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Overlays add additional visual information on top of your code graph. They change node colors, sizes, or add badges based on external data.

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What Are Overlays?

An overlay is a visual layer that augments the base graph with additional data:
OverlayData SourceVisual Effect
Git ActivityGit historyColor by change frequency
Test CoverageCoverage reportsColor by coverage %
ComplexityStatic analysisSize by complexity
Code OwnershipGit blameColor by author/team

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Available Overlays

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Built-in Overlays

# List available overlays
curl http://localhost:5050/api/overlays

{
  "plugins": [
    {
      "id": "git-activity",
      "name": "Git Activity",
      "description": "Visualize code churn from git history",
      "overlays": [
        {
          "id": "churn",
          "name": "Change Frequency",
          "type": "color",
          "legend": { "low": "#22c55e", "high": "#ef4444" }
        }
      ]
    },
    {
      "id": "test-coverage",
      "name": "Test Coverage",
      "description": "Show test coverage percentages",
      "overlays": [
        {
          "id": "coverage",
          "name": "Line Coverage",
          "type": "color",
          "legend": { "0%": "#ef4444", "50%": "#f59e0b", "100%": "#22c55e" }
        }
      ]
    }
  ]
}

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Applying an Overlay

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Via UI

  1. Click the “Overlays” button in the toolbar
  2. Select an overlay from the list
  3. Click “Apply”

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Via API

# Apply git activity overlay
curl -X POST http://localhost:5050/api/overlays/git-activity/apply

# Check application status
curl http://localhost:5050/api/overlays/git-activity/status

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Via CLI

codegraph overlay apply git-activity
codegraph overlay apply test-coverage --report coverage.xml

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Git Activity Overlay

Shows which parts of your codebase change most frequently.

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Setup

# Apply git activity (analyzes last 6 months by default)
codegraph overlay apply git-activity

# Custom time range
codegraph overlay apply git-activity --since "2024-01-01" --until "2024-06-01"

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What It Shows

MetricVisualMeaning
Change frequencyColor (green → red)How often this file changes
Lines changedNode sizeTotal lines added/removed
AuthorsBadgeNumber of contributors
High churn + many authors often indicates problematic code that’s hard to maintain.

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Test Coverage Overlay

Visualize which code is tested.

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Setup

First, generate a coverage report: 
# Using coverlet
dotnet test --collect:"XPlat Code Coverage"
Then apply the overlay: 
codegraph overlay apply test-coverage --report ./TestResults/*/coverage.cobertura.xml

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What It Shows

CoverageColor
0-30%Red
30-70%Yellow
70-90%Light green
90-100%Green

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Complexity Overlay

Highlight complex code that might need refactoring.

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Setup

codegraph overlay apply complexity

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Metrics

MetricDescription
Cyclomatic complexityNumber of decision points
Cognitive complexityHow hard to understand
Lines of codeRaw size

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Code Ownership Overlay

See who owns which parts of the codebase.

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Setup

codegraph overlay apply ownership

# With team mapping
codegraph overlay apply ownership --teams teams.json
teams.json: 
{
  "teams": {
    "Platform": ["[email protected]", "[email protected]"],
    "Product": ["[email protected]", "[email protected]"]
  }
}

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What It Shows

  • Each team gets a unique color
  • Shared ownership shows blended colors
  • Orphaned code (no recent commits) shows gray

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Removing Overlays

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Via UI

  1. Click “Overlays” button
  2. Click “Remove” next to active overlay

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Via API

curl -X DELETE http://localhost:5050/api/overlays/git-activity/apply

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Via CLI

codegraph overlay remove git-activity

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Combining Overlays

You can have multiple overlays active: 
# Apply multiple overlays
codegraph overlay apply git-activity
codegraph overlay apply test-coverage --report coverage.xml

# In UI, overlays can be toggled independently

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Creating Custom Overlays

See the Custom Overlays guide to create your own.

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What’s Next?

GPU Layout

Speed up layout for large graphs

Custom Overlays

Create your own overlay plugins