TermBuf::Cell

The most columns one grapheme cluster may occupy: a lead and up to three continuations.

Two is what a cluster costs almost everywhere, and the buffer was built for a pair. iTerm2 3.6.11 advances three for a Devanagari conjunct carrying a spacing vowel sign, so a pair is not enough — see Unicode::WidthPolicy#conjunct_spacing_adds?. Four leaves room above the widest reading anyone has measured without letting a bad measurement run away with a row.

An empty cell carrying style, which is what a cleared or scrolled-away part of the screen holds.

A cell continuing the cluster to its left.

Whether the cell holds a space and nothing else, ignoring its style.

The cell's character, or '\0' when this cell continues a wide one. When cluster is set, this is the cluster's first code point and the full text lives in the pool.

ClusterPool id for a multi code point grapheme cluster, or ClusterPool::NONE when char says everything.

Whether this cell continues the cluster to its left.

Whether this cell's glyph may paint outside the columns it was given.

Measured rather than reasoned about. A cluster's ink runs past its own columns often enough to matter: ﷺ is charged one column and painted across three, an uncomposed 👨‍👩 is charged two and painted across four, and neither terminal measured repaints the cell it draws over. Every case seen was non-ASCII and no ASCII character in four runs painted outside its cell, which is what keeps the repaint off ordinary text.

Id into the buffer's StyleTable.

The text this cell paints, resolving a cluster id through pool. Falls back to the base character if pool does not know the cluster, so that rendering a grid against the wrong pool degrades rather than raising.

Same as #inspect(io).

Whether this cell leads a cluster taking more than its own column.

Cells this character occupies: zero for a continuation, one for a narrow character, and up to MAX_WIDTH for a cluster the terminal advances further for.