Spreads Mode Document Metadata & High-DPI Persistence
Designing multi-page booklets, magazines, and greeting cards often involves switching between single-page layouts and side-by-side two-page spreads. In version 5.1.9, Open Publisher resolved an issue where single-page publications configured with high-DPI print resolutions (such as 200 DPI or 300 DPI) accidentally opened in two-page spread mode. Spreads mode is now driven entirely by explicit document metadata rather than arbitrary pixel dimension thresholds.
📖Single-Page vs. Two-Page Spread Layout Mode
Spreads mode is preserved authoritatively in document metadata, preventing high-resolution files from opening as spreads.
The Legacy Pixel Width Inference Flaw
Investigation revealed that the file loader contained a legacy inference rule intended for early document versions that lacked dedicated spreads metadata:
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Width Threshold Assumption: The loader in io/publisher-file-loader.js executed state.isSpreadMode = w >= 1500, assuming that any page width of 1500px or greater represented two facing pages side-by-side (such as 2x A4 at 96 DPI = 1588px).
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High-DPI Collision: While this assumption worked at 96 DPI, any standard single-page document saved at higher print resolutions exceeded the 1500px boundary (for instance, single A4 at 200 DPI is 1654px; single A4 at 300 DPI is 2480px).
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Unintended Mode Activation: Consequently, single-page print flyers and brochures saved at 300 DPI reopened with Spreads mode enabled, splitting single pages across two facing viewports.
Metadata-Driven Spreads Contract
The width-based inference was removed across the loading and saving architecture:
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Authoritative Metadata: The application now reads state.isSpreadMode = !!data.isSpreadMode directly from the file schema. If a publication was saved with spreads active, it opens with spreads; if saved in single-page mode, it remains strictly single-page.
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Safe Legacy Default: For older legacy documents predating the metadata field, the loader defaults cleanly to false. Users can toggle spreads manually from the Layout menu whenever desired.
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Comprehensive Load Path Audit: Verified full consistency across native file loading, Dashboard recent cards, history undo/redo snapshots, and document serialization.
Designing Booklets & Facing Pages
When designing facing spreads (such as magazine centerfolds or event programs), toggle Two-Page Spread from the Page Setup menu under the Layout tab. Open Publisher aligns even and odd pages side-by-side, allowing you to design continuous graphics across the binding gutter with full export fidelity.
Tip: When exporting a spreads publication to PDF, you can choose between individual single sheets for commercial printing or composite two-page spreads for digital viewing.