Zaniah records the drawing it already performs without taking ownership of PDF pages, paper sizes, or export dialogs. Require zaniah/vector and render a normal element tree offscreen:
document = Zaniah::Vector.record(width: 960, height: 540, theme: Zaniah::Theme.light) { slide } document.commands.each { |command| export_command(command) }
To inspect a displayed frame, attach a recorder before rendering. Scene#clear resets its commands each frame; save recorder.document before the next frame.
recorder = Zaniah::Vector::Recorder.new window.scene.vector_sink = recorder window.tick document = recorder.document window.scene.vector_sink = nil
Document#width and #height are logical pixels. A Recorder attached to a window receives that window’s content size; a recorder attached to a bare Scene may instead be initialized with width: and height:. Coordinates use a top-left origin and downward y axis; colors are sRGB. Every command carries its transform, clip, opacity, layer, and sequence. Document#commands is sorted by layer and then sequence, matching Scene#each_command.
| Command | Export information |
|---|---|
Quad |
Bounds, fill color or gradient, corner radii, border widths/color/style |
Shadow |
Bounds, corner radii, color, blur, spread, inset |
Path |
Alhena outline, fill, stroke, stroke width, fill rule and stroke cap/join |
GlyphRun |
Alhena font, size, [glyph_id, x, baseline_y] triples, original text and UTF-8 byte clusters |
Image |
Decoded Zaniah::Image, bounds and source rectangle, plus a frozen pixel snapshot |
Underline |
Position, thickness and wave flag |
Raster |
Frozen source texture bytes, pixel dimensions/format, tint and source rectangle |
Ordinary sprites and packed sprite batches become Raster; bitmap-color text uses that fallback for the whole line. Simple SVG fills and strokes become Path commands. SVG clipping, gradients, dash arrays, masks, group opacity, and references use a Raster fallback, so they are not silently omitted. The Raster bytes are a snapshot at recording time, even if the source texture changes later. The converter must crop to source, apply color and opacity, then respect transform and clip. It may rasterize a Path or GlyphRun when its output format lacks an equivalent vector primitive.
The headless offscreen API works on every OS and does not require a GPU. Attaching a recorder to macOS, Windows, X11, or Wayland uses the same Scene path. The TUI backend captures its terminal cells as a single Raster fallback at an 8-by-20 cell grid, using a bundled font approximation; terminal font appearance is outside Zaniah’s control. Use the offscreen API when scalable text is required.
See ADR 016 for why this is separate from the GPU command stream. Vector and list documents the SVG input subset.