intellij-slint/docs/plans/2026-01-29-slint-lsp-integration-design.md

Slint LSP Integration Design

Date: 2026-01-29 Status: Approved Phase: Phase 1 - Core LSP Features

Overview

Implement complete Slint LSP integration into IntelliJ IDEA, enabling standard LSP features (diagnostics, completion, goto definition, hover, formatting, etc.) through IntelliJ's built-in LSP framework.

Architecture

Component Structure

IntelliJ IDEA (LSP Client)
    ↓
SlintLspServerSupportProvider (Entry point)
    ↓
SlintLspServerDescriptor (Server configuration)
    ↓
Slint LSP Server (External process)

Core Components

1. File Type System

   • SlintLanguage: Language definition
   • SlintFileType: File type definition with .slint extension
   • File icon and description

2. LSP Server Integration

   • SlintLspServerSupportProvider: LSP entry point (exists, needs refinement)
   • SlintLspServerDescriptor: Server configuration (rename from FooLspServerDescriptor)
   • Automatic capability negotiation via LSP initialize handshake

3. Syntax Highlighting

   • Use TextMate grammar from official Slint VSCode extension
   • SlintTextMateProvider: TextMate bundle provider

4. LSP Feature Mapping (automatic via IntelliJ)

   • Diagnostics → Error/warning annotations
   • Completion → Code completion UI
   • Goto Definition → Ctrl+Click navigation
   • Hover → Quick documentation
   • Formatting → Code formatting actions
   • References → Find usages
   • Rename → Refactor rename

Implementation Plan

1. File Type System

Files to create:

• src/main/kotlin/me/zhouxi/slint/lang/SlintLanguage.kt
• src/main/kotlin/me/zhouxi/slint/lang/SlintFileType.kt

Changes to plugin.xml:

• Register <fileType> extension

2. LSP Server Configuration

Files to modify:

• src/main/kotlin/me/zhouxi/slint/lsp/SlintLspServerSupportProvider.kt
  • Rename FooLspServerDescriptor → SlintLspServerDescriptor
  • Use file.fileType == SlintFileType instead of string comparison

3. Syntax Highlighting

Resources to add:

• Download slint.tmLanguage.json from Slint GitHub
• Place in src/main/resources/textmate/

Files to create:

• src/main/kotlin/me/zhouxi/slint/lang/syntax/SlintTextMateProvider.kt

Changes to plugin.xml:

• Register <textMate.bundleProvider> extension

4. Testing

Test files to create:

• Sample .slint files for manual testing
• Verify: diagnostics, completion, goto definition, hover, formatting

Design Decisions

• Use IntelliJ LSP Framework: Leverage built-in LSP client, no manual protocol implementation
• TextMate for Syntax: Use official grammar, zero maintenance
• Minimal Custom Code: Only implement required extension points
• Type-Safe File Detection: Use FileType comparison instead of string extension checks

Out of Scope (Phase 2)

• Live Preview integration (Slint-specific feature)
• Custom UI components
• Advanced project configuration

Success Criteria

• .slint files recognized by IntelliJ
• LSP server starts automatically when .slint file opened
• Syntax highlighting works
• Code completion provides suggestions
• Diagnostics show errors/warnings
• Goto definition navigates correctly
• Hover shows documentation
• Code formatting works