mps-aspect-editor

name	mps-aspect-editor
description	Use when creating or changing MPS editor definitions — the overall workflow from scaffolding a `ConceptEditorDeclaration` through componentizing reusable `EditorComponentDeclaration`s, refining cell models and cell layouts, applying style sheets and indent-layout style items, wiring smart references, leveraging inheritance via super-concepts and interfaces, inspecting (`print_node_json`, `show_node_representation`) and validating (`check_root_node_problems`). Covers `jetbrains.mps.lang.editor` cell models (`CellModel_RefNode`/`CellModel_RefNodeList`/`CellModel_RefCell`/`CellModel_Property`/`CellModel_Constant`), layout choices, and JSON blueprints for common editor shapes. For the non-layout side (action maps, keymaps, transformation/substitute menus) use `mps-aspect-editor-menus-and-keymaps`.
type	reference

MPS Editor — Technical Reference

The jetbrains.mps.lang.editor language defines projectional editors as trees of cell models (display elements) with cell layouts and style items. This skill is the technical lookup: concept names, suffixes, style classes, and the rules that decide which cell model to use where.

Critical Directives

• Always use CellModel_RefNodeList for 0..n or 1..n children. CellModel_RefNode is for single cardinality only.
• Use IndentLayoutOnNewLineStyleClassItem (apply to the cell that should start on a new line) instead of the legacy IndentLayoutNewLineStyle (applied to the cell before the break) — the latter is easier to get wrong.
• Reference cells: set the internal CellModel_Property (e.g. name) inside an InlineEditorComponent to readOnly=true so the referenced target cannot be accidentally renamed through the editor.
• Smart references: no wrapping layout cell — just a single CellModel_RefCell whose editorComponent is an InlineEditorComponent with a CellModel_Property (relationDeclaration: name, readOnly: true).
• List empty state: always use emptyCellModel (e.g. a CellModel_Constant "<no items>") so the user can see and click into empty lists.
• Inheritance: components can be reused if defined for the concept, its super-concepts, or implemented interfaces.
• Stylesheets: check for existing style classes in extended languages before creating new ones in a StyleSheet node.

Common Workflow

1. Scaffold first — mps_mcp_scaffold_editor builds a default editor that wires properties/children/references to sensible cell models.
2. Componentize reusable pieces into EditorComponentDeclaration.
3. Refine cell choice and layout using the catalog below.
4. Inspect with mps_mcp_print_node_json (structural) and mps_mcp_show_node_representation (textual / HTML projection).
5. Validate with mps_mcp_check_root_node_problems.

Related Skills

• mps-aspect-editor-menus-and-keymaps — for action maps, cell keymaps, transformation menus, substitute menus, side transforms, paste wrappers, copy-paste handlers, completion styling, and reference presentation. Use this skill alongside that one when authoring an editor end-to-end.
• mps-aspect-structure-concepts — concept declarations supply the relations (properties / children / references) the editor wires up.
• mps-language-aspects-overview — for the broader authoring order around editors.

Reference Index

• Open references/cell-models.md for the catalog of cell-model concepts (ConceptEditorDeclaration, EditorComponentDeclaration, CellModel_Collection, CellModel_Constant, CellModel_Property, CellModel_ReadOnlyModelAccessor, CellModel_RefNode, CellModel_RefNodeList, CellModel_RefCell, CellModel_Component, InlineEditorComponent) with their suffixes and purpose.
• Open references/indent-layout-styles.md for the style-item catalog (IndentLayoutOnNewLineStyleClassItem, IndentLayoutIndentStyleClassItem, IndentLayoutNewLineChildrenStyleClassItem, SelectableStyleSheetItem) used inside CellLayout_Indent.
• Open references/editor-patterns.md for ready-to-paste JSON / pseudo-code patterns: indented child on a new line, named concept with keyword header, transparent list, smart-reference cell, and a minimal ConceptEditorDeclaration JSON template.
• Open references/stylesheet-values.md for the enum literals accepted by stylesheet items: _Colors_Enum (darkBlue, gray, darkGreen, black, …) for ForegroundColorStyleClassItem.color and other color items, _FontStyle_Enum (PLAIN, BOLD, ITALIC, BOLD_ITALIC, QUERY) for FontStyleStyleClassItem.style, plus UnderlineStyle and FocusPolicy.