Text-bearing Entity Format-Code Integration

Audit of which entities carry MText-style inline format codes (\H, \W, \Q, \T, \A, \C, \c, \f, \F, \p…q[lcrjd]…;, \L\l, \O\o, \K\k, \S…;, \U+XXXX, \M, \X, { }) and whether their renderer currently honours them.

The MTEXT entity itself was upgraded to a run-aware parser + renderer in commit f12e864; this file tracks the follow-up work for the other text-bearing entities.

Status matrix

Entity	Content format	Current renderer	Needs integration
MTEXT	MText codes	Run-aware parser + run renderer	Done
TABLE cell	MText codes (`\f` `\C` `\H` standard in real DXF)	Raw string → `cxf::tessellate_text_ex`; codes are rendered as literal glyphs	Yes — high priority
MLEADER (`LeaderContentType::MText`)	MText codes	`strip_mtext_codes` + `split_mtext_lines` (legacy strip path); codes are dropped silently	Yes — high priority
ATTRIB / ATTDEF with `mtext_flag = MultiLine / ConstantMultiLine`	MText codes	Text-style render (single-line layout)	Yes — conditional on flag
DIMENSION `text_override`	MText codes (rare)	Usually rendered via the baked `block_name` sub-entity path (which goes through MTEXT)	Optional — only matters for unbaked dim text
TEXT	`%%x` specials only	`cxf::tessellate_text_ex` handles specials	No
TOLERANCE	Feature Control Frame (structured)	Dedicated FCF pipeline	No
LEADER (legacy single-leader)	Plain text	Dedicated pipeline	No

What each entity loses today

TABLE cell

Real-world AutoCAD tables emit every cell as an MText-formatted string — font changes, per-column colour, height overrides, paragraph alignment. The current call site at src/entities/table.rs:245-253 passes the raw string to cxf::tessellate_text_ex, which only recognises the %%x specials and the \L\l \O\o \K\k decoration markers. Every other \<letter>…; block falls through and gets drawn as a literal backslash + letter sequence, so a cell like \C7;Red shows up as the visible text \C7;Red on screen.

This is the most visible regression to fix.

MLEADER (MText content)

Two parallel call sites strip codes via strip_mtext_codes + split_mtext_lines:

The codes are silently dropped rather than rendered as glyph noise, so the text looks plausible — but every inline override (font / colour / height / paragraph align) is invisible. The two copies should be folded into the shared run renderer at the same time as the integration.

ATTRIB / ATTDEF (when `mtext_flag` is set)

AttributeDefinition::mtext_flag and AttributeEntity::mtext_flag carry MTextFlag::MultiLine / ConstantMultiLine when the attribute value is authored as MText. Current attribute rendering treats the value as a single Text line regardless of the flag. When the flag is set, the value should flow through the MText pipeline.

DIMENSION `text_override`

Modern AutoCAD typically bakes dimensions into a *D### block whose sub-entities include an MTEXT carrying any inline formatting. That path already goes through the run renderer via the block-defn cache. The text_override field on the unbaked Dimension can contain MText codes, but in practice the codes appear in the baked block. Lowest priority.

Refactor strategy

Extract a shared helper:

fn render_mtext_string(
    value: &str,
    entity_height: f32,
    base_wf: f32,
    base_oblique: f32,
    base_font: &str,
    rect_w: f32,
    attach_h_anchor: f32,
    attach_v_anchor: f32,
    rotation: f32,
    insertion: Vec3,
    line_spacing_factor: f32,
    is_upside_down: bool,
    is_vertical: bool,
) -> Vec<TextStroke>;

Then have MTEXT, TABLE cell, MLEADER (and MText-flag ATTRIB) all call it. This collapses the four nearly-identical layout loops into one and makes the inline-code coverage uniform across entities.

Suggested order

TABLE — restores visibly broken rendering in any DXF/DWG that uses inline cell formatting (which is most of them).
MLEADER — restores the silent-fail formatting. Touches two call sites; fold them into the shared helper at the same time.
ATTRIB / ATTDEF — gated on mtext_flag. Touches one call site.
DIMENSION text_override — optional; only matters for unbaked dims.

Out of scope

TEXT entity does not accept MText codes (DXF spec), only %%x specials, which cxf::tessellate_text_ex already handles.
TOLERANCE uses a structured FCF representation; no MText codes apply.
Legacy LEADER (single-leader, pre-MLEADER) carries plain text only.

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