self) -> bool

Whether or not this LayoutNode is in a user agent widget shadow DOM.

fn set_uses_content_attribute_with_attr( &self, _uses_content_attribute_with_attr: bool, )

Set whether or not this node has an active pseudo-element style with a content attribute that uses attr.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors