dtourolle 202dacf350 fix(page): separate measurement context from the render canvas (S3)
add_child invalidated the canvas but left _draw bound to it, and the draw
property only rebuilt when _draw was None. Callers therefore got a context
pointing at a discarded image while page._canvas stayed None. table_layouter
reads page._canvas directly, so every image inside a table cell laid out after
any other content silently degraded to a grey [Image: WxH] placeholder.

The property now rebuilds when either half is missing. On its own that would
make layout allocate a full-page RGBA canvas per line, because layout measures
text through the page - so measurement moves to page.measurement_draw, a 1x1
scratch context that is never invalidated. Its mode matches the render canvas
so that Text's width cache does not hold two entries per word.

Children built against the scratch context are re-bound to the live canvas by
render_children, which already synchronised _draw and _canvas; that behaviour
was incidental and is now load-bearing and documented as such.

Regenerating the examples shows table images rendering as images rather than
placeholders. The empty header row in the second table of example 05 is
unrelated and pre-existing - row height ignores cell padding, so text is clipped
as padding grows - recorded as evidence under S6.
2026-08-06 22:37:24 +02:00
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PyWebLayout

Project Status

Badge Description
Test Coverage Test Coverage - Percentage of code covered by unit tests
Documentation Coverage Documentation Coverage - Percentage of code with docstrings
License License - Project licensing information
A Python library for HTML-like layout and rendering.

📋 Note: Badges show results from the commit referenced in the URLs. Red "error" badges indicate build failures for that specific step.

Description

PyWebLayout is a Python library for HTML-like layout and rendering to paginated images. It provides a flexible page rendering system with support for borders, padding, text layout, and HTML parsing.

Key Features

Page Rendering System

  • 📄 Flexible Page Layouts - Create pages with customizable sizes, borders, and padding
  • 🎨 Styling System - Control backgrounds, border colors, and spacing
  • 📐 Multiple Layouts - Support for portrait, landscape, and square pages
  • 🖼️ Image Output - Render pages to PIL Images (PNG, JPEG, etc.)

Text and HTML Support

  • 📝 HTML Parsing - Parse HTML content into structured document blocks
  • 🔤 Font Support - Multiple font sizes, weights, and styles
  • 🎨 Dynamic Font Families - Switch between Sans, Serif, and Monospace fonts on-the-fly
  • ↔️ Text Alignment - Left, center, right, and justified text
  • 📖 Rich Content - Headings, paragraphs, bold, italic, and more
  • 📊 Table Rendering - Full HTML table support with headers, borders, and styling
  • 🔘 Interactive Elements - Buttons, forms, and links with callback support

Architecture

  • Abstract/Concrete Separation - Clean separation between content structure and rendering
  • Extensible Design - Easy to extend with custom renderables
  • Type-safe - Comprehensive type hints throughout the codebase

Installation

pip install pyWebLayout

Quick Start

Basic Page Rendering

from pyWebLayout.concrete.page import Page
from pyWebLayout.style.page_style import PageStyle

# Create a styled page
page_style = PageStyle(
    border_width=2,
    border_color=(200, 200, 200),
    padding=(30, 30, 30, 30),  # top, right, bottom, left
    background_color=(255, 255, 255)
)

page = Page(size=(600, 800), style=page_style)

# Render to image
image = page.render()
image.save("my_page.png")

HTML Content Parsing

from pyWebLayout.io.readers.html_extraction import parse_html_string
from pyWebLayout.style import Font

# Parse HTML to structured blocks
html = """
<h1>Document Title</h1>
<p>First paragraph with <b>bold</b> text.</p>
<p>Second paragraph with more content.</p>
"""

base_font = Font(font_size=14)
blocks = parse_html_string(html, base_font=base_font)

# blocks is a list of structured content (Paragraph, Heading, etc.)

Visual Examples

The library supports various page layouts and configurations:

Page Styles
Page Rendering
Different borders, padding, and backgrounds
HTML Content
Text Layout
Parsed HTML with various text styles
Page Layouts
Page Layouts
Portrait, landscape, and square formats
Table Rendering
Table Rendering
HTML tables with headers and styling
Interactive Elements
Interactive Elements
Buttons, forms, and callback binding
🆕 Pagination & PageBreak
Pagination
Multi-page documents with explicit and automatic breaks
🆕 Link Navigation
Links
All 4 link types: Internal, External, API, Function
🆕 Comprehensive Forms
Forms
All 14 form field types with validation
🆕 Dynamic Font Family Switching
Font Switching
Switch between Sans, Serif, and Monospace fonts instantly

Examples

The examples/ directory contains working demonstrations:

Getting Started

🆕 Advanced Features (NEW)

Run any example:

cd examples
python 01_simple_page_rendering.py
python 08_pagination_demo.py  # NEW: Multi-page documents

All new examples include comprehensive test coverage! Run tests with:

python -m pytest tests/examples/ -v  # 30 tests, all passing ✅

Coverage Impact: The new examples fill critical documentation gaps:

  • PageBreak: 0% → 100% (had NO examples before)
  • LinkText: 14% → 100% (all 4 link types demonstrated)
  • FormFields: 14% → 100% (all 14 field types demonstrated)

See examples/README.md for detailed documentation.

Font Family Switching (NEW )

PyWebLayout now supports dynamic font family switching in the ereader, allowing readers to change fonts on-the-fly without losing their reading position!

Quick Example

from pyWebLayout.style.fonts import BundledFont
from pyWebLayout.layout.ereader_manager import create_ereader_manager

# Create an ereader
manager = create_ereader_manager(blocks, page_size=(600, 800))

# Switch to serif font
manager.set_font_family(BundledFont.SERIF)

# Switch to monospace font
manager.set_font_family(BundledFont.MONOSPACE)

# Restore original fonts
manager.set_font_family(None)

# Query current font
current = manager.get_font_family()

Features

  • 3 Bundled Fonts: Sans, Serif, and Monospace (DejaVu font family)
  • Instant Switching: Change fonts without recreating the document
  • Position Preservation: Reading position maintained across font changes
  • Attribute Preservation: Bold, italic, size, and color are preserved
  • Smart Caching: Automatic cache invalidation for optimal performance

Learn more: See FONT_SWITCHING_FEATURE.md for complete documentation.

Documentation

License

MIT License

Author

Duncan Tourolle - duncan@tourolle.paris

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