gecko-dev/servo/components/layout/table.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/. */

//! CSS table formatting contexts.

#![deny(unsafe_blocks)]

use block::{BlockFlow, ISizeAndMarginsComputer, MarginsMayCollapseFlag};
use block::{ISizeConstraintInput, ISizeConstraintSolution};
use construct::FlowConstructor;
use context::LayoutContext;
use floats::FloatKind;
use flow::{self, Flow, FlowClass, IMPACTED_BY_LEFT_FLOATS, IMPACTED_BY_RIGHT_FLOATS};
use flow::ImmutableFlowUtils;
use fragment::{Fragment, FragmentBorderBoxIterator};
use layout_debug;
use model::{IntrinsicISizes, IntrinsicISizesContribution};
use table_row::CellIntrinsicInlineSize;
use table_wrapper::TableLayout;
use wrapper::ThreadSafeLayoutNode;

use geom::{Point2D, Rect};
use servo_util::geometry::Au;
use servo_util::logical_geometry::LogicalRect;
use std::cmp::max;
use std::fmt;
use style::{ComputedValues, CSSFloat};
use style::computed_values::{LengthOrPercentageOrAuto, table_layout};
use std::sync::Arc;

/// A table flow corresponded to the table's internal table fragment under a table wrapper flow.
/// The properties `position`, `float`, and `margin-*` are used on the table wrapper fragment,
/// not table fragment per CSS 2.1 § 10.5.
#[derive(RustcEncodable)]
pub struct TableFlow {
    pub block_flow: BlockFlow,

    /// Information about the intrinsic inline-sizes of each column, computed bottom-up during
    /// intrinsic inline-size bubbling.
    pub column_intrinsic_inline_sizes: Vec<ColumnIntrinsicInlineSize>,

    /// Information about the actual inline-sizes of each column, computed top-down during actual
    /// inline-size bubbling.
    pub column_computed_inline_sizes: Vec<ColumnComputedInlineSize>,

    /// Table-layout property
    pub table_layout: TableLayout,
}

impl TableFlow {
    pub fn from_node_and_fragment(node: &ThreadSafeLayoutNode,
                                  fragment: Fragment)
                                  -> TableFlow {
        let mut block_flow = BlockFlow::from_node_and_fragment(node, fragment);
        let table_layout = if block_flow.fragment().style().get_table().table_layout ==
                              table_layout::T::fixed {
            TableLayout::Fixed
        } else {
            TableLayout::Auto
        };
        TableFlow {
            block_flow: block_flow,
            column_intrinsic_inline_sizes: Vec::new(),
            column_computed_inline_sizes: Vec::new(),
            table_layout: table_layout
        }
    }

    pub fn from_node(constructor: &mut FlowConstructor,
                     node: &ThreadSafeLayoutNode)
                     -> TableFlow {
        let mut block_flow = BlockFlow::from_node(constructor, node);
        let table_layout = if block_flow.fragment().style().get_table().table_layout ==
                              table_layout::T::fixed {
            TableLayout::Fixed
        } else {
            TableLayout::Auto
        };
        TableFlow {
            block_flow: block_flow,
            column_intrinsic_inline_sizes: Vec::new(),
            column_computed_inline_sizes: Vec::new(),
            table_layout: table_layout
        }
    }

    pub fn float_from_node(constructor: &mut FlowConstructor,
                           node: &ThreadSafeLayoutNode,
                           float_kind: FloatKind)
                           -> TableFlow {
        let mut block_flow = BlockFlow::float_from_node(constructor, node, float_kind);
        let table_layout = if block_flow.fragment().style().get_table().table_layout ==
                              table_layout::T::fixed {
            TableLayout::Fixed
        } else {
            TableLayout::Auto
        };
        TableFlow {
            block_flow: block_flow,
            column_intrinsic_inline_sizes: Vec::new(),
            column_computed_inline_sizes: Vec::new(),
            table_layout: table_layout
        }
    }

    /// Update the corresponding value of `self_inline_sizes` if a value of `kid_inline_sizes` has
    /// a larger value than one of `self_inline_sizes`. Returns the minimum and preferred inline
    /// sizes.
    fn update_automatic_column_inline_sizes(
            parent_inline_sizes: &mut Vec<ColumnIntrinsicInlineSize>,
            child_cell_inline_sizes: &[CellIntrinsicInlineSize])
            -> IntrinsicISizes {
        let mut total_inline_sizes = IntrinsicISizes::new();
        let mut column_index = 0;
        for child_cell_inline_size in child_cell_inline_sizes.iter() {
            for _ in range(0, child_cell_inline_size.column_span) {
                if column_index < parent_inline_sizes.len() {
                    // We already have some intrinsic size information for this column. Merge it in
                    // according to the rules specified in INTRINSIC § 4.
                    let parent_sizes = &mut parent_inline_sizes[column_index];
                    if child_cell_inline_size.column_span > 1 {
                        // TODO(pcwalton): Perform the recursive algorithm specified in INTRINSIC §
                        // 4. For now we make this column contribute no width.
                    } else {
                        let column_size = &child_cell_inline_size.column_size;
                        *parent_sizes = ColumnIntrinsicInlineSize {
                            minimum_length: max(parent_sizes.minimum_length,
                                                column_size.minimum_length),
                            percentage: parent_sizes.greatest_percentage(column_size),
                            preferred: max(parent_sizes.preferred, column_size.preferred),
                            constrained: parent_sizes.constrained || column_size.constrained,
                        }
                    }
                } else {
                    // We discovered a new column. Initialize its data.
                    debug_assert!(column_index == parent_inline_sizes.len());
                    if child_cell_inline_size.column_span > 1 {
                        // TODO(pcwalton): Perform the recursive algorithm specified in INTRINSIC §
                        // 4. For now we make this column contribute no width.
                        parent_inline_sizes.push(ColumnIntrinsicInlineSize::new())
                    } else {
                        parent_inline_sizes.push(child_cell_inline_size.column_size)
                    }
                }

                total_inline_sizes.minimum_inline_size = total_inline_sizes.minimum_inline_size +
                    parent_inline_sizes[column_index].minimum_length;
                total_inline_sizes.preferred_inline_size =
                    total_inline_sizes.preferred_inline_size +
                    parent_inline_sizes[column_index].preferred;

                column_index += 1
            }
        }

        total_inline_sizes
    }

    /// Assign block-size for table flow.
    ///
    /// TODO(#2014, pcwalton): This probably doesn't handle margin collapse right.
    ///
    /// inline(always) because this is only ever called by in-order or non-in-order top-level
    /// methods
    #[inline(always)]
    fn assign_block_size_table_base<'a>(&mut self, layout_context: &'a LayoutContext<'a>) {
        self.block_flow.assign_block_size_block_base(layout_context, MarginsMayCollapseFlag::MarginsMayNotCollapse);
    }

    /// Updates the minimum and preferred inline-size calculation for a single row. This is
    /// factored out into a separate function because we process children of rowgroups too.
    fn update_column_inline_sizes_for_row(child: &mut Flow,
                                          column_inline_sizes: &mut Vec<ColumnIntrinsicInlineSize>,
                                          computation: &mut IntrinsicISizesContribution,
                                          did_first_row: &mut bool,
                                          table_layout: TableLayout) {
        // Read column inline-sizes from the table-row, and assign inline-size=0 for the columns
        // not defined in the column group.
        //
        // FIXME: Need to read inline-sizes from either table-header-group OR the first table-row.
        debug_assert!(child.is_table_row());
        let row = child.as_table_row();
        match table_layout {
            TableLayout::Fixed => {
                // Fixed table layout only looks at the first row.
                //
                // FIXME(pcwalton): This is really inefficient. We should stop after the first row!
                if !*did_first_row {
                    *did_first_row = true;
                    for cell_inline_size in row.cell_intrinsic_inline_sizes.iter() {
                        column_inline_sizes.push(cell_inline_size.column_size);
                    }
                }
            }
            TableLayout::Auto => {
                computation.union_block(&TableFlow::update_automatic_column_inline_sizes(
                    column_inline_sizes,
                    row.cell_intrinsic_inline_sizes.as_slice()))
            }
        }
    }
}

impl Flow for TableFlow {
    fn class(&self) -> FlowClass {
        FlowClass::Table
    }

    fn as_table<'a>(&'a mut self) -> &'a mut TableFlow {
        self
    }

    fn as_immutable_table<'a>(&'a self) -> &'a TableFlow {
        self
    }

    fn as_block<'a>(&'a mut self) -> &'a mut BlockFlow {
        &mut self.block_flow
    }

    fn column_intrinsic_inline_sizes<'a>(&'a mut self) -> &'a mut Vec<ColumnIntrinsicInlineSize> {
        &mut self.column_intrinsic_inline_sizes
    }

    fn column_computed_inline_sizes<'a>(&'a mut self) -> &'a mut Vec<ColumnComputedInlineSize> {
        &mut self.column_computed_inline_sizes
    }

    /// The specified column inline-sizes are set from column group and the first row for the fixed
    /// table layout calculation.
    /// The maximum min/pref inline-sizes of each column are set from the rows for the automatic
    /// table layout calculation.
    fn bubble_inline_sizes(&mut self) {
        let _scope = layout_debug_scope!("table::bubble_inline_sizes {:x}",
                                         self.block_flow.base.debug_id());

        let mut computation = IntrinsicISizesContribution::new();
        let mut did_first_row = false;
        for kid in self.block_flow.base.child_iter() {
            debug_assert!(kid.is_proper_table_child());
            if kid.is_table_colgroup() {
                for specified_inline_size in kid.as_table_colgroup().inline_sizes.iter() {
                    self.column_intrinsic_inline_sizes.push(ColumnIntrinsicInlineSize {
                        minimum_length: match *specified_inline_size {
                            LengthOrPercentageOrAuto::Auto | LengthOrPercentageOrAuto::Percentage(_) => Au(0),
                            LengthOrPercentageOrAuto::Length(length) => length,
                        },
                        percentage: match *specified_inline_size {
                            LengthOrPercentageOrAuto::Auto | LengthOrPercentageOrAuto::Length(_) => 0.0,
                            LengthOrPercentageOrAuto::Percentage(percentage) => percentage,
                        },
                        preferred: Au(0),
                        constrained: false,
                    })
                }
            } else if kid.is_table_rowgroup() {
                for grandkid in flow::mut_base(kid).child_iter() {
                    TableFlow::update_column_inline_sizes_for_row(
                        grandkid,
                        &mut self.column_intrinsic_inline_sizes,
                        &mut computation,
                        &mut did_first_row,
                        self.table_layout)
                }
            } else if kid.is_table_row() {
                TableFlow::update_column_inline_sizes_for_row(
                        kid,
                        &mut self.column_intrinsic_inline_sizes,
                        &mut computation,
                        &mut did_first_row,
                        self.table_layout)
            }
        }

        self.block_flow.base.intrinsic_inline_sizes = computation.finish()
    }

    /// Recursively (top-down) determines the actual inline-size of child contexts and fragments.
    /// When called on this context, the context has had its inline-size set by the parent context.
    fn assign_inline_sizes(&mut self, layout_context: &LayoutContext) {
        let _scope = layout_debug_scope!("table::assign_inline_sizes {:x}",
                                            self.block_flow.base.debug_id());
        debug!("assign_inline_sizes({}): assigning inline_size for flow", "table");

        // The position was set to the containing block by the flow's parent.
        let containing_block_inline_size = self.block_flow.base.block_container_inline_size;

        let mut num_unspecified_inline_sizes = 0;
        let mut total_column_inline_size = Au(0);
        for column_inline_size in self.column_intrinsic_inline_sizes.iter() {
            let this_column_inline_size = column_inline_size.minimum_length;
            if this_column_inline_size == Au(0) {
                num_unspecified_inline_sizes += 1
            } else {
                total_column_inline_size = total_column_inline_size + this_column_inline_size
            }
        }

        let inline_size_computer = InternalTable;

        inline_size_computer.compute_used_inline_size(&mut self.block_flow,
                                                      layout_context,
                                                      containing_block_inline_size);

        let inline_start_content_edge = self.block_flow.fragment.border_padding.inline_start;
        let padding_and_borders = self.block_flow.fragment.border_padding.inline_start_end();
        let content_inline_size =
            self.block_flow.fragment.border_box.size.inline - padding_and_borders;

        match self.table_layout {
            TableLayout::Fixed => {
                // In fixed table layout, we distribute extra space among the unspecified columns
                // if there are any, or among all the columns if all are specified.
                self.column_computed_inline_sizes.clear();
                if num_unspecified_inline_sizes == 0 {
                    let ratio = content_inline_size.to_subpx() /
                        total_column_inline_size.to_subpx();
                    for column_inline_size in self.column_intrinsic_inline_sizes.iter() {
                        self.column_computed_inline_sizes.push(ColumnComputedInlineSize {
                            size: column_inline_size.minimum_length.scale_by(ratio),
                        });
                    }
                } else if num_unspecified_inline_sizes != 0 {
                    let extra_column_inline_size =
                        (content_inline_size - total_column_inline_size) /
                        num_unspecified_inline_sizes;
                    for column_inline_size in self.column_intrinsic_inline_sizes.iter() {
                        if column_inline_size.minimum_length == Au(0) &&
                                column_inline_size.percentage == 0.0 {
                            self.column_computed_inline_sizes.push(ColumnComputedInlineSize {
                                size: extra_column_inline_size / num_unspecified_inline_sizes,
                            });
                        } else {
                            self.column_computed_inline_sizes.push(ColumnComputedInlineSize {
                                size: column_inline_size.minimum_length,
                            });
                        }
                    }
                }
            }
            _ => {
                // The table wrapper already computed the inline-sizes and propagated them down
                // to us.
            }
        }

        // As tables are always wrapped inside a table wrapper, they are never impacted by floats.
        self.block_flow.base.flags.remove(IMPACTED_BY_LEFT_FLOATS);
        self.block_flow.base.flags.remove(IMPACTED_BY_RIGHT_FLOATS);

        self.block_flow.propagate_assigned_inline_size_to_children(
            layout_context,
            inline_start_content_edge,
            content_inline_size,
            Some(self.column_computed_inline_sizes.as_slice()));
    }

    fn assign_block_size<'a>(&mut self, ctx: &'a LayoutContext<'a>) {
        debug!("assign_block_size: assigning block_size for table");
        self.assign_block_size_table_base(ctx);
    }

    fn compute_absolute_position(&mut self) {
        self.block_flow.compute_absolute_position()
    }

    fn generated_containing_block_rect(&self) -> LogicalRect<Au> {
        self.block_flow.generated_containing_block_rect()
    }

    fn update_late_computed_inline_position_if_necessary(&mut self, inline_position: Au) {
        self.block_flow.update_late_computed_inline_position_if_necessary(inline_position)
    }

    fn update_late_computed_block_position_if_necessary(&mut self, block_position: Au) {
        self.block_flow.update_late_computed_block_position_if_necessary(block_position)
    }

    fn build_display_list(&mut self, layout_context: &LayoutContext) {
        self.block_flow.build_display_list(layout_context);
    }

    fn repair_style(&mut self, new_style: &Arc<ComputedValues>) {
        self.block_flow.repair_style(new_style)
    }

    fn compute_overflow(&self) -> Rect<Au> {
        self.block_flow.compute_overflow()
    }

    fn iterate_through_fragment_border_boxes(&self,
                                             iterator: &mut FragmentBorderBoxIterator,
                                             stacking_context_position: &Point2D<Au>) {
        self.block_flow.iterate_through_fragment_border_boxes(iterator, stacking_context_position)
    }
}

impl fmt::Show for TableFlow {
    /// Outputs a debugging string describing this table flow.
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "TableFlow: {:?}", self.block_flow)
    }
}

/// Table, TableRowGroup, TableRow, TableCell types.
/// Their inline-sizes are calculated in the same way and do not have margins.
pub struct InternalTable;

impl ISizeAndMarginsComputer for InternalTable {
    /// Compute the used value of inline-size, taking care of min-inline-size and max-inline-size.
    ///
    /// CSS Section 10.4: Minimum and Maximum inline-sizes
    fn compute_used_inline_size(&self,
                                block: &mut BlockFlow,
                                ctx: &LayoutContext,
                                parent_flow_inline_size: Au) {
        let input = self.compute_inline_size_constraint_inputs(block,
                                                               parent_flow_inline_size,
                                                               ctx);
        let solution = self.solve_inline_size_constraints(block, &input);

        self.set_inline_size_constraint_solutions(block, solution);
    }

    /// Solve the inline-size and margins constraints for this block flow.
    fn solve_inline_size_constraints(&self, _: &mut BlockFlow, input: &ISizeConstraintInput)
                               -> ISizeConstraintSolution {
        ISizeConstraintSolution::new(input.available_inline_size, Au(0), Au(0))
    }
}

/// Information about the intrinsic inline sizes of columns within a table.
///
/// During table inline-size bubbling, we might need to store both a percentage constraint and a
/// specific width constraint. For instance, one cell might say that it wants to be 100 pixels wide
/// in the inline direction and another cell might say that it wants to take up 20% of the inline-
/// size of the table. Now because we bubble up these constraints during the bubble-inline-sizes
/// phase of layout, we don't know yet how wide the table is ultimately going to be in the inline
/// direction. As we need to pick the maximum width of all cells for a column (in this case, the
/// maximum of 100 pixels and 20% of the table), the preceding constraint means that we must
/// potentially store both a specified width *and* a specified percentage, so that the inline-size
/// assignment phase of layout will know which one to pick.
#[derive(Clone, RustcEncodable, Show, Copy)]
pub struct ColumnIntrinsicInlineSize {
    /// The preferred intrinsic inline size.
    pub preferred: Au,
    /// The largest specified size of this column as a length.
    pub minimum_length: Au,
    /// The largest specified size of this column as a percentage (`width` property).
    pub percentage: CSSFloat,
    /// Whether the column inline size is *constrained* per INTRINSIC § 4.1.
    pub constrained: bool,
}

impl ColumnIntrinsicInlineSize {
    /// Returns a newly-initialized `ColumnIntrinsicInlineSize` with all fields blank.
    pub fn new() -> ColumnIntrinsicInlineSize {
        ColumnIntrinsicInlineSize {
            preferred: Au(0),
            minimum_length: Au(0),
            percentage: 0.0,
            constrained: false,
        }
    }

    /// Returns the true minimum size of this column, given the containing block's inline size.
    /// Beware that this is generally only correct for fixed table layout. (Compare CSS 2.1 §
    /// 17.5.2.1 with the algorithm in INTRINSIC § 4.)
    pub fn minimum(&self, containing_block_inline_size: Au) -> Au {
        max(self.minimum_length, containing_block_inline_size.scale_by(self.percentage))
    }

    /// Returns the higher of the two percentages specified in `self` and `other`.
    pub fn greatest_percentage(&self, other: &ColumnIntrinsicInlineSize) -> CSSFloat {
        if self.percentage > other.percentage {
            self.percentage
        } else {
            other.percentage
        }
    }
}

/// The actual inline size for each column.
///
/// TODO(pcwalton): There will probably be some `border-collapse`-related info in here too
/// eventually.
#[derive(RustcEncodable, Copy)]
pub struct ColumnComputedInlineSize {
    /// The computed size of this inline column.
    pub size: Au,
}