json-canvas

JSON Canvas Skill

File Structure

A canvas file (.canvas) contains two top-level arrays following the JSON Canvas Spec 1.0:

{
  "nodes": [],
  "edges": []
}

• nodes (optional): Array of node objects
• edges (optional): Array of edge objects connecting nodes

Common Workflows

1. Create a New Canvas

1. Create a .canvas file with the base structure {"nodes": [], "edges": []}
2. Generate unique 16-character hex IDs for each node (e.g., "6f0ad84f44ce9c17")
3. Add nodes with required fields: id, type, x, y, width, height
4. Add edges referencing valid node IDs via fromNode and toNode
5. Validate: Parse the JSON to confirm it is valid. Verify all fromNode/toNode values exist in the nodes array

2. Add a Node to an Existing Canvas

1. Read and parse the existing .canvas file
2. Generate a unique ID that does not collide with existing node or edge IDs
3. Choose position (x, y) that avoids overlapping existing nodes (leave 50-100px spacing)
4. Append the new node object to the nodes array
5. Optionally add edges connecting the new node to existing nodes
6. Validate: Confirm all IDs are unique and all edge references resolve to existing nodes

3. Connect Two Nodes

1. Identify the source and target node IDs
2. Generate a unique edge ID
3. Set fromNode and toNode to the source and target IDs
4. Optionally set fromSide/toSide (top, right, bottom, left) for anchor points
5. Optionally set label for descriptive text on the edge
6. Append the edge to the edges array
7. Validate: Confirm both fromNode and toNode reference existing node IDs

4. Edit an Existing Canvas

1. Read and parse the .canvas file as JSON
2. Locate the target node or edge by id
3. Modify the desired attributes (text, position, color, etc.)
4. Write the updated JSON back to the file
5. Validate: Re-check all ID uniqueness and edge reference integrity after editing

Nodes

Nodes are objects placed on the canvas. Array order determines z-index: first node = bottom layer, last node = top layer.

Generic Node Attributes

Attribute	Required	Type	Description
id	Yes	string	Unique 16-char hex identifier
type	Yes	string	text, file, link, or group
x	Yes	integer	X position in pixels
y	Yes	integer	Y position in pixels
width	Yes	integer	Width in pixels
height	Yes	integer	Height in pixels
color	No	canvasColor	Preset "1"-"6" or hex (e.g., "#FF0000")

Text Nodes

Attribute	Required	Type	Description
text	Yes	string	Plain text with Markdown syntax

{
  "id": "6f0ad84f44ce9c17",
  "type": "text",
  "x": 0,
  "y": 0,
  "width": 400,
  "height": 200,
  "text": "# Hello World\n\nThis is **Markdown** content."
}

Newline pitfall: Use \n for line breaks in JSON strings. Do not use the literal \\n -- Obsidian renders that as the characters \ and n.

File Nodes

Attribute	Required	Type	Description
file	Yes	string	Path to file within the system
subpath	No	string	Link to heading or block (starts with #)

{
  "id": "a1b2c3d4e5f67890",
  "type": "file",
  "x": 500,
  "y": 0,
  "width": 400,
  "height": 300,
  "file": "Attachments/diagram.png"
}

Link Nodes

Attribute	Required	Type	Description
url	Yes	string	External URL

{
  "id": "c3d4e5f678901234",
  "type": "link",
  "x": 1000,
  "y": 0,
  "width": 400,
  "height": 200,
  "url": "https://obsidian.md"
}

Group Nodes

Groups are visual containers for organizing other nodes. Position child nodes inside the group's bounds.

Attribute	Required	Type	Description
label	No	string	Text label for the group
background	No	string	Path to background image
backgroundStyle	No	string	cover, ratio, or repeat

{
  "id": "d4e5f6789012345a",
  "type": "group",
  "x": -50,
  "y": -50,
  "width": 1000,
  "height": 600,
  "label": "Project Overview",
  "color": "4"
}

Edges

Edges connect nodes via fromNode and toNode IDs.

Attribute	Required	Type	Default	Description
id	Yes	string	-	Unique identifier
fromNode	Yes	string	-	Source node ID
fromSide	No	string	-	top, right, bottom, or left
fromEnd	No	string	none	none or arrow
toNode	Yes	string	-	Target node ID
toSide	No	string	-	top, right, bottom, or left
toEnd	No	string	arrow	none or arrow
color	No	canvasColor	-	Line color
label	No	string	-	Text label

{
  "id": "0123456789abcdef",
  "fromNode": "6f0ad84f44ce9c17",
  "fromSide": "right",
  "toNode": "a1b2c3d4e5f67890",
  "toSide": "left",
  "toEnd": "arrow",
  "label": "leads to"
}

Colors

The canvasColor type accepts either a hex string or a preset number:

Preset	Color
"1"	Red
"2"	Orange
"3"	Yellow
"4"	Green
"5"	Cyan
"6"	Purple

Preset color values are intentionally undefined -- applications use their own brand colors.

ID Generation

Generate 16-character lowercase hexadecimal strings (64-bit random value):

"6f0ad84f44ce9c17"
"a3b2c1d0e9f8a7b6"

Layout Guidelines

• Coordinates can be negative (canvas extends infinitely)
• x increases right, y increases down; position is the top-left corner
• Space nodes 50-100px apart; leave 20-50px padding inside groups
• Align to grid (multiples of 10 or 20) for cleaner layouts

Node Type	Suggested Width	Suggested Height
Small text	200-300	80-150
Medium text	300-450	150-300
Large text	400-600	300-500
File preview	300-500	200-400
Link preview	250-400	100-200

Validation Checklist

After creating or editing a canvas file, verify:

1. All id values are unique across both nodes and edges
2. Every fromNode and toNode references an existing node ID
3. Required fields are present for each node type (text for text nodes, file for file nodes, url for link nodes)
4. type is one of: text, file, link, group
5. fromSide/toSide values are one of: top, right, bottom, left
6. fromEnd/toEnd values are one of: none, arrow
7. Color presets are "1" through "6" or valid hex (e.g., "#FF0000")
8. JSON is valid and parseable

If validation fails, check for duplicate IDs, dangling edge references, or malformed JSON strings (especially unescaped newlines in text content).

Complete Examples

See references/EXAMPLES.md for full canvas examples including mind maps, project boards, research canvases, and flowcharts.

References

• JSON Canvas Spec 1.0
• JSON Canvas GitHub