quartable

A Quarto extension that adds column spans, row spans, partial horizontal lines (clines), full midrules, vertical lines and per-cell alignment overrides to Markdown pipe tables. Targets HTML, Reveal.js and PDF/LaTeX with a single source.

Scope. quartable is PDF/LaTeX-first: that's the target it was designed for and where every feature is fully supported. HTML and Reveal.js are supported as best-effort secondary targets — most features render correctly there, with a few documented gaps (see the Compatibility matrix). The maintainer does not intend to grow the extension into a fully-featured table renderer for every output format; contributions are welcome for HTML/Reveal polish and additional features (see CONTRIBUTING.md).

Live documentation

The project page is a landing that links to self-documenting renderings of every feature in all three output formats — each example shows its markdown source above the rendered table:

• Landing — https://zinc75.github.io/quarto-quartable/
• HTML demo — https://zinc75.github.io/quarto-quartable/test_quartable.html
• PDF demo — https://zinc75.github.io/quarto-quartable/test_quartable.pdf
• Reveal.js slides — https://zinc75.github.io/quarto-quartable/test_reveal_quartable.html

Installation

From the directory of your Quarto project:

quarto add zinc75/quarto-quartable

Then enable the filter in your document's YAML front matter:

filters:
  - quartable

Quick example

| Group           | Item | Value 1  | Value 2  |
|-----------------|------|---------:|---------:|
| [Group A]{rs=3} | x1   | 0.71     | 2.1      |
| ^               | x2   | 0.68     | 2.0      |
| ^               | x3   | 0.74     | 2.3      |
| ===             |      |          |          |
| [Group B]{rs=2} | x4   | 0.89     | 3.4      |
| ^               | x5   | 0.87     | 3.3      |

[Group A]{rs=3} merges three rows; ^ marks continuation cells; === draws a midrule between the two groups.

Syntax reference

Column span — {cs=N}

| Item | [Measurements]{cs=3} |    |    |
|------|----------------------|----|----|
|      | T1                   | T2 | T3 |
| x1   | 0.71                 | 0.68 | 0.74 |

The cell with cs=N merges the next N-1 placeholder cells. You must write N-1 empty cells immediately after it (pipe-table syntax requires all cells on every row).

Row span — {rs=N} + ^

| Group           | Item |
|-----------------|------|
| [Group A]{rs=3} | x1   |
| ^               | x2   |
| ^               | x3   |

The cell with rs=N merges with the next N-1 rows. Continuation cells must be a single ^ character. (Empty placeholder cells also work, but ^ makes the intent explicit.)

Midrule — ===

| Group | Value |
|-------|------:|
| ===   |       |
| A     | 12    |
| A     | 8     |
| ===   |       |
| B     | 15    |

A row whose first cell contains exactly === is replaced with a full-width horizontal separator.

A === placed as the first row of the body (immediately after the Markdown header separator |---|) is treated as an explicit head/body separator. By design, no head/body separator is drawn automatically — see Design choices.

Cline (partial horizontal line) — ===N-M

| A | B | C | D |
|---|---|---|---|
| 1 | 2 | 3 | 4 |
| ===2-3 |  |  |  |
| 5 | 6 | 7 | 8 |

===N-M draws a partial line over columns N..M only. A single column N is shorthand for N-N. Multiple ranges and single columns can be combined: ===1-2,4-5, ===2-3,5, ===1,2-3,4. In LaTeX this emits one \cmidrule(lr){…} per range (booktabs partial rule, lighter weight with trimmed ends, matching the booktabs aesthetic).

Vertical lines on colspans — {cs=N .vl}, {cs=N .vr}, rspan=K

| Item | [Measurements]{cs=2 .vr} |   | Note |
|------|---------------------------|---|------|
| A    | 1                         | 2 | foo  |
| B    | 3                         | 4 | bar  |

.vl adds a vertical line on the left boundary of the colspan cell, .vr adds one on the right. The line spans the full table by default; add rspan=K to limit it to the declaring row plus K-1 rows below:

| Item | [Measurements]{cs=2 .vr rspan=2} |   | Note |

Vlines are honoured on any cell. On a regular (single-column) cell the boundary is the cell's own left/right edge; on a colspan cell it is the left/right edge of the merged span.

Per-cell alignment override — align=l|c|r

| Item        |   Value |
|-------------|--------:|
| `[total]{align=l}` | 1234.5 |

The align= attribute forces an alignment on a single cell, overriding the column's Markdown alignment. Both short (l, c, r) and long (left, center, right) values are accepted. Without align=, regular cells inherit the column alignment as usual; colspan cells default to centered.

Compatibility matrix

Feature	HTML	Reveal.js	PDF / LaTeX
cs=N	✅	✅	✅
rs=N + ^	✅	✅	✅
===	✅	✅	✅
===N-M	✅	✅	✅
align=l|c|r	✅	✅	✅
.vl / .vr	❌	❌	✅

Tables that use any quartable feature are rendered with a booktabs-inspired style in HTML/Reveal (no per-row borders, only the explicit rules added by the filter). Regular Quarto tables that don't use any quartable feature keep their default Quarto styling untouched.

HTML/Reveal support for vlines is on the roadmap — contributions welcome (see CONTRIBUTING.md).

Design choices

• No automatic head/body separator. quartable does not draw a separator between the table header and the body. This follows booktabs' philosophy of leaving that decision to the author (the separator becomes ambiguous when the header contains column spans or row spans). The Pandoc-generated \midrule\endhead is removed from the LaTeX output for tables that use any quartable feature. To request a head/body separator explicitly, place a === row as the first row of the body (immediately after the |---| header separator). The filter detects the leading ===, restores the natural booktabs \midrule in LaTeX, and tags the table with the quartable-head-sep class for HTML/Reveal so the bundled CSS draws the matching border on the last header row.
• Vertical lines, despite booktabs. The booktabs author actively discourages vertical rules. quartable nonetheless implements .vl / .vr (LaTeX only for now) because they are useful in specific cases — typically to demarcate a colspan group, or to draw a partial vertical separator alongside a \cmidrule. Keep them rare.

Limitations

• Vlines are LaTeX-only in v0.1. HTML and Reveal silently ignore them.
• Rowspan in the table header: Pandoc does not honour row_span on cells inside tbl.head. When quartable detects a rowspan in the header, it moves the header rows into the first body so the rowspan can be rendered. The visual <thead> distinction is lost on those tables.
• Full-height vlines + complex column specs: when Pandoc generates a p{...} column spec (e.g. on tables with width hints), the full-height vline injection in the column spec is skipped and a warning is printed to stderr. Use rspan=N instead for those tables.
• Vlines + booktabs rules: vertical lines have small visible gaps where they cross \toprule, \midrule and \bottomrule (intrinsic to booktabs — its author actively discourages vertical rules). The effect is more pronounced on heavy \toprule/\bottomrule. If gap- free intersections are critical, override booktabs rules with \hline in your own preamble.
• Partial cline + colspan: in HTML, when a cline range partially overlaps a colspan cell, the CSS border-bottom is applied to the whole cell (HTML can't draw a border on a fragment of a cell). LaTeX draws the line correctly because \cline operates on column boundaries.

Development

The repository ships with a test document that exercises every feature:

quarto preview test_quartable.qmd --to html
quarto preview test_quartable.qmd --to pdf
quarto preview test_reveal_quartable.qmd

The PDF target keeps the intermediate .tex (keep-tex: true) so you can inspect the LaTeX directly when debugging.

License

MIT — see LICENSE for the full text.