Important

SIL.TextEditing has moved into Motif: sillsdev/motif/textediting. This repository is archived. Its history up to the move (commit c23cc53) stays here; new work happens in Motif, where the folder keeps its own build, solution, ADRs and CI (ADR 0034, Motif ADR 0092). It can be pulled out again into its own repository or into FieldWorks. Open issues moved to Motif with the textediting label:

Old and new issue numbers

Here	In Motif
#5	motif#20
#6	motif#21
#8	motif#22
#41	motif#23
#50	motif#24
#51	motif#25
#61	motif#26
#74	motif#27
#82	motif#28
#94	motif#29
#104	motif#30
#119	motif#31
#123	motif#32
#124	motif#33
#125	motif#34
#126	motif#35
#128	motif#36
#129	motif#37
#131	motif#38
#132	motif#39
#133	motif#40
#134	motif#41
#137	motif#42
#144	motif#43
#145	motif#44
#150	motif#45
#152	motif#46
#153	motif#47
#154	motif#48
#155	motif#49
#159	motif#50
#161	motif#51
#162	motif#52
#163	motif#53
#164	motif#54
#167	motif#55
#168	motif#56
#170	motif#57
#172	motif#58
#173	motif#59
#175	motif#60
#177	motif#61

SIL.TextEditing

Rich text editing for Avalonia in which every run of text knows its writing system.

SIL.TextEditing is being built as the rich text field for FieldWorks and Motif, and for any Avalonia app that edits multilingual text. Each run carries its own writing system, so Latin, Arabic and Devanagari share one paragraph and each keeps its own font, spelling dictionary and keyboard. The run model is shaped like FieldWorks' ITsString, and an adapter maps it to and from liblcm. One source tree builds against Avalonia 11.3 for FieldWorks (.NET Framework 4.8, inside WinForms) and Avalonia 12 for Motif (.NET 10). Text can be written as FieldWorks Markdown, a strict profile of Pandoc Markdown that Pandoc reads the same way the library does. The host owns the data and the undo stack; the field edits what it is given.

Status: unreleased. The API will change. Everything outside the Roadmap is built and tested today.

Hindi, Tamil and Thai, shaped, with a conjunct selected as one cluster	Inline pictures in left-to-right and right-to-left text
Properties the editor does not know survive every edit	Spelling per writing system; blue where a word mixes two
A notation box with a language service: chips and diagnostics	Tables, lists and headings, switched on or off per field
Inside WinForms on .NET Framework 4.8: FieldWorks' shape	NFD, stacked marks and surrogate pairs

What people and agents edit

The first paragraph of the picture above, as FieldWorks Markdown, the form a person or an AI agent reads and edits:

The word [كتاب]{ws=ar} means book; [مرحبا بالعالم]{ws=ar} means hello world.

Unmarked text is the analysis writing system (English here); [...]{ws=ar} is another writing system and [...]{.v} the vernacular. A new run starts wherever the writing system or a property changes, so nothing numbers runs or records offsets. The two right-to-left paragraphs of the picture share one ::: {rightToLeft=1} block. A file adds a short front matter, generated by the writer, that names the writing systems (the format).

The same text has four forms, and only the first two are meant to be edited by hand:

Form	What it is for	Edited by hand
FieldWorks Markdown (*.fw.md)	People, AI agents, files and diffs; Pandoc reads it the same way	Yes
Record file	A whole FieldWorks record: a YAML frame whose rich values are FieldWorks Markdown (record files)	Yes
Document, Paragraph, Run	The editor's model in memory: per run the text, writing system and property bag; per paragraph the host's key	No: the playground's developer mode dumps it in its "Model (debug)" tab
liblcm ITsString	FieldWorks' storage; the LCModel adapter maps it to and from the run model	No

An agent's edit is a text edit. Change the gloss and mark a vernacular word:

-The word [كتاب]{ws=ar} means book; [مرحبا بالعالم]{ws=ar} means hello world.
+The word [كتاب]{ws=ar} means [kitabu]{.v}; [مرحبا بالعالم]{ws=ar} means hello world.

The reader checks it: a malformed span or an unknown writing system is a finding with a line, a column and, where one exists, the exact fix (findings), and nothing is applied while there is an error. The host applies the rest as one undo step. In the playground, edit the Markdown beside the field and press Apply; MarkdownTabTests makes this very edit.

Why it's different

• A writing system on every run. A Run holds text, a writing-system id, a property bag keyed by FieldWorks property numbers, and object data, as an ITsString run does. The editor carries properties it does not understand through every edit. The LCModel adapter round-trips real liblcm strings (ADR 0016, 111 tests per target).
• Both Avalonia lines from one source tree. Avalonia 11.3.17 on net48 inside WinForms, and Avalonia 12.1.2 on net10.0, with a few small per-version differences, listed (ADR 0009). The surface tests run on both: 777 on net48, 778 on net10.0.
• FieldWorks editing behaviour. Arrow keys are logical by paragraph direction, text is stored as NFD, Backspace and Delete work as in FieldWorks (ADR 0018). Complex shaping and inline objects. Screen readers get FieldWorks' MSAA level (name, role, value) through Avalonia's peers; in WinForms the host needs a small fix first (ADR 0017).
• FieldWorks Markdown that Pandoc agrees with. Read lenient, write strict. 664 tests run Pandoc 3.9.0.2 itself: 334 fixture cases (every one without an error finding, bar a few excluded with a stated reason), 200 generated documents and record files and the 5 link forms must read to the same structure; 124 more check that what Pandoc reads as another construct is reported; one pins the version (ADR 0028).
• Records as files. A whole record as one file: a YAML frame typed by a schema that is data, FieldWorks Markdown in the rich values, and a JSON Schema for editors (ADR 0032).
• The host stays in charge. The host owns data and undo (ADR 0003), and supplies the dictionaries, keyboards, clipboard forms, language services and the blocks a field allows.
• Ready for native AOT. SIL.TextEditing, SIL.TextEditing.Avalonia and SIL.TextEditing.Markdown are trimmable and AOT-compatible on net10.0 (the LCModel adapter is not). CI's tests/AotCheck publishes all three native AOT, rooted whole so any trim or AOT warning fails, and runs the Markdown converter, record files and the libpalaso writing-system path in the published exe.

The whole suite passes with 0 failures on net48 and net10.0. Passing tests per target, Release, main 7e77466 (2026-11-06), Pandoc on PATH. Opt-in tests that skip by default are not counted: 11 screenshot generators (TEXTEDITING_SCREENSHOTS) and 3 real-clipboard tests (TEXTEDITING_REAL_CLIPBOARD).

Tests	Model	Avalonia	Markdown	LCModel	Playground	SecondDispatcher
net48	416	777	3843	111	304	—
net10.0	416	778	3843	111	304	3

Quick start

Windows, the .NET 10 SDK and the .NET Framework 4.8 targeting pack:

dotnet build SIL.TextEditing.sln
dotnet test  SIL.TextEditing.sln

Try it:

run desktop10     # Avalonia desktop window on .NET 10, Avalonia 12
run desktop48     # the same window on .NET Framework 4.8, Avalonia 11.3.17
run winforms48    # WinForms form: TextBox, playground, TextBox (FieldWorks' shape)
run desktop10 --scenario "Inline picture (ORC)"

run.cmd and run.ps1 build the host and start it. The playground shows what a person writing sees: a scenario picker, the field, and beside it the field as FieldWorks Markdown, which you can edit and apply. Select some text and a small bar appears over it: bold, italic, underline, writing system and character style, and under More the paragraph style and a picture. Developer mode (the check box, or --dev) adds every switch, the model's runs and the event log. The scenarios: bidi, Indic and Thai shaping, NFD, inline pictures, unknown properties, spelling, the environment box, long documents. The Pandoc tests need pandoc on PATH.

Projects

Project	What it is
src/SIL.TextEditing	The UI-free run model, editing, clipboard forms and paste rules. No Avalonia, no liblcm.
src/SIL.TextEditing.Avalonia	RichTextField, the control.
src/SIL.TextEditing.Markdown	FieldWorks Markdown and record files. Trimmable and AOT-compatible.
src/SIL.TextEditing.LCModel	The ITsString adapter and the TsString XML clipboard form.
samples/SIL.TextEditing.Playground	The shared playground UI both hosts and the integration tests use.
samples/Playground.Desktop	The playground in a plain Avalonia window, net48 and net10.0.
samples/Host48	The playground inside a WinForms form, net48: FieldWorks' shape.
tests/*	Model, surface, Markdown, LCModel, playground, second-dispatcher, real-clipboard and AOT tests.

Libraries target netstandard2.0 and net10.0. Details: Projects and tests.

Documentation

• Reference: the run model, editing, clipboard, spelling, the language service, rendering, the two Avalonia versions, the LCModel adapter, the Markdown library, known limitations.
• Formats: FieldWorks Markdown, record files, the clipboard forms, tables, and every finding id.
• Decisions: the architecture decision records.
• Feature inventory: FieldWorks' editing features and where each stands here.
• Manual testing: the checklist a person runs.
• Glossary: the words this project uses.
• Screenshots: every image, and how to regenerate it.

Roadmap

Planned, not built:

• Word-compatible copy and paste. HTML and RTF out, HTML in, in a new SIL.TextEditing.WordInterchange project (ADR 0031, clipboard plan).
• Real tables in the field (#152, tables plan).
• SIL.TextEditing.Project: LCModel-backed record I/O and the record schema built from liblcm metadata (ADR 0031, ADR 0033).
• The fwmd command-line checker (#161).
• The FieldWorks Markdown clipboard form (#168).
• Editor integration: an inline WYSIWYG and Markdown source mode, and a VS Code extension with a language server. The playground's Markdown pane is a host-side sketch of the source mode. The plan and a proposed ADR are awaiting owner decisions (#170).
• Retiring the liblcm refusals once FieldWorks pins a liblcm with its fixes #410, #413 and #414 (#159).

Contributing

Read AGENTS.md first: the rules for layering, packages, tests and commits apply to people and agents alike. Known limitations are in docs/reference/limitations.md.

Licence

MIT, copyright SIL Global. See LICENSE. FieldWorks code is LGPL and is not copied here: FieldWorks behaviour is re-implemented from documentation, standards, tests and observed behaviour (ADR 0010).