# Mailshieldai Opencode Canvas Opencode Canvas

> Document Canvas

- Skill: `tomevault-io/mailshieldai-opencode-canvas-opencode-canvas` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/mailshieldai-opencode-canvas-opencode-canvas`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/mailshieldai-opencode-canvas-opencode-canvas/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/mailshieldai-opencode-canvas-opencode-canvas

---


# Document Canvas

Display markdown documents with optional text selection and diff highlighting.

## Example Prompts

Try asking Claude:

- "Draft an email to the marketing team about the Q1 product launch"
- "Help me edit this blog post - show it so I can highlight the parts to revise"
- "Write a project proposal and let me review it"
- "Show me the README so I can select sections to update"
- "Compose a response to this customer complaint"

## Scenarios

### `display` (default)
Read-only document view with markdown rendering. User can scroll but cannot select text.

```typescript
canvas_spawn({
  kind: "document",
  scenario: "display",
  config: JSON.stringify({
    content: "# Hello World\n\nThis is **markdown** content.",
    title: "My Document"
  })
})
```

### `edit`
Interactive document view with text selection. User can click and drag to select text, which is sent via IPC in real-time.

- Renders markdown with syntax highlighting (headers, bold, italic, code, links, lists, blockquotes)
- Diff highlighting: green background for additions, red for deletions
- Click and drag to select text
- Selection automatically sent via IPC

```typescript
canvas_spawn({
  kind: "document",
  scenario: "edit",
  config: JSON.stringify({
    content: "# My Blog Post\n\nThis is the **introduction** to my post.\n\n## Section One\n\n- Point one\n- Point two",
    title: "Blog Post Draft",
    diffs: [
      {startOffset: 50, endOffset: 62, type: "add"}
    ]
  })
})
```

### `email-preview`
Specialized view for email content display.

```typescript
canvas_spawn({
  kind: "document",
  scenario: "email-preview",
  config: JSON.stringify({
    content: "Dear Team,\n\nPlease review the attached document.\n\nBest regards,\nAlice",
    title: "RE: Project Update"
  })
})
```

## Configuration

```typescript
interface DocumentConfig {
  content: string;        // Markdown content
  title?: string;         // Document title (shown in header)
  diffs?: DocumentDiff[]; // Optional diff markers for highlighting
  readOnly?: boolean;     // Disable selection (default: false for edit)
}

interface DocumentDiff {
  startOffset: number;    // Character offset in content
  endOffset: number;
  type: "add" | "delete";
}
```

## Markdown Rendering

Supported markdown features:
- **Headers** (`# H1`, `## H2`, etc.)
- **Bold** (`**text**`)
- **Italic** (`*text*`)
- **Code** (`` `inline` `` and fenced blocks)
- **Links** (`[text](url)`)
- **Lists** (`-` or `*` bullets)
- **Blockquotes** (`>`)

## Selection Result

```typescript
interface DocumentSelection {
  selectedText: string;   // The selected text
  startOffset: number;    // Start character offset
  endOffset: number;      // End character offset
  startLine: number;      // Line number (1-based)
  endLine: number;
  startColumn: number;    // Column in start line
  endColumn: number;
}
```

## Controls

- **Mouse click and drag**: Select text (edit scenario)
- `Up/Down` or scroll: Navigate document
- `q` or `Esc`: Close/cancel

## API Usage

```typescript
// Display read-only document
canvas_spawn({
  kind: "document",
  scenario: "display",
  config: JSON.stringify({
    content: "# My Document\n\nContent here.",
    title: "View Mode",
  })
});

// Interactive editing with selection
canvas_spawn({
  kind: "document",
  scenario: "edit",
  config: JSON.stringify({
    content: "# My Document\n\nSelect some **text** here.",
    title: "Edit Mode",
    diffs: [{ startOffset: 20, endOffset: 30, type: "add" }],
  })
});

// Get current selection from a running canvas
canvas_selection({ id: "document-1234567890-abc123" });
// Returns: { success: true, selection: { selectedText: "text", startOffset: 30, endOffset: 34 } }
```

---
> Source: [mailshieldai/opencode-canvas](https://github.com/mailshieldai/opencode-canvas) — distributed by [TomeVault](https://tomevault.io).
<!-- tomevault:4.0:skill_md:2026-07-01 -->