gecko-dev/servo/components/layout/sequential.rs

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

//! Implements sequential traversals over the DOM and flow trees.

use app_units::Au;
use context::LayoutContext;
use display_list::{DisplayListBuildState, StackingContextCollectionState};
use euclid::{Point2D, Vector2D};
use floats::SpeculatedFloatPlacement;
use flow::{Flow, ImmutableFlowUtils, FlowFlags, GetBaseFlow};
use fragment::{FragmentBorderBoxIterator, CoordinateSystem};
use generated_content::ResolveGeneratedContent;
use incremental::RelayoutMode;
use servo_config::opts;
use style::servo::restyle_damage::ServoRestyleDamage;
use traversal::{AssignBSizes, AssignISizes, BubbleISizes, BuildDisplayList};
use traversal::{InorderFlowTraversal, PostorderFlowTraversal, PreorderFlowTraversal};
use webrender_api::LayoutPoint;

pub fn resolve_generated_content(root: &mut Flow, layout_context: &LayoutContext) {
    ResolveGeneratedContent::new(&layout_context).traverse(root, 0);
}

/// Run the main layout passes sequentially.
pub fn reflow(root: &mut Flow, layout_context: &LayoutContext, relayout_mode: RelayoutMode) {
    fn doit(flow: &mut Flow,
            assign_inline_sizes: AssignISizes,
            assign_block_sizes: AssignBSizes,
            relayout_mode: RelayoutMode) {
        // Force reflow children during this traversal. This is needed when we failed
        // the float speculation of a block formatting context and need to fix it.
        if relayout_mode == RelayoutMode::Force {
            flow.mut_base()
                .restyle_damage
                .insert(ServoRestyleDamage::REFLOW_OUT_OF_FLOW | ServoRestyleDamage::REFLOW);
        }

        if assign_inline_sizes.should_process(flow) {
            assign_inline_sizes.process(flow);
        }

        for kid in flow.mut_base().child_iter_mut() {
            doit(kid, assign_inline_sizes, assign_block_sizes, relayout_mode);
        }

        if assign_block_sizes.should_process(flow) {
            assign_block_sizes.process(flow);
        }
    }

    if opts::get().bubble_inline_sizes_separately {
        let bubble_inline_sizes = BubbleISizes {
            layout_context: &layout_context,
        };
        bubble_inline_sizes.traverse(root);
    }

    let assign_inline_sizes = AssignISizes {
        layout_context: &layout_context,
    };
    let assign_block_sizes = AssignBSizes {
        layout_context: &layout_context,
    };

    doit(root, assign_inline_sizes, assign_block_sizes, relayout_mode);
}

pub fn build_display_list_for_subtree<'a>(flow_root: &mut Flow,
                                          layout_context: &'a LayoutContext)
                                          -> DisplayListBuildState<'a> {
    let mut state = StackingContextCollectionState::new(layout_context.id);
    flow_root.collect_stacking_contexts(&mut state);

    let state = DisplayListBuildState::new(layout_context, state);
    let mut build_display_list = BuildDisplayList {
        state: state,
    };
    build_display_list.traverse(flow_root);
    build_display_list.state
}

pub fn iterate_through_flow_tree_fragment_border_boxes(root: &mut Flow, iterator: &mut FragmentBorderBoxIterator) {
    fn doit(flow: &mut Flow,
            level: i32,
            iterator: &mut FragmentBorderBoxIterator,
            stacking_context_position: &Point2D<Au>) {
        flow.iterate_through_fragment_border_boxes(iterator, level, stacking_context_position);

        for kid in flow.mut_base().child_iter_mut() {
            let mut stacking_context_position = *stacking_context_position;
            if kid.is_block_flow() && kid.as_block().fragment.establishes_stacking_context() {
                stacking_context_position = Point2D::new(kid.as_block().fragment.margin.inline_start, Au(0)) +
                                            kid.base().stacking_relative_position +
                                            stacking_context_position.to_vector();
                let relative_position = kid.as_block()
                    .stacking_relative_border_box(CoordinateSystem::Own);
                if let Some(matrix) = kid.as_block()
                       .fragment
                       .transform_matrix(&relative_position) {
                    let transform_matrix = matrix.transform_point2d(&LayoutPoint::zero());
                    stacking_context_position = stacking_context_position +
                                                Vector2D::new(Au::from_f32_px(transform_matrix.x),
                                                              Au::from_f32_px(transform_matrix.y))
                }
            }
            doit(kid, level + 1, iterator, &stacking_context_position);
        }
    }

    doit(root, 0, iterator, &Point2D::zero());
}

pub fn store_overflow(layout_context: &LayoutContext, flow: &mut Flow) {
    if !flow.base().restyle_damage.contains(ServoRestyleDamage::STORE_OVERFLOW) {
        return;
    }

    for kid in flow.mut_base().child_iter_mut() {
        store_overflow(layout_context, kid);
    }

    flow.store_overflow(layout_context);

    flow.mut_base()
        .restyle_damage
        .remove(ServoRestyleDamage::STORE_OVERFLOW);
}

/// Guesses how much inline size will be taken up by floats on the left and right sides of the
/// given flow. This is needed to speculatively calculate the inline sizes of block formatting
/// contexts. The speculation typically succeeds, but if it doesn't we have to lay it out again.
pub fn guess_float_placement(flow: &mut Flow) {
    if !flow.base().restyle_damage.intersects(ServoRestyleDamage::REFLOW) {
        return;
    }

    let mut floats_in = SpeculatedFloatPlacement::compute_floats_in_for_first_child(flow);
    for kid in flow.mut_base().child_iter_mut() {
        if kid.base().flags.contains(FlowFlags::IS_ABSOLUTELY_POSITIONED) {
            // Do not propagate floats in or out, but do propogate between kids.
            guess_float_placement(kid);
        } else {
            floats_in.compute_floats_in(kid);
            kid.mut_base().speculated_float_placement_in = floats_in;
            guess_float_placement(kid);
            floats_in = kid.base().speculated_float_placement_out;
        }
    }
    floats_in.compute_floats_out(flow);
    flow.mut_base().speculated_float_placement_out = floats_in
}