40 lines
2.2 KiB
Markdown
40 lines
2.2 KiB
Markdown
## Context
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The current PPT editor uses an image-first model: each slide is a Frame whose primary content is a full-slide image plus light `pptMeta`. This maps naturally to PowerPoint slide transitions, but not to element-level animation.
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`pptxgenjs@4.0.1` does not expose a slide transition API, so exported PPTX transition support requires writing transition XML into `ppt/slides/slideN.xml` after generation.
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## Goals
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- Store transition configuration per PPT page without duplicating media data.
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- Offer a right-click submenu that is quick to scan and works via hover.
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- Make in-app slideshow playback honor the selected transition.
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- Make downloaded PPTX files contain matching slide transition metadata.
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- Keep memory usage bounded for high-page-count decks.
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## Non-Goals
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- Element-level animation such as text fly-in, object emphasis, or path animation.
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- New dependency-heavy PPT generation pipeline.
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- Auto-advance timing unless added in a later change.
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## Decisions
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- Use a small enum-like `PPTSlideTransitionType` with PowerPoint-aligned names: none, fade, push, wipe, split, cover, uncover.
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- Store transition data on `PPTFrameMeta.transition` with a duration in milliseconds.
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- Apply playback effects as CSS transforms/opacity on a lightweight overlay around the visible Frame area.
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- Export transitions by generating a Blob/ArrayBuffer from `pptxgenjs`, loading it through the existing `jszip` dependency, patching slide XML, then triggering the same download behavior.
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- Treat unsupported or malformed transition metadata as `none`.
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## Risks / Trade-offs
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- OOXML transition tags can vary across PowerPoint/WPS/Keynote. Keep the initial transition set small and test generated XML directly.
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- PPTX post-processing holds the generated PPTX zip in memory. Avoid additional image decoding or full-slide rasterization during this phase.
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- In-app CSS playback can approximate PowerPoint transitions but will not be pixel-perfect for every office suite.
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## Validation
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- Unit test transition sanitization and XML injection.
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- Targeted PPT export test verifies generated slide XML contains expected transition tags.
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- Manual browser check verifies right-click hover submenu, metadata persistence, and slideshow transition playback.
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