Pretext Justify
MYQ315 downloadsOptimal Knuth-Plass text justification for reading view.
- Overview
- Scorecard
- Updates7
Knuth-Plass optimal line-breaking for the Obsidian reading view. Replaces the browser's default word-wrap with typographically optimal paragraph layout.
Features
| Feature | Description |
|---|---|
| Optimal line breaking | Shortest-path DP over feasible break candidates; minimizes accumulated paragraph badness |
| Hyphenation | Optional soft-hyphen insertion for more even spacing |
| Last-line handling | Last line left-aligned; overflow prevention via DP penalty |
| Resize responsiveness | Auto re-justifies on width change, throttled via rAF (2 paragraphs per frame) |
| Inline formatting | Preserves bold, italic, links, code — anything the reading view renders within a paragraph |
| Fully offline | All processing happens locally — no network requests, no telemetry, no analytics |
How it works
The plugin uses a dynamic programming algorithm developed by Donald Knuth and Michael Plass for TeX. It enumerates all feasible break positions (word boundaries and soft hyphens), builds a graph where each edge is weighted by a "badness" cost, and finds the shortest path through:
dp[j] = min over i<j of dp[i] + badness(i, j)
The badness function combines:
- Cubic stretch/shrink ratio — the core Knuth cost, proportional to |ratio|³
- River penalty — heavy cost when inter-word spacing exceeds 150% of normal, preventing visual "rivers" of white space
- Tight penalty — cost when spacing drops below the configured threshold, avoiding cramped lines
- Hyphen penalty — small constant that prefers natural word breaks over hyphenated ones
For the last line, the algorithm penalizes break choices whose natural width (word text + normal spaces) exceeds the container, favoring solutions where the last line fits without compression.
The plugin uses Pretext for text measurement via Canvas API, and preserves DOM structure by extracting character ranges from a clone of the original paragraph — inline formatting survives the transformation.
Third-party code
This plugin bundles @chenglou/pretext (MIT) for Canvas-based text measurement. See the LICENSE file for the full MIT terms.
Configuration
| Setting | Default | Description |
|---|---|---|
| Hyphenation | On | Insert soft hyphens for more even spacing |
| Minimum spacing ratio | 0.50 | Lowest allowed word spacing as a fraction of normal space (0.30–0.90) |
| Tight penalty threshold | 0.75 | Fraction of normal space below which the algorithm penalizes tight lines (0.50–1.00) |
| Text cache size | 200 | Number of paragraphs cached to avoid remeasurement on resize (50–1000) |
Compliance
- No network access — all processing is local to the device. No data is sent or received.
- No telemetry — no analytics, no crash reporting, no usage tracking of any kind.
- No ads — the plugin displays no advertisements.
- No self-updating — updates are handled exclusively through Obsidian's built-in plugin update mechanism.
Development
git clone https://github.com/TYBLHQY/obsidian-pretext
cd obsidian-pretext
npm install
npm run build
Copy main.js, manifest.json, and styles.css to your vault's .obsidian/plugins/pretext-justify/.
License
MIT