engrapha-diagrams 0.1.1

Vector-native PDF diagram toolkit for ReportLab Platypus

Transparency Notice: Built to solve my own frustration with inconsistent AI-generated notes. Heavy AI assistance was used for code generation, but the architecture, testing, and curation are mine.

📊 engrapha_diagrams

Project Status: Early alpha — feedback welcome!

Vector-native PDF diagram toolkit for ReportLab Platypus. Draw complex diagrams natively inside your ReportLab documents with a clean, pythonic API.

No raster images, no external command-line tools, and no internet connection required. All diagram types compile directly to reportlab.graphics.shapes.Drawing objects that wrap seamlessly as Platypus Flowables.

---

🚀 Features

• Flowchart: ANSI/ISO flowchart symbols (terminals, processes, decisions, io, connectors).
• SequenceDiagram: UML sequence diagrams (actors, lifelines, activation bars, message arrows, dividers).
• ClassDiagram: UML class diagrams (class boxes, headers, attributes, methods, relations).
• ERDiagram: Entity-Relationship diagrams (entities, relations, primary key and multi-value attributes).
• StateMachine: DFA/NFA and process state diagrams (states, transitions, initial/accepting indicators).
• NetworkDiagram: Network topology (hosts, servers, databases, links).
• ArchitectureDiagram: System architecture topologies with clients, services, databases, queues, and auto-routed connections.
• AWSDiagram: Cloud infrastructure architecture with AWS icons (EC2, S3, RDS, Lambda, SQS).
• GitDiagram: Git branch timeline diagrams with commits, merges, and distinct branch lanes.
• SchemaDiagram: Database table schema definition diagrams with field types, primary keys, and foreign-key links.
• C4ContainerDiagram: C4 Model container diagrams with System Context, Container, Component layers, and descriptive relationships.
• TimingDiagram: Digital waveform timing diagrams.
• LayeredStack: OSI model, TCP/IP stack, memory hierarchy.
• Standalone Export: Save drawings directly to PDF, SVG, and PNG/JPG formats.

---

📦 Installation

Install the package locally from the monorepo root:

pip install ./packages/engrapha_diagrams

---

🎨 Supported Diagram Types & Examples

1. Flowchart

Draw processes, decisions, and connectors with auto-layout or manual coordinates.

import engrapha_diagrams as ed

# Create a horizontal flowchart with a custom scale factor
fc = ed.Flowchart(
    width=400,
    height=150,
    direction="LR",      # 'TB' (top-to-bottom, default) or 'LR' (left-to-right)
    scale_factor=1.0,    # Optional manual override for text/box sizing (default: auto-computed)
)
fc.terminal("start", "START")
fc.process("calc", "Compute Sum")
fc.decision("check", "Sum > 100?")
fc.terminal("end", "END")

fc.edge("start", "calc")
fc.edge("calc", "check")
fc.edge("check", "end", branch="yes")
fc.edge("check", "calc", branch="no", orthogonal=True)

2. Sequence Diagram

Draw actor interactions over lifelines.

import engrapha_diagrams as ed

seq = ed.SequenceDiagram(width=400, height=220)
seq.actor("c", "Client")
seq.actor("s", "Server")

seq.activate("c")
seq.message("c", "s", "HTTP GET /index.html")
seq.activate("s")
seq.divider("Internal Processing")
# Arrow styles: 'solid' (default), 'dashed', 'solid_open', 'dashed_open'
seq.message("s", "c", "200 OK (HTML Document)", arrow="dashed")
seq.deactivate("s")
seq.deactivate("c")

3. Layered Stack

Draw OSI stacks, memory hierarchies, or layered architectures.

import engrapha_diagrams as ed

stack = ed.LayeredStack(width=300, height=180)
stack.layer("Application", sublabel="HTTP, DNS")
stack.layer("Transport", sublabel="TCP, UDP")
stack.divider()  # Draw a thicker divider line after Transport layer
stack.layer("Network", sublabel="IP, ICMP")
stack.layer("Link", sublabel="Ethernet")

4. Network Diagram

Draw network topologies with hosts, clouds, switches, routers, and firewalls.

import engrapha_diagrams as ed

net = ed.NetworkDiagram(width=500, height=220)
net.node("inet", "Internet", x=50, y=110, kind="cloud")
net.node("fw", "Firewall", x=160, y=110, kind="firewall")
net.node("sw", "Core Switch", x=270, y=110, kind="switch")
net.node("srv", "Web Server", x=380, y=150, kind="server")
net.node("db", "Database", x=380, y=70, kind="database")

net.link("inet", "fw")
net.link("fw", "sw")
net.link("sw", "srv")
net.link("sw", "db")

# Also supports building standard topologies programmatically:
# net.star_topology(center_id="sw", center_label="Switch", spoke_ids=["h1", "h2", "h3"])
# net.bus_topology(node_ids=["n1", "n2", "n3"])
# net.ring_topology(node_ids=["r1", "r2", "r3"])
# net.mesh_topology(node_ids=["m1", "m2", "m3"])
# net.tree_topology(parent_child_map={"root": ["child1", "child2"]})

5. UML Class Diagram

Draw UML class diagrams with visibility, attributes, and methods.

import engrapha_diagrams as ed

cd = ed.ClassDiagram(width=400, height=250, class_w=120)
cd.uml_class("Shape", "Shape", stereotype="abstract", methods=["+ area(): double"])
cd.uml_class("Circle", "Circle", attributes=["- radius: double"], methods=["+ area(): double"])
# Relationship kinds: 'inheritance', 'realization', 'composition', 'aggregation', 'association', 'dependency'
cd.relate("Circle", "Shape", kind="inheritance")

6. Entity-Relationship Diagram (ER)

Draw entity-relationship diagrams (Chen notation) with cardinalities.

import engrapha_diagrams as ed

er = ed.ERDiagram(width=450, height=200)
er.entity("Customer")
er.relationship("Buys")
er.entity("Product")
er.entity_attributes("Customer", [("ID", {"pk": True}), "Name"])
er.entity_attributes("Product", [("SKU", {"pk": True}), "Price"])
er.connect("Customer", "Buys", card_from="1", card_to="N")
er.connect("Product", "Buys", card_from="1", card_to="N")

7. State Machine (DFA / Process Transitions)

Draw finite state automata or lifecycle models.

import engrapha_diagrams as ed

sm = ed.StateMachine(width=400, height=180)
sm.state("s0", "Init", x=70, y=90, initial=True)
sm.state("s1", "Active", x=200, y=90)
sm.state("s2", "Success", x=330, y=90, accepting=True)

sm.transition("s0", "s1", label="start")
sm.transition("s1", "s1", label="process")
sm.transition("s1", "s2", label="complete")

8. Timing Diagram

Draw digital timing signal waveforms.

import engrapha_diagrams as ed

td = ed.TimingDiagram(width=400, height=150)
td.clock("CLK", period=20.0, cycles=6)
td.signal("RESET", transitions=[(0, 1), (15, 0)])
td.signal("DATA", transitions=[(0, 0), (35, 1), (75, 0)])

9. Database Schema Diagram

Draw database table structures with primary/foreign keys and relationships.

import engrapha_diagrams as ed

schema = ed.SchemaDiagram(width=450, height=200)
schema.table("users", [
    ("id", "INTEGER", {"pk": True}),
    ("email", "VARCHAR", {}),
    ("created_at", "TIMESTAMP", {})
])
schema.table("orders", [
    ("id", "INTEGER", {"pk": True}),
    ("user_id", "INTEGER", {"fk": True}),
    ("total", "DECIMAL", {})
])
schema.relation("orders", "user_id", "users", "id")

10. Service Architecture Diagram

Draw multi-tier system topologies (clients, microservices, databases, queues) with automatic or manual layouts.

import engrapha_diagrams as ed

# Supports orientation: 'horizontal' (default) or 'vertical'
arch = ed.ArchitectureDiagram(width=450, height=220, orientation="horizontal")
arch.client("web", "Web Client")
arch.service("api", "Gateway API")
arch.database("db", "Main Database")
arch.queue("q", "Message Broker")

arch.connect("web", "api", "HTTPS")
arch.connect("api", "db", "TCP/3306")
arch.connect("api", "q", "AMQP")

11. C4 Container Diagram

Draw C4 Model Container views to document software systems, containers, technologies, and relationships.

import engrapha_diagrams as ed

c4 = ed.C4ContainerDiagram(width=400, height=200)
c4.system("user", "Customer")
c4.container("web", "SPA (React)", "Provides shopping UI")
c4.container("api", "API Application (Go)", "Handles business logic")
c4.container("db", "Database (Postgres)", "Stores order data")

c4.relate("user", "web", "Uses")
c4.relate("web", "api", "Makes API calls to")
c4.relate("api", "db", "Reads/Writes to")

12. Git Branch Flow Diagram

Draw commits, branch lanes, merges, and timelines horizontally.

import engrapha_diagrams as ed

git = ed.GitDiagram(width=400, height=150)
git.commit("main", "C1: Initial Commit")
git.branch("main", "feature")
git.commit("feature", "C2: Implement login")
git.commit("main", "C3: Hotfix bug")
git.merge("feature", "main", "C4: Merge feature/login")

13. AWS Diagram

Draw AWS cloud infrastructure diagrams using vector-native AWS icons.

import engrapha_diagrams as ed

# Supports orientation: 'horizontal' (default) or 'vertical'
aws = ed.AWSDiagram(width=450, height=220, orientation="horizontal")
# Supported node methods: ec2(), rds(), s3(), lambda_fn(), sqs()
aws.ec2("web", "Web Server")
aws.rds("db", "RDS PostgreSQL")
aws.s3("bucket", "S3 Storage")
aws.sqs("queue", "Job Queue")

aws.connect("web", "db", "SQL Connection")
aws.connect("web", "bucket", "Uploads")
aws.connect("web", "queue", "Events")

---

🎨 Diagram Theming & Integration

engrapha_diagrams comes with built-in dark and light themes, and can dynamically inherit themes from engrapha_notes for consistent visual layouts.

1. Using Preset Diagram Themes

Apply a theme directly to your builder instance:

import engrapha_diagrams as ed

# Use preset theme (ed.DARK or ed.LIGHT)
diagram = ed.Flowchart(width=300, height=200, theme=ed.LIGHT)

2. Matching Notes Theme (Integration)

Derive matching diagram settings from the active document notes theme:

import engrapha_notes as en
import engrapha_diagrams as ed

# 1. Set the notes theme
en.set_theme(en.OCEAN_DARK)

# 2. Derive the matching diagram theme
diag_theme = ed.DiagramTheme.from_notes_theme(en.get_theme())

# 3. Apply it to your diagrams
fc = ed.Flowchart(width=400, height=200, theme=diag_theme)

3. Customizing & Overriding Themes

Modify a theme on the fly using model_copy(update={...}):

# Create a print-optimized black-and-white diagram theme
bw_theme = ed.DiagramTheme.from_notes_theme(en.get_theme()).model_copy(
    update={
        "stack_colors": ("#ffffff", "#ffffff", "#ffffff"),
        "stack_stroke": "#000000",
        "stack_text": "#000000",
        "stack_sublabel_text": "#000000",
        "bg": "#ffffff",
        "text": "#000000",
        "node_fill": "#ffffff",
        "node_stroke": "#000000",
        "node_text": "#000000",
        "font_name": "Times-Roman",
        "font_name_bold": "Times-Bold",
        "font_name_italic": "Times-Italic",
    }
)
# Apply to stack diagram
stack = ed.LayeredStack(width=300, height=180, theme=bw_theme)

---

💾 Standalone Export

Export your diagrams directly to vector or raster formats without a ReportLab story:

diagram = ed.Flowchart(width=300, height=200)
diagram.terminal("s", "START").terminal("e", "END").edge("s", "e")

# Save to PDF (vector)
diagram.save("output.pdf")

# Save to SVG (vector)
diagram.save("output.svg")

# Save to PNG (raster)
diagram.save("output.png")

---

📝 Integration with engrapha_notes

To embed a vector diagram into an Engrapha notes document, call .as_flowable() and pass it to en.add(...):

import engrapha_notes as en
import engrapha_diagrams as ed

fc = ed.Flowchart(width=en.CW, height=200)
fc.terminal("s", "START").terminal("e", "END").edge("s", "e")

# Add the diagram flowables directly
en.add(fc.as_flowable())

Static Type-Checking (Pyright / Pylance)

If you see static type warnings in your IDE:

Argument of type "list[Unknown]" cannot be assigned to parameter "x" of type "Flowable" in function "add"

This happens because .as_flowable() returns a list[Flowable] (which packages the drawing flowable along with its optional caption Paragraph flowable) rather than a single raw Flowable.

engrapha_notes handles this union type cleanly. Calling en.add(diagram.as_flowable()) is type-safe and fully compliant.

---

💻 Command Line Interface (CLI)

The package exposes a command-line script alias to show a comprehensive API guide and Markdown DSL reference:

engrapha-diagrams
# or: engrapha-diagram, engrapha_diagrams, engrapha_diagram, pdfdiagrams, pdfdiagram

Run it to display:

1. Complete Python constructors and methods for all 13 diagram types.
2. Standalone export guidelines.
3. Matching diagram settings and themes.
4. Full syntax reference for the diagram DSL (used when embedding drawings in engrapha-notes Markdown compiler documents).

[!IMPORTANT] Compilation requires engrapha: The diagram CLI (engrapha-diagrams) is for reference only. To actually compile a Markdown document containing these diagram blocks, you must install the engrapha-notes package and use the main engrapha compiler CLI:

pip install engrapha-notes[all]
engrapha input.md --output output.pdf

---

📋 Requirements & License

• Python >= 3.11
• reportlab >= 4.5.1
• pydantic >= 2.13.4
• Licensed under the MIT License.