Module layout_2013::flow

Servo’s experimental layout system builds a tree of Flow and Fragment objects and solves layout constraints to obtain positions and display attributes of tree nodes. Positions are computed in several tree traversals driven by the fundamental data dependencies required by inline and block layout.

Flows are interior nodes in the layout tree and correspond closely to flow contexts in the CSS specification. Flows are responsible for positioning their child flow contexts and fragments. Flows have purpose-specific fields, such as auxiliary line structs, out-of-flow child lists, and so on.

Currently, the important types of flows are:

• BlockFlow: A flow that establishes a block context. It has several child flows, each of which are positioned according to block formatting context rules (CSS block boxes). Block flows also contain a single box to represent their rendered borders, padding, etc. The BlockFlow at the root of the tree has special behavior: it stretches to the boundaries of the viewport.

• InlineFlow: A flow that establishes an inline context. It has a flat list of child fragments/flows that are subject to inline layout and line breaking and structs to represent line breaks and mapping to CSS boxes, for the purpose of handling getClientRects() and similar methods.

Structs

• AbsoluteDescendantInfo
  Information about each absolutely-positioned descendant of the given flow.
• AbsoluteDescendantIter
• AbsoluteDescendants
  Absolutely-positioned descendants of this flow.
• BaseFlow
  Data common to all flows.
• ContainingBlockLink
  A link to a flow’s containing block.
• EarlyAbsolutePositionInfo
  Information needed to compute absolute (i.e. viewport-relative) flow positions (not to be confused with absolutely-positioned flows) that is computed during block-size assignment.
• FlowFlags
  Flags used in flows.
• FragmentationContext
• LateAbsolutePositionInfo
  Information needed to compute absolute (i.e. viewport-relative) flow positions (not to be confused with absolutely-positioned flows) that is computed during final position assignment.
• OpaqueFlow
  A wrapper for the pointer address of a flow. These pointer addresses may only be compared for equality with other such pointer addresses, never dereferenced.

Enums

• FlowClass
• ForceNonfloatedFlag
  Whether a base flow should be forced to be nonfloated. This can affect e.g. TableFlow, which is never floated because the table wrapper flow is the floated one.

Traits

• Flow
  Virtual methods that make up a float context.
• GetBaseFlow
  Methods to get the BaseFlow from any HasBaseFlow type.
• HasBaseFlow
  This marker trait indicates that a type is a struct with #[repr(C)] whose first field is of type BaseFlow or some type that also implements this trait.
• ImmutableFlowUtils
• MutableFlowUtils
• MutableOwnedFlowUtils