draw.io Diagram Skill

1. Basic Rules

• Edit only .drawio files
• Do not directly edit .drawio.png files
• Use auto-generated .drawio.png by pre-commit hook in slides

2. Font Settings

For diagrams used in Quarto slides, specify defaultFontFamily in mxGraphModel tag:

<mxGraphModel defaultFontFamily="Noto Sans JP" ...>

Also explicitly specify fontFamily in each text element's style attribute:

style="text;html=1;fontSize=27;fontFamily=Noto Sans JP;"

3. Conversion Commands

See conversion script at scripts/convert-drawio-to-png.sh.

# Convert all .drawio files
mise exec -- pre-commit run --all-files

# Convert specific .drawio file
mise exec -- pre-commit run convert-drawio-to-png --files assets/my-diagram.drawio

# Run script directly (using skill's script)
bash ~/.claude/skills/draw-io/scripts/convert-drawio-to-png.sh assets/diagram1.drawio

Internal command used:

drawio -x -f png -s 2 -t -o output.drawio.png input.drawio

Option	Description
-x	Export mode
-f png	PNG format output
-s 2	2x scale (high resolution)
-t	Transparent background
-o	Output file path

4. Layout Adjustment

4.1. Coordinate Adjustment Steps

1. Open .drawio file in text editor (plain XML format)
2. Find mxCell for element to adjust (search by value attribute for text)
3. Adjust coordinates in mxGeometry tag
   • x: Position from left
   • y: Position from top
   • width: Width
   • height: Height
4. Run conversion and verify

4.2. Coordinate Calculation

• Element center coordinate = y + (height / 2)
• To align multiple elements, calculate and match center coordinates

5. Design Principles

5.1. Basic Principles

• Clarity: Create simple, visually clean diagrams
• Consistency: Unify colors, fonts, icon sizes, line thickness
• Accuracy: Do not sacrifice accuracy for simplification

5.2. Element Rules

• Label all elements
• Use arrows to indicate direction (prefer 2 unidirectional arrows over bidirectional)
• Use latest official icons
• Add legend to explain custom symbols

5.3. Accessibility

• Ensure sufficient color contrast
• Use patterns in addition to colors

5.4. Progressive Disclosure

Separate complex systems into staged diagrams:

Diagram Type	Purpose
Context Diagram	System overview from external perspective
System Diagram	Main components and relationships
Component Diagram	Technical details and integration points
Deployment Diagram	Infrastructure configuration
Data Flow Diagram	Data flow and transformation
Sequence Diagram	Time-series interactions

5.5. Metadata

Include title, description, last updated, author, and version in diagrams.

6. Best Practices

6.1. Background Color

• Remove background="#ffffff"
• Transparent background adapts to various themes

6.2. Font Size

• Use 1.5x standard font size (around 18px) for PDF readability

6.3. Japanese Text Width

• Allow 30-40px per character
• Insufficient width causes unintended line breaks

<!-- For 10-character text, allow 300-400px -->
<mxGeometry x="140" y="60" width="400" height="40" />

6.4. Arrow Placement

• Always place arrows at back (position in XML right after Title)
• Position arrows to avoid overlapping with labels
• Keep arrow start/end at least 20px from label bottom edge

<!-- Title -->
<mxCell id="title" value="..." .../>

<!-- Arrows (back layer) -->
<mxCell id="arrow1" style="edgeStyle=..." .../>

<!-- Other elements (front layer) -->
<mxCell id="box1" .../>

6.5. Arrow Connection to Text Labels

For text elements, exitX/exitY don't work, so use explicit coordinates:

<!-- Good: Explicit coordinates with sourcePoint/targetPoint -->
<mxCell id="arrow" style="..." edge="1" parent="1">
  <mxGeometry relative="1" as="geometry">
    <mxPoint x="1279" y="500" as="sourcePoint"/>
    <mxPoint x="119" y="500" as="targetPoint"/>
    <Array as="points">
      <mxPoint x="1279" y="560"/>
      <mxPoint x="119" y="560"/>
    </Array>
  </mxGeometry>
</mxCell>

6.6. edgeLabel Offset Adjustment

Adjust offset attribute to distance arrow labels from arrows:

<!-- Place above arrow (negative value to distance) -->
<mxPoint x="0" y="-40" as="offset"/>

<!-- Place below arrow (positive value to distance) -->
<mxPoint x="0" y="40" as="offset"/>

6.7. Remove Unnecessary Elements

• Remove decorative icons irrelevant to context
• Example: If ECR exists, separate Docker icon is unnecessary

6.8. Labels and Headings

• Service name only: 1 line
• Service name + supplementary info: 2 lines with line break
• Redundant notation (e.g., ECR Container Registry): shorten to 1 line
• Use <br> tag for line breaks

6.9. Background Frame and Internal Element Placement

When placing elements inside background frames (grouping boxes), ensure sufficient margin.

• YOU MUST: Internal elements must have at least 30px margin from frame boundary
• YOU MUST: Account for rounded corners (rounded=1) and stroke width
• YOU MUST: Always visually verify PNG output for overflow

Coordinate calculation verification:

Background frame: y=20, height=400 -> range is y=20-420
Internal element top: frame y + 30 or more (e.g., y=50)
Internal element bottom: frame y + height - 30 or less (e.g., up to y=390)

Bad example (may overflow):

<!-- Background frame -->
<mxCell id="bg" style="rounded=1;strokeWidth=3;...">
  <mxGeometry x="500" y="20" width="560" height="400" />
</mxCell>
<!-- Text: y=30 is too close to frame top (y=20) -->
<mxCell id="label" value="Title" style="text;...">
  <mxGeometry x="510" y="30" width="540" height="35" />
</mxCell>

Good example (sufficient margin):

<!-- Background frame -->
<mxCell id="bg" style="rounded=1;strokeWidth=3;...">