Dasu — Sheet Layout Tool Project

a work in progress :)

出す (dasu) — Japanese: to output / to print

A free, open-source browser-based sheet layout tool built for the Bonsai BIM / IfcOpenShell ecosystem — and anyone else who needs to compose print-ready drawing sheets without proprietary software.

Developed independently for the benefit of the OSArch and Bonsai communities and everyone else.

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What is it?

Dasu is a single HTML file that runs entirely in your browser. No install. No subscription. No cloud. No vendor lock-in. Open it in Chrome or Edge (other browsers have not been tested) and it works — on a home PC, a locked-down government machine, a borrowed laptop or your phone.

Confession

I am using Claude AI to do this project, I had an idea of what I wanted the app to look like and how it should work but no idea how to write the HTML.

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Quick Start

1. Download dasu.html
2. Open in Edge or Chrome (I don't know if it works in other browsers) — directly as a local file (Ctrl+O)
3. Choose a template from the Start dialog
4. Drag SVG, PNG, JPG, or PDF files onto the sheet

For DXF import and Bonsai BIM live connection, also run the bridge server (work in progress):

python bridge/dasu_bridge.py

Terminology

• Elements: external stuff that has been placed on drawing sheets. Elements can be SVG, PNG, JPG, PDF, DXF (work in progress)
• Objects: internal things like Annotations, lines, circles, polygons, text and dimensions

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Features

Sheet Canvas

• A4 · A3 · A2 · A1 · Letter, portrait/landscape
• Configurable grid (1–25 mm), zoom/pan, fit-to-sheet
• Sheet background permanently locked
• Elements cannot be placed behind sheet background

Import Sources - Elements

• SVG — drag-drop or file picker (Inkscape SVGs fully supported)
• PNG / JPG — drag-drop or file picker
• PDF — page picker with 1×–4× render resolution
• DXF — converted via bridge server (ezdxf, work in progress)
• Bonsai BIM — live push from Blender N-panel via bridge (work in progress)

Bonsai SVG Intelligence

• Auto-reads data-scale — scale field pre-populated on import
• Detects xmlns:ifc= namespace
• Style Manager — edit CSS classes (IfcWall, PredefinedType-LINEWORK etc.) per drawing. Presets:Regional Drawing Standard, Greyscale Print, Colour by Class. Preserve white fills option keeps text/marker backgrounds intact.

Element Panel

• Position, size (mm), scale label drives resize (centre-anchored, reversible, 10× warning)
• Order, align, mirror, crop, lock
• Colour Override — Original / Black / Greyscale / Single colour
• Bonsai BIM Drawing section with Style Manager access
• DXF Layers section

Snap Engine

• Grid snap, sheet edges/centres, element edges/centres, equal spacing
• Smart guides, ortho lock (Ctrl), angle snap (Shift)
• Arrow key nudge

Annotation Tools - Objects (not trying to be a CAD app)

• Line, Polyline/Polygon, Rectangle, Circle/Ellipse, Arrow/Leader
• Dimension — three-click workflow, H/V/A modes, live rubber-band, scale-aware
• Text — formatting, background box, revision cloud border
• All annotate tools suspend element selection

Canvas UX

• ☰ Elements panel — list all elements, toggle hide/show and lock per element
• Lock icon on hover only — clean canvas, icon appears only on mouse-over
• Shift+rotate — snaps to lineAngleSnap increment
• Copy (Ctrl+C) / Paste internal (Ctrl+Shift+V) / Paste OS (Ctrl+V)
• Duplicate (Ctrl+D), Select all (Ctrl+A), Order (Ctrl+[/])
• Space to pan, G to toggle grid, S to toggle snap

Sheets

• Duplicate sheet — Shift+click + or right-click tab
• Delete sheet — right-click tab
• Rename sheet — double-click tab or right-click tab

File System

• .bprint format — Portable or Referenced
• Save As with OS native folder picker
• Auto-save to IndexedDB, recent files, templates, start dialog

Export

• PDF (jsPDF), SVG, browser Print
• Outputs panel pinned to left sidebar bottom

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Bonsai BIM Bridge

python bridge/dasu_bridge.py

Listens on localhost:7821. Handles:

• Live drawing push from Blender N-panel
• DXF→SVG conversion via ezdxf (pip install ezdxf Pillow)
• In-app ezdxf install button (no terminal needed)

One-click startup (Windows)

@echo off
start "" python C:\dasu\bridge\dasu_bridge.py
timeout /t 2
start msedge "file:///C:/dasu/dasu.html"

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Tech Stack

Library	Licence	Purpose
Fabric.js 5.3.1	MIT	Canvas
jsPDF 2.5.1	MIT	PDF export
PDF.js 3.11	Apache 2.0	PDF import
ezdxf (bridge)	MIT	DXF→SVG

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Project Structure

dasu/
├── dasu.html
├── bridge/dasu_bridge.py
├── blender/dasu_panel.py
├── docs/
│   ├── dasu-onepager.docx
│   └── dasu-kb-shortcuts.xlsx
├── README.md
├── CHANGELOG.md
└── .gitignore

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Licence

MIT

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Dasu.print v0.4.0-alpha · 出す · github.com/4nigel/dasu