1 //! Generate files suitable for use with [Graphviz](https://www.graphviz.org/)
3 //! The `render` function generates output (e.g., an `output.dot` file) for
4 //! use with [Graphviz](https://www.graphviz.org/) by walking a labeled
5 //! graph. (Graphviz can then automatically lay out the nodes and edges
6 //! of the graph, and also optionally render the graph as an image or
7 //! other [output formats](
8 //! https://www.graphviz.org/content/output-formats), such as SVG.)
10 //! Rather than impose some particular graph data structure on clients,
11 //! this library exposes two traits that clients can implement on their
12 //! own structs before handing them over to the rendering function.
14 //! Note: This library does not yet provide access to the full
15 //! expressiveness of the [DOT language](
16 //! https://www.graphviz.org/doc/info/lang.html). For example, there are
17 //! many [attributes](https://www.graphviz.org/content/attrs) related to
18 //! providing layout hints (e.g., left-to-right versus top-down, which
19 //! algorithm to use, etc). The current intention of this library is to
20 //! emit a human-readable .dot file with very regular structure suitable
21 //! for easy post-processing.
25 //! The first example uses a very simple graph representation: a list of
26 //! pairs of ints, representing the edges (the node set is implicit).
27 //! Each node label is derived directly from the int representing the node,
28 //! while the edge labels are all empty strings.
30 //! This example also illustrates how to use `Cow<[T]>` to return
31 //! an owned vector or a borrowed slice as appropriate: we construct the
32 //! node vector from scratch, but borrow the edge list (rather than
33 //! constructing a copy of all the edges from scratch).
35 //! The output from this example renders five nodes, with the first four
36 //! forming a diamond-shaped acyclic graph and then pointing to the fifth
40 //! #![feature(rustc_private)]
42 //! use std::io::Write;
43 //! use rustc_graphviz as dot;
46 //! type Ed = (isize,isize);
47 //! struct Edges(Vec<Ed>);
49 //! pub fn render_to<W: Write>(output: &mut W) {
50 //! let edges = Edges(vec![(0,1), (0,2), (1,3), (2,3), (3,4), (4,4)]);
51 //! dot::render(&edges, output).unwrap()
54 //! impl<'a> dot::Labeller<'a> for Edges {
57 //! fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new("example1").unwrap() }
59 //! fn node_id(&'a self, n: &Nd) -> dot::Id<'a> {
60 //! dot::Id::new(format!("N{}", *n)).unwrap()
64 //! impl<'a> dot::GraphWalk<'a> for Edges {
67 //! fn nodes(&self) -> dot::Nodes<'a,Nd> {
68 //! // (assumes that |N| \approxeq |E|)
69 //! let &Edges(ref v) = self;
70 //! let mut nodes = Vec::with_capacity(v.len());
72 //! nodes.push(s); nodes.push(t);
79 //! fn edges(&'a self) -> dot::Edges<'a,Ed> {
80 //! let &Edges(ref edges) = self;
81 //! (&edges[..]).into()
84 //! fn source(&self, e: &Ed) -> Nd { let &(s,_) = e; s }
86 //! fn target(&self, e: &Ed) -> Nd { let &(_,t) = e; t }
89 //! # pub fn main() { render_to(&mut Vec::new()) }
93 //! # pub fn render_to<W:std::io::Write>(output: &mut W) { unimplemented!() }
95 //! use std::fs::File;
96 //! let mut f = File::create("example1.dot").unwrap();
101 //! Output from first example (in `example1.dot`):
104 //! digraph example1 {
110 //! N0 -> N1[label=""];
111 //! N0 -> N2[label=""];
112 //! N1 -> N3[label=""];
113 //! N2 -> N3[label=""];
114 //! N3 -> N4[label=""];
115 //! N4 -> N4[label=""];
119 //! The second example illustrates using `node_label` and `edge_label` to
120 //! add labels to the nodes and edges in the rendered graph. The graph
121 //! here carries both `nodes` (the label text to use for rendering a
122 //! particular node), and `edges` (again a list of `(source,target)`
125 //! This example also illustrates how to use a type (in this case the edge
126 //! type) that shares substructure with the graph: the edge type here is a
127 //! direct reference to the `(source,target)` pair stored in the graph's
128 //! internal vector (rather than passing around a copy of the pair
129 //! itself). Note that this implies that `fn edges(&'a self)` must
130 //! construct a fresh `Vec<&'a (usize,usize)>` from the `Vec<(usize,usize)>`
131 //! edges stored in `self`.
133 //! Since both the set of nodes and the set of edges are always
134 //! constructed from scratch via iterators, we use the `collect()` method
135 //! from the `Iterator` trait to collect the nodes and edges into freshly
136 //! constructed growable `Vec` values (rather than using `Cow` as in the
137 //! first example above).
139 //! The output from this example renders four nodes that make up the
140 //! Hasse-diagram for the subsets of the set `{x, y}`. Each edge is
141 //! labeled with the ⊆ character (specified using the HTML character
145 //! #![feature(rustc_private)]
147 //! use std::io::Write;
148 //! use rustc_graphviz as dot;
151 //! type Ed<'a> = &'a (usize, usize);
152 //! struct Graph { nodes: Vec<&'static str>, edges: Vec<(usize,usize)> }
154 //! pub fn render_to<W: Write>(output: &mut W) {
155 //! let nodes = vec!["{x,y}","{x}","{y}","{}"];
156 //! let edges = vec![(0,1), (0,2), (1,3), (2,3)];
157 //! let graph = Graph { nodes: nodes, edges: edges };
159 //! dot::render(&graph, output).unwrap()
162 //! impl<'a> dot::Labeller<'a> for Graph {
164 //! type Edge = Ed<'a>;
165 //! fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new("example2").unwrap() }
166 //! fn node_id(&'a self, n: &Nd) -> dot::Id<'a> {
167 //! dot::Id::new(format!("N{}", n)).unwrap()
169 //! fn node_label<'b>(&'b self, n: &Nd) -> dot::LabelText<'b> {
170 //! dot::LabelText::LabelStr(self.nodes[*n].into())
172 //! fn edge_label<'b>(&'b self, _: &Ed) -> dot::LabelText<'b> {
173 //! dot::LabelText::LabelStr("⊆".into())
177 //! impl<'a> dot::GraphWalk<'a> for Graph {
179 //! type Edge = Ed<'a>;
180 //! fn nodes(&self) -> dot::Nodes<'a,Nd> { (0..self.nodes.len()).collect() }
181 //! fn edges(&'a self) -> dot::Edges<'a,Ed<'a>> { self.edges.iter().collect() }
182 //! fn source(&self, e: &Ed) -> Nd { let & &(s,_) = e; s }
183 //! fn target(&self, e: &Ed) -> Nd { let & &(_,t) = e; t }
186 //! # pub fn main() { render_to(&mut Vec::new()) }
190 //! # pub fn render_to<W:std::io::Write>(output: &mut W) { unimplemented!() }
192 //! use std::fs::File;
193 //! let mut f = File::create("example2.dot").unwrap();
194 //! render_to(&mut f)
198 //! The third example is similar to the second, except now each node and
199 //! edge now carries a reference to the string label for each node as well
200 //! as that node's index. (This is another illustration of how to share
201 //! structure with the graph itself, and why one might want to do so.)
203 //! The output from this example is the same as the second example: the
204 //! Hasse-diagram for the subsets of the set `{x, y}`.
207 //! #![feature(rustc_private)]
209 //! use std::io::Write;
210 //! use rustc_graphviz as dot;
212 //! type Nd<'a> = (usize, &'a str);
213 //! type Ed<'a> = (Nd<'a>, Nd<'a>);
214 //! struct Graph { nodes: Vec<&'static str>, edges: Vec<(usize,usize)> }
216 //! pub fn render_to<W: Write>(output: &mut W) {
217 //! let nodes = vec!["{x,y}","{x}","{y}","{}"];
218 //! let edges = vec![(0,1), (0,2), (1,3), (2,3)];
219 //! let graph = Graph { nodes: nodes, edges: edges };
221 //! dot::render(&graph, output).unwrap()
224 //! impl<'a> dot::Labeller<'a> for Graph {
225 //! type Node = Nd<'a>;
226 //! type Edge = Ed<'a>;
227 //! fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new("example3").unwrap() }
228 //! fn node_id(&'a self, n: &Nd<'a>) -> dot::Id<'a> {
229 //! dot::Id::new(format!("N{}", n.0)).unwrap()
231 //! fn node_label<'b>(&'b self, n: &Nd<'b>) -> dot::LabelText<'b> {
233 //! dot::LabelText::LabelStr(self.nodes[i].into())
235 //! fn edge_label<'b>(&'b self, _: &Ed<'b>) -> dot::LabelText<'b> {
236 //! dot::LabelText::LabelStr("⊆".into())
240 //! impl<'a> dot::GraphWalk<'a> for Graph {
241 //! type Node = Nd<'a>;
242 //! type Edge = Ed<'a>;
243 //! fn nodes(&'a self) -> dot::Nodes<'a,Nd<'a>> {
244 //! self.nodes.iter().map(|s| &s[..]).enumerate().collect()
246 //! fn edges(&'a self) -> dot::Edges<'a,Ed<'a>> {
247 //! self.edges.iter()
248 //! .map(|&(i,j)|((i, &self.nodes[i][..]),
249 //! (j, &self.nodes[j][..])))
252 //! fn source(&self, e: &Ed<'a>) -> Nd<'a> { let &(s,_) = e; s }
253 //! fn target(&self, e: &Ed<'a>) -> Nd<'a> { let &(_,t) = e; t }
256 //! # pub fn main() { render_to(&mut Vec::new()) }
260 //! # pub fn render_to<W:std::io::Write>(output: &mut W) { unimplemented!() }
262 //! use std::fs::File;
263 //! let mut f = File::create("example3.dot").unwrap();
264 //! render_to(&mut f)
270 //! * [Graphviz](https://www.graphviz.org/)
272 //! * [DOT language](https://www.graphviz.org/doc/info/lang.html)
275 html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/",
276 test(attr(allow(unused_variables), deny(warnings)))
282 use std::borrow::Cow;
284 use std::io::prelude::*;
286 /// The text for a graphviz label on a node or edge.
287 pub enum LabelText<'a> {
288 /// This kind of label preserves the text directly as is.
290 /// Occurrences of backslashes (`\`) are escaped, and thus appear
291 /// as backslashes in the rendered label.
292 LabelStr(Cow<'a, str>),
294 /// This kind of label uses the graphviz label escString type:
295 /// <https://www.graphviz.org/content/attrs#kescString>
297 /// Occurrences of backslashes (`\`) are not escaped; instead they
298 /// are interpreted as initiating an escString escape sequence.
300 /// Escape sequences of particular interest: in addition to `\n`
301 /// to break a line (centering the line preceding the `\n`), there
302 /// are also the escape sequences `\l` which left-justifies the
303 /// preceding line and `\r` which right-justifies it.
304 EscStr(Cow<'a, str>),
306 /// This uses a graphviz [HTML string label][html]. The string is
307 /// printed exactly as given, but between `<` and `>`. **No
308 /// escaping is performed.**
310 /// [html]: https://www.graphviz.org/content/node-shapes#html
311 HtmlStr(Cow<'a, str>),
314 /// The style for a node or edge.
315 /// See <https://www.graphviz.org/doc/info/attrs.html#k:style> for descriptions.
316 /// Note that some of these are not valid for edges.
317 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
332 pub fn as_slice(self) -> &'static str {
335 Style::Solid => "solid",
336 Style::Dashed => "dashed",
337 Style::Dotted => "dotted",
338 Style::Bold => "bold",
339 Style::Rounded => "rounded",
340 Style::Diagonals => "diagonals",
341 Style::Filled => "filled",
342 Style::Striped => "striped",
343 Style::Wedged => "wedged",
348 // There is a tension in the design of the labelling API.
350 // For example, I considered making a `Labeller<T>` trait that
351 // provides labels for `T`, and then making the graph type `G`
352 // implement `Labeller<Node>` and `Labeller<Edge>`. However, this is
353 // not possible without functional dependencies. (One could work
354 // around that, but I did not explore that avenue heavily.)
356 // Another approach that I actually used for a while was to make a
357 // `Label<Context>` trait that is implemented by the client-specific
358 // Node and Edge types (as well as an implementation on Graph itself
359 // for the overall name for the graph). The main disadvantage of this
360 // second approach (compared to having the `G` type parameter
361 // implement a Labelling service) that I have encountered is that it
362 // makes it impossible to use types outside of the current crate
363 // directly as Nodes/Edges; you need to wrap them in newtype'd
364 // structs. See e.g., the `No` and `Ed` structs in the examples. (In
365 // practice clients using a graph in some other crate would need to
366 // provide some sort of adapter shim over the graph anyway to
367 // interface with this library).
369 // Another approach would be to make a single `Labeller<N,E>` trait
370 // that provides three methods (graph_label, node_label, edge_label),
371 // and then make `G` implement `Labeller<N,E>`. At first this did not
372 // appeal to me, since I had thought I would need separate methods on
373 // each data variant for dot-internal identifiers versus user-visible
374 // labels. However, the identifier/label distinction only arises for
375 // nodes; graphs themselves only have identifiers, and edges only have
378 // So in the end I decided to use the third approach described above.
380 /// `Id` is a Graphviz `ID`.
386 /// Creates an `Id` named `name`.
388 /// The caller must ensure that the input conforms to an
389 /// identifier format: it must be a non-empty string made up of
390 /// alphanumeric or underscore characters, not beginning with a
391 /// digit (i.e., the regular expression `[a-zA-Z_][a-zA-Z_0-9]*`).
393 /// (Note: this format is a strict subset of the `ID` format
394 /// defined by the DOT language. This function may change in the
395 /// future to accept a broader subset, or the entirety, of DOT's
398 /// Passing an invalid string (containing spaces, brackets,
399 /// quotes, ...) will return an empty `Err` value.
400 pub fn new<Name: Into<Cow<'a, str>>>(name: Name) -> Result<Id<'a>, ()> {
401 let name = name.into();
402 match name.chars().next() {
403 Some(c) if c.is_ascii_alphabetic() || c == '_' => {}
406 if !name.chars().all(|c| c.is_ascii_alphanumeric() || c == '_') {
413 pub fn as_slice(&'a self) -> &'a str {
418 /// Each instance of a type that implements `Label<C>` maps to a
419 /// unique identifier with respect to `C`, which is used to identify
420 /// it in the generated .dot file. They can also provide more
421 /// elaborate (and non-unique) label text that is used in the graphviz
424 /// The graph instance is responsible for providing the DOT compatible
425 /// identifiers for the nodes and (optionally) rendered labels for the nodes and
426 /// edges, as well as an identifier for the graph itself.
427 pub trait Labeller<'a> {
431 /// Must return a DOT compatible identifier naming the graph.
432 fn graph_id(&'a self) -> Id<'a>;
434 /// Maps `n` to a unique identifier with respect to `self`. The
435 /// implementor is responsible for ensuring that the returned name
436 /// is a valid DOT identifier.
437 fn node_id(&'a self, n: &Self::Node) -> Id<'a>;
439 /// Maps `n` to one of the [graphviz `shape` names][1]. If `None`
440 /// is returned, no `shape` attribute is specified.
442 /// [1]: https://www.graphviz.org/content/node-shapes
443 fn node_shape(&'a self, _node: &Self::Node) -> Option<LabelText<'a>> {
447 /// Maps `n` to a label that will be used in the rendered output.
448 /// The label need not be unique, and may be the empty string; the
449 /// default is just the output from `node_id`.
450 fn node_label(&'a self, n: &Self::Node) -> LabelText<'a> {
451 LabelStr(self.node_id(n).name)
454 /// Maps `e` to a label that will be used in the rendered output.
455 /// The label need not be unique, and may be the empty string; the
456 /// default is in fact the empty string.
457 fn edge_label(&'a self, _e: &Self::Edge) -> LabelText<'a> {
461 /// Maps `n` to a style that will be used in the rendered output.
462 fn node_style(&'a self, _n: &Self::Node) -> Style {
466 /// Maps `e` to a style that will be used in the rendered output.
467 fn edge_style(&'a self, _e: &Self::Edge) -> Style {
472 /// Escape tags in such a way that it is suitable for inclusion in a
473 /// Graphviz HTML label.
474 pub fn escape_html(s: &str) -> String {
475 s.replace('&', "&").replace('\"', """).replace('<', "<").replace('>', ">")
478 impl<'a> LabelText<'a> {
479 pub fn label<S: Into<Cow<'a, str>>>(s: S) -> LabelText<'a> {
483 pub fn html<S: Into<Cow<'a, str>>>(s: S) -> LabelText<'a> {
487 fn escape_char<F>(c: char, mut f: F)
492 // not escaping \\, since Graphviz escString needs to
493 // interpret backslashes; see EscStr above.
496 for c in c.escape_default() {
502 fn escape_str(s: &str) -> String {
503 let mut out = String::with_capacity(s.len());
505 LabelText::escape_char(c, |c| out.push(c));
510 /// Renders text as string suitable for a label in a .dot file.
511 /// This includes quotes or suitable delimiters.
512 pub fn to_dot_string(&self) -> String {
514 LabelStr(ref s) => format!("\"{}\"", s.escape_default()),
515 EscStr(ref s) => format!("\"{}\"", LabelText::escape_str(&s)),
516 HtmlStr(ref s) => format!("<{}>", s),
520 /// Decomposes content into string suitable for making EscStr that
521 /// yields same content as self. The result obeys the law
522 /// render(`lt`) == render(`EscStr(lt.pre_escaped_content())`) for
523 /// all `lt: LabelText`.
524 fn pre_escaped_content(self) -> Cow<'a, str> {
528 if s.contains('\\') {
529 (&*s).escape_default().to_string().into()
538 /// Puts `suffix` on a line below this label, with a blank line separator.
539 pub fn suffix_line(self, suffix: LabelText<'_>) -> LabelText<'static> {
540 let mut prefix = self.pre_escaped_content().into_owned();
541 let suffix = suffix.pre_escaped_content();
542 prefix.push_str(r"\n\n");
543 prefix.push_str(&suffix);
544 EscStr(prefix.into())
548 pub type Nodes<'a, N> = Cow<'a, [N]>;
549 pub type Edges<'a, E> = Cow<'a, [E]>;
551 // (The type parameters in GraphWalk should be associated items,
552 // when/if Rust supports such.)
554 /// GraphWalk is an abstraction over a directed graph = (nodes,edges)
555 /// made up of node handles `N` and edge handles `E`, where each `E`
556 /// can be mapped to its source and target nodes.
558 /// The lifetime parameter `'a` is exposed in this trait (rather than
559 /// introduced as a generic parameter on each method declaration) so
560 /// that a client impl can choose `N` and `E` that have substructure
561 /// that is bound by the self lifetime `'a`.
563 /// The `nodes` and `edges` method each return instantiations of
564 /// `Cow<[T]>` to leave implementors the freedom to create
565 /// entirely new vectors or to pass back slices into internally owned
567 pub trait GraphWalk<'a> {
571 /// Returns all the nodes in this graph.
572 fn nodes(&'a self) -> Nodes<'a, Self::Node>;
573 /// Returns all of the edges in this graph.
574 fn edges(&'a self) -> Edges<'a, Self::Edge>;
575 /// The source node for `edge`.
576 fn source(&'a self, edge: &Self::Edge) -> Self::Node;
577 /// The target node for `edge`.
578 fn target(&'a self, edge: &Self::Edge) -> Self::Node;
581 #[derive(Clone, PartialEq, Eq, Debug)]
582 pub enum RenderOption {
592 /// Renders directed graph `g` into the writer `w` in DOT syntax.
593 /// (Simple wrapper around `render_opts` that passes a default set of options.)
594 pub fn render<'a, N, E, G, W>(g: &'a G, w: &mut W) -> io::Result<()>
598 G: Labeller<'a, Node = N, Edge = E> + GraphWalk<'a, Node = N, Edge = E>,
601 render_opts(g, w, &[])
604 /// Renders directed graph `g` into the writer `w` in DOT syntax.
605 /// (Main entry point for the library.)
606 pub fn render_opts<'a, N, E, G, W>(g: &'a G, w: &mut W, options: &[RenderOption]) -> io::Result<()>
610 G: Labeller<'a, Node = N, Edge = E> + GraphWalk<'a, Node = N, Edge = E>,
613 writeln!(w, "digraph {} {{", g.graph_id().as_slice())?;
615 // Global graph properties
616 let mut graph_attrs = Vec::new();
617 let mut content_attrs = Vec::new();
619 if let Some(fontname) = options.iter().find_map(|option| {
620 if let RenderOption::Fontname(fontname) = option { Some(fontname) } else { None }
622 font = format!(r#"fontname="{}""#, fontname);
623 graph_attrs.push(&font[..]);
624 content_attrs.push(&font[..]);
626 if options.contains(&RenderOption::DarkTheme) {
627 graph_attrs.push(r#"bgcolor="black""#);
628 graph_attrs.push(r#"fontcolor="white""#);
629 content_attrs.push(r#"color="white""#);
630 content_attrs.push(r#"fontcolor="white""#);
632 if !(graph_attrs.is_empty() && content_attrs.is_empty()) {
633 writeln!(w, r#" graph[{}];"#, graph_attrs.join(" "))?;
634 let content_attrs_str = content_attrs.join(" ");
635 writeln!(w, r#" node[{}];"#, content_attrs_str)?;
636 writeln!(w, r#" edge[{}];"#, content_attrs_str)?;
639 let mut text = Vec::new();
640 for n in g.nodes().iter() {
642 let id = g.node_id(n);
644 let escaped = &g.node_label(n).to_dot_string();
646 write!(text, "{}", id.as_slice()).unwrap();
648 if !options.contains(&RenderOption::NoNodeLabels) {
649 write!(text, "[label={}]", escaped).unwrap();
652 let style = g.node_style(n);
653 if !options.contains(&RenderOption::NoNodeStyles) && style != Style::None {
654 write!(text, "[style=\"{}\"]", style.as_slice()).unwrap();
657 if let Some(s) = g.node_shape(n) {
658 write!(text, "[shape={}]", &s.to_dot_string()).unwrap();
661 writeln!(text, ";").unwrap();
667 for e in g.edges().iter() {
668 let escaped_label = &g.edge_label(e).to_dot_string();
670 let source = g.source(e);
671 let target = g.target(e);
672 let source_id = g.node_id(&source);
673 let target_id = g.node_id(&target);
675 write!(text, "{} -> {}", source_id.as_slice(), target_id.as_slice()).unwrap();
677 if !options.contains(&RenderOption::NoEdgeLabels) {
678 write!(text, "[label={}]", escaped_label).unwrap();
681 let style = g.edge_style(e);
682 if !options.contains(&RenderOption::NoEdgeStyles) && style != Style::None {
683 write!(text, "[style=\"{}\"]", style.as_slice()).unwrap();
686 writeln!(text, ";").unwrap();