summaryrefslogtreecommitdiff
path: root/crates/typst-layout/src/grid/layouter.rs
diff options
context:
space:
mode:
Diffstat (limited to 'crates/typst-layout/src/grid/layouter.rs')
-rw-r--r--crates/typst-layout/src/grid/layouter.rs1582
1 files changed, 1582 insertions, 0 deletions
diff --git a/crates/typst-layout/src/grid/layouter.rs b/crates/typst-layout/src/grid/layouter.rs
new file mode 100644
index 00000000..7c94617d
--- /dev/null
+++ b/crates/typst-layout/src/grid/layouter.rs
@@ -0,0 +1,1582 @@
+use std::fmt::Debug;
+
+use typst_library::diag::{bail, SourceResult};
+use typst_library::engine::Engine;
+use typst_library::foundations::{Resolve, StyleChain};
+use typst_library::layout::{
+ Abs, Axes, Dir, Fr, Fragment, Frame, FrameItem, Length, Point, Region, Regions, Rel,
+ Size, Sizing,
+};
+use typst_library::text::TextElem;
+use typst_library::visualize::Geometry;
+use typst_syntax::Span;
+use typst_utils::{MaybeReverseIter, Numeric};
+
+use super::{
+ generate_line_segments, hline_stroke_at_column, vline_stroke_at_row, Cell, CellGrid,
+ LinePosition, LineSegment, Repeatable, Rowspan, UnbreakableRowGroup,
+};
+
+/// Performs grid layout.
+pub struct GridLayouter<'a> {
+ /// The grid of cells.
+ pub(super) grid: &'a CellGrid<'a>,
+ /// The regions to layout children into.
+ pub(super) regions: Regions<'a>,
+ /// The inherited styles.
+ pub(super) styles: StyleChain<'a>,
+ /// Resolved column sizes.
+ pub(super) rcols: Vec<Abs>,
+ /// The sum of `rcols`.
+ pub(super) width: Abs,
+ /// Resolve row sizes, by region.
+ pub(super) rrows: Vec<Vec<RowPiece>>,
+ /// Rows in the current region.
+ pub(super) lrows: Vec<Row>,
+ /// The amount of unbreakable rows remaining to be laid out in the
+ /// current unbreakable row group. While this is positive, no region breaks
+ /// should occur.
+ pub(super) unbreakable_rows_left: usize,
+ /// Rowspans not yet laid out because not all of their spanned rows were
+ /// laid out yet.
+ pub(super) rowspans: Vec<Rowspan>,
+ /// The initial size of the current region before we started subtracting.
+ pub(super) initial: Size,
+ /// Frames for finished regions.
+ pub(super) finished: Vec<Frame>,
+ /// Whether this is an RTL grid.
+ pub(super) is_rtl: bool,
+ /// The simulated header height.
+ /// This field is reset in `layout_header` and properly updated by
+ /// `layout_auto_row` and `layout_relative_row`, and should not be read
+ /// before all header rows are fully laid out. It is usually fine because
+ /// header rows themselves are unbreakable, and unbreakable rows do not
+ /// need to read this field at all.
+ pub(super) header_height: Abs,
+ /// The simulated footer height for this region.
+ /// The simulation occurs before any rows are laid out for a region.
+ pub(super) footer_height: Abs,
+ /// The span of the grid element.
+ pub(super) span: Span,
+}
+
+/// Details about a resulting row piece.
+#[derive(Debug)]
+pub struct RowPiece {
+ /// The height of the segment.
+ pub height: Abs,
+ /// The index of the row.
+ pub y: usize,
+}
+
+/// Produced by initial row layout, auto and relative rows are already finished,
+/// fractional rows not yet.
+pub(super) enum Row {
+ /// Finished row frame of auto or relative row with y index.
+ /// The last parameter indicates whether or not this is the last region
+ /// where this row is laid out, and it can only be false when a row uses
+ /// `layout_multi_row`, which in turn is only used by breakable auto rows.
+ Frame(Frame, usize, bool),
+ /// Fractional row with y index and disambiguator.
+ Fr(Fr, usize, usize),
+}
+
+impl Row {
+ /// Returns the `y` index of this row.
+ fn index(&self) -> usize {
+ match self {
+ Self::Frame(_, y, _) => *y,
+ Self::Fr(_, y, _) => *y,
+ }
+ }
+}
+
+impl<'a> GridLayouter<'a> {
+ /// Create a new grid layouter.
+ ///
+ /// This prepares grid layout by unifying content and gutter tracks.
+ pub fn new(
+ grid: &'a CellGrid<'a>,
+ regions: Regions<'a>,
+ styles: StyleChain<'a>,
+ span: Span,
+ ) -> Self {
+ // We use these regions for auto row measurement. Since at that moment,
+ // columns are already sized, we can enable horizontal expansion.
+ let mut regions = regions;
+ regions.expand = Axes::new(true, false);
+
+ Self {
+ grid,
+ regions,
+ styles,
+ rcols: vec![Abs::zero(); grid.cols.len()],
+ width: Abs::zero(),
+ rrows: vec![],
+ lrows: vec![],
+ unbreakable_rows_left: 0,
+ rowspans: vec![],
+ initial: regions.size,
+ finished: vec![],
+ is_rtl: TextElem::dir_in(styles) == Dir::RTL,
+ header_height: Abs::zero(),
+ footer_height: Abs::zero(),
+ span,
+ }
+ }
+
+ /// Determines the columns sizes and then layouts the grid row-by-row.
+ pub fn layout(mut self, engine: &mut Engine) -> SourceResult<Fragment> {
+ self.measure_columns(engine)?;
+
+ if let Some(Repeatable::Repeated(footer)) = &self.grid.footer {
+ // Ensure rows in the first region will be aware of the possible
+ // presence of the footer.
+ self.prepare_footer(footer, engine, 0)?;
+ if matches!(self.grid.header, None | Some(Repeatable::NotRepeated(_))) {
+ // No repeatable header, so we won't subtract it later.
+ self.regions.size.y -= self.footer_height;
+ }
+ }
+
+ for y in 0..self.grid.rows.len() {
+ if let Some(Repeatable::Repeated(header)) = &self.grid.header {
+ if y < header.end {
+ if y == 0 {
+ self.layout_header(header, engine, 0)?;
+ self.regions.size.y -= self.footer_height;
+ }
+ // Skip header rows during normal layout.
+ continue;
+ }
+ }
+
+ if let Some(Repeatable::Repeated(footer)) = &self.grid.footer {
+ if y >= footer.start {
+ if y == footer.start {
+ self.layout_footer(footer, engine, self.finished.len())?;
+ }
+ continue;
+ }
+ }
+
+ self.layout_row(y, engine, 0)?;
+ }
+
+ self.finish_region(engine, true)?;
+
+ // Layout any missing rowspans.
+ // There are only two possibilities for rowspans not yet laid out
+ // (usually, a rowspan is laid out as soon as its last row, or any row
+ // after it, is laid out):
+ // 1. The rowspan was fully empty and only spanned fully empty auto
+ // rows, which were all prevented from being laid out. Those rowspans
+ // are ignored by 'layout_rowspan', and are not of any concern.
+ //
+ // 2. The rowspan's last row was an auto row at the last region which
+ // was not laid out, and no other rows were laid out after it. Those
+ // might still need to be laid out, so we check for them.
+ for rowspan in std::mem::take(&mut self.rowspans) {
+ self.layout_rowspan(rowspan, None, engine)?;
+ }
+
+ self.render_fills_strokes()
+ }
+
+ /// Layout the given row.
+ pub(super) fn layout_row(
+ &mut self,
+ y: usize,
+ engine: &mut Engine,
+ disambiguator: usize,
+ ) -> SourceResult<()> {
+ // Skip to next region if current one is full, but only for content
+ // rows, not for gutter rows, and only if we aren't laying out an
+ // unbreakable group of rows.
+ let is_content_row = !self.grid.is_gutter_track(y);
+ if self.unbreakable_rows_left == 0 && self.regions.is_full() && is_content_row {
+ self.finish_region(engine, false)?;
+ }
+
+ if is_content_row {
+ // Gutter rows have no rowspans or possibly unbreakable cells.
+ self.check_for_rowspans(disambiguator, y);
+ self.check_for_unbreakable_rows(y, engine)?;
+ }
+
+ // Don't layout gutter rows at the top of a region.
+ if is_content_row || !self.lrows.is_empty() {
+ match self.grid.rows[y] {
+ Sizing::Auto => self.layout_auto_row(engine, disambiguator, y)?,
+ Sizing::Rel(v) => {
+ self.layout_relative_row(engine, disambiguator, v, y)?
+ }
+ Sizing::Fr(v) => self.lrows.push(Row::Fr(v, y, disambiguator)),
+ }
+ }
+
+ self.unbreakable_rows_left = self.unbreakable_rows_left.saturating_sub(1);
+
+ Ok(())
+ }
+
+ /// Add lines and backgrounds.
+ fn render_fills_strokes(mut self) -> SourceResult<Fragment> {
+ let mut finished = std::mem::take(&mut self.finished);
+ let frame_amount = finished.len();
+ for ((frame_index, frame), rows) in
+ finished.iter_mut().enumerate().zip(&self.rrows)
+ {
+ if self.rcols.is_empty() || rows.is_empty() {
+ continue;
+ }
+
+ // Render grid lines.
+ // We collect lines into a vector before rendering so we can sort
+ // them based on thickness, such that the lines with largest
+ // thickness are drawn on top; and also so we can prepend all of
+ // them at once in the frame, as calling prepend() for each line,
+ // and thus pushing all frame items forward each time, would result
+ // in quadratic complexity.
+ let mut lines = vec![];
+
+ // Which line position to look for in the list of lines for a
+ // track, such that placing lines with those positions will
+ // correspond to placing them before the given track index.
+ //
+ // If the index represents a gutter track, this means the list of
+ // lines will actually correspond to the list of lines in the
+ // previous index, so we must look for lines positioned after the
+ // previous index, and not before, to determine which lines should
+ // be placed before gutter.
+ //
+ // Note that the maximum index is always an odd number when
+ // there's gutter, so we must check for it to ensure we don't give
+ // it the same treatment as a line before a gutter track.
+ let expected_line_position = |index, is_max_index: bool| {
+ if self.grid.is_gutter_track(index) && !is_max_index {
+ LinePosition::After
+ } else {
+ LinePosition::Before
+ }
+ };
+
+ // Render vertical lines.
+ // Render them first so horizontal lines have priority later.
+ for (x, dx) in points(self.rcols.iter().copied()).enumerate() {
+ let dx = if self.is_rtl { self.width - dx } else { dx };
+ let is_end_border = x == self.grid.cols.len();
+ let expected_vline_position = expected_line_position(x, is_end_border);
+
+ let vlines_at_column = self
+ .grid
+ .vlines
+ .get(if !self.grid.has_gutter {
+ x
+ } else if is_end_border {
+ // The end border has its own vector of lines, but
+ // dividing it by 2 and flooring would give us the
+ // vector of lines with the index of the last column.
+ // Add 1 so we get the border's lines.
+ x / 2 + 1
+ } else {
+ // If x is a gutter column, this will round down to the
+ // index of the previous content column, which is
+ // intentional - the only lines which can appear before
+ // a gutter column are lines for the previous column
+ // marked with "LinePosition::After". Therefore, we get
+ // the previous column's lines. Worry not, as
+ // 'generate_line_segments' will correctly filter lines
+ // based on their LinePosition for us.
+ //
+ // If x is a content column, this will correctly return
+ // its index before applying gutters, so nothing
+ // special here (lines with "LinePosition::After" would
+ // then be ignored for this column, as we are drawing
+ // lines before it, not after).
+ x / 2
+ })
+ .into_iter()
+ .flatten()
+ .filter(|line| line.position == expected_vline_position);
+
+ let tracks = rows.iter().map(|row| (row.y, row.height));
+
+ // Determine all different line segments we have to draw in
+ // this column, and convert them to points and shapes.
+ //
+ // Even a single, uniform line might generate more than one
+ // segment, if it happens to cross a colspan (over which it
+ // must not be drawn).
+ let segments = generate_line_segments(
+ self.grid,
+ tracks,
+ x,
+ vlines_at_column,
+ vline_stroke_at_row,
+ )
+ .map(|segment| {
+ let LineSegment { stroke, offset: dy, length, priority } = segment;
+ let stroke = (*stroke).clone().unwrap_or_default();
+ let thickness = stroke.thickness;
+ let half = thickness / 2.0;
+ let target = Point::with_y(length + thickness);
+ let vline = Geometry::Line(target).stroked(stroke);
+ (
+ thickness,
+ priority,
+ Point::new(dx, dy - half),
+ FrameItem::Shape(vline, self.span),
+ )
+ });
+
+ lines.extend(segments);
+ }
+
+ // Render horizontal lines.
+ // They are rendered second as they default to appearing on top.
+ // First, calculate their offsets from the top of the frame.
+ let hline_offsets = points(rows.iter().map(|piece| piece.height));
+
+ // Additionally, determine their indices (the indices of the
+ // rows they are drawn on top of). In principle, this will
+ // correspond to the rows' indices directly, except for the
+ // last hline index, which must be (amount of rows) in order to
+ // draw the table's bottom border.
+ let hline_indices = rows
+ .iter()
+ .map(|piece| piece.y)
+ .chain(std::iter::once(self.grid.rows.len()));
+
+ // Converts a row to the corresponding index in the vector of
+ // hlines.
+ let hline_index_of_row = |y: usize| {
+ if !self.grid.has_gutter {
+ y
+ } else if y == self.grid.rows.len() {
+ y / 2 + 1
+ } else {
+ // Check the vlines loop for an explanation regarding
+ // these index operations.
+ y / 2
+ }
+ };
+
+ let get_hlines_at = |y| {
+ self.grid
+ .hlines
+ .get(hline_index_of_row(y))
+ .map(Vec::as_slice)
+ .unwrap_or(&[])
+ };
+
+ let mut prev_y = None;
+ for (y, dy) in hline_indices.zip(hline_offsets) {
+ // Position of lines below the row index in the previous iteration.
+ let expected_prev_line_position = prev_y
+ .map(|prev_y| {
+ expected_line_position(
+ prev_y + 1,
+ prev_y + 1 == self.grid.rows.len(),
+ )
+ })
+ .unwrap_or(LinePosition::Before);
+
+ // FIXME: In the future, directly specify in 'self.rrows' when
+ // we place a repeated header rather than its original rows.
+ // That would let us remove most of those verbose checks, both
+ // in 'lines.rs' and here. Those checks also aren't fully
+ // accurate either, since they will also trigger when some rows
+ // have been removed between the header and what's below it.
+ let is_under_repeated_header = self
+ .grid
+ .header
+ .as_ref()
+ .and_then(Repeatable::as_repeated)
+ .zip(prev_y)
+ .is_some_and(|(header, prev_y)| {
+ // Note: 'y == header.end' would mean we're right below
+ // the NON-REPEATED header, so that case should return
+ // false.
+ prev_y < header.end && y > header.end
+ });
+
+ // If some grid rows were omitted between the previous resolved
+ // row and the current one, we ensure lines below the previous
+ // row don't "disappear" and are considered, albeit with less
+ // priority. However, don't do this when we're below a header,
+ // as it must have more priority instead of less, so it is
+ // chained later instead of before. The exception is when the
+ // last row in the header is removed, in which case we append
+ // both the lines under the row above us and also (later) the
+ // lines under the header's (removed) last row.
+ let prev_lines = prev_y
+ .filter(|prev_y| {
+ prev_y + 1 != y
+ && (!is_under_repeated_header
+ || self
+ .grid
+ .header
+ .as_ref()
+ .and_then(Repeatable::as_repeated)
+ .is_some_and(|header| prev_y + 1 != header.end))
+ })
+ .map(|prev_y| get_hlines_at(prev_y + 1))
+ .unwrap_or(&[]);
+
+ let expected_hline_position =
+ expected_line_position(y, y == self.grid.rows.len());
+
+ let hlines_at_y = get_hlines_at(y)
+ .iter()
+ .filter(|line| line.position == expected_hline_position);
+
+ let top_border_hlines = if prev_y.is_none() && y != 0 {
+ // For lines at the top of the region, give priority to
+ // the lines at the top border.
+ get_hlines_at(0)
+ } else {
+ &[]
+ };
+
+ let mut expected_header_line_position = LinePosition::Before;
+ let header_hlines = if let Some((Repeatable::Repeated(header), prev_y)) =
+ self.grid.header.as_ref().zip(prev_y)
+ {
+ if is_under_repeated_header
+ && (!self.grid.has_gutter
+ || matches!(
+ self.grid.rows[prev_y],
+ Sizing::Rel(length) if length.is_zero()
+ ))
+ {
+ // For lines below a header, give priority to the
+ // lines originally below the header rather than
+ // the lines of what's below the repeated header.
+ // However, no need to do that when we're laying
+ // out the header for the first time, since the
+ // lines being normally laid out then will be
+ // precisely the lines below the header.
+ //
+ // Additionally, we don't repeat lines above the row
+ // below the header when gutter is enabled, since, in
+ // that case, there will be a gutter row between header
+ // and content, so no lines should overlap. The
+ // exception is when the gutter at the end of the
+ // header has a size of zero, which happens when only
+ // column-gutter is specified, for example. In that
+ // case, we still repeat the line under the gutter.
+ expected_header_line_position = expected_line_position(
+ header.end,
+ header.end == self.grid.rows.len(),
+ );
+ get_hlines_at(header.end)
+ } else {
+ &[]
+ }
+ } else {
+ &[]
+ };
+
+ // The effective hlines to be considered at this row index are
+ // chained in order of increasing priority:
+ // 1. Lines from the row right above us, if needed;
+ // 2. Lines from the current row (usually, only those are
+ // present);
+ // 3. Lines from the top border (above the top cells, hence
+ // 'before' position only);
+ // 4. Lines from the header above us, if present.
+ let hlines_at_row =
+ prev_lines
+ .iter()
+ .filter(|line| line.position == expected_prev_line_position)
+ .chain(hlines_at_y)
+ .chain(
+ top_border_hlines
+ .iter()
+ .filter(|line| line.position == LinePosition::Before),
+ )
+ .chain(header_hlines.iter().filter(|line| {
+ line.position == expected_header_line_position
+ }));
+
+ let tracks = self.rcols.iter().copied().enumerate();
+
+ // Normally, given an hline above row y, the row above it is
+ // 'y - 1' (if y > 0). However, sometimes that's not true, for
+ // example if 'y - 1' is in a previous region, or if 'y - 1'
+ // was an empty auto row which was removed. Therefore, we tell
+ // the hlines at this index which row is actually above them in
+ // the laid out region so they can include that row's bottom
+ // strokes in the folding process.
+ let local_top_y = prev_y;
+
+ // When we're in the last region, the bottom border stroke
+ // doesn't necessarily gain priority like it does in previous
+ // regions.
+ let in_last_region = frame_index + 1 == frame_amount;
+
+ // Determine all different line segments we have to draw in
+ // this row, and convert them to points and shapes.
+ let segments = generate_line_segments(
+ self.grid,
+ tracks,
+ y,
+ hlines_at_row,
+ |grid, y, x, stroke| {
+ hline_stroke_at_column(
+ grid,
+ rows,
+ local_top_y,
+ in_last_region,
+ y,
+ x,
+ stroke,
+ )
+ },
+ )
+ .map(|segment| {
+ let LineSegment { stroke, offset: dx, length, priority } = segment;
+ let stroke = (*stroke).clone().unwrap_or_default();
+ let thickness = stroke.thickness;
+ let half = thickness / 2.0;
+ let dx = if self.is_rtl { self.width - dx - length } else { dx };
+ let target = Point::with_x(length + thickness);
+ let hline = Geometry::Line(target).stroked(stroke);
+ (
+ thickness,
+ priority,
+ Point::new(dx - half, dy),
+ FrameItem::Shape(hline, self.span),
+ )
+ });
+
+ // Draw later (after we sort all lines below.)
+ lines.extend(segments);
+
+ prev_y = Some(y);
+ }
+
+ // Sort by increasing thickness, so that we draw larger strokes
+ // on top. When the thickness is the same, sort by priority.
+ //
+ // Sorting by thickness avoids layering problems where a smaller
+ // hline appears "inside" a larger vline. When both have the same
+ // size, hlines are drawn on top (since the sort is stable, and
+ // they are pushed later).
+ lines.sort_by_key(|(thickness, priority, ..)| (*thickness, *priority));
+
+ // Render cell backgrounds.
+ // We collect them into a vector so they can all be prepended at
+ // once to the frame, together with lines.
+ let mut fills = vec![];
+
+ // Reverse with RTL so that later columns start first.
+ let mut dx = Abs::zero();
+ for (x, &col) in self.rcols.iter().enumerate().rev_if(self.is_rtl) {
+ let mut dy = Abs::zero();
+ for row in rows {
+ // We want to only draw the fill starting at the parent
+ // positions of cells. However, sometimes the parent
+ // position is absent from the current region, either
+ // because the first few rows of a rowspan were empty auto
+ // rows and thus removed from layout, or because the parent
+ // cell was in a previous region (in which case we'd want
+ // to draw its fill again, in the current region).
+ // Therefore, we first analyze the parent position to see
+ // if the current row would be the first row spanned by the
+ // parent cell in this region. If so, this means we have to
+ // start drawing the cell's fill here. If not, we ignore
+ // the position `(x, row.y)`, as its fill will already have
+ // been rendered before.
+ //
+ // Note: In the case of gutter rows, we have to check the
+ // row below before discarding them fully, because a
+ // gutter row might be the first row spanned by a rowspan
+ // in this region (e.g. if the first row was empty and
+ // therefore removed), so its fill could start in that
+ // gutter row. That's why we use
+ // 'effective_parent_cell_position'.
+ let parent = self
+ .grid
+ .effective_parent_cell_position(x, row.y)
+ .filter(|parent| {
+ // Ensure this is the first column spanned by the
+ // cell before drawing its fill, otherwise we
+ // already rendered its fill in a previous
+ // iteration of the outer loop (and/or this is a
+ // gutter column, which we ignore).
+ //
+ // Additionally, we should only draw the fill when
+ // this row is the local parent Y for this cell,
+ // that is, the first row spanned by the cell's
+ // parent in this region, because if the parent
+ // cell's fill was already drawn in a previous
+ // region, we must render it again in later regions
+ // spanned by that cell. Note that said condition
+ // always holds when the current cell has a rowspan
+ // of 1 and we're not currently at a gutter row.
+ parent.x == x
+ && (parent.y == row.y
+ || rows
+ .iter()
+ .find(|row| row.y >= parent.y)
+ .is_some_and(|first_spanned_row| {
+ first_spanned_row.y == row.y
+ }))
+ });
+
+ if let Some(parent) = parent {
+ let cell = self.grid.cell(parent.x, parent.y).unwrap();
+ let fill = cell.fill.clone();
+ if let Some(fill) = fill {
+ let rowspan = self.grid.effective_rowspan_of_cell(cell);
+ let height = if rowspan == 1 {
+ row.height
+ } else {
+ rows.iter()
+ .filter(|row| {
+ (parent.y..parent.y + rowspan).contains(&row.y)
+ })
+ .map(|row| row.height)
+ .sum()
+ };
+ let width = self.cell_spanned_width(cell, x);
+ // In the grid, cell colspans expand to the right,
+ // so we're at the leftmost (lowest 'x') column
+ // spanned by the cell. However, in RTL, cells
+ // expand to the left. Therefore, without the
+ // offset below, cell fills would start at the
+ // rightmost visual position of a cell and extend
+ // over to unrelated columns to the right in RTL.
+ // We avoid this by ensuring the fill starts at the
+ // very left of the cell, even with colspan > 1.
+ let offset =
+ if self.is_rtl { -width + col } else { Abs::zero() };
+ let pos = Point::new(dx + offset, dy);
+ let size = Size::new(width, height);
+ let rect = Geometry::Rect(size).filled(fill);
+ fills.push((pos, FrameItem::Shape(rect, self.span)));
+ }
+ }
+ dy += row.height;
+ }
+ dx += col;
+ }
+
+ // Now we render each fill and stroke by prepending to the frame,
+ // such that both appear below cell contents. Fills come first so
+ // that they appear below lines.
+ frame.prepend_multiple(
+ fills
+ .into_iter()
+ .chain(lines.into_iter().map(|(_, _, point, shape)| (point, shape))),
+ );
+ }
+
+ Ok(Fragment::frames(finished))
+ }
+
+ /// Determine all column sizes.
+ fn measure_columns(&mut self, engine: &mut Engine) -> SourceResult<()> {
+ // Sum of sizes of resolved relative tracks.
+ let mut rel = Abs::zero();
+
+ // Sum of fractions of all fractional tracks.
+ let mut fr = Fr::zero();
+
+ // Resolve the size of all relative columns and compute the sum of all
+ // fractional tracks.
+ for (&col, rcol) in self.grid.cols.iter().zip(&mut self.rcols) {
+ match col {
+ Sizing::Auto => {}
+ Sizing::Rel(v) => {
+ let resolved =
+ v.resolve(self.styles).relative_to(self.regions.base().x);
+ *rcol = resolved;
+ rel += resolved;
+ }
+ Sizing::Fr(v) => fr += v,
+ }
+ }
+
+ // Size that is not used by fixed-size columns.
+ let available = self.regions.size.x - rel;
+ if available >= Abs::zero() {
+ // Determine size of auto columns.
+ let (auto, count) = self.measure_auto_columns(engine, available)?;
+
+ // If there is remaining space, distribute it to fractional columns,
+ // otherwise shrink auto columns.
+ let remaining = available - auto;
+ if remaining >= Abs::zero() {
+ self.grow_fractional_columns(remaining, fr);
+ } else {
+ self.shrink_auto_columns(available, count);
+ }
+ }
+
+ // Sum up the resolved column sizes once here.
+ self.width = self.rcols.iter().sum();
+
+ Ok(())
+ }
+
+ /// Total width spanned by the cell (among resolved columns).
+ /// Includes spanned gutter columns.
+ pub(super) fn cell_spanned_width(&self, cell: &Cell, x: usize) -> Abs {
+ let colspan = self.grid.effective_colspan_of_cell(cell);
+ self.rcols.iter().skip(x).take(colspan).sum()
+ }
+
+ /// Measure the size that is available to auto columns.
+ fn measure_auto_columns(
+ &mut self,
+ engine: &mut Engine,
+ available: Abs,
+ ) -> SourceResult<(Abs, usize)> {
+ let mut auto = Abs::zero();
+ let mut count = 0;
+ let all_frac_cols = self
+ .grid
+ .cols
+ .iter()
+ .enumerate()
+ .filter(|(_, col)| col.is_fractional())
+ .map(|(x, _)| x)
+ .collect::<Vec<_>>();
+
+ // Determine size of auto columns by laying out all cells in those
+ // columns, measuring them and finding the largest one.
+ for (x, &col) in self.grid.cols.iter().enumerate() {
+ if col != Sizing::Auto {
+ continue;
+ }
+
+ let mut resolved = Abs::zero();
+ for y in 0..self.grid.rows.len() {
+ // We get the parent cell in case this is a merged position.
+ let Some(parent) = self.grid.parent_cell_position(x, y) else {
+ continue;
+ };
+ if parent.y != y {
+ // Don't check the width of rowspans more than once.
+ continue;
+ }
+ let cell = self.grid.cell(parent.x, parent.y).unwrap();
+ let colspan = self.grid.effective_colspan_of_cell(cell);
+ if colspan > 1 {
+ let last_spanned_auto_col = self
+ .grid
+ .cols
+ .iter()
+ .enumerate()
+ .skip(parent.x)
+ .take(colspan)
+ .rev()
+ .find(|(_, col)| **col == Sizing::Auto)
+ .map(|(x, _)| x);
+
+ if last_spanned_auto_col != Some(x) {
+ // A colspan only affects the size of the last spanned
+ // auto column.
+ continue;
+ }
+ }
+
+ if colspan > 1
+ && self.regions.size.x.is_finite()
+ && !all_frac_cols.is_empty()
+ && all_frac_cols
+ .iter()
+ .all(|x| (parent.x..parent.x + colspan).contains(x))
+ {
+ // Additionally, as a heuristic, a colspan won't affect the
+ // size of auto columns if it already spans all fractional
+ // columns, since those would already expand to provide all
+ // remaining available after auto column sizing to that
+ // cell. However, this heuristic is only valid in finite
+ // regions (pages without 'auto' width), since otherwise
+ // the fractional columns don't expand at all.
+ continue;
+ }
+
+ // Sum the heights of spanned rows to find the expected
+ // available height for the cell, unless it spans a fractional
+ // or auto column.
+ let rowspan = self.grid.effective_rowspan_of_cell(cell);
+ let height = self
+ .grid
+ .rows
+ .iter()
+ .skip(y)
+ .take(rowspan)
+ .try_fold(Abs::zero(), |acc, col| {
+ // For relative rows, we can already resolve the correct
+ // base and for auto and fr we could only guess anyway.
+ match col {
+ Sizing::Rel(v) => Some(
+ acc + v
+ .resolve(self.styles)
+ .relative_to(self.regions.base().y),
+ ),
+ _ => None,
+ }
+ })
+ .unwrap_or_else(|| self.regions.base().y);
+
+ // Don't expand this auto column more than the cell actually
+ // needs. To do this, we check how much the other, previously
+ // resolved columns provide to the cell in terms of width
+ // (if it is a colspan), and subtract this from its expected
+ // width when comparing with other cells in this column. Note
+ // that, since this is the last auto column spanned by this
+ // cell, all other auto columns will already have been resolved
+ // and will be considered.
+ // Only fractional columns will be excluded from this
+ // calculation, which can lead to auto columns being expanded
+ // unnecessarily when cells span both a fractional column and
+ // an auto column. One mitigation for this is the heuristic
+ // used above to not expand the last auto column spanned by a
+ // cell if it spans all fractional columns in a finite region.
+ let already_covered_width = self.cell_spanned_width(cell, parent.x);
+
+ let size = Size::new(available, height);
+ let pod = Region::new(size, Axes::splat(false));
+ let frame = cell.layout(engine, 0, self.styles, pod.into())?.into_frame();
+ resolved.set_max(frame.width() - already_covered_width);
+ }
+
+ self.rcols[x] = resolved;
+ auto += resolved;
+ count += 1;
+ }
+
+ Ok((auto, count))
+ }
+
+ /// Distribute remaining space to fractional columns.
+ fn grow_fractional_columns(&mut self, remaining: Abs, fr: Fr) {
+ if fr.is_zero() {
+ return;
+ }
+
+ for (&col, rcol) in self.grid.cols.iter().zip(&mut self.rcols) {
+ if let Sizing::Fr(v) = col {
+ *rcol = v.share(fr, remaining);
+ }
+ }
+ }
+
+ /// Redistribute space to auto columns so that each gets a fair share.
+ fn shrink_auto_columns(&mut self, available: Abs, count: usize) {
+ let mut last;
+ let mut fair = -Abs::inf();
+ let mut redistribute = available;
+ let mut overlarge = count;
+ let mut changed = true;
+
+ // Iteratively remove columns that don't need to be shrunk.
+ while changed && overlarge > 0 {
+ changed = false;
+ last = fair;
+ fair = redistribute / (overlarge as f64);
+
+ for (&col, &rcol) in self.grid.cols.iter().zip(&self.rcols) {
+ // Remove an auto column if it is not overlarge (rcol <= fair),
+ // but also hasn't already been removed (rcol > last).
+ if col == Sizing::Auto && rcol <= fair && rcol > last {
+ redistribute -= rcol;
+ overlarge -= 1;
+ changed = true;
+ }
+ }
+ }
+
+ // Redistribute space fairly among overlarge columns.
+ for (&col, rcol) in self.grid.cols.iter().zip(&mut self.rcols) {
+ if col == Sizing::Auto && *rcol > fair {
+ *rcol = fair;
+ }
+ }
+ }
+
+ /// Layout a row with automatic height. Such a row may break across multiple
+ /// regions.
+ fn layout_auto_row(
+ &mut self,
+ engine: &mut Engine,
+ disambiguator: usize,
+ y: usize,
+ ) -> SourceResult<()> {
+ // Determine the size for each region of the row. If the first region
+ // ends up empty for some column, skip the region and remeasure.
+ let mut resolved = match self.measure_auto_row(
+ engine,
+ disambiguator,
+ y,
+ true,
+ self.unbreakable_rows_left,
+ None,
+ )? {
+ Some(resolved) => resolved,
+ None => {
+ self.finish_region(engine, false)?;
+ self.measure_auto_row(
+ engine,
+ disambiguator,
+ y,
+ false,
+ self.unbreakable_rows_left,
+ None,
+ )?
+ .unwrap()
+ }
+ };
+
+ // Nothing to layout.
+ if resolved.is_empty() {
+ return Ok(());
+ }
+
+ // Layout into a single region.
+ if let &[first] = resolved.as_slice() {
+ let frame = self.layout_single_row(engine, disambiguator, first, y)?;
+ self.push_row(frame, y, true);
+
+ if self
+ .grid
+ .header
+ .as_ref()
+ .and_then(Repeatable::as_repeated)
+ .is_some_and(|header| y < header.end)
+ {
+ // Add to header height.
+ self.header_height += first;
+ }
+
+ return Ok(());
+ }
+
+ // Expand all but the last region.
+ // Skip the first region if the space is eaten up by an fr row.
+ let len = resolved.len();
+ for ((i, region), target) in self
+ .regions
+ .iter()
+ .enumerate()
+ .zip(&mut resolved[..len - 1])
+ .skip(self.lrows.iter().any(|row| matches!(row, Row::Fr(..))) as usize)
+ {
+ // Subtract header and footer heights from the region height when
+ // it's not the first.
+ target.set_max(
+ region.y
+ - if i > 0 {
+ self.header_height + self.footer_height
+ } else {
+ Abs::zero()
+ },
+ );
+ }
+
+ // Layout into multiple regions.
+ let fragment = self.layout_multi_row(engine, disambiguator, &resolved, y)?;
+ let len = fragment.len();
+ for (i, frame) in fragment.into_iter().enumerate() {
+ self.push_row(frame, y, i + 1 == len);
+ if i + 1 < len {
+ self.finish_region(engine, false)?;
+ }
+ }
+
+ Ok(())
+ }
+
+ /// Measure the regions sizes of an auto row. The option is always `Some(_)`
+ /// if `can_skip` is false.
+ /// If `unbreakable_rows_left` is positive, this function shall only return
+ /// a single frame. Useful when an unbreakable rowspan crosses this auto
+ /// row.
+ /// The `row_group_data` option is used within the unbreakable row group
+ /// simulator to predict the height of the auto row if previous rows in the
+ /// group were placed in the same region.
+ pub(super) fn measure_auto_row(
+ &self,
+ engine: &mut Engine,
+ disambiguator: usize,
+ y: usize,
+ can_skip: bool,
+ unbreakable_rows_left: usize,
+ row_group_data: Option<&UnbreakableRowGroup>,
+ ) -> SourceResult<Option<Vec<Abs>>> {
+ let breakable = unbreakable_rows_left == 0;
+ let mut resolved: Vec<Abs> = vec![];
+ let mut pending_rowspans: Vec<(usize, usize, Vec<Abs>)> = vec![];
+
+ for x in 0..self.rcols.len() {
+ // Get the parent cell in case this is a merged position.
+ let Some(parent) = self.grid.parent_cell_position(x, y) else {
+ // Skip gutter columns.
+ continue;
+ };
+ if parent.x != x {
+ // Only check the height of a colspan once.
+ continue;
+ }
+ // The parent cell is never a gutter or merged position.
+ let cell = self.grid.cell(parent.x, parent.y).unwrap();
+ let rowspan = self.grid.effective_rowspan_of_cell(cell);
+
+ if rowspan > 1 {
+ let last_spanned_auto_row = self
+ .grid
+ .rows
+ .iter()
+ .enumerate()
+ .skip(parent.y)
+ .take(rowspan)
+ .rev()
+ .find(|(_, &row)| row == Sizing::Auto)
+ .map(|(y, _)| y);
+
+ if last_spanned_auto_row != Some(y) {
+ // A rowspan should only affect the height of its last
+ // spanned auto row.
+ continue;
+ }
+ }
+
+ let measurement_data = self.prepare_auto_row_cell_measurement(
+ parent,
+ cell,
+ breakable,
+ row_group_data,
+ );
+ let size = Axes::new(measurement_data.width, measurement_data.height);
+ let backlog =
+ measurement_data.backlog.unwrap_or(&measurement_data.custom_backlog);
+
+ let pod = if !breakable {
+ // Force cell to fit into a single region when the row is
+ // unbreakable, even when it is a breakable rowspan, as a best
+ // effort.
+ let mut pod: Regions = Region::new(size, self.regions.expand).into();
+ pod.full = measurement_data.full;
+
+ if measurement_data.frames_in_previous_regions > 0 {
+ // Best effort to conciliate a breakable rowspan which
+ // started at a previous region going through an
+ // unbreakable auto row. Ensure it goes through previously
+ // laid out regions, but stops at this one when measuring.
+ pod.backlog = backlog;
+ }
+
+ pod
+ } else {
+ // This row is breakable, so measure the cell normally, with
+ // the initial height and backlog determined previously.
+ let mut pod = self.regions;
+ pod.size = size;
+ pod.backlog = backlog;
+ pod.full = measurement_data.full;
+ pod.last = measurement_data.last;
+
+ pod
+ };
+
+ let frames =
+ cell.layout(engine, disambiguator, self.styles, pod)?.into_frames();
+
+ // Skip the first region if one cell in it is empty. Then,
+ // remeasure.
+ if let Some([first, rest @ ..]) =
+ frames.get(measurement_data.frames_in_previous_regions..)
+ {
+ if can_skip
+ && breakable
+ && first.is_empty()
+ && rest.iter().any(|frame| !frame.is_empty())
+ {
+ return Ok(None);
+ }
+ }
+
+ // Skip frames from previous regions if applicable.
+ let mut sizes = frames
+ .iter()
+ .skip(measurement_data.frames_in_previous_regions)
+ .map(|frame| frame.height())
+ .collect::<Vec<_>>();
+
+ // Don't expand this row more than the cell needs.
+ // To figure out how much height the cell needs, we must first
+ // subtract, from the cell's expected height, the already resolved
+ // heights of its spanned rows. Note that this is the last spanned
+ // auto row, so all previous auto rows were already resolved, as
+ // well as fractional rows in previous regions.
+ // Additionally, we subtract the heights of fixed-size rows which
+ // weren't laid out yet, since those heights won't change in
+ // principle.
+ // Upcoming fractional rows are ignored.
+ // Upcoming gutter rows might be removed, so we need to simulate
+ // them.
+ if rowspan > 1 {
+ let should_simulate = self.prepare_rowspan_sizes(
+ y,
+ &mut sizes,
+ cell,
+ parent.y,
+ rowspan,
+ unbreakable_rows_left,
+ &measurement_data,
+ );
+
+ if should_simulate {
+ // Rowspan spans gutter and is breakable. We'll need to
+ // run a simulation to predict how much this auto row needs
+ // to expand so that the rowspan's contents fit into the
+ // table.
+ pending_rowspans.push((parent.y, rowspan, sizes));
+ continue;
+ }
+ }
+
+ let mut sizes = sizes.into_iter();
+
+ for (target, size) in resolved.iter_mut().zip(&mut sizes) {
+ target.set_max(size);
+ }
+
+ // New heights are maximal by virtue of being new. Note that
+ // this extend only uses the rest of the sizes iterator.
+ resolved.extend(sizes);
+ }
+
+ // Simulate the upcoming regions in order to predict how much we need
+ // to expand this auto row for rowspans which span gutter.
+ if !pending_rowspans.is_empty() {
+ self.simulate_and_measure_rowspans_in_auto_row(
+ y,
+ &mut resolved,
+ &pending_rowspans,
+ unbreakable_rows_left,
+ row_group_data,
+ disambiguator,
+ engine,
+ )?;
+ }
+
+ debug_assert!(breakable || resolved.len() <= 1);
+
+ Ok(Some(resolved))
+ }
+
+ /// Layout a row with relative height. Such a row cannot break across
+ /// multiple regions, but it may force a region break.
+ fn layout_relative_row(
+ &mut self,
+ engine: &mut Engine,
+ disambiguator: usize,
+ v: Rel<Length>,
+ y: usize,
+ ) -> SourceResult<()> {
+ let resolved = v.resolve(self.styles).relative_to(self.regions.base().y);
+ let frame = self.layout_single_row(engine, disambiguator, resolved, y)?;
+
+ if self
+ .grid
+ .header
+ .as_ref()
+ .and_then(Repeatable::as_repeated)
+ .is_some_and(|header| y < header.end)
+ {
+ // Add to header height.
+ self.header_height += resolved;
+ }
+
+ // Skip to fitting region, but only if we aren't part of an unbreakable
+ // row group. We use 'in_last_with_offset' so our 'in_last' call
+ // properly considers that a header and a footer would be added on each
+ // region break.
+ let height = frame.height();
+ while self.unbreakable_rows_left == 0
+ && !self.regions.size.y.fits(height)
+ && !in_last_with_offset(self.regions, self.header_height + self.footer_height)
+ {
+ self.finish_region(engine, false)?;
+
+ // Don't skip multiple regions for gutter and don't push a row.
+ if self.grid.is_gutter_track(y) {
+ return Ok(());
+ }
+ }
+
+ self.push_row(frame, y, true);
+
+ Ok(())
+ }
+
+ /// Layout a row with fixed height and return its frame.
+ fn layout_single_row(
+ &mut self,
+ engine: &mut Engine,
+ disambiguator: usize,
+ height: Abs,
+ y: usize,
+ ) -> SourceResult<Frame> {
+ if !self.width.is_finite() {
+ bail!(self.span, "cannot create grid with infinite width");
+ }
+
+ if !height.is_finite() {
+ bail!(self.span, "cannot create grid with infinite height");
+ }
+
+ let mut output = Frame::soft(Size::new(self.width, height));
+ let mut pos = Point::zero();
+
+ // Reverse the column order when using RTL.
+ for (x, &rcol) in self.rcols.iter().enumerate().rev_if(self.is_rtl) {
+ if let Some(cell) = self.grid.cell(x, y) {
+ // Rowspans have a separate layout step
+ if cell.rowspan.get() == 1 {
+ let width = self.cell_spanned_width(cell, x);
+ let size = Size::new(width, height);
+ let mut pod: Regions = Region::new(size, Axes::splat(true)).into();
+ if self.grid.rows[y] == Sizing::Auto
+ && self.unbreakable_rows_left == 0
+ {
+ // Cells at breakable auto rows have lengths relative
+ // to the entire page, unlike cells in unbreakable auto
+ // rows.
+ pod.full = self.regions.full;
+ }
+ let frame = cell
+ .layout(engine, disambiguator, self.styles, pod)?
+ .into_frame();
+ let mut pos = pos;
+ if self.is_rtl {
+ // In the grid, cell colspans expand to the right,
+ // so we're at the leftmost (lowest 'x') column
+ // spanned by the cell. However, in RTL, cells
+ // expand to the left. Therefore, without the
+ // offset below, the cell's contents would be laid out
+ // starting at its rightmost visual position and extend
+ // over to unrelated cells to its right in RTL.
+ // We avoid this by ensuring the rendered cell starts at
+ // the very left of the cell, even with colspan > 1.
+ let offset = -width + rcol;
+ pos.x += offset;
+ }
+ output.push_frame(pos, frame);
+ }
+ }
+
+ pos.x += rcol;
+ }
+
+ Ok(output)
+ }
+
+ /// Layout a row spanning multiple regions.
+ fn layout_multi_row(
+ &mut self,
+ engine: &mut Engine,
+ disambiguator: usize,
+ heights: &[Abs],
+ y: usize,
+ ) -> SourceResult<Fragment> {
+ // Prepare frames.
+ let mut outputs: Vec<_> = heights
+ .iter()
+ .map(|&h| Frame::soft(Size::new(self.width, h)))
+ .collect();
+
+ // Prepare regions.
+ let size = Size::new(self.width, heights[0]);
+ let mut pod: Regions = Region::new(size, Axes::splat(true)).into();
+ pod.full = self.regions.full;
+ pod.backlog = &heights[1..];
+
+ // Layout the row.
+ let mut pos = Point::zero();
+ for (x, &rcol) in self.rcols.iter().enumerate().rev_if(self.is_rtl) {
+ if let Some(cell) = self.grid.cell(x, y) {
+ // Rowspans have a separate layout step
+ if cell.rowspan.get() == 1 {
+ let width = self.cell_spanned_width(cell, x);
+ pod.size.x = width;
+
+ // Push the layouted frames into the individual output frames.
+ let fragment =
+ cell.layout(engine, disambiguator, self.styles, pod)?;
+ for (output, frame) in outputs.iter_mut().zip(fragment) {
+ let mut pos = pos;
+ if self.is_rtl {
+ let offset = -width + rcol;
+ pos.x += offset;
+ }
+ output.push_frame(pos, frame);
+ }
+ }
+ }
+
+ pos.x += rcol;
+ }
+
+ Ok(Fragment::frames(outputs))
+ }
+
+ /// Push a row frame into the current region.
+ /// The `is_last` parameter must be `true` if this is the last frame which
+ /// will be pushed for this particular row. It can be `false` for rows
+ /// spanning multiple regions.
+ fn push_row(&mut self, frame: Frame, y: usize, is_last: bool) {
+ self.regions.size.y -= frame.height();
+ self.lrows.push(Row::Frame(frame, y, is_last));
+ }
+
+ /// Finish rows for one region.
+ pub(super) fn finish_region(
+ &mut self,
+ engine: &mut Engine,
+ last: bool,
+ ) -> SourceResult<()> {
+ if self
+ .lrows
+ .last()
+ .is_some_and(|row| self.grid.is_gutter_track(row.index()))
+ {
+ // Remove the last row in the region if it is a gutter row.
+ self.lrows.pop().unwrap();
+ }
+
+ // If no rows other than the footer have been laid out so far, and
+ // there are rows beside the footer, then don't lay it out at all.
+ // This check doesn't apply, and is thus overridden, when there is a
+ // header.
+ let mut footer_would_be_orphan = self.lrows.is_empty()
+ && !in_last_with_offset(
+ self.regions,
+ self.header_height + self.footer_height,
+ )
+ && self
+ .grid
+ .footer
+ .as_ref()
+ .and_then(Repeatable::as_repeated)
+ .is_some_and(|footer| footer.start != 0);
+
+ if let Some(Repeatable::Repeated(header)) = &self.grid.header {
+ if self.grid.rows.len() > header.end
+ && self
+ .grid
+ .footer
+ .as_ref()
+ .and_then(Repeatable::as_repeated)
+ .map_or(true, |footer| footer.start != header.end)
+ && self.lrows.last().is_some_and(|row| row.index() < header.end)
+ && !in_last_with_offset(
+ self.regions,
+ self.header_height + self.footer_height,
+ )
+ {
+ // Header and footer would be alone in this region, but there are more
+ // rows beyond the header and the footer. Push an empty region.
+ self.lrows.clear();
+ footer_would_be_orphan = true;
+ }
+ }
+
+ let mut laid_out_footer_start = None;
+ if let Some(Repeatable::Repeated(footer)) = &self.grid.footer {
+ // Don't layout the footer if it would be alone with the header in
+ // the page, and don't layout it twice.
+ if !footer_would_be_orphan
+ && self.lrows.iter().all(|row| row.index() < footer.start)
+ {
+ laid_out_footer_start = Some(footer.start);
+ self.layout_footer(footer, engine, self.finished.len())?;
+ }
+ }
+
+ // Determine the height of existing rows in the region.
+ let mut used = Abs::zero();
+ let mut fr = Fr::zero();
+ for row in &self.lrows {
+ match row {
+ Row::Frame(frame, _, _) => used += frame.height(),
+ Row::Fr(v, _, _) => fr += *v,
+ }
+ }
+
+ // Determine the size of the grid in this region, expanding fully if
+ // there are fr rows.
+ let mut size = Size::new(self.width, used).min(self.initial);
+ if fr.get() > 0.0 && self.initial.y.is_finite() {
+ size.y = self.initial.y;
+ }
+
+ // The frame for the region.
+ let mut output = Frame::soft(size);
+ let mut pos = Point::zero();
+ let mut rrows = vec![];
+ let current_region = self.finished.len();
+
+ // Place finished rows and layout fractional rows.
+ for row in std::mem::take(&mut self.lrows) {
+ let (frame, y, is_last) = match row {
+ Row::Frame(frame, y, is_last) => (frame, y, is_last),
+ Row::Fr(v, y, disambiguator) => {
+ let remaining = self.regions.full - used;
+ let height = v.share(fr, remaining);
+ (self.layout_single_row(engine, disambiguator, height, y)?, y, true)
+ }
+ };
+
+ let height = frame.height();
+
+ // Ensure rowspans which span this row will have enough space to
+ // be laid out over it later.
+ for rowspan in self
+ .rowspans
+ .iter_mut()
+ .filter(|rowspan| (rowspan.y..rowspan.y + rowspan.rowspan).contains(&y))
+ .filter(|rowspan| {
+ rowspan.max_resolved_row.map_or(true, |max_row| y > max_row)
+ })
+ {
+ // If the first region wasn't defined yet, it will have the
+ // initial value of usize::MAX, so we can set it to the current
+ // region's index.
+ if rowspan.first_region > current_region {
+ rowspan.first_region = current_region;
+ // The rowspan starts at this region, precisely at this
+ // row. In other regions, it will start at dy = 0.
+ rowspan.dy = pos.y;
+ // When we layout the rowspan later, the full size of the
+ // pod must be equal to the full size of the first region
+ // it appears in.
+ rowspan.region_full = self.regions.full;
+ }
+ let amount_missing_heights = (current_region + 1)
+ .saturating_sub(rowspan.heights.len() + rowspan.first_region);
+
+ // Ensure the vector of heights is long enough such that the
+ // last height is the one for the current region.
+ rowspan
+ .heights
+ .extend(std::iter::repeat(Abs::zero()).take(amount_missing_heights));
+
+ // Ensure that, in this region, the rowspan will span at least
+ // this row.
+ *rowspan.heights.last_mut().unwrap() += height;
+
+ if is_last {
+ // Do not extend the rowspan through this row again, even
+ // if it is repeated in a future region.
+ rowspan.max_resolved_row = Some(y);
+ }
+ }
+
+ // We use a for loop over indices to avoid borrow checking
+ // problems (we need to mutate the rowspans vector, so we can't
+ // have an iterator actively borrowing it). We keep a separate
+ // 'i' variable so we can step the counter back after removing
+ // a rowspan (see explanation below).
+ let mut i = 0;
+ while let Some(rowspan) = self.rowspans.get(i) {
+ // Layout any rowspans which end at this row, but only if this is
+ // this row's last frame (to avoid having the rowspan stop being
+ // laid out at the first frame of the row).
+ // Any rowspans ending before this row are laid out even
+ // on this row's first frame.
+ if laid_out_footer_start.map_or(true, |footer_start| {
+ // If this is a footer row, then only lay out this rowspan
+ // if the rowspan is contained within the footer.
+ y < footer_start || rowspan.y >= footer_start
+ }) && (rowspan.y + rowspan.rowspan < y + 1
+ || rowspan.y + rowspan.rowspan == y + 1 && is_last)
+ {
+ // Rowspan ends at this or an earlier row, so we take
+ // it from the rowspans vector and lay it out.
+ // It's safe to pass the current region as a possible
+ // region for the rowspan to be laid out in, even if
+ // the rowspan's last row was at an earlier region,
+ // because the rowspan won't have an entry for this
+ // region in its 'heights' vector if it doesn't span
+ // any rows in this region.
+ //
+ // Here we don't advance the index counter ('i') because
+ // a new element we haven't checked yet in this loop
+ // will take the index of the now removed element, so
+ // we have to check the same index again in the next
+ // iteration.
+ let rowspan = self.rowspans.remove(i);
+ self.layout_rowspan(rowspan, Some((&mut output, &rrows)), engine)?;
+ } else {
+ i += 1;
+ }
+ }
+
+ output.push_frame(pos, frame);
+ rrows.push(RowPiece { height, y });
+ pos.y += height;
+ }
+
+ self.finish_region_internal(output, rrows);
+
+ if !last {
+ let disambiguator = self.finished.len();
+ if let Some(Repeatable::Repeated(footer)) = &self.grid.footer {
+ self.prepare_footer(footer, engine, disambiguator)?;
+ }
+
+ if let Some(Repeatable::Repeated(header)) = &self.grid.header {
+ // Add a header to the new region.
+ self.layout_header(header, engine, disambiguator)?;
+ }
+
+ // Ensure rows don't try to overrun the footer.
+ self.regions.size.y -= self.footer_height;
+ }
+
+ Ok(())
+ }
+
+ /// Advances to the next region, registering the finished output and
+ /// resolved rows for the current region in the appropriate vectors.
+ pub(super) fn finish_region_internal(
+ &mut self,
+ output: Frame,
+ resolved_rows: Vec<RowPiece>,
+ ) {
+ self.finished.push(output);
+ self.rrows.push(resolved_rows);
+ self.regions.next();
+ self.initial = self.regions.size;
+ }
+}
+
+/// Turn an iterator of extents into an iterator of offsets before, in between,
+/// and after the extents, e.g. [10mm, 5mm] -> [0mm, 10mm, 15mm].
+pub(super) fn points(
+ extents: impl IntoIterator<Item = Abs>,
+) -> impl Iterator<Item = Abs> {
+ let mut offset = Abs::zero();
+ std::iter::once(Abs::zero()).chain(extents).map(move |extent| {
+ offset += extent;
+ offset
+ })
+}
+
+/// Checks if the first region of a sequence of regions is the last usable
+/// region, assuming that the last region will always be occupied by some
+/// specific offset height, even after calling `.next()`, due to some
+/// additional logic which adds content automatically on each region turn (in
+/// our case, headers).
+pub(super) fn in_last_with_offset(regions: Regions<'_>, offset: Abs) -> bool {
+ regions.backlog.is_empty()
+ && regions.last.map_or(true, |height| regions.size.y + offset == height)
+}
generated by cgit v1.2.3 (git 2.25.1) at 2026-03-15 11:32:36 +0000