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66 lines
4.0 KiB
Markdown
66 lines
4.0 KiB
Markdown
# pdfcraft-annot
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Comments (annotations), ISO 32000-2 §12.5. Layer L3, depends on `pdfcraft-cos`, `pdfcraft-fonts` and `pdfcraft-model`.
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## What it does
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- **Builders** for the comment types Acrobat's commenting tools create: sticky note (`Text` +
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`Popup`), highlight, underline, strikethrough, squiggly, rectangle (`Square`), oval (`Circle`),
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line and arrow (`Line` with `/LE`), freehand drawing (`Ink`) and text box (`FreeText`).
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- **Appearance streams** (`appearance::build`) generated from the annotation dictionary, so new
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and restyled comments look the same in every viewer. Highlights multiply (`/BM /Multiply`).
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A line's leader lines (`/LL`, `/LLE`, `/LLO`) and caption (`/Cap`, `/CP`, `/CO`) are drawn as
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ISO 32000-2 Table 178 places them, the caption in black Helvetica 10.
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Note icons are PdfCraft's own drawings. Text boxes use standard Helvetica (WinAnsi), with
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line breaking by approximate Helvetica proportions (no font program is bundled). Text it can't
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draw (in a text box, callout, Fill & Sign text, line caption, measurement label or dynamic
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stamp's by-line; `appearance::undrawable_text`) is kept as typed and drawn as `?`, and the comment is marked with
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the first such character (`pdfcraft_fonts::UNDRAWN_MARK`) so the engine reports the edit and
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flattening refuses to make it permanent. Two refusals (`AnnotError::Undrawable`): a redaction
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mark's overlay text, which becomes page content when applied; and a restyle or resize of a
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comment another program drew with a font that has those characters, whose appearance is kept
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rather than redrawn with `?` (new text for it is taken).
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- **Edits:** reply (`/IRT`), set review status (a `/State` reply, as Acrobat's "Set status"
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does), change text, move, resize, restyle, delete (with pop-up and replies).
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## API sketch
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```rust
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let index = add_annotation(&mut doc, &NewAnnotation { page, shape, style, contents, author }, &meta)?;
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add_reply(&mut doc, page, index, "Agreed", "Ada", &meta)?;
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set_review_state(&mut doc, page, index, ReviewState::Accepted, "Ada", &meta)?;
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move_annotation(&mut doc, page, index, dx, dy, &meta)?;
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set_style(&mut doc, page, index, StyleChange::new(Some(rgb), Some(0.5), Some(2.0), None), &meta)?;
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delete_annotation(&mut doc, page, index)?;
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signature_image(&doc, page, index)?; // embedded image XObject of Fill & Sign signature/initials
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```
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A comment is addressed by `(page, index in /Annots)`, the same pair
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`pdfcraft_render::Annotation` reports. `Meta` carries the date and the `/NM` id so edits stay
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deterministic; the engine supplies them.
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## Fidelity rules
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- Unknown keys are kept. Inline annotation dictionaries are promoted to indirect objects only
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when an edit needs a reference to them.
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- `set_style` refuses (and changes nothing) when it cannot redraw the comment, e.g. stamps,
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cloudy borders or callouts, instead of leaving a stale appearance.
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- Replies get the parent's `/Rect` and an empty appearance: they appear in comment lists but
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never paint a second icon.
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- Resizing a stamp changes its `/Rect` and preserves its original appearance and resources;
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viewers scale that appearance into the new rectangle. Locked stamps refuse the edit.
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- Picture stamps (a natural-size or explicit-rectangle image, a PDF page, or an image
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signature) and PdfCraft's rubber stamps counterrotate their appearance on rotated pages, so
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the picture or label reads upright as the page is displayed. Restyling a picture stamp keeps
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that appearance matrix. The rotation is the page's `/Rotate` at placement.
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- Sticky notes and file attachments are not counterrotated: they carry the NoRotate flag and
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their icon is drawn in an unturned 20 × 20 box. A viewer keeps them upright on a turned page,
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about the upper-left corner of `/Rect` (ISO 32000-2 §12.5.3). PdfCraft's renderer does so
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(vendored hayro-interpret patch 37), and `Summary::no_rotate` tells the UI where the icon is
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drawn.
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## Not yet
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Callouts, polygons and polylines, clouds, carets (insert/replace text), stamps, file
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attachments, rich text (`/RC`, `/DS`), and the shared named-appearance cache Acrobat writes.
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