retex_engine/

build.rs

//! Building boxes and lists (*TeX: The Program* §1055–§1135, with e-TeX's
//! and LuaTeX's changes).
//!
//! LuaTeX differences implemented here (established with black-box tests):
//!
//! * a paragraph starts with a local paragraph node (`\localpar`), then
//!   the indentation box;
//! * `\-` takes its pre-break text from the language's `\prehyphenchar`
//!   and its penalty from `\exhyphenpenalty`; `\discretionary` takes
//!   `\hyphenpenalty` (both at the time the node is made) and accepts an
//!   optional `penalty <int>`;
//! * `\hpack`, `\vpack` and `\tpack` build boxes like `\hbox`, `\vbox` and
//!   `\vtop` but without node processing;
//! * the boundary commands append boundary nodes, and start a paragraph in
//!   vertical mode.

use crate::Engine;
use crate::cmd::Cmd;
use crate::eqtb::{Loc, Val};
use crate::glue::{FIL, FILL, Glue};
use crate::input::TokKind;
use crate::maincontrol::{BoxContext, IGNORE_DEPTH, Mode, ModeKind};
use crate::nodes::{BoxData, NodeData, NodeRef, glue_sub, id, kern_sub};
use crate::primitives_gen::{assign_dimen as dp, assign_glue as gp, assign_int as ip};
use crate::save::{GroupCode, SaveEntry};
use crate::scan::ValLevel;
use crate::token::Token;
use crate::typeset::NULL_FLAG;

/// Modifiers (`chr` codes) of list-building commands, LuaTeX numbering.
#[allow(missing_docs)]
pub mod chr {
    pub const BOX: u32 = 0;
    pub const COPY: u32 = 1;
    pub const LAST_BOX: u32 = 2;
    pub const VSPLIT: u32 = 3;
    pub const TPACK: u32 = 4;
    pub const VPACK: u32 = 5;
    pub const HPACK: u32 = 6;
    pub const VTOP: u32 = 7;
    pub const VBOX: u32 = 8;
    pub const HBOX: u32 = 141;
    pub const SHIPOUT: u32 = 98;
    pub const FIL: u32 = 0;
    pub const FILL: u32 = 1;
    pub const SS: u32 = 2;
    pub const FIL_NEG: u32 = 3;
    pub const SKIP: u32 = 4;
    pub const MSKIP: u32 = 5;
    pub const NOINDENT: u32 = 0;
    pub const INDENT: u32 = 1;
    pub const QUITVMODE: u32 = 2;
}

/// The specification of a box being built (`to`/`spread`).
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum PackSpec {
    /// `to <dimen>`.
    Exactly(i32),
    /// `spread <dimen>` (or natural size with 0).
    Additional(i32),
}

impl PackSpec {
    /// The natural size (`natural`).
    pub const NATURAL: PackSpec = PackSpec::Additional(0);
}

const BOX_FLAG: i64 = 1 << 40;
const GLOBAL_BOX_FLAG: i64 = BOX_FLAG + 0x1_0000;
const SHIP_OUT_FLAG: i64 = BOX_FLAG + 0x2_0000;
const LEADER_FLAG: i64 = BOX_FLAG + 0x3_0000;

/// Encodes a box context for the save stack.
pub fn ctx_to_i64(c: BoxContext) -> i64 {
    match c {
        BoxContext::Shift(s) => i64::from(s),
        BoxContext::SetBox(n) => BOX_FLAG + i64::from(n),
        BoxContext::GlobalSetBox(n) => GLOBAL_BOX_FLAG + i64::from(n),
        BoxContext::Shipout => SHIP_OUT_FLAG,
        BoxContext::Leaders(s) => LEADER_FLAG + i64::from(s),
    }
}

/// Decodes a box context from the save stack.
pub fn ctx_from_i64(v: i64) -> BoxContext {
    if v < BOX_FLAG {
        BoxContext::Shift(v as i32)
    } else if v < GLOBAL_BOX_FLAG {
        BoxContext::SetBox((v - BOX_FLAG) as u32)
    } else if v < SHIP_OUT_FLAG {
        BoxContext::GlobalSetBox((v - GLOBAL_BOX_FLAG) as u32)
    } else if v == SHIP_OUT_FLAG {
        BoxContext::Shipout
    } else {
        BoxContext::Leaders((v - LEADER_FLAG) as u16)
    }
}

/// `norm_min`.
pub fn norm_min(h: i32) -> u8 {
    h.clamp(1, 63) as u8
}

impl Engine {
    /// Pushes an auxiliary value (TeX's `saved(0):=v; incr(save_ptr)`).
    pub fn push_saved(&mut self, v: i64) {
        self.save.stack.push(SaveEntry::Value(v));
    }

    /// Pops an auxiliary value.
    pub fn pop_saved(&mut self) -> i64 {
        match self.save.stack.pop() {
            Some(SaveEntry::Value(v)) => v,
            other => {
                if let Some(e) = other {
                    self.save.stack.push(e);
                }
                debug_assert!(false, "save stack out of sync");
                0
            }
        }
    }

    /// The auxiliary value `k` entries below the top (`saved(-1-k)`).
    pub fn peek_saved(&self, k: usize) -> i64 {
        let n = self.save.stack.len();
        match self.save.stack.get(n.wrapping_sub(1 + k)) {
            Some(SaveEntry::Value(v)) => *v,
            _ => 0,
        }
    }

    /// Replaces the auxiliary value `k` entries below the top.
    pub fn set_peek_saved(&mut self, k: usize, v: i64) {
        let n = self.save.stack.len();
        if let Some(SaveEntry::Value(x)) = self.save.stack.get_mut(n.wrapping_sub(1 + k)) {
            *x = v;
        }
    }

    /// A glue node for glue parameter `sub` (`new_param_glue`).
    pub fn new_param_glue(&mut self, sub: u16) -> NodeRef {
        let g = self.eqtb.glue(glue_param_of_subtype(sub));
        self.new_node(
            id::GLUE,
            sub,
            NodeData::Glue {
                spec: g,
                leader: NodeRef::NULL,
            },
        )
    }

    /// A glue node with the given specification.
    pub fn new_glue_node(&mut self, spec: Glue, sub: u16) -> NodeRef {
        self.new_node(
            id::GLUE,
            sub,
            NodeData::Glue {
                spec,
                leader: NodeRef::NULL,
            },
        )
    }

    /// A kern node.
    pub fn new_kern_node(&mut self, w: i32, sub: u16) -> NodeRef {
        self.new_node(
            id::KERN,
            sub,
            NodeData::Kern {
                kern: w,
                expansion_factor: 0,
            },
        )
    }

    /// A penalty node.
    pub fn new_penalty_node(&mut self, m: i32) -> NodeRef {
        self.new_node(id::PENALTY, 0, NodeData::Penalty { penalty: m })
    }

    /// An empty box (`new_null_box`) with the current attributes.
    pub fn new_null_box_node(&mut self, hlist: bool) -> NodeRef {
        let p = self.nodes.new_null_box(hlist);
        if self.eqtb.attrs_in_use {
            let a = self.cur_attr();
            self.nodes.set_attr(p, a);
        }
        p
    }

    /// Commands that build lists and boxes (the cases of `main_control`
    /// not handled in [`crate::maincontrol`]).
    pub fn typeset_command(&mut self) {
        use ModeKind as K;
        let kind = self.mode.abs_kind();
        let cmd = self.cur_cmd;
        match (kind, cmd) {
            // Things that start a paragraph.
            (
                K::Vertical,
                Cmd::Letter
                | Cmd::OtherChar
                | Cmd::CharNum
                | Cmd::CharGiven
                | Cmd::MathShift
                | Cmd::MathShiftCs
                | Cmd::UnHbox
                | Cmd::Vrule
                | Cmd::Accent
                | Cmd::Discretionary
                | Cmd::Hskip
                | Cmd::Valign
                | Cmd::ExSpace
                | Cmd::Boundary
                | Cmd::CharGhost
                | Cmd::MathCharNum
                | Cmd::MathGiven
                | Cmd::XmathGiven,
            ) => {
                self.back_input();
                self.new_graf(true);
            }
            (K::Horizontal, Cmd::MathCharNum | Cmd::MathGiven | Cmd::XmathGiven) => {
                self.math_char_in_text();
            }
            (K::Vertical, Cmd::StartPar) => {
                let c = self.cur_chr;
                self.new_graf(c != chr::NOINDENT);
            }
            (K::Horizontal | K::Math, Cmd::StartPar) => self.indent_in_hmode(),
            (K::Vertical, Cmd::Hrule) | (K::Horizontal | K::Math, Cmd::Vrule) => {
                let r = self.scan_rule_spec();
                self.tail_append(r);
                if kind == K::Vertical {
                    self.cur_list_mut().prev_depth = IGNORE_DEPTH;
                } else if kind == K::Horizontal {
                    self.cur_list_mut().space_factor = 1000;
                }
            }
            (K::Vertical, Cmd::Nohrule) | (K::Horizontal | K::Math, Cmd::Novrule) => {
                let r = self.scan_rule_spec();
                self.nodes.set_subtype(r, 3);
                self.tail_append(r);
                if kind == K::Vertical {
                    self.cur_list_mut().prev_depth = IGNORE_DEPTH;
                } else if kind == K::Horizontal {
                    self.cur_list_mut().space_factor = 1000;
                }
            }
            (K::Vertical, Cmd::Vskip)
            | (K::Horizontal | K::Math, Cmd::Hskip)
            | (K::Math, Cmd::Mskip) => self.append_glue(),
            (_, Cmd::Kern) | (K::Math, Cmd::Mkern) => self.append_kern(),
            (K::Vertical, Cmd::Hmove) | (K::Horizontal | K::Math, Cmd::Vmove) => {
                let t = self.cur_chr;
                self.scan_normal_dimen();
                let v = self.cur_val;
                self.scan_box(BoxContext::Shift(if t == 0 { v } else { -v }));
            }
            (_, Cmd::LeaderShip) => {
                let c = self.cur_chr;
                if c == chr::SHIPOUT {
                    self.scan_box(BoxContext::Shipout);
                } else if c >= glue_sub::A_LEADERS as u32 {
                    self.scan_box(BoxContext::Leaders(c as u16));
                } else {
                    // Other LuaTeX shipping variants are not supported.
                    self.scan_box(BoxContext::Shipout);
                }
            }
            (_, Cmd::MakeBox) => self.begin_box(BoxContext::Shift(0)),
            (K::Vertical, Cmd::ParEnd) => {
                self.normal_paragraph();
                if self.mode.is_privileged() {
                    self.build_page();
                }
            }
            (K::Horizontal, Cmd::ParEnd) => {
                if self.input.align_state < 0 {
                    self.off_save();
                }
                self.end_graf();
                if self.mode == Mode::Vertical {
                    self.build_page();
                }
            }
            (K::Horizontal, Cmd::Stop | Cmd::Vskip | Cmd::Hrule | Cmd::UnVbox | Cmd::Halign) => {
                self.head_for_vmode()
            }
            (_, Cmd::Insert) | (K::Horizontal | K::Math, Cmd::Vadjust) => {
                self.begin_insert_or_adjust()
            }
            (K::Vertical, Cmd::Vadjust) => self.report_illegal_case(),
            (_, Cmd::Mark) => self.make_mark(),
            (_, Cmd::BreakPenalty) => self.append_penalty(),
            (_, Cmd::RemoveItem) => self.delete_last(),
            (K::Vertical, Cmd::UnVbox) | (K::Horizontal | K::Math, Cmd::UnHbox) => self.unpackage(),
            (K::Horizontal, Cmd::ItalCorr) => self.append_italic_correction(),
            (K::Math, Cmd::ItalCorr) => {
                let k = self.new_kern_node(0, kern_sub::USER);
                self.tail_append(k);
            }
            (K::Vertical, Cmd::ItalCorr) => self.report_illegal_case(),
            (K::Horizontal | K::Math, Cmd::Discretionary) => self.append_discretionary(),
            (K::Horizontal, Cmd::Accent) => self.make_accent(),
            (K::Horizontal, Cmd::Boundary) => self.append_boundary(),
            (K::Horizontal, Cmd::CharGhost) => self.append_ghost(),
            (_, Cmd::CarRet | Cmd::TabMark) => self.align_error(),
            (_, Cmd::NoAlign) => self.no_align_error(),
            (_, Cmd::Omit) => self.omit_error(),
            (K::Vertical, Cmd::Halign) | (K::Horizontal, Cmd::Valign) => self.init_align(),
            (K::Math, Cmd::Halign) => {
                if self.privileged() {
                    if self.save.cur_group == GroupCode::MathShift {
                        self.init_align();
                    } else {
                        self.off_save();
                    }
                }
            }
            (K::Vertical | K::Horizontal, Cmd::Endv) => self.do_endv(),
            (_, Cmd::EndCsName) => self.cs_error(),
            (_, Cmd::AssignLocalBox) => self.begin_local_box(),
            (K::Horizontal, Cmd::MathShift | Cmd::MathShiftCs) => self.init_math(),
            (K::Math, _) => self.math_command(),
            (
                K::Vertical | K::Horizontal,
                Cmd::SupMark
                | Cmd::SubMark
                | Cmd::MathComp
                | Cmd::DelimNum
                | Cmd::LeftRight
                | Cmd::Above
                | Cmd::Radical
                | Cmd::MathStyle
                | Cmd::MathChoice
                | Cmd::Vcenter
                | Cmd::NonScript
                | Cmd::Mkern
                | Cmd::LimitSwitch
                | Cmd::Mskip
                | Cmd::MathAccent
                | Cmd::SuperSubScript
                | Cmd::NoSuperSubScript,
            ) => self.insert_dollar_sign(),
            (K::Vertical | K::Horizontal, Cmd::EqNo) => self.report_illegal_case(),
            (_, Cmd::Option) => {
                // \mathoption: scanned and ignored.
                self.scan_int();
                self.scan_optional_equals();
                self.scan_int();
            }
            (_, Cmd::Node) => {
                self.scan_int();
            }
            _ => {
                let (c, r) = (self.cur_cmd, self.cur_chr);
                let s = self.print_to_string(|e| e.print_cmd_chr(c, r));
                self.not_implemented(&String::from_utf8_lossy(&s));
            }
        }
    }

    /// `\hskip`, `\vskip`, `\hfil`, … (`append_glue`).
    pub fn append_glue(&mut self) {
        let s = self.cur_chr;
        let g = match s {
            chr::FIL => Glue {
                stretch: retex_arith::UNITY,
                stretch_order: FIL,
                ..Glue::ZERO
            },
            chr::FILL => Glue {
                stretch: retex_arith::UNITY,
                stretch_order: FILL,
                ..Glue::ZERO
            },
            chr::SS => Glue {
                stretch: retex_arith::UNITY,
                stretch_order: FIL,
                shrink: retex_arith::UNITY,
                shrink_order: FIL,
                ..Glue::ZERO
            },
            chr::FIL_NEG => Glue {
                stretch: -retex_arith::UNITY,
                stretch_order: FIL,
                ..Glue::ZERO
            },
            chr::SKIP => {
                self.scan_glue(ValLevel::Glue);
                self.cur_glue
            }
            _ => {
                self.scan_glue(ValLevel::Mu);
                self.cur_glue
            }
        };
        let sub = if s == chr::MSKIP {
            glue_sub::MU_GLUE
        } else {
            glue_sub::USER
        };
        let p = self.new_glue_node(g, sub);
        self.tail_append(p);
    }

    /// `\kern`, `\mkern` (`append_kern`).
    pub fn append_kern(&mut self) {
        let s = self.cur_chr as u16;
        let mu = s == glue_sub::MU_GLUE;
        self.scan_dimen(mu, false, false);
        let v = self.cur_val;
        let p = self.new_kern_node(
            v,
            if mu {
                glue_sub::MU_GLUE
            } else {
                kern_sub::USER
            },
        );
        self.tail_append(p);
    }

    /// Scans `\hrule`/`\vrule` dimensions (`scan_rule_spec`).
    pub fn scan_rule_spec(&mut self) -> NodeRef {
        let vertical_rule = matches!(self.cur_cmd, Cmd::Vrule | Cmd::Novrule);
        let (mut w, mut h, mut d) = if vertical_rule {
            (26214, NULL_FLAG, NULL_FLAG)
        } else {
            (NULL_FLAG, 26214, 0)
        };
        let (mut left, mut right) = (0, 0);
        loop {
            if self.scan_keyword("width") {
                self.scan_normal_dimen();
                w = self.cur_val;
                continue;
            }
            if self.scan_keyword("height") {
                self.scan_normal_dimen();
                h = self.cur_val;
                continue;
            }
            if self.scan_keyword("depth") {
                self.scan_normal_dimen();
                d = self.cur_val;
                continue;
            }
            if self.scan_keyword("left") {
                self.scan_normal_dimen();
                left = self.cur_val;
                continue;
            }
            if self.scan_keyword("right") {
                self.scan_normal_dimen();
                right = self.cur_val;
                continue;
            }
            break;
        }
        self.new_node(
            id::RULE,
            0,
            NodeData::Rule {
                width: w,
                depth: d,
                height: h,
                dir: 0,
                index: 0,
                left,
                right,
            },
        )
    }

    /// Scans a box specification and pushes it with a new group
    /// (`scan_spec`); `ctx` is the box context to save, if any.
    pub fn scan_spec(&mut self, c: GroupCode, ctx: Option<i64>) {
        // LuaTeX accepts `attr <n> <v>` and one direction before
        // to/spread: `dir <TLT…>` or `bdir <number>` (observed: a number
        // outside 0..3 means TLT; a second direction is not a keyword).
        let mut dir: i64 = -1;
        loop {
            if self.scan_keyword("attr") {
                self.scan_register_num();
                self.scan_optional_equals();
                self.scan_int();
                continue;
            }
            if dir < 0 && self.scan_keyword("dir") {
                dir = i64::from(self.scan_direction_spec());
                continue;
            }
            if dir < 0 && self.scan_keyword("bdir") {
                self.scan_int();
                dir = if (0..=3).contains(&self.cur_val) {
                    i64::from(self.cur_val)
                } else {
                    0
                };
                continue;
            }
            break;
        }
        let is_box = matches!(
            c,
            GroupCode::Hbox | GroupCode::AdjustedHbox | GroupCode::Vbox | GroupCode::Vtop
        );
        if dir < 0 && is_box {
            dir = i64::from(self.default_box_dir());
        }
        let spec = if self.scan_keyword("to") {
            self.scan_normal_dimen();
            PackSpec::Exactly(self.cur_val)
        } else if self.scan_keyword("spread") {
            self.scan_normal_dimen();
            PackSpec::Additional(self.cur_val)
        } else {
            PackSpec::NATURAL
        };
        if let Some(v) = ctx {
            self.push_saved(v);
        }
        let (code, v) = match spec {
            PackSpec::Exactly(v) => (0, v),
            PackSpec::Additional(v) => (1, v),
        };
        self.push_saved(code);
        self.push_saved(i64::from(v));
        self.push_saved(dir);
        self.new_save_level(c);
        self.begin_box_dirs(c, dir as i32);
        self.scan_left_brace();
    }

    /// Pops the specification pushed by `scan_spec` (for `\vcenter`).
    pub fn pop_spec_pub(&mut self) -> (PackSpec, i64) {
        self.pop_spec()
    }

    /// Pops the specification pushed by `scan_spec`: (spec, dir).
    fn pop_spec(&mut self) -> (PackSpec, i64) {
        let dir = self.pop_saved();
        let v = self.pop_saved() as i32;
        let code = self.pop_saved();
        (
            if code == 0 {
                PackSpec::Exactly(v)
            } else {
                PackSpec::Additional(v)
            },
            dir,
        )
    }

    /// Scans a box and builds it in context `ctx` (`scan_box`).
    pub fn scan_box(&mut self, ctx: BoxContext) {
        self.get_nonblank_nonrelax_noncall();
        if self.cur_cmd == Cmd::MakeBox {
            self.begin_box(ctx);
        } else if matches!(ctx, BoxContext::Leaders(_))
            && matches!(
                self.cur_cmd,
                Cmd::Hrule | Cmd::Vrule | Cmd::Nohrule | Cmd::Novrule
            )
        {
            let r = self.scan_rule_spec();
            self.box_end(ctx, r);
        } else {
            self.print_err("A <box> was supposed to be here");
            self.help(&[
                "I was expecting to see \\hbox or \\vbox or \\copy or \\box or",
                "something like that. So you might find something missing in",
                "your output. But keep trying; you can fix this later.",
            ]);
            self.back_error();
        }
    }

    /// Starts building a box of the kind given by `cur_chr`, or fetches a
    /// box register (`begin_box`).
    pub fn begin_box(&mut self, ctx: BoxContext) {
        let cur_box: NodeRef;
        match self.cur_chr {
            chr::BOX => {
                self.scan_register_num();
                let n = self.cur_val as usize;
                cur_box = self.eqtb.boxes[n].val;
                self.eqtb.boxes[n].val = NodeRef::NULL;
            }
            chr::COPY => {
                self.scan_register_num();
                let b = self.eqtb.boxes[self.cur_val as usize].val;
                cur_box = self.copy_node_list(b);
            }
            chr::LAST_BOX => {
                cur_box = self.take_last_box();
            }
            chr::VSPLIT => {
                self.scan_register_num();
                let n = self.cur_val as u32;
                if !self.scan_keyword("to") {
                    self.print_err("Missing `to' inserted");
                    self.help(&[
                        "I'm working on `\\vsplit<box number> to <dimen>';",
                        "will look for the <dimen> next.",
                    ]);
                    self.error();
                }
                self.scan_normal_dimen();
                let h = self.cur_val;
                cur_box = self.vsplit(n, h);
            }
            c => {
                // Initiate the construction of an hbox or vbox.
                let k = match c {
                    chr::HBOX | chr::HPACK => ModeKind::Horizontal,
                    _ => ModeKind::Vertical,
                };
                let ctxv = ctx_to_i64(ctx);
                // The packing variant is remembered with the context.
                self.push_saved(i64::from(c));
                if k == ModeKind::Horizontal {
                    if matches!(ctx, BoxContext::Shift(_))
                        && self.mode.abs_kind() == ModeKind::Vertical
                    {
                        self.scan_spec(GroupCode::AdjustedHbox, Some(ctxv));
                    } else {
                        self.scan_spec(GroupCode::Hbox, Some(ctxv));
                    }
                } else {
                    if c == chr::VBOX || c == chr::VPACK {
                        self.scan_spec(GroupCode::Vbox, Some(ctxv));
                    } else {
                        self.scan_spec(GroupCode::Vtop, Some(ctxv));
                    }
                    self.normal_paragraph();
                }
                if k == ModeKind::Vertical {
                    self.push_nest(Mode::InternalVertical);
                    self.cur_list_mut().prev_depth = IGNORE_DEPTH;
                    let t = self
                        .eqtb
                        .toks_param(crate::primitives_gen::assign_toks::EVERYVBOX)
                        .clone();
                    if !t.is_empty() {
                        self.begin_token_list(t, TokKind::EveryVboxText);
                    }
                } else {
                    self.push_nest(Mode::RestrictedHorizontal);
                    self.cur_list_mut().space_factor = 1000;
                    let t = self
                        .eqtb
                        .toks_param(crate::primitives_gen::assign_toks::EVERYHBOX)
                        .clone();
                    if !t.is_empty() {
                        self.begin_token_list(t, TokKind::EveryHboxText);
                    }
                }
                return;
            }
        }
        self.box_end(ctx, cur_box);
    }

    /// Copies a node list (`copy_node_list`).
    pub fn copy_node_list(&mut self, p: NodeRef) -> NodeRef {
        if p.is_null() {
            return p;
        }
        self.nodes.copy_node(p)
    }

    /// `\lastbox`: removes the last box from the current list.
    fn take_last_box(&mut self) -> NodeRef {
        if self.mode.abs_kind() == ModeKind::Math {
            self.you_cant();
            self.help(&["Sorry; this \\lastbox will be void."]);
            self.error();
            return NodeRef::NULL;
        }
        let (head, tail) = (self.cur_list().head, self.cur_list().tail);
        if self.mode == Mode::Vertical && head == tail {
            self.you_cant();
            self.help(&[
                "Sorry...I usually can't take things from the current page.",
                "This \\lastbox will therefore be void.",
            ]);
            self.error();
            return NodeRef::NULL;
        }
        if tail == head {
            return NodeRef::NULL;
        }
        let t = self.nodes.id(tail);
        if t != id::HLIST && t != id::VLIST {
            return NodeRef::NULL;
        }
        let p = self.nodes.prev(tail);
        let p = if p.is_null() { self.find_prev(tail) } else { p };
        self.nodes.set_next(p, NodeRef::NULL);
        self.nodes.set_prev(tail, NodeRef::NULL);
        self.cur_list_mut().tail = p;
        if let Some(b) = self.nodes.box_data_mut(tail) {
            b.shift = 0;
        }
        tail
    }

    /// Finds the predecessor of `q` in the current list by a linear scan.
    fn find_prev(&self, q: NodeRef) -> NodeRef {
        let mut p = self.cur_list().head;
        while !p.is_null() {
            let n = self.nodes.next(p);
            if n == q {
                return p;
            }
            p = n;
        }
        self.cur_list().head
    }

    /// Does the right thing with a finished box (`box_end`).
    pub fn box_end(&mut self, ctx: BoxContext, cur_box: NodeRef) {
        match ctx {
            BoxContext::Shift(s) => {
                if cur_box.is_null() {
                    return;
                }
                if let Some(b) = self.nodes.box_data_mut(cur_box) {
                    b.shift = s;
                }
                match self.mode.abs_kind() {
                    ModeKind::Vertical => {
                        self.append_box_with_adjustments(cur_box);
                        if self.mode.is_privileged() {
                            self.build_page();
                        }
                    }
                    ModeKind::Horizontal => {
                        self.cur_list_mut().space_factor = 1000;
                        self.tail_append(cur_box);
                    }
                    _ => {
                        self.math_box_end(cur_box);
                    }
                }
            }
            BoxContext::SetBox(n) => self.set_box_register(n, false, cur_box),
            BoxContext::GlobalSetBox(n) => self.set_box_register(n, true, cur_box),
            BoxContext::Shipout => {
                if !cur_box.is_null() {
                    self.ship_out(cur_box);
                }
            }
            BoxContext::Leaders(sub) => {
                if cur_box.is_null() {
                    return;
                }
                self.get_nonblank_nonrelax_noncall();
                let v = self.mode.abs_kind() == ModeKind::Vertical;
                if (self.cur_cmd == Cmd::Hskip && !v) || (self.cur_cmd == Cmd::Vskip && v) {
                    self.append_glue();
                    let t = self.cur_list().tail;
                    self.nodes.set_subtype(t, sub);
                    if let NodeData::Glue { leader, .. } = self.nodes.data_mut(t) {
                        *leader = cur_box;
                    }
                } else {
                    self.print_err("Leaders not followed by proper glue");
                    self.help(&[
                        "You should say `\\leaders <box or rule><hskip or vskip>'.",
                        "I found the <box or rule>, but there's no suitable",
                        "<hskip or vskip>, so I'm ignoring these leaders.",
                    ]);
                    self.back_error();
                    self.nodes.flush_list(cur_box);
                }
            }
        }
    }

    /// Starts collecting `\vadjust` and `\insert` material in `hpack`
    /// (TeX's `adjust_tail:=adjust_head`).
    pub fn start_adjust_lists(&mut self) {
        if self.ts.adjust_head.is_null() {
            self.ts.adjust_head = self.nodes.new_temp();
            self.ts.pre_adjust_head = self.nodes.new_temp();
        }
        self.nodes.set_next(self.ts.adjust_head, NodeRef::NULL);
        self.nodes.set_next(self.ts.pre_adjust_head, NodeRef::NULL);
        self.ts.adjust_tail = Some(self.ts.adjust_head);
        self.ts.pre_adjust_tail = Some(self.ts.pre_adjust_head);
    }

    /// Appends the material of one adjustment list to the current list.
    fn append_adjust_list(&mut self, head: NodeRef) {
        let first = self.nodes.next(head);
        if first.is_null() {
            return;
        }
        let tail = self.cur_list().tail;
        self.nodes.link(tail, first);
        let t = self.nodes.tail_of(first);
        self.cur_list_mut().tail = t;
        self.nodes.set_next(head, NodeRef::NULL);
    }

    /// Appends a box to a vertical list with the adjustment material that
    /// `hpack` removed from it (§1076).
    fn append_box_with_adjustments(&mut self, b: NodeRef) {
        let active = self.ts.adjust_tail.is_some();
        if active {
            let h = self.ts.pre_adjust_head;
            self.append_adjust_list(h);
        }
        self.append_to_vlist(b);
        if active {
            let h = self.ts.adjust_head;
            self.append_adjust_list(h);
        }
        self.ts.adjust_tail = None;
        self.ts.pre_adjust_tail = None;
    }

    /// Stores a box in a register, freeing the old contents when they are
    /// not saved for restoration.
    pub fn set_box_register(&mut self, n: u32, global: bool, b: NodeRef) {
        let old = self.eqtb.boxes[n as usize].val;
        let old_level = self.eqtb.boxes[n as usize].level;
        let saved = !global && old_level != self.save.cur_level && self.save.cur_level > 1;
        self.define(global, Loc::Box(n), Val::Node(b));
        if !saved && !old.is_null() && old != b {
            self.nodes.flush_list(old);
        }
    }

    /// Finishes an `\hbox`, `\vbox` or `\vtop` (`package`).
    fn package(&mut self, vtop: bool) {
        let d = self.eqtb.dimen(dp::BOXMAXDEPTH);
        let group = self.save.cur_group;
        self.unsave();
        self.end_box_dirs();
        let (spec, dir) = self.pop_spec();
        let ctx = ctx_from_i64(self.pop_saved());
        let kind = self.pop_saved() as u32;
        let head = self.cur_list().head;
        let first = self.nodes.next(head);
        self.nodes.set_next(head, NodeRef::NULL);
        let cur_box = if self.mode == Mode::RestrictedHorizontal {
            let first = if kind == chr::HPACK {
                first
            } else {
                let first = self.node_process_list(first, crate::nodeproc::Context::Hbox);
                let g = if group == GroupCode::AdjustedHbox {
                    "adjusted_hbox"
                } else {
                    "hbox"
                };
                self.filter_list("hpack_filter", first, g)
            };
            self.pack_dir = dir as i8;
            self.hpack(first, spec)
        } else {
            let first = if kind == chr::VPACK || kind == chr::TPACK {
                first
            } else {
                self.filter_list("vpack_filter", first, if vtop { "vtop" } else { "vbox" })
            };
            self.pack_dir = dir as i8;
            let b = self.vpackage(first, spec, d);
            if vtop {
                // Readjust the height and depth for \vtop.
                let p = self.nodes.list_ptr(b);
                let h = if !p.is_null() && self.nodes.id(p) <= id::RULE {
                    self.node_height(p)
                } else {
                    0
                };
                if let Some(bd) = self.nodes.box_data_mut(b) {
                    bd.depth = bd.depth - h + bd.height;
                    bd.height = h;
                }
            }
            b
        };
        if self.nodes.id(cur_box) == id::HLIST {
            self.nodes.set_subtype(cur_box, 2);
        }
        self.pop_nest();
        self.box_end(ctx, cur_box);
    }

    /// The height of a box or rule node.
    pub fn node_height(&self, p: NodeRef) -> i32 {
        match self.nodes.data(p) {
            NodeData::Box(b) => b.height,
            NodeData::Unset { b, .. } => b.height,
            NodeData::Rule { height, .. } => *height,
            _ => 0,
        }
    }

    /// The depth of a box or rule node.
    pub fn node_depth(&self, p: NodeRef) -> i32 {
        match self.nodes.data(p) {
            NodeData::Box(b) => b.depth,
            NodeData::Unset { b, .. } => b.depth,
            NodeData::Rule { depth, .. } => *depth,
            _ => 0,
        }
    }

    /// Makes a local paragraph node with the current local parameters.
    pub fn new_local_par(&mut self) -> NodeRef {
        let lb = self.eqtb.local_box[0].val;
        let rb = self.eqtb.local_box[1].val;
        let box_left = self.copy_node_list(lb);
        let box_right = self.copy_node_list(rb);
        let box_left_width = if lb.is_null() {
            0
        } else {
            self.nodes.width(lb)
        };
        let box_right_width = if rb.is_null() {
            0
        } else {
            self.nodes.width(rb)
        };
        let dir = self.dir_param(crate::primitives_gen::assign_dir::PARDIR) as i8;
        self.new_node(
            id::LOCAL_PAR,
            0,
            NodeData::LocalPar {
                pen_inter: self.eqtb.int(ip::LOCALINTERLINEPENALTY),
                pen_broken: self.eqtb.int(ip::LOCALBROKENPENALTY),
                dir,
                box_left,
                box_left_width,
                box_right,
                box_right_width,
            },
        )
    }

    /// Starts a paragraph (`new_graf`).
    pub fn new_graf(&mut self, indented: bool) {
        self.cur_list_mut().prev_graf = 0;
        let (head, tail) = (self.cur_list().head, self.cur_list().tail);
        if self.mode == Mode::Vertical || head != tail {
            let g = self.new_param_glue(glue_sub::PAR_SKIP);
            self.tail_append(g);
        }
        self.push_nest(Mode::Horizontal);
        self.cur_list_mut().space_factor = 1000;
        let l = self.cur_lang() as i32;
        self.cur_list_mut().clang = l;
        let lp = self.new_local_par();
        self.tail_append(lp);
        self.par_text_dir();
        if indented {
            let b = self.new_null_box_node(true);
            let w = self.eqtb.dimen(dp::PARINDENT);
            let dir = self.dir_param(crate::primitives_gen::assign_dir::PARDIR) as i8;
            if let Some(bd) = self.nodes.box_data_mut(b) {
                bd.width = w;
                bd.dir = dir;
            }
            self.nodes.set_subtype(b, 3);
            self.tail_append(b);
        }
        let t = self
            .eqtb
            .toks_param(crate::primitives_gen::assign_toks::EVERYPAR)
            .clone();
        if !t.is_empty() {
            self.begin_token_list(t, TokKind::EveryParText);
        }
        if self.nest.len() == 2 {
            self.build_page();
        }
    }

    /// `\indent` in horizontal or math mode (`indent_in_hmode`).
    fn indent_in_hmode(&mut self) {
        if self.cur_chr == chr::INDENT {
            let b = self.new_null_box_node(true);
            let w = self.eqtb.dimen(dp::PARINDENT);
            if let Some(bd) = self.nodes.box_data_mut(b) {
                bd.width = w;
            }
            if self.mode.abs_kind() == ModeKind::Horizontal {
                self.cur_list_mut().space_factor = 1000;
                self.tail_append(b);
            } else {
                self.math_box_end(b);
            }
        }
    }

    /// Commands that end a paragraph in horizontal mode
    /// (`head_for_vmode`).
    fn head_for_vmode(&mut self) {
        if self.mode.is_inner() {
            if self.cur_cmd != Cmd::Hrule {
                self.off_save();
            } else {
                self.print_err("You can't use `");
                self.print_esc_str("hrule");
                self.printer.print_str("' here except with leaders");
                self.help(&[
                    "To put a horizontal rule in an hbox or an alignment,",
                    "you should use \\leaders or \\hrulefill (see The TeXbook).",
                ]);
                self.error();
            }
        } else {
            self.back_input();
            self.cur_tok = Token::cs(self.par_token_cs);
            self.back_input();
            if let Some(crate::input::Level::Tokens(t)) = self.input.stack.last_mut() {
                t.kind = TokKind::Inserted;
            }
        }
    }

    /// Ends a paragraph (`end_graf`).
    pub fn end_graf(&mut self) {
        if self.mode == Mode::Horizontal {
            let (head, tail) = (self.cur_list().head, self.cur_list().tail);
            // A paragraph holding nothing but its \localpar node is empty
            // too: LuaTeX discards it.
            let only_local_par = self.nodes.next(head) == tail
                && matches!(self.nodes.data(tail), NodeData::LocalPar { .. });
            if head == tail || only_local_par {
                self.nodes.flush_list(tail);
                self.pop_nest();
            } else {
                let wp = self.eqtb.int(ip::WIDOWPENALTY);
                self.line_break(wp);
            }
            self.normal_paragraph();
            self.err.error_count = 0;
        }
    }

    /// Resets paragraph shape parameters (`normal_paragraph`).
    pub fn normal_paragraph(&mut self) {
        use crate::primitives_gen::set_etex_shape as es;
        if self.eqtb.int(ip::LOOSENESS) != 0 {
            self.eq_define(Loc::IntPar(ip::LOOSENESS), Val::Int(0));
        }
        if self.eqtb.dimen(dp::HANGINDENT) != 0 {
            self.eq_define(Loc::DimenPar(dp::HANGINDENT), Val::Int(0));
        }
        if self.eqtb.int(ip::HANGAFTER) != 1 {
            self.eq_define(Loc::IntPar(ip::HANGAFTER), Val::Int(1));
        }
        if self.eqtb.par_shape.val.is_some() {
            self.eq_define(Loc::ParShape, Val::Shape(None));
        }
        if self.eqtb.etex_shape[es::INTERLINEPENALTIES as usize]
            .val
            .is_some()
        {
            self.eq_define(Loc::EtexShape(es::INTERLINEPENALTIES), Val::Shape(None));
        }
    }

    /// `\insert` and `\vadjust` (`begin_insert_or_adjust`).
    fn begin_insert_or_adjust(&mut self) {
        let v: i64 = if self.cur_cmd == Cmd::Vadjust {
            let pre = self.scan_keyword("pre");
            if pre { -2 } else { -1 }
        } else {
            self.scan_register_num();
            let mut n = self.cur_val;
            if n == self.output_box_num() {
                self.print_err("You can't ");
                self.print_esc_str("insert");
                self.printer.print_int(i64::from(n));
                self.help(&["I'm changing to \\insert0; box \\outputbox is special."]);
                self.error();
                n = 0;
            }
            i64::from(n)
        };
        self.push_saved(v);
        self.new_save_level(GroupCode::Insert);
        self.scan_left_brace();
        self.normal_paragraph();
        self.push_nest(Mode::InternalVertical);
        self.cur_list_mut().prev_depth = IGNORE_DEPTH;
    }

    /// The box register used by the output routine (`\outputbox`).
    pub fn output_box_num(&self) -> i32 {
        let n = self.eqtb.int(ip::OUTPUTBOX);
        if (0..65536).contains(&n) { n } else { 255 }
    }

    /// Ends an insertion or adjustment group (§1100).
    fn finish_insert_group(&mut self) {
        self.end_graf();
        let q = self.eqtb.glue(gp::SPLITTOPSKIP);
        let d = self.eqtb.dimen(dp::SPLITMAXDEPTH);
        let f = self.eqtb.int(ip::FLOATINGPENALTY);
        self.unsave();
        let n = self.pop_saved();
        let head = self.cur_list().head;
        let first = self.nodes.next(head);
        self.nodes.set_next(head, NodeRef::NULL);
        let p = self.vpack(first, PackSpec::NATURAL);
        self.pop_nest();
        let list = self.nodes.list_ptr(p);
        self.nodes.set_list_ptr(p, NodeRef::NULL);
        let (h, dd) = match self.nodes.box_data(p) {
            Some(b) => (b.height, b.depth),
            None => (0, 0),
        };
        if n >= 0 {
            let node = self.new_node(
                id::INS,
                n as u16,
                NodeData::Ins {
                    cost: f,
                    depth: d,
                    height: h + dd,
                    spec: q,
                    head: list,
                },
            );
            self.tail_append(node);
        } else {
            let node = self.new_node(
                id::ADJUST,
                if n == -2 { 1 } else { 0 },
                NodeData::Adjust { head: list },
            );
            self.tail_append(node);
        }
        self.nodes.free(p);
        if self.nest.len() == 1 {
            self.build_page();
        }
    }

    /// `\mark`, `\marks` (`make_mark`).
    fn make_mark(&mut self) {
        let c: u32 = if self.cur_chr == 0 {
            0
        } else if self.cur_chr == 1 {
            // \clearmarks n
            self.scan_register_num();
            let n = self.cur_val as u32;
            self.marks.classes.remove(&n);
            return;
        } else {
            self.scan_register_num();
            self.cur_val as u32
        };
        let toks = self.scan_toks_expanded();
        let p = self.new_node(
            id::MARK,
            0,
            NodeData::Mark {
                class: c,
                mark: std::rc::Rc::from(toks),
            },
        );
        self.tail_append(p);
    }

    /// `\penalty` (`append_penalty`).
    fn append_penalty(&mut self) {
        self.scan_int();
        let p = self.new_penalty_node(self.cur_val);
        self.tail_append(p);
        if self.mode == Mode::Vertical {
            self.build_page();
        }
    }

    /// `\unskip`, `\unkern`, `\unpenalty` (`delete_last`).
    fn delete_last(&mut self) {
        let (head, tail) = (self.cur_list().head, self.cur_list().tail);
        let want = self.cur_chr as u8;
        if self.mode == Mode::Vertical && tail == head {
            // Apologize, unless \unskip follows non-glue.
            if want != id::GLUE || self.page.last_glue.is_some() {
                self.you_cant();
                let l0 = if want == id::KERN {
                    "Try `I\\kern-\\lastkern' instead."
                } else if want != id::GLUE {
                    "Perhaps you can make the output routine do it."
                } else {
                    "Try `I\\vskip-\\lastskip' instead."
                };
                self.help(&[
                    "Sorry...I usually can't take things from the current page.",
                    l0,
                ]);
                self.error();
            }
            return;
        }
        if tail == head || self.nodes.id(tail) != want {
            return;
        }
        let p = self.find_prev(tail);
        self.nodes.set_next(p, NodeRef::NULL);
        self.nodes.flush_list(tail);
        self.cur_list_mut().tail = p;
    }

    /// `\unhbox`, `\unvbox`, `\unhcopy`, `\unvcopy`, `\pagediscards`,
    /// `\splitdiscards` (`unpackage`).
    fn unpackage(&mut self) {
        let c = self.cur_chr;
        if c > chr::COPY {
            // \pagediscards (2), \splitdiscards (3).
            let k = c as usize;
            let p = self.ts.disc_ptr[k];
            self.ts.disc_ptr[k] = NodeRef::NULL;
            if !p.is_null() {
                let tail = self.cur_list().tail;
                self.nodes.link(tail, p);
                let t = self.nodes.tail_of(p);
                self.cur_list_mut().tail = t;
            }
            return;
        }
        self.scan_register_num();
        let n = self.cur_val as usize;
        let p = self.eqtb.boxes[n].val;
        if p.is_null() {
            return;
        }
        let t = self.nodes.id(p);
        let k = self.mode.abs_kind();
        if k == ModeKind::Math
            || (k == ModeKind::Vertical && t != id::VLIST)
            || (k == ModeKind::Horizontal && t != id::HLIST)
        {
            self.print_err("Incompatible list can't be unboxed");
            self.help(&[
                "Sorry, Pandora. (You sneaky devil.)",
                "I refuse to unbox an \\hbox in vertical mode or vice versa.",
                "And I can't open any boxes in math mode.",
            ]);
            self.error();
            return;
        }
        let list = if c == chr::COPY {
            let l = self.nodes.list_ptr(p);
            self.nodes.copy_list(l)
        } else {
            let l = self.nodes.list_ptr(p);
            self.nodes.set_list_ptr(p, NodeRef::NULL);
            self.eqtb.boxes[n].val = NodeRef::NULL;
            self.nodes.free(p);
            l
        };
        let list = if t == id::HLIST {
            self.strip_margin_kerns(list)
        } else {
            list
        };
        if !list.is_null() {
            let tail = self.cur_list().tail;
            self.nodes.link(tail, list);
            let t = self.nodes.tail_of(list);
            self.cur_list_mut().tail = t;
        }
    }

    /// `\/` (`append_italic_correction`).
    fn append_italic_correction(&mut self) {
        let (head, tail) = (self.cur_list().head, self.cur_list().tail);
        if tail == head {
            return;
        }
        let Some(g) = self.nodes.glyph(tail) else {
            return;
        };
        let (f, c) = (g.font, g.chr);
        let ic = self.font_char_dimen(f, c, 3);
        let k = self.new_kern_node(ic, kern_sub::ITALIC);
        self.tail_append(k);
    }

    /// `\-` and `\discretionary` (`append_discretionary`).
    fn append_discretionary(&mut self) {
        let c = self.cur_chr;
        if c == 1 {
            // \- : LuaTeX's explicit discretionary.
            let pen = self.eqtb.int(ip::EXHYPHENPENALTY);
            let d = self.new_node(
                id::DISC,
                1,
                NodeData::Disc {
                    pre: NodeRef::NULL,
                    post: NodeRef::NULL,
                    replace: NodeRef::NULL,
                    penalty: pen,
                },
            );
            let lang = self.cur_lang();
            let (pre_c, post_c) = {
                let l = self.lang_params(lang);
                (l.pre_hyphen_char, l.post_hyphen_char)
            };
            let f = self.eqtb.cur_font.val;
            let pre = if pre_c > 0 {
                self.new_char_node(f, pre_c as u32)
            } else {
                NodeRef::NULL
            };
            let post = if post_c > 0 {
                self.new_char_node(f, post_c as u32)
            } else {
                NodeRef::NULL
            };
            self.nodes.set_disc_lists(d, (pre, post, NodeRef::NULL));
            self.tail_append(d);
            return;
        }
        let mut pen = self.eqtb.int(ip::HYPHENPENALTY);
        if self.scan_keyword("penalty") {
            self.scan_int();
            pen = self.cur_val;
        }
        let d = self.new_node(
            id::DISC,
            if c == 2 { 2 } else { 0 },
            NodeData::Disc {
                pre: NodeRef::NULL,
                post: NodeRef::NULL,
                replace: NodeRef::NULL,
                penalty: pen,
            },
        );
        self.tail_append(d);
        self.push_saved(0);
        self.new_save_level(GroupCode::Disc);
        self.scan_left_brace();
        self.push_nest(Mode::RestrictedHorizontal);
        self.cur_list_mut().space_factor = 1000;
    }

    /// Handles the end of a discretionary sublist
    /// (`build_discretionary`).
    fn build_discretionary(&mut self) {
        self.unsave();
        // Prune the current list to glyphs, kerns, boxes and rules.
        let head = self.cur_list().head;
        let mut q = head;
        let mut p = self.nodes.next(q);
        while !p.is_null() {
            let t = self.nodes.id(p);
            if !matches!(t, id::GLYPH | id::KERN | id::HLIST | id::VLIST | id::RULE) {
                self.print_err("Improper discretionary list");
                self.help(&["Discretionary lists must contain only boxes and kerns."]);
                self.error();
                self.begin_diagnostic();
                self.printer
                    .print_nl("The following discretionary sublist has been deleted:");
                self.show_box(p);
                self.end_diagnostic(true);
                self.nodes.flush_list(p);
                self.nodes.set_next(q, NodeRef::NULL);
                break;
            }
            q = p;
            p = self.nodes.next(q);
        }
        let list = self.nodes.next(head);
        self.nodes.set_next(head, NodeRef::NULL);
        if !list.is_null() {
            self.nodes.set_prev(list, NodeRef::NULL);
        }
        self.pop_nest();
        let k = self.pop_saved();
        let d = self.cur_list().tail;
        let (mut pre, mut post, mut rep) = self.nodes.disc_lists(d);
        match k {
            0 => pre = list,
            1 => post = list,
            _ => {
                if !list.is_null() && self.mode.abs_kind() == ModeKind::Math {
                    self.print_err("Illegal math ");
                    self.print_esc_str("discretionary");
                    self.help(&[
                        "Sorry: The third part of a discretionary break must be",
                        "empty, in math formulas. I had to delete your third part.",
                    ]);
                    self.nodes.flush_list(list);
                    self.error();
                } else {
                    rep = list;
                }
                self.nodes.set_disc_lists(d, (pre, post, rep));
                return;
            }
        }
        self.nodes.set_disc_lists(d, (pre, post, rep));
        self.push_saved(k + 1);
        self.new_save_level(GroupCode::Disc);
        self.scan_left_brace();
        self.push_nest(Mode::RestrictedHorizontal);
        self.cur_list_mut().space_factor = 1000;
    }

    /// `\accent` (`make_accent`).
    fn make_accent(&mut self) {
        self.scan_char_num();
        let f = self.eqtb.cur_font.val;
        let p = self.new_char_node(f, self.cur_val as u32);
        let x = self.x_height(f);
        let s = f64::from(self.font(f).params.get(1).copied().unwrap_or(0)) / 65536.0;
        let a = self.char_width(f, self.cur_val as u32);
        self.do_assignments();
        let mut q = NodeRef::NULL;
        let f2 = self.eqtb.cur_font.val;
        if matches!(self.cur_cmd, Cmd::Letter | Cmd::OtherChar | Cmd::CharGiven) {
            q = self.new_char_node(f2, self.cur_chr);
        } else if self.cur_cmd == Cmd::CharNum {
            self.scan_char_num();
            q = self.new_char_node(f2, self.cur_val as u32);
        } else {
            self.back_input();
        }
        let mut p = p;
        if !q.is_null() {
            let t = f64::from(self.font(f2).params.get(1).copied().unwrap_or(0)) / 65536.0;
            let qc = self.nodes.glyph(q).map_or(0, |g| g.chr);
            let w = self.char_width(f2, qc);
            let h = self.font_char_dimen(f2, qc, 1);
            if h != x {
                p = self.hpack(p, PackSpec::NATURAL);
                if let Some(b) = self.nodes.box_data_mut(p) {
                    b.shift = x - h;
                }
            }
            let delta =
                ((f64::from(w - a)) / 2.0 + f64::from(h) * t - f64::from(x) * s).round() as i32;
            let r = self.new_kern_node(delta, kern_sub::ACCENT);
            self.tail_append(r);
            self.tail_append(p);
            let k = self.new_kern_node(-a - delta, kern_sub::ACCENT);
            self.tail_append(k);
            p = q;
        }
        self.tail_append(p);
        self.cur_list_mut().space_factor = 1000;
    }

    /// The width of character `c` in font `f` (0 if absent).
    #[inline]
    pub fn char_width(&self, f: u32, c: u32) -> i32 {
        self.font(f).chars.get(&c).map_or(0, |m| m.width)
    }

    /// Executes assignments until a non-assignment (`do_assignments`).
    pub fn do_assignments(&mut self) {
        loop {
            self.get_nonblank_nonrelax_noncall();
            if self.cur_cmd <= Cmd::MAX_NON_PREFIXED {
                return;
            }
            self.err.set_box_allowed = false;
            self.prefixed_command();
            self.err.set_box_allowed = true;
        }
    }

    /// `\boundary`, `\noboundary`, `\protrusionboundary`,
    /// `\wordboundary`.
    pub fn append_boundary(&mut self) {
        let c = self.cur_chr;
        let v = if c == 1 || c == 2 {
            self.scan_int();
            self.cur_val
        } else {
            0
        };
        let p = self.new_node(id::BOUNDARY, c as u16, NodeData::Boundary { value: v });
        self.tail_append(p);
    }

    /// `\leftghost`, `\rightghost`.
    fn append_ghost(&mut self) {
        let right = self.cur_chr == 1;
        self.scan_char_num();
        let f = self.eqtb.cur_font.val;
        let g = self.new_char_node(f, self.cur_val as u32);
        let sub = crate::nodes::glyph_sub::GHOST
            | if right {
                crate::nodes::glyph_sub::RIGHT
            } else {
                crate::nodes::glyph_sub::LEFT
            };
        self.nodes.set_subtype(g, sub);
        self.tail_append(g);
    }

    /// `\localleftbox{…}`, `\localrightbox{…}`.
    fn begin_local_box(&mut self) {
        let k = self.cur_chr;
        self.push_saved(i64::from(k));
        self.new_save_level(GroupCode::LocalBox);
        self.scan_left_brace();
        self.push_nest(Mode::RestrictedHorizontal);
        self.cur_list_mut().space_factor = 1000;
    }

    /// Ends a `\localleftbox`/`\localrightbox` group.
    fn finish_local_box(&mut self) {
        self.unsave();
        let k = self.pop_saved() as usize;
        let head = self.cur_list().head;
        let first = self.nodes.next(head);
        self.nodes.set_next(head, NodeRef::NULL);
        self.pop_nest();
        let b = if first.is_null() {
            NodeRef::NULL
        } else {
            let first = self.node_process_list(first, crate::nodeproc::Context::Hbox);
            let b = self.hpack(first, PackSpec::NATURAL);
            self.nodes.set_subtype(b, 2);
            b
        };
        self.eq_define(Loc::LocalBox(k as u32), Val::Node(b));
        if self.mode == Mode::Horizontal {
            // A change of the local boxes inserts a new local par node.
            let lp = self.new_local_par();
            self.tail_append(lp);
        }
    }

    /// Recovers from a misplaced `&`, `\span` or `\cr` (`align_error`).
    fn align_error(&mut self) {
        if self.input.align_state.abs() > 2 {
            self.print_err("Misplaced ");
            self.print_cmd_chr(self.cur_cmd, self.cur_chr);
            if self.cur_tok == Token::char(Cmd::TabMark, '&' as u32) {
                self.help(&[
                    "I can't figure out why you would want to use a tab mark",
                    "here. If you just want an ampersand, the remedy is",
                    "simple: Just type `I\\&' now. But if some right brace",
                    "up above has ended a previous alignment prematurely,",
                    "you're probably due for more error messages, and you",
                    "might try typing `S' now just to see what is salvageable.",
                ]);
            } else {
                self.help(&[
                    "I can't figure out why you would want to use a tab mark",
                    "or \\cr or \\span just now. If something like a right brace",
                    "up above has ended a previous alignment prematurely,",
                    "you're probably due for more error messages, and you",
                    "might try typing `S' now just to see what is salvageable.",
                ]);
            }
            self.error();
        } else {
            self.back_input();
            if self.input.align_state < 0 {
                self.print_err("Missing { inserted");
                self.input.align_state += 1;
                self.cur_tok = Token::LEFT_BRACE;
            } else {
                self.print_err("Missing } inserted");
                self.input.align_state -= 1;
                self.cur_tok = Token::RIGHT_BRACE;
            }
            self.help(&[
                "I've put in what seems to be necessary to fix",
                "the current column of the current alignment.",
                "Try to go on, since this might almost work.",
            ]);
            self.ins_error();
        }
    }

    fn no_align_error(&mut self) {
        self.print_err("Misplaced ");
        self.print_esc_str("noalign");
        self.help(&[
            "I expect to see \\noalign only after the \\cr of",
            "an alignment. Proceed, and I'll ignore this case.",
        ]);
        self.error();
    }

    fn omit_error(&mut self) {
        self.print_err("Misplaced ");
        self.print_esc_str("omit");
        self.help(&[
            "I expect to see \\omit only after tab marks or the \\cr of",
            "an alignment. Proceed, and I'll ignore this case.",
        ]);
        self.error();
    }

    fn cs_error(&mut self) {
        self.print_err("Extra ");
        self.print_esc_str("endcsname");
        self.help(&["I'm ignoring this, since I wasn't doing a \\csname."]);
        self.error();
    }

    /// Appends a box to the current vertical list with interline glue
    /// (`append_to_vlist`).
    pub fn append_to_vlist(&mut self, b: NodeRef) {
        let pd = self.cur_list().prev_depth;
        if pd > IGNORE_DEPTH {
            let bs = self.eqtb.glue(gp::BASELINESKIP);
            let h = self.node_height(b);
            let d = bs.width - pd - h;
            let p = if d < self.eqtb.dimen(dp::LINESKIPLIMIT) {
                self.new_param_glue(glue_sub::LINE_SKIP)
            } else {
                let g = Glue { width: d, ..bs };
                self.new_glue_node(g, glue_sub::BASELINE_SKIP)
            };
            self.tail_append(p);
        }
        self.tail_append(b);
        let d = self.node_depth(b);
        self.cur_list_mut().prev_depth = d;
    }

    /// Right braces closing box groups and other non-simple groups
    /// (cases of `handle_right_brace`).
    pub fn handle_right_brace_typesetting(&mut self) {
        match self.save.cur_group {
            GroupCode::Hbox => self.package(false),
            GroupCode::AdjustedHbox => {
                self.start_adjust_lists();
                self.package(false);
            }
            GroupCode::Vbox => {
                self.end_graf();
                self.package(false);
            }
            GroupCode::Vtop => {
                self.end_graf();
                self.package(true);
            }
            GroupCode::Insert => self.finish_insert_group(),
            GroupCode::Output => self.resume_output(),
            GroupCode::Disc => self.build_discretionary(),
            GroupCode::Align => {
                self.back_input();
                self.cur_tok = Token::cs(self.cs.frozen_cr);
                self.print_err("Missing ");
                self.print_esc_str("cr");
                self.printer.print_str(" inserted");
                self.help(&["I'm guessing that you meant to end an alignment here."]);
                self.ins_error();
            }
            GroupCode::NoAlign => {
                self.end_graf();
                self.unsave();
                self.align_peek();
            }
            GroupCode::LocalBox => self.finish_local_box(),
            GroupCode::Vcenter | GroupCode::Math | GroupCode::MathChoice => self.math_right_brace(),
            _ => self.confusion("rightbrace"),
        }
    }
}

/// The glue parameter (eqtb index) belonging to a glue subtype.
pub fn glue_param_of_subtype(sub: u16) -> u32 {
    match sub {
        glue_sub::LINE_SKIP => gp::LINESKIP,
        glue_sub::BASELINE_SKIP => gp::BASELINESKIP,
        glue_sub::PAR_SKIP => gp::PARSKIP,
        glue_sub::ABOVE_DISPLAY => gp::ABOVEDISPLAYSKIP,
        glue_sub::BELOW_DISPLAY => gp::BELOWDISPLAYSKIP,
        glue_sub::ABOVE_DISPLAY_SHORT => gp::ABOVEDISPLAYSHORTSKIP,
        glue_sub::BELOW_DISPLAY_SHORT => gp::BELOWDISPLAYSHORTSKIP,
        glue_sub::LEFT_SKIP => gp::LEFTSKIP,
        glue_sub::RIGHT_SKIP => gp::RIGHTSKIP,
        glue_sub::TOP_SKIP => gp::TOPSKIP,
        glue_sub::SPLIT_TOP_SKIP => gp::SPLITTOPSKIP,
        glue_sub::TAB_SKIP => gp::TABSKIP,
        glue_sub::SPACE_SKIP => gp::SPACESKIP,
        glue_sub::XSPACE_SKIP => gp::XSPACESKIP,
        glue_sub::PAR_FILL_SKIP => gp::PARFILLSKIP,
        glue_sub::MATH_SKIP => gp::MATHSURROUNDSKIP,
        _ => gp::LINESKIP,
    }
}

/// Fields of a fresh box with the given dimensions (helper for tests).
pub fn box_with(width: i32, height: i32, depth: i32) -> BoxData {
    BoxData {
        width,
        height,
        depth,
        ..BoxData::default()
    }
}