v0.23.0

Added

• Components convert to Node (From<X> and From<&X>): Axes, Callout,
  CodeExplainer, FlowDiagram, LowerThird, ChapterMarker, Matrix,
  Table, TitleCard, EndCard, BulletList go wherever a node does, e.g.
  caption.next_to(&end_card, Side::Bottom).
• Txt::font_size, Txt::weight and Code::font_size take integers too:
  .font_size(64).
• .scale(..) on a builder takes one number, a pair or a Vec2:
  .scale(1.5), .scale((2.0, 0.5)), .scale(2).
• oxframe check: low_contrast reads the pixels behind text that lies
  over a shader, an image, a video, Custom, particles or 3D. The frame is
  drawn without text and the ratio is the median over the text's box; it
  must last 0.5 s to count, so something moving past a label is not
  reported. Text over plain fills is judged as before.
• A custom WGSL shade (Shader::source, Shader::file) is painted, not
  only checked: an interpreter over naga's IR runs it on the CPU, a tile of
  pixels at a time, with the same bytes on every OS (about 0.13 s for a
  1080p frame in a release build). Textures, samplers and derivatives are
  a shader_error. The playground does not paint it.
• Inputs of a custom shader: .input("photo", Input::file("photo.png"))
  (or Input::image(include_bytes!(..))) is read in WGSL with
  sample_photo(uv). With .input("scene", Input::frame()) the shader
  reads what was drawn before it and is painted over it inside its box,
  e.g. sample_scene(i.screen / ox.resolution). Calling sample_x with no
  input x is a shader_error that says how to add it.
• Shader::size(width, height), like width and height together.
• Example magnifier: a lens written in WGSL that reads the frame.
• .offscreen() on any node: it is drawn only for a shader that reads it
  with Input::node(handle) (sample_<name>(uv), uv across the node's
  box), never on screen, and check skips it.

Changed

• lens_drops, node.effect(..) and a frame-reading shader work inside a
  group with opacity below 1, a blur, a clip, a blend, a shadow or another
  effect. The group is drawn in parts on its own, then faded or blurred as
  a whole; a shader in it reads what the group drew before it. check no
  longer reports input_cycle.

Fixed

• check no longer reports covers_text for a custom shader that reads
  the frame (Input::frame()): the text shows through it, as under
  lens_drops. InspectNode has a reads_frame field.
• A vector's label (axes.vector(..).label("i")) sits off to the side of
  the tip, so a vector along an axis no longer puts its label on the axis
  line.

Breaking

• Signal::set takes impl Into<T>, like Signal::to, so
  text.set("Done") and fill.set(Accent) work. A value converted with a
  bare .into() no longer infers its type: drop the .into().
  Before: m.cell(0, 1).text().set("7".into()); → after:
  m.cell(0, 1).text().set("7");
• Node::scale() returns ScaleSignal, a Signal<Vec2> (it derefs to one)
  whose to and set also take one number for both axes:
  node.scale().to(1.2, 0.3). Code that names the type changes.
  Before: let s: Signal<Vec2> = node.scale(); → after:
  let s: Signal<Vec2> = node.scale().signal(); (or .into()).
• lint::Sample has a contrast field (measured contrast per text node).
  Before: Sample { time, nodes } → after:
  Sample { time, nodes, contrast: Vec::new() }.
• Input is no longer Copy (it can hold an image); Input::name takes
  &self. Clone it where it was copied.
• InspectNode has a reads_frame field; add reads_frame: false where
  you build one.