Diagram Creation for Specific Slide

Focus on creating diagrams for a specific slide with multi-platform support (Mermaid, PlantUML, Excalidraw) using evidence-based cognitive load limits and colorblind-safe design.

Evidence Base: Diagram design follows research-based principles for cognitive load (max 7-9 nodes), colorblind accessibility, and visual clarity. See references/presentation-best-practices.md for guidelines.

Multi-Platform: Diagrams are automatically generated in all enabled formats (configurable in default.json or per-presentation slidev.config.json). Mermaid code is embedded inline by default, with PlantUML and Excalidraw alternatives saved for flexibility.

Execution

IMPORTANT - File Organization:

• Source files (.mmd, .puml, .excalidraw) → Always save to ./diagrams/
• Rendered images (.svg, .png) → Save to ./public/images/<slide-title>/
• This keeps sources version-controlled separately from generated outputs

CRITICAL - Embedding Rules:

• Mermaid: CAN be embedded inline in markdown (Slidev renders it)
• PlantUML: NEVER embed - only reference rendered SVG images
• Excalidraw: NEVER embed - only reference rendered SVG images

1. Parse Slide Number

Extract from $ARGUMENTS:

• Must be valid number
• If missing: Ask "Which slide number should we create a diagram for?"

2. Read Target Slide

Find slides.md and locate slide:

• Extract slide content
• Check if diagram already exists
• Understand slide topic and content

Show user the slide:

## Slide [N]: [Title]

**Current Content:**
[Slide content]

**Existing Visual:** [Yes: diagram type / No]

3. Analyze Content for Diagram Type (Evidence-Based)

Determine Best Platform (Mermaid vs Excalidraw vs PlantUML):

Analyze slide content to determine which platform best conveys the concept:

Use Excalidraw (invoke skill) when:

• Conceptual relationships need spatial layout
• Architecture with nested components (frames for boundaries)
• Brainstorming/ideation context (hand-drawn aesthetic)
• Informal, approachable style needed (whiteboard feel)
• Annotations and callouts would add value
• Mind maps or radial structures
• Keywords detected: "architecture", "components", "system design", "overview", "spatial"

Use Mermaid (standard flow) when:

• Linear process/workflow flows
• Sequence diagrams (time-based interactions)
• State machines (formal state transitions)
• Gantt charts (project timelines)
• ER diagrams (database schemas)
• Formal, structured diagrams preferred

Use PlantUML when:

• Formal UML notation required
• Deployment diagrams
• Complex class diagrams

If Excalidraw is best fit:

CRITICAL: Excalidraw Workflow (NEVER embed JSON in markdown)

1. Invoke the Excalidraw Generation skill using Skill tool:

   skill: "slidev:excalidraw-generation"
   

2. The skill will:

   • Create Excalidraw JSON at diagrams/<slug>.excalidraw
   • Render to SVG at public/images/<slug>/diagram-excalidraw.svg
   • NOT embed JSON in markdown

3. Add SVG image reference to slide (NOT the JSON):

   ![Diagram](./public/images/<slug>/diagram-excalidraw.svg)
   

The skill takes over the complete generation process with semantic redesign approach.

If Mermaid/PlantUML is best fit, continue below:

Use visual-design skill to determine appropriate Mermaid diagram types:

Process/Workflow → Flowchart (max 7-9 nodes) System Interaction → Sequence Diagram (max 5-7 participants) Data Structure → Class/ER Diagram (max 6-8 entities) State Changes → State Diagram (max 7-9 states) Timeline → Gantt Chart (max 6-8 tasks) Architecture → Component/Deployment Diagram (max 7-9 components)

Cognitive load research: Working memory handles 7±2 items. Keep diagrams within this limit for instant comprehension.

4. Generate Multiple Diagram Options

Create 2-4 variations showing different approaches:

## Diagram Options for Slide [N]

### Option 1: Flowchart (Top-Down) ⚡

**Best for:** Showing linear process flow

**Evidence-based design:**
- **Node count**: 7 nodes (within 7±2 cognitive load limit ✓)
- **Colorblind-safe**: Blue + Orange palette (verified safe)
- **Contrast**: All text meets 4.5:1 minimum
- **Readability**: Sans-serif labels, clear arrows

**Diagram:**
```mermaid
%%{init: {'theme':'base', 'themeVariables': {
  'primaryColor':'#3b82f6',
  'primaryTextColor':'#fff',
  'primaryBorderColor':'#2563eb',
  'lineColor':'#6b7280',
  'secondaryColor':'#f97316'
}}}%%
graph TD
    A[Start: User Request] --> B{Validate Input}
    B -->|Valid| C[Process Request]
    B -->|Invalid| D[Return Error]
    C --> E[Save to Database]
    E --> F[Return Success]
    D --> G[End]
    F --> G

Element count check: Diagram = 1 element. Verify total slide elements ≤6.

Pros:

• Clear linear flow
• Shows decision points
• Easy to follow
• Within cognitive load limit (7 nodes)

Cons:

• Takes more vertical space

---

Option 2: Flowchart (Left-Right) ⚡

Best for: Fitting in wide slides

Diagram:

%%{init: {'theme':'base', 'themeVariables': {'primaryColor':'#3b82f6'}}}%%
graph LR
    A[Input] --> B[Validate]
    B --> C[Process]
    C --> D[Save]
    D --> E[Output]

Pros:

• Compact, fits in image-right layout
• Clean and simple

Cons:

• Less detail than Option 1

---

Option 3: Sequence Diagram ⚡

Best for: Showing interactions over time

Diagram:

sequenceDiagram
    participant User
    participant API
    participant Database

    User->>API: Request
    API->>API: Validate
    API->>Database: Query
    Database-->>API: Data
    API-->>User: Response

Pros:

• Shows temporal flow
• Clear component interactions

Cons:

• Different perspective than flowchart

---

Option 4: State Diagram ⚡

Best for: Showing status changes

Diagram:

stateDiagram-v2
    [*] --> Pending
    Pending --> Processing
    Processing --> Success
    Processing --> Error
    Error --> Pending : Retry
    Success --> [*]

Pros:

• Shows state transitions
• Clear lifecycle

Cons:

• More abstract

---

Which option works best for your slide?

1. Flowchart Top-Down (detailed)
2. Flowchart Left-Right (compact)
3. Sequence Diagram (interaction focus)
4. State Diagram (lifecycle focus)
5. Let me create a custom variation

### 5. Generate Multi-Platform Diagram

Based on user selection, generate diagram in all enabled formats:

**Step 1: Extract slide title for directory naming**
Read the slide to get its title for creating organized storage.

**Step 2: Generate all formats using orchestration script**
```bash
${CLAUDE_PLUGIN_ROOT}/scripts/generate-multi-platform-diagram.sh \
  "[Slide Title]" \
  "[Mermaid Code]" \
  "."

This automatically:

• Creates diagrams/ directory for source files
• Creates public/images/<slide-title-mangled>/ directory for rendered images
• Generates Mermaid source (diagrams/<slug>.mmd) and rendered image (public/images/<slug>/diagram.svg)
• Translates to PlantUML (diagrams/<slug>.puml) and renders if enabled
• Translates to Excalidraw (diagrams/<slug>.excalidraw) and renders if enabled
• Applies colorblind-safe theme to all formats

Directory Structure:

diagrams/                            # ALL sources (top-level, version controlled)
  ├── <slug>.mmd                     # Mermaid source
  ├── <slug>.puml                    # PlantUML source
  └── <slug>.excalidraw              # Excalidraw JSON source

public/images/<slug>/                # Rendered images only
  ├── diagram.svg                    # Mermaid rendered
  ├── diagram-plantuml.svg           # PlantUML rendered
  └── diagram-excalidraw.svg         # Excalidraw rendered

NO EXCEPTIONS: Sources ALWAYS go in ./diagrams/, renders go in ./public/images/<slug>/

Step 3: Embed Mermaid inline in slide (default) Add diagram directly to slide:

# Slide Title

Content before diagram

```mermaid
[chosen diagram code with theme variables]

Remaining content

**Step 4: Show user all generated formats**
```markdown
✅ Diagram Generated for Slide [N]: [Title]

**Embedded in slide**: Mermaid (inline rendering by Slidev)

**Source files in** `diagrams/`:
- `[slug].mmd` - Mermaid source
- `[slug].puml` - PlantUML source (if enabled)
- `[slug].excalidraw` - Excalidraw JSON source (if enabled)

**Rendered images in** `public/images/[mangled-title]/`:
- `diagram.svg` - Mermaid rendered (if mmdc available)
- `diagram-plantuml.svg` - PlantUML rendered (if enabled)
- `diagram-excalidraw.svg` - Excalidraw rendered (if enabled)

**To switch formats in slide:**
Replace mermaid code block with image reference:
![Diagram](./public/images/[mangled-title]/diagram-plantuml.svg)

**To edit sources:**
- Mermaid: Edit `diagrams/[slug].mmd`
- PlantUML: Edit `diagrams/[slug].puml`
- Excalidraw: Open `diagrams/[slug].excalidraw` at https://excalidraw.com

6. Customize Diagram

Offer customization:

Theme Colors (Colorblind-Safe): "Should we adjust the colors to match your presentation theme?"

Apply colorblind-safe theme (Blue + Orange verified safe):

%%{init: {'theme':'base', 'themeVariables': {
  'primaryColor':'#3b82f6',      /* Blue - 8.6:1 contrast */
  'secondaryColor':'#f97316',    /* Orange - 3.4:1 (headings) */
  'lineColor':'#6b7280',         /* Gray - neutral */
  'tertiaryColor':'#8b5cf6'      /* Purple - accent */
}}}%%

Accessibility verification:

• Blue on white: 8.6:1 contrast ✓
• Orange on white: 3.4:1 (headings ≥24pt only) ✓
• Safe for deuteranopia, protanopia, tritanopia ✓

Complexity (Evidence-Based Limits): "Should we simplify (fewer nodes) or add more detail?"

Cognitive load guidance:

• Current nodes: [X]
• Recommended max: 7-9 nodes (working memory limit)
• If >9 nodes: Strongly recommend splitting into multiple slides
• If <5 nodes: Can add detail if needed

Adjust based on feedback while enforcing evidence-based limits.

Layout: "Should we use a different layout?"

• Change graph TD to graph LR
• Rearrange nodes
• Adjust spacing

7. Preview and Iterate

Show updated slide:

## Updated Slide [N]

[Full slide with new diagram]

---

**Changes:**
- Added [diagram type]
- Applied theme colors
- [Other changes]

Does this work? Any adjustments needed?

Allow iteration:

• Tweak diagram
• Change type
• Adjust colors
• Simplify/complexify

8. Final Confirmation

Once satisfied:

## ✅ Diagram Added to Slide [N]

**Diagram Type:** [Type]
**Rendering:** [Inline / Offline SVG]
**Theme:** [Colors applied]

**Preview:**
```bash
cd [presentation-dir]
slidev slides.md

Navigate to slide [N] to see diagram.

Edit Diagram: Diagram code is in slides.md at slide [N]. Edit directly or run /slidev:diagram [N] again.

## Diagram Types Reference

Quick guide for user:

**Flowchart** - Processes, workflows, algorithms
- `graph TD` (top-down) or `graph LR` (left-right)
- Rectangles, diamonds (decisions), arrows

**Sequence** - API calls, interactions, message flow
- Shows temporal sequence
- Participants and messages

**Class** - Object models, data structures
- Classes with attributes/methods
- Relationships (inheritance, association)

**State** - Lifecycles, status transitions
- States and transitions
- Start/end states

**ER** - Database schemas, data relationships
- Entities and relationships
- Cardinality

**Gantt** - Timelines, schedules, roadmaps
- Tasks over time
- Dependencies

## Advanced Options

**Multiple diagrams:**
"Should we add multiple diagrams to this slide?"
- Use `two-cols` layout
- Show different perspectives
- Before/after comparison

**Interactive diagrams:**
"Want to add click animations?"
```markdown
```mermaid{click:1}
graph TD
    A --> B
    B --> C

**Custom styling:**
"Want to customize beyond theme colors?"
- Node shapes
- Line styles
- Icons in nodes
- Custom CSS

## Error Handling

**Diagram too complex:**
- Simplify (max 7-9 nodes recommended)
- Split into multiple diagrams
- Use higher-level abstraction

**Rendering issues:**
- Fall back to inline
- Check mermaid syntax
- Provide code for manual rendering

**Doesn't fit slide:**
- Try different layout (LR vs TD)
- Use image-right layout
- Make diagram full-slide

## Evidence-Based Diagram Quality Standards

**Cognitive Load (CRITICAL):**
- ✓ Max 7-9 nodes/elements (working memory research)
- ✓ If >9: Split into multiple diagrams or slides
- ✓ Progressive disclosure: Build complex diagrams across slides

**Accessibility (REQUIRED):**
- ✓ Colorblind-safe palette (Blue + Orange verified)
- ✓ Don't rely on color alone (use labels + shapes + patterns)
- ✓ High contrast: 4.5:1+ for all text
- ✓ Font sizes: Match slide minimum (≥18pt equivalent)

**Visual Clarity:**
- ✓ Clear directional flow (typically left-to-right or top-to-bottom)
- ✓ Consistent node naming and shapes
- ✓ Minimal crossing lines (reduce visual complexity)
- ✓ Adequate spacing between elements

**Element Count:**
- Diagram counts as **1 element** in total slide count
- Verify: diagram + bullets + other content ≤6 total elements

## Tips

- **Enforce cognitive load limit** (max 7-9 nodes, split if more)
- **Use colorblind-safe theme** (Blue #3b82f6 + Orange #f97316)
- **Don't rely on color alone** (add labels and shapes)
- **Apply theme colors consistently** for cohesion
- **Test in preview** before finalizing
- **Consider slide layout** when choosing diagram type (TD vs LR)
- **Simplify complex diagrams** (higher abstraction level or multiple slides)

Inform user diagram is complete!