The MTEXT text entry opens a text box on the canvas at the text's location and
width instead of a dialog: font, height, bold, italic, underline, overline,
colour, paragraph alignment, lists, tab and special characters, plus a ruler for
the paragraph's indents and tab stops. Text, per-character formats and paragraph
properties live in engine::mtext_edit (parse and write MTEXT codes, opaque codes
kept verbatim), tested headlessly.
Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>
Co-authored-by: Brandon Thomas <echelon@gmail.com>
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