dtourolle
456824d6d6
render_page_backward searched for the previous page's start: estimate a block index, lay out forward, bisect on the block difference, up to ten times. Both the estimator and the adjuster pinned word_index to 0 and moved only block_index - but pages routinely start mid-block, so the answer was not in the search space. The loop could never match, exhausted its iterations and fell through to a fallback that jumped to the start of the document. Measured on a document with one 1200-word paragraph, whose page starts are (0,0), (2,208), (2,494), (2,780): three of four backward calls returned (0,0), each after ten full page layouts. The bisection was unsound in its own space too - 40 small paragraphs, every page starting on a block boundary, also failed. Pagination is a pure function, so the page before P is the q with next(q) == P, and it is found by replaying the chain forward rather than guessing q. Three sources: the chain recorded as pages are laid out forward (exact, one layout, covers paging back and forth); replay from the block containing P and then from earlier blocks (exact when P lies on that chain); and failing that, the last start before P, which overlaps slightly rather than skipping content. warm: 4/4 exact, 1 layout each cold, fresh layouter per call: 12/13 exact, worst 17 layouts cold, repeated back presses: ~4 layouts per turn Each step returns a page ending exactly where the reader is, so paging back never skips or repeats content. That chain can differ from the one seen reading forward from page one if the reader arrived by a jump - pagination from a different start is a different chain, and nothing can recover the original without replaying the whole document. Complementary to S11 rather than caused by it: before S11 forward pagination dead-ended at the first page-spanning block, so mid-block starts never arose and the block-granular search looked adequate.
PyWebLayout
Project Status
| Badge | Description |
|---|---|
 |
Test Coverage - Percentage of code covered by unit tests |
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Documentation Coverage - Percentage of code with docstrings |
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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 Different borders, padding, and backgrounds |
HTML Content Parsed HTML with various text styles |
Page Layouts Portrait, landscape, and square formats |
Table Rendering HTML tables with headers and styling |
Interactive Elements Buttons, forms, and callback binding |
|
🆕 Pagination & PageBreak Multi-page documents with explicit and automatic breaks |
🆕 Link Navigation All 4 link types: Internal, External, API, Function |
🆕 Comprehensive Forms All 14 form field types with validation |
|
🆕 Dynamic Font Family Switching Switch between Sans, Serif, and Monospace fonts instantly |
|
Examples
The examples/ directory contains working demonstrations:
Getting Started
- 01_simple_page_rendering.py - Introduction to the Page system
- 02_text_and_layout.py - HTML parsing and text rendering
- 03_page_layouts.py - Different page configurations
- 04_table_rendering.py - HTML table rendering with styling
- 05_html_table_with_images.py - Tables with embedded images
- 06_functional_elements_demo.py - Interactive buttons and forms with callbacks
- 08_bundled_fonts_demo.py - Using the bundled DejaVu font families
🆕 Advanced Features (NEW)
- 08_pagination_demo.py - Multi-page documents with PageBreak (11 tests)
- 09_link_navigation_demo.py - All link types and navigation (10 tests)
- 10_forms_demo.py - All 14 form field types (9 tests)
- 11_font_family_switching_demo.py - 🆕 Dynamic font switching in ereader
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
- ARCHITECTURE.md - Abstract/Concrete architecture guide
- FONT_SWITCHING_FEATURE.md - 🆕 Font family switching guide
- examples/README.md - Complete examples guide with tests
- docs/images/README.md - Visual documentation index
- pyWebLayout/layout/README_EREADER_API.md - EbookReader API reference
- API Reference - See docstrings in source code
License
MIT License
Author
Duncan Tourolle - duncan@tourolle.paris