[tannevaled]

What

officecanvas: a second paint.Canvas consumer beside pdfcanvas. PageLayout.PaintVector draws through it and it records the page as the objects an editable office slide is made of, format-neutral, in device pixels:

• KindFill — filled outlines (Rect flagged when the outline is its box; rings keep their holes, EvenOdd);
• KindGradient — the innermost clip's outline filled with a gradient: PaintVector's constant-opacity shadings of one CSS gradient are merged back into one stop list (positions mapped onto the box's projection for linear, radius fraction for radial), with transparent stops across the gaps — so uncover's "colour, then transparent" corner is one shape again;
• KindText — one text box per line: consecutive glyph runs on one baseline join, the gap between words a space; runs split by face, size, colour, link (from PageLayout.Links), invisibility (text over a rasterised element → zero alpha) and letter-spacing (measured from the glyph positions);
• KindImage — pictures, cropped to the clip's bounds (a background-size: cover image);
• Page.Background — a fill covering the page before anything else.

Faces: family and style from the font's name table (Windows records preferred; the OS/2 weight/slant when the table calls every face "Regular", unless the family name carries the weight — "Lato Black" stays a family), embeddability from OS/2 fsType (installable or editable only). SFNT(font) reassembles the font file from its tables (offset table, directory with checksums, head.checkSumAdjustment) so a deck can embed the very font the slide was laid out with — tested: Inter round-trips through opentype.Parse. Shape.Render(scale) draws a gradient shape as an antialiased picture for formats whose gradients are poorer (ODF's two colours, DrawingML's circle-only radial).

Why here

Same pattern as pdfcanvas: the consumer of paint.Canvas lives next to it. It does not import go-ooxml or go-odf (the engine stays free of office libraries; they stay free of the engine); go-slides maps the neutral Page to both. go-slides PR: editable --pptx/--odp.

Verification (go-slides internal/cmd/officecheck)

LibreOffice 25.8 renders the editable decks to PDF, poppler to pages, compared with export.Rasterize: 0.04–1.9 % of pixels off by > 48 on the benchmark and oracle decks (glyph edges, different rasteriser), text extracted by pdftotext (2,240 words on 100 slides).

Bounds

SFNT refuses past 32 MiB; Render past 16 Mpx; the name parser bounds every record to the table.

MINOR → v0.10.0.

🤖 Generated with Claude Code