Fletcher (noun) a maker of arrows

A Typst package for drawing diagrams with arrows, built on top of CeTZ.

#import "@preview/fletcher:0.4.2" as fletcher: node, edge

#fletcher.diagram(cell-size: 15mm, $
  G edge(f, ->) edge("d", pi, ->>) & im(f) \
  G slash ker(f) edge("ur", tilde(f), "hook-->")
$)

// https://xkcd.com/1195/
#import fletcher.shapes: diamond
#set text(font: "Comic Neue", weight: 600)

#fletcher.diagram( 
  node-stroke: 1pt,
  edge-stroke: 1pt,
  node((0,0), [Start], corner-radius: 2pt, extrude: (0, 3)),
  edge("-|>"),
  node((0,1), align(center)[
    Hey, wait,\ this flowchart\ is a trap!
  ], shape: diamond),
  edge("d,r,u,l", "-|>", [Yes], label-pos: 0.1)
)

#fletcher.diagram(
  node-stroke: .1em,
  node-fill: gradient.radial(blue.lighten(80%), blue, center: (30%, 20%), radius: 80%),
  spacing: 4em,
  edge((-1,0), "r", "-|>", `open(path)`, label-pos: 0, label-side: center),
  node((0,0), `reading`, radius: 2em),
  edge(`read()`, "-|>"),
  node((1,0), `eof`, radius: 2em),
  edge(`close()`, "-|>"),
  node((2,0), `closed`, radius: 2em, extrude: (-2.5, 0)),
  edge((0,0), (0,0), `read()`, "--|>", bend: 130deg),
  edge((0,0), (2,0), `close()`, "-|>", bend: -40deg),
)

#fletcher.diagram($
  e^- edge("rd", "-<|-") & & & edge("ld", "-|>-") e^+ \
  & edge(gamma, "wave") \
  e^+ edge("ru", "-|>-") & & & edge("lu", "-<|-") e^- \
$)

#import fletcher.shapes: house, hexagon
#set text(font: "Fira Sans")

#let blob(pos, label, tint: white, ..args) = node(
  pos, align(center, label),
  width: 25mm,
  fill: tint.lighten(60%),
  stroke: 1pt + tint.darken(20%),
  corner-radius: 5pt,
  ..args,
)

#fletcher.diagram(
  spacing: 8pt,
  cell-size: (8mm, 10mm),
  edge-stroke: 1pt,
  edge-corner-radius: 5pt,
  mark-scale: 70%,

  blob((0,1), [Add & Norm], tint: yellow, shape: hexagon),
  edge(),
  blob((0,2), [Multi-Head\ Attention], tint: orange),
  blob((0,4), [Input], shape: house.with(angle: 30deg),
    width: auto, tint: red),

  for x in (-.3, -.1, +.1, +.3) {
    edge((0,2.8), (x,2.8), (x,2), "-|>")
  },
  edge((0,2.8), (0,4)),

  edge((0,3), "l,uu,r", "--|>"),
  edge((0,1), (0, 0.35), "r", (1,3), "r,u", "-|>"),
  edge((1,2), "d,rr,uu,l", "--|>"),

  blob((2,0), [Softmax], tint: green),
  edge("<|-"),
  blob((2,1), [Add & Norm], tint: yellow, shape: hexagon),
  edge(),
  blob((2,2), [Feed\ Forward], tint: blue),
)

Todo/wishlist

• [x] Mathematical arrow styles
• [x] Also allow &-delimited equations for specifying nodes
• [ ] Support CeTZ arrowheads
• [x] Support arbitrary node shapes drawn with CeTZ
• [ ] Allow referring to node coordinates by their content?
• [ ] Support loops connecting a node to itself
• [x] More ergonomic syntax to avoid repeating coordinates?
• [x] Poly-edges with multiple segments
• [x] Add way to adjust edge connection points while still having them snap to node edges
• [x] Zig-zags and waves

Change log

0.4.2

• Improve edge-to-node snapping. Edges can terminate anywhere near a node (not just at its center) and will automatically snap to the node outline. Added snap-to option to edge().
• Fixed node inset being half the amount specified. If upgrading from previous version, you will need to divide node inset values by two to preserve diagram layout.
• Add decorations option to edge() for CeTZ path decorations ("wave", "zigzag", and "coil", also accepted as positional string arguments).

0.4.1

• Support custom node shapes! Edges connect to node outlines automatically.
  • New shapes submodule, containing diamond, pill, parallelogram, hexagon, and other node shapes.
• Allow edges to have multiple segments.
  • Add vertices an corner-radius options to edge().
  • Relative coordinate shorthands may be comma separated to signify multiple segments, e.g., "r,u,ll".
• Add dodge option to edge() to adjust end points.
• Support cetz:0.2.0.

0.4.0

• Add ability to specify diagrams in math-mode, using & to separate nodes.
• Allow implicit and relative edge coordinates, e.g., edge("d") becomes edge(prev-node, (0, 1)).
• Add ability to place marks anywhere along an edge. Shorthands now accept an optional middle mark, for example |->-| and hook-/->>.
• Add “hanging tail” correction to marks on curved edges. Marks now rotate a bit to fit more comfortably along tightly curving arcs.
• Add more arrowheads for the sake of it: }>, <{, /, \, x, X, * (solid dot), @ (solid circle).
• Add axes option to diagram() to control the direction of each axis in the diagram’s coordinate system.
• Add width, height and radius options to node() for explicit control over size.
• Add corner-radius option to node().
• Add stroke option to edge() replacing thickness and paint options.
• Add edge-stroke option to diagram() replacing edge-thickness.

0.3.0

• Make round-style arrow heads better approximate the default math font.
• Add solid arrow heads with shorthand <|-, -|> and double-bar ||-, -||.
• Add an extrude option to node() which duplicates and extrudes the node’s stroke, enabling double stroke effects.

0.2.0

• Experimental support for customising arrowheads.
• Add right-angled edges with edge(..., corner: left/right).