Avalonia.Controls.Documents.Serialization.Pdf 12.3.0

• net10.0

  • Avalonia.Controls.Documents (>= 12.3.0)
  • AvaloniaUI.Licensing (>= 3.1.2)

• net8.0

  • Avalonia.Controls.Documents (>= 12.3.0)
  • AvaloniaUI.Licensing (>= 3.1.2)

## 12.3.0

Adds to 12.2.3 and removes nothing: every type and member a 12.2.3 build could reference is still there with the same signature, checked against the released packages on every build.

### Features
- Footnote numbers render like the view's containers: the number in the document's `FootnoteNumberFormat`, in the note's first run's font and color at the superscript scale with tabular figures, its ink a quarter em before the content at the top of the note's first line, inside one number strip every note shares, at least 1.5 em of the document's root font and wide enough for the last ordinal. The strip was a fixed 24 device-independent pixels before.
- Per-section page setup: a `Section` declaring `PageWidth`/`PageHeight`/`PagePadding` gets its own pages - the section starts on a fresh page (entering and leaving are section-break edges, which also sever keep-with-next chains like explicit breaks), its content composes and wraps at ITS content width, its pages fill against ITS content height, and each PDF page carries its own MediaBox and margins (a landscape section between portrait pages emits a landscape page). Unset values inherit the document's; explicit `PdfSerializerOptions.PageSize`/`Margins` remain the uniform-paper override. The paged screen view breaks the same document on identical boundaries.
- Footnotes render as a per-page notes region, Word-style: each `Footnote` body composes once at the content width and draws at the bottom of the page whose content carries its anchor, below a short separator rule and with its number as marker chrome in the note's padding strip. The anchor's line reserves its notes' heights against the page band (one separator per page with notes), so a line that no longer fits the reduced band pushes to the next page together with its notes - the reserve uses the same separator constant and fit rule as the paged screen view, and both engines break anchored documents on identical boundaries. Hyperlinks inside note bodies keep their annotations; an anchor without a matching note body reserves nothing.
- Page bands render on every page: each page shows the header and footer `PageBandPolicy` resolves for its section and position (the section of the page's first line; its first-page reference on its first page, else the document's first-page band on page one, else its even band on even pages, else the section's running reference, else the document's default band), composed once per content width from the band's nested snapshot and emitted in the margin areas one band distance from the sheet edge, clipped to the margin. A band with page-number fields composes per page, so PAGE and NUMPAGES show the page's numbers. Previously bands were skipped entirely.
- Page bands push the body like in the paged view: a band that outgrows its margin grows the page's body inset to the band distance plus the band's height, the paginator fills the reduced height (`LayoutPaginator.Paginate` takes a per-page inset resolver, `PdfPageBands.ResolveInsets`), and the band emits unclipped inside the inset; a band with page-count fields paginates again until the page count is stable. Link annotations use the page's own paper and inset.
- Keep rules are honored in pagination: `Block.KeepTogether`, `Block.KeepWithNext` (chains of flagged blocks move as one, giving up when the chain exceeds a page), and `Paragraph.WidowControl` (on by default - at least two lines on each side of a break, so three-line paragraphs never split). The cut decisions come from the same policy the paged screen view consults, keeping print output identical to print layout. Since widow control defaults on, page breaks of existing exports can move by a line.
- `PdfSerializer`: write-only `IDocumentSerializer` that paginates FlowDocument content and emits vector PDF 1.7. The pipeline is UI-free (no controls, no dispatcher) and runs on any thread once an Avalonia platform (font manager + text shaper) is initialized.
- Text: paragraphs laid out with the same `TextLayout` engine as the editor (line breaking, wrapping, alignment, line height, letter spacing, bidi, font fallback); glyph-exact output via `Tf`/`Tm`/`TJ` with kerning adjustments and glyph offsets; underline/strikethrough/overline; run and block backgrounds; faux bold/oblique emulation for simulated faces.
- Fonts: an embedded typeface becomes one Type0 font with full-file embedding (`FontFile2`, or `FontFile3`/OpenType for CFF), `W` widths and a `ToUnicode` CMap. A typeface whose program stays out of the file - `PdfFontEmbedding.None`, an `OS/2` fsType that forbids embedding, a TrueType collection, or a face with no readable stream - becomes a simple font instead: single-byte character codes over `WinAnsiEncoding` with a `Differences` array for anything outside it, its own `Widths` array and a one-byte `ToUnicode` CMap, so the substituted face renders and copies out the document's text. The fsType gate tests each licence bit on its own, so a font restricted to bitmap embedding (bit 9) or one pairing the restricted-licence bit with another usage bit is refused. Subsetting is not supported yet (`PdfFontEmbedding.Subset` behaves like `Full`). Color fonts embed but render as monochrome outlines in viewers; variable fonts render their default instance.
- `PdfSerializerOptions.Diagnostics`: an optional callback receiving one `PdfDiagnostic` per fidelity loss the export accepted rather than failed on - a font left unembedded and the reason, a color or variable font no viewer can reproduce. Export raises nothing without a sink, so the checks cost nothing when unused.
- Blocks: lists (bullet shapes and numbered markers with the editor's shared marker column), tables (Pixel/Auto/Star columns, merged cells, vertical alignment, row-group/row/cell backgrounds, interior gridlines), sections, images (JPEG passthrough, everything else re-encoded with an alpha SMask), hyperlink annotations.
- Pagination: page size and margins from options, the document (`PageWidth`/`PageHeight`/`PagePadding`), or A4/2 cm defaults; lines never split; table rows paginate atomically by their row box (a pushed row lands on the next page with its cell padding intact, and rows covered by a row-spanning cell move together with their anchor row, so merged cells are never sliced); explicit page breaks honored via the new `Block.BreakPageBefore`/`BlockFormatting.PageBreakBefore`.
- A `PdfSerializerOptions.PageSize` that is not finite and positive on both axes is rejected before any byte reaches the target stream, instead of writing `/MediaBox [0 0 NaN NaN]` into a file no viewer opens. A non-finite or negative `Margins` component falls back to the 2 cm default on a section's pages as well as the document's.
- `PdfSerializerOptions`: page geometry, font embedding mode, document metadata (`Title`/`Author`/`Subject`/`Keywords`/`Language`), and a deterministic mode (fixed creation date and file id) for byte-stable output.
- Layout parity with the on-screen editor is enforced by tests that compare the export engine against the headless view line-for-line.

### Fixes
- The export paginated against the default page-band distance whatever the document declared, so a header or footer at any other distance broke pages where the screen and print did not - about two lines per A4 page at a one-inch distance. It reads `DocumentFormatting.PageBandDistance` now.