📚 Add embedded text editor MVP documentation

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Elena Torro
2026-01-30 11:11:14 +01:00
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# Text Editor Architecture
## Overview (Simplified)
```mermaid
flowchart TB
subgraph Browser["Browser / DOM"]
CE[contenteditable]
Events[DOM Events]
end
subgraph CLJS["ClojureScript"]
InputHandler[text_editor_input.cljs]
Bindings[text_editor.cljs]
ContentCache[(content cache)]
end
subgraph WASM["WASM Boundary"]
FFI["_text_editor_* functions"]
end
subgraph Rust["Rust"]
subgraph StateModule["state/text_editor.rs"]
TES[TextEditorState]
Selection[TextSelection]
Cursor[TextCursor]
end
subgraph WASMImpl["wasm/text_editor.rs"]
StateOps[start / stop]
CursorOps[cursor / selection]
EditOps[insert / delete]
ExportOps[export content]
end
subgraph RenderMod["render/text_editor.rs"]
RenderOverlay[render_overlay]
end
Shapes[(ShapesPool)]
end
subgraph Skia["Skia"]
Canvas[Canvas]
Paragraph[Paragraph layout]
end
%% Flow
CE --> Events
Events --> InputHandler
InputHandler --> Bindings
Bindings --> FFI
FFI --> StateOps & CursorOps & EditOps & ExportOps
StateOps --> TES
CursorOps --> TES
EditOps --> TES
EditOps --> Shapes
ExportOps --> Shapes
TES --> Selection --> Cursor
RenderOverlay --> TES
RenderOverlay --> Shapes
Shapes --> Paragraph
RenderOverlay --> Canvas
Paragraph --> Canvas
ExportOps --> ContentCache
ContentCache --> InputHandler
```
---
## Detailed Architecture
```mermaid
flowchart TB
subgraph Browser["Browser / DOM"]
CE[contenteditable element]
KeyEvents[keydown / keyup]
MouseEvents[mousedown / mousemove]
IME[compositionstart / end]
end
subgraph CLJS["ClojureScript Layer"]
subgraph InputMod["text_editor_input.cljs"]
EventHandler[Event Handler]
BlinkLoop[RAF Blink Loop]
SyncFn[sync-content!]
end
subgraph BindingsMod["text_editor.cljs"]
direction TB
StartStop[start / stop]
CursorFns[set-cursor / move]
SelectFns[select-all / extend]
EditFns[insert / delete]
ExportFns[export-content]
StyleFns[apply-style]
end
ContentCache[(shape-text-contents<br/>atom)]
end
subgraph WASM["WASM Boundary"]
direction TB
FFI_State["_text_editor_start<br/>_text_editor_stop<br/>_text_editor_is_active"]
FFI_Cursor["_text_editor_set_cursor_from_point<br/>_text_editor_move_cursor<br/>_text_editor_select_all"]
FFI_Edit["_text_editor_insert_text<br/>_text_editor_delete_backward<br/>_text_editor_insert_paragraph"]
FFI_Query["_text_editor_export_content<br/>_text_editor_get_selection<br/>_text_editor_poll_event"]
FFI_Render["_text_editor_render_overlay<br/>_text_editor_update_blink"]
end
subgraph Rust["Rust Layer"]
subgraph StateMod["state/text_editor.rs"]
TES[TextEditorState]
Selection[TextSelection]
Cursor[TextCursor]
Events[EditorEvent queue]
end
subgraph WASMMod["wasm/text_editor.rs"]
direction TB
WStateOps[State ops]
WCursorOps[Cursor ops]
WEditOps[Edit ops]
WQueryOps[Query ops]
end
subgraph RenderMod["render/text_editor.rs"]
RenderOverlay[render_overlay]
RenderCursor[render_cursor]
RenderSelection[render_selection]
end
Shapes[(ShapesPool<br/>TextContent)]
end
subgraph Skia["Skia"]
Canvas[Canvas]
SkParagraph[textlayout::Paragraph]
TextBoxes[get_rects_for_range]
end
%% Browser to CLJS
CE --> KeyEvents & MouseEvents & IME
KeyEvents --> EventHandler
MouseEvents --> EventHandler
IME --> EventHandler
%% CLJS internal
EventHandler --> StartStop & CursorFns & EditFns & SelectFns
BlinkLoop --> FFI_Render
SyncFn --> ExportFns
ExportFns --> ContentCache
ContentCache --> SyncFn
StyleFns --> ContentCache
%% CLJS to WASM
StartStop --> FFI_State
CursorFns --> FFI_Cursor
SelectFns --> FFI_Cursor
EditFns --> FFI_Edit
ExportFns --> FFI_Query
%% WASM to Rust impl
FFI_State --> WStateOps
FFI_Cursor --> WCursorOps
FFI_Edit --> WEditOps
FFI_Query --> WQueryOps
FFI_Render --> RenderOverlay
%% Rust internal
WStateOps --> TES
WCursorOps --> TES
WEditOps --> TES
WEditOps --> Shapes
WQueryOps --> TES
WQueryOps --> Shapes
TES --> Selection
Selection --> Cursor
TES --> Events
%% Render flow
RenderOverlay --> RenderCursor & RenderSelection
RenderCursor --> TES
RenderSelection --> TES
RenderCursor --> Shapes
RenderSelection --> Shapes
%% Skia
Shapes --> SkParagraph
SkParagraph --> TextBoxes
RenderCursor --> Canvas
RenderSelection --> Canvas
```
---
## Key Files
| Layer | File | Purpose |
|-------|------|---------|
| DOM | - | contenteditable captures keyboard/IME input |
| CLJS | `text_editor_input.cljs` | Event handling, blink loop, content sync |
| CLJS | `text_editor.cljs` | WASM bindings, content cache, style application |
| Rust | `state/text_editor.rs` | TextEditorState, TextSelection, TextCursor |
| Rust | `wasm/text_editor.rs` | WASM exported functions |
| Rust | `render/text_editor.rs` | Cursor & selection overlay rendering |
## Data Flow
1. **Input**: DOM events → ClojureScript handler → WASM function → Rust state
2. **Edit**: Rust modifies TextContent in ShapesPool → triggers layout
3. **Sync**: Export content → merge with cached styles → update shape
4. **Render**: RAF loop → render_overlay → Skia draws cursor/selection