rustc_graphviz/
lib.rs

1//! Generate files suitable for use with [Graphviz](https://www.graphviz.org/)
2//!
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](https://www.graphviz.org/docs/outputs), such as SVG.)
8//!
9//! Rather than impose some particular graph data structure on clients,
10//! this library exposes two traits that clients can implement on their
11//! own structs before handing them over to the rendering function.
12//!
13//! Note: This library does not yet provide access to the full
14//! expressiveness of the [DOT language](https://www.graphviz.org/doc/info/lang.html).
15//! For example, there are many [attributes](https://www.graphviz.org/doc/info/attrs.html)
16//! related to providing layout hints (e.g., left-to-right versus top-down, which
17//! algorithm to use, etc). The current intention of this library is to
18//! emit a human-readable .dot file with very regular structure suitable
19//! for easy post-processing.
20//!
21//! # Examples
22//!
23//! The first example uses a very simple graph representation: a list of
24//! pairs of ints, representing the edges (the node set is implicit).
25//! Each node label is derived directly from the int representing the node,
26//! while the edge labels are all empty strings.
27//!
28//! This example also illustrates how to use `Cow<[T]>` to return
29//! an owned vector or a borrowed slice as appropriate: we construct the
30//! node vector from scratch, but borrow the edge list (rather than
31//! constructing a copy of all the edges from scratch).
32//!
33//! The output from this example renders five nodes, with the first four
34//! forming a diamond-shaped acyclic graph and then pointing to the fifth
35//! which is cyclic.
36//!
37//! ```rust
38//! #![feature(rustc_private)]
39//!
40//! use std::io::Write;
41//! use rustc_graphviz as dot;
42//!
43//! type Nd = isize;
44//! type Ed = (isize,isize);
45//! struct Edges(Vec<Ed>);
46//!
47//! pub fn render_to<W: Write>(output: &mut W) {
48//!     let edges = Edges(vec![(0,1), (0,2), (1,3), (2,3), (3,4), (4,4)]);
49//!     dot::render(&edges, output).unwrap()
50//! }
51//!
52//! impl<'a> dot::Labeller<'a> for Edges {
53//!     type Node = Nd;
54//!     type Edge = Ed;
55//!     fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new("example1").unwrap() }
56//!
57//!     fn node_id(&'a self, n: &Nd) -> dot::Id<'a> {
58//!         dot::Id::new(format!("N{}", *n)).unwrap()
59//!     }
60//! }
61//!
62//! impl<'a> dot::GraphWalk<'a> for Edges {
63//!     type Node = Nd;
64//!     type Edge = Ed;
65//!     fn nodes(&self) -> dot::Nodes<'a,Nd> {
66//!         // (assumes that |N| \approxeq |E|)
67//!         let &Edges(ref v) = self;
68//!         let mut nodes = Vec::with_capacity(v.len());
69//!         for &(s,t) in v {
70//!             nodes.push(s); nodes.push(t);
71//!         }
72//!         nodes.sort();
73//!         nodes.dedup();
74//!         nodes.into()
75//!     }
76//!
77//!     fn edges(&'a self) -> dot::Edges<'a,Ed> {
78//!         let &Edges(ref edges) = self;
79//!         (&edges[..]).into()
80//!     }
81//!
82//!     fn source(&self, e: &Ed) -> Nd { let &(s,_) = e; s }
83//!
84//!     fn target(&self, e: &Ed) -> Nd { let &(_,t) = e; t }
85//! }
86//!
87//! # pub fn main() { render_to(&mut Vec::new()) }
88//! ```
89//!
90//! ```no_run
91//! # pub fn render_to<W:std::io::Write>(output: &mut W) { unimplemented!() }
92//! pub fn main() {
93//!     use std::fs::File;
94//!     let mut f = File::create("example1.dot").unwrap();
95//!     render_to(&mut f)
96//! }
97//! ```
98//!
99//! Output from first example (in `example1.dot`):
100//!
101//! ```dot
102//! digraph example1 {
103//!     N0[label="N0"];
104//!     N1[label="N1"];
105//!     N2[label="N2"];
106//!     N3[label="N3"];
107//!     N4[label="N4"];
108//!     N0 -> N1[label=""];
109//!     N0 -> N2[label=""];
110//!     N1 -> N3[label=""];
111//!     N2 -> N3[label=""];
112//!     N3 -> N4[label=""];
113//!     N4 -> N4[label=""];
114//! }
115//! ```
116//!
117//! The second example illustrates using `node_label` and `edge_label` to
118//! add labels to the nodes and edges in the rendered graph. The graph
119//! here carries both `nodes` (the label text to use for rendering a
120//! particular node), and `edges` (again a list of `(source,target)`
121//! indices).
122//!
123//! This example also illustrates how to use a type (in this case the edge
124//! type) that shares substructure with the graph: the edge type here is a
125//! direct reference to the `(source,target)` pair stored in the graph's
126//! internal vector (rather than passing around a copy of the pair
127//! itself). Note that this implies that `fn edges(&'a self)` must
128//! construct a fresh `Vec<&'a (usize,usize)>` from the `Vec<(usize,usize)>`
129//! edges stored in `self`.
130//!
131//! Since both the set of nodes and the set of edges are always
132//! constructed from scratch via iterators, we use the `collect()` method
133//! from the `Iterator` trait to collect the nodes and edges into freshly
134//! constructed growable `Vec` values (rather than using `Cow` as in the
135//! first example above).
136//!
137//! The output from this example renders four nodes that make up the
138//! Hasse-diagram for the subsets of the set `{x, y}`. Each edge is
139//! labeled with the &sube; character (specified using the HTML character
140//! entity `&sube`).
141//!
142//! ```rust
143//! #![feature(rustc_private)]
144//!
145//! use std::io::Write;
146//! use rustc_graphviz as dot;
147//!
148//! type Nd = usize;
149//! type Ed<'a> = &'a (usize, usize);
150//! struct Graph { nodes: Vec<&'static str>, edges: Vec<(usize,usize)> }
151//!
152//! pub fn render_to<W: Write>(output: &mut W) {
153//!     let nodes = vec!["{x,y}","{x}","{y}","{}"];
154//!     let edges = vec![(0,1), (0,2), (1,3), (2,3)];
155//!     let graph = Graph { nodes: nodes, edges: edges };
156//!
157//!     dot::render(&graph, output).unwrap()
158//! }
159//!
160//! impl<'a> dot::Labeller<'a> for Graph {
161//!     type Node = Nd;
162//!     type Edge = Ed<'a>;
163//!     fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new("example2").unwrap() }
164//!     fn node_id(&'a self, n: &Nd) -> dot::Id<'a> {
165//!         dot::Id::new(format!("N{}", n)).unwrap()
166//!     }
167//!     fn node_label(&self, n: &Nd) -> dot::LabelText<'_> {
168//!         dot::LabelText::LabelStr(self.nodes[*n].into())
169//!     }
170//!     fn edge_label(&self, _: &Ed<'_>) -> dot::LabelText<'_> {
171//!         dot::LabelText::LabelStr("&sube;".into())
172//!     }
173//! }
174//!
175//! impl<'a> dot::GraphWalk<'a> for Graph {
176//!     type Node = Nd;
177//!     type Edge = Ed<'a>;
178//!     fn nodes(&self) -> dot::Nodes<'a,Nd> { (0..self.nodes.len()).collect() }
179//!     fn edges(&'a self) -> dot::Edges<'a,Ed<'a>> { self.edges.iter().collect() }
180//!     fn source(&self, e: &Ed<'_>) -> Nd { let & &(s,_) = e; s }
181//!     fn target(&self, e: &Ed<'_>) -> Nd { let & &(_,t) = e; t }
182//! }
183//!
184//! # pub fn main() { render_to(&mut Vec::new()) }
185//! ```
186//!
187//! ```no_run
188//! # pub fn render_to<W:std::io::Write>(output: &mut W) { unimplemented!() }
189//! pub fn main() {
190//!     use std::fs::File;
191//!     let mut f = File::create("example2.dot").unwrap();
192//!     render_to(&mut f)
193//! }
194//! ```
195//!
196//! The third example is similar to the second, except now each node and
197//! edge now carries a reference to the string label for each node as well
198//! as that node's index. (This is another illustration of how to share
199//! structure with the graph itself, and why one might want to do so.)
200//!
201//! The output from this example is the same as the second example: the
202//! Hasse-diagram for the subsets of the set `{x, y}`.
203//!
204//! ```rust
205//! #![feature(rustc_private)]
206//!
207//! use std::io::Write;
208//! use rustc_graphviz as dot;
209//!
210//! type Nd<'a> = (usize, &'a str);
211//! type Ed<'a> = (Nd<'a>, Nd<'a>);
212//! struct Graph { nodes: Vec<&'static str>, edges: Vec<(usize,usize)> }
213//!
214//! pub fn render_to<W: Write>(output: &mut W) {
215//!     let nodes = vec!["{x,y}","{x}","{y}","{}"];
216//!     let edges = vec![(0,1), (0,2), (1,3), (2,3)];
217//!     let graph = Graph { nodes: nodes, edges: edges };
218//!
219//!     dot::render(&graph, output).unwrap()
220//! }
221//!
222//! impl<'a> dot::Labeller<'a> for Graph {
223//!     type Node = Nd<'a>;
224//!     type Edge = Ed<'a>;
225//!     fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new("example3").unwrap() }
226//!     fn node_id(&'a self, n: &Nd<'a>) -> dot::Id<'a> {
227//!         dot::Id::new(format!("N{}", n.0)).unwrap()
228//!     }
229//!     fn node_label(&self, n: &Nd<'_>) -> dot::LabelText<'_> {
230//!         let &(i, _) = n;
231//!         dot::LabelText::LabelStr(self.nodes[i].into())
232//!     }
233//!     fn edge_label(&self, _: &Ed<'_>) -> dot::LabelText<'_> {
234//!         dot::LabelText::LabelStr("&sube;".into())
235//!     }
236//! }
237//!
238//! impl<'a> dot::GraphWalk<'a> for Graph {
239//!     type Node = Nd<'a>;
240//!     type Edge = Ed<'a>;
241//!     fn nodes(&'a self) -> dot::Nodes<'a,Nd<'a>> {
242//!         self.nodes.iter().map(|s| &s[..]).enumerate().collect()
243//!     }
244//!     fn edges(&'a self) -> dot::Edges<'a,Ed<'a>> {
245//!         self.edges.iter()
246//!             .map(|&(i,j)|((i, &self.nodes[i][..]),
247//!                           (j, &self.nodes[j][..])))
248//!             .collect()
249//!     }
250//!     fn source(&self, e: &Ed<'a>) -> Nd<'a> { let &(s,_) = e; s }
251//!     fn target(&self, e: &Ed<'a>) -> Nd<'a> { let &(_,t) = e; t }
252//! }
253//!
254//! # pub fn main() { render_to(&mut Vec::new()) }
255//! ```
256//!
257//! ```no_run
258//! # pub fn render_to<W:std::io::Write>(output: &mut W) { unimplemented!() }
259//! pub fn main() {
260//!     use std::fs::File;
261//!     let mut f = File::create("example3.dot").unwrap();
262//!     render_to(&mut f)
263//! }
264//! ```
265//!
266//! # References
267//!
268//! * [Graphviz](https://www.graphviz.org/)
269//!
270//! * [DOT language](https://www.graphviz.org/doc/info/lang.html)
271
272// tidy-alphabetical-start
273#![allow(internal_features)]
274#![doc(
275    html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/",
276    test(attr(allow(unused_variables), deny(warnings)))
277)]
278#![doc(rust_logo)]
279#![feature(rustdoc_internals)]
280// tidy-alphabetical-end
281
282use std::borrow::Cow;
283use std::io;
284use std::io::prelude::*;
285
286use LabelText::*;
287
288/// The text for a graphviz label on a node or edge.
289pub enum LabelText<'a> {
290    /// This kind of label preserves the text directly as is.
291    ///
292    /// Occurrences of backslashes (`\`) are escaped, and thus appear
293    /// as backslashes in the rendered label.
294    LabelStr(Cow<'a, str>),
295
296    /// This kind of label uses the graphviz label escString type:
297    /// <https://www.graphviz.org/docs/attr-types/escString>
298    ///
299    /// Occurrences of backslashes (`\`) are not escaped; instead they
300    /// are interpreted as initiating an escString escape sequence.
301    ///
302    /// Escape sequences of particular interest: in addition to `\n`
303    /// to break a line (centering the line preceding the `\n`), there
304    /// are also the escape sequences `\l` which left-justifies the
305    /// preceding line and `\r` which right-justifies it.
306    EscStr(Cow<'a, str>),
307
308    /// This uses a graphviz [HTML string label][html]. The string is
309    /// printed exactly as given, but between `<` and `>`. **No
310    /// escaping is performed.**
311    ///
312    /// [html]: https://www.graphviz.org/doc/info/shapes.html#html
313    HtmlStr(Cow<'a, str>),
314}
315
316/// The style for a node or edge.
317/// See <https://www.graphviz.org/docs/attr-types/style/> for descriptions.
318/// Note that some of these are not valid for edges.
319#[derive(Copy, Clone, PartialEq, Eq, Debug)]
320pub enum Style {
321    None,
322    Solid,
323    Dashed,
324    Dotted,
325    Bold,
326    Rounded,
327    Diagonals,
328    Filled,
329    Striped,
330    Wedged,
331}
332
333impl Style {
334    pub fn as_slice(self) -> &'static str {
335        match self {
336            Style::None => "",
337            Style::Solid => "solid",
338            Style::Dashed => "dashed",
339            Style::Dotted => "dotted",
340            Style::Bold => "bold",
341            Style::Rounded => "rounded",
342            Style::Diagonals => "diagonals",
343            Style::Filled => "filled",
344            Style::Striped => "striped",
345            Style::Wedged => "wedged",
346        }
347    }
348}
349
350// There is a tension in the design of the labelling API.
351//
352// For example, I considered making a `Labeller<T>` trait that
353// provides labels for `T`, and then making the graph type `G`
354// implement `Labeller<Node>` and `Labeller<Edge>`. However, this is
355// not possible without functional dependencies. (One could work
356// around that, but I did not explore that avenue heavily.)
357//
358// Another approach that I actually used for a while was to make a
359// `Label<Context>` trait that is implemented by the client-specific
360// Node and Edge types (as well as an implementation on Graph itself
361// for the overall name for the graph). The main disadvantage of this
362// second approach (compared to having the `G` type parameter
363// implement a Labelling service) that I have encountered is that it
364// makes it impossible to use types outside of the current crate
365// directly as Nodes/Edges; you need to wrap them in newtype'd
366// structs. See e.g., the `No` and `Ed` structs in the examples. (In
367// practice clients using a graph in some other crate would need to
368// provide some sort of adapter shim over the graph anyway to
369// interface with this library).
370//
371// Another approach would be to make a single `Labeller<N,E>` trait
372// that provides three methods (graph_label, node_label, edge_label),
373// and then make `G` implement `Labeller<N,E>`. At first this did not
374// appeal to me, since I had thought I would need separate methods on
375// each data variant for dot-internal identifiers versus user-visible
376// labels. However, the identifier/label distinction only arises for
377// nodes; graphs themselves only have identifiers, and edges only have
378// labels.
379//
380// So in the end I decided to use the third approach described above.
381
382/// `Id` is a Graphviz `ID`.
383pub struct Id<'a> {
384    name: Cow<'a, str>,
385}
386
387impl<'a> Id<'a> {
388    /// Creates an `Id` named `name`.
389    ///
390    /// The caller must ensure that the input conforms to an
391    /// identifier format: it must be a non-empty string made up of
392    /// alphanumeric or underscore characters, not beginning with a
393    /// digit (i.e., the regular expression `[a-zA-Z_][a-zA-Z_0-9]*`).
394    ///
395    /// (Note: this format is a strict subset of the `ID` format
396    /// defined by the DOT language. This function may change in the
397    /// future to accept a broader subset, or the entirety, of DOT's
398    /// `ID` format.)
399    ///
400    /// Passing an invalid string (containing spaces, brackets,
401    /// quotes, ...) will return an empty `Err` value.
402    pub fn new<Name: Into<Cow<'a, str>>>(name: Name) -> Result<Id<'a>, ()> {
403        let name = name.into();
404        match name.chars().next() {
405            Some(c) if c.is_ascii_alphabetic() || c == '_' => {}
406            _ => return Err(()),
407        }
408        if !name.chars().all(|c| c.is_ascii_alphanumeric() || c == '_') {
409            return Err(());
410        }
411
412        Ok(Id { name })
413    }
414
415    pub fn as_slice(&'a self) -> &'a str {
416        &self.name
417    }
418}
419
420/// Each instance of a type that implements `Label<C>` maps to a
421/// unique identifier with respect to `C`, which is used to identify
422/// it in the generated .dot file. They can also provide more
423/// elaborate (and non-unique) label text that is used in the graphviz
424/// rendered output.
425
426/// The graph instance is responsible for providing the DOT compatible
427/// identifiers for the nodes and (optionally) rendered labels for the nodes and
428/// edges, as well as an identifier for the graph itself.
429pub trait Labeller<'a> {
430    type Node;
431    type Edge;
432
433    /// Must return a DOT compatible identifier naming the graph.
434    fn graph_id(&'a self) -> Id<'a>;
435
436    /// Maps `n` to a unique identifier with respect to `self`. The
437    /// implementor is responsible for ensuring that the returned name
438    /// is a valid DOT identifier.
439    fn node_id(&'a self, n: &Self::Node) -> Id<'a>;
440
441    /// Maps `n` to one of the [graphviz `shape` names][1]. If `None`
442    /// is returned, no `shape` attribute is specified.
443    ///
444    /// [1]: https://www.graphviz.org/doc/info/shapes.html
445    fn node_shape(&'a self, _node: &Self::Node) -> Option<LabelText<'a>> {
446        None
447    }
448
449    /// Maps `n` to a label that will be used in the rendered output.
450    /// The label need not be unique, and may be the empty string; the
451    /// default is just the output from `node_id`.
452    fn node_label(&'a self, n: &Self::Node) -> LabelText<'a> {
453        LabelStr(self.node_id(n).name)
454    }
455
456    /// Maps `e` to a label that will be used in the rendered output.
457    /// The label need not be unique, and may be the empty string; the
458    /// default is in fact the empty string.
459    fn edge_label(&'a self, _e: &Self::Edge) -> LabelText<'a> {
460        LabelStr("".into())
461    }
462
463    /// Maps `n` to a style that will be used in the rendered output.
464    fn node_style(&'a self, _n: &Self::Node) -> Style {
465        Style::None
466    }
467
468    /// Maps `e` to a style that will be used in the rendered output.
469    fn edge_style(&'a self, _e: &Self::Edge) -> Style {
470        Style::None
471    }
472}
473
474/// Escape tags in such a way that it is suitable for inclusion in a
475/// Graphviz HTML label.
476pub fn escape_html(s: &str) -> String {
477    s.replace('&', "&amp;")
478        .replace('\"', "&quot;")
479        .replace('<', "&lt;")
480        .replace('>', "&gt;")
481        .replace('\n', "<br align=\"left\"/>")
482}
483
484impl<'a> LabelText<'a> {
485    pub fn label<S: Into<Cow<'a, str>>>(s: S) -> LabelText<'a> {
486        LabelStr(s.into())
487    }
488
489    pub fn html<S: Into<Cow<'a, str>>>(s: S) -> LabelText<'a> {
490        HtmlStr(s.into())
491    }
492
493    fn escape_char<F>(c: char, mut f: F)
494    where
495        F: FnMut(char),
496    {
497        match c {
498            // not escaping \\, since Graphviz escString needs to
499            // interpret backslashes; see EscStr above.
500            '\\' => f(c),
501            _ => {
502                for c in c.escape_default() {
503                    f(c)
504                }
505            }
506        }
507    }
508    fn escape_str(s: &str) -> String {
509        let mut out = String::with_capacity(s.len());
510        for c in s.chars() {
511            LabelText::escape_char(c, |c| out.push(c));
512        }
513        out
514    }
515
516    /// Renders text as string suitable for a label in a .dot file.
517    /// This includes quotes or suitable delimiters.
518    pub fn to_dot_string(&self) -> String {
519        match *self {
520            LabelStr(ref s) => format!("\"{}\"", s.escape_default()),
521            EscStr(ref s) => format!("\"{}\"", LabelText::escape_str(s)),
522            HtmlStr(ref s) => format!("<{s}>"),
523        }
524    }
525}
526
527pub type Nodes<'a, N> = Cow<'a, [N]>;
528pub type Edges<'a, E> = Cow<'a, [E]>;
529
530// (The type parameters in GraphWalk should be associated items,
531// when/if Rust supports such.)
532
533/// GraphWalk is an abstraction over a directed graph = (nodes,edges)
534/// made up of node handles `N` and edge handles `E`, where each `E`
535/// can be mapped to its source and target nodes.
536///
537/// The lifetime parameter `'a` is exposed in this trait (rather than
538/// introduced as a generic parameter on each method declaration) so
539/// that a client impl can choose `N` and `E` that have substructure
540/// that is bound by the self lifetime `'a`.
541///
542/// The `nodes` and `edges` method each return instantiations of
543/// `Cow<[T]>` to leave implementors the freedom to create
544/// entirely new vectors or to pass back slices into internally owned
545/// vectors.
546pub trait GraphWalk<'a> {
547    type Node: Clone;
548    type Edge: Clone;
549
550    /// Returns all the nodes in this graph.
551    fn nodes(&'a self) -> Nodes<'a, Self::Node>;
552    /// Returns all of the edges in this graph.
553    fn edges(&'a self) -> Edges<'a, Self::Edge>;
554    /// The source node for `edge`.
555    fn source(&'a self, edge: &Self::Edge) -> Self::Node;
556    /// The target node for `edge`.
557    fn target(&'a self, edge: &Self::Edge) -> Self::Node;
558}
559
560#[derive(Clone, PartialEq, Eq, Debug)]
561pub enum RenderOption {
562    NoEdgeLabels,
563    NoNodeLabels,
564    NoEdgeStyles,
565    NoNodeStyles,
566
567    Fontname(String),
568    DarkTheme,
569}
570
571/// Renders directed graph `g` into the writer `w` in DOT syntax.
572/// (Simple wrapper around `render_opts` that passes a default set of options.)
573pub fn render<'a, N, E, G, W>(g: &'a G, w: &mut W) -> io::Result<()>
574where
575    N: Clone + 'a,
576    E: Clone + 'a,
577    G: Labeller<'a, Node = N, Edge = E> + GraphWalk<'a, Node = N, Edge = E>,
578    W: Write,
579{
580    render_opts(g, w, &[])
581}
582
583/// Renders directed graph `g` into the writer `w` in DOT syntax.
584/// (Main entry point for the library.)
585pub fn render_opts<'a, N, E, G, W>(g: &'a G, w: &mut W, options: &[RenderOption]) -> io::Result<()>
586where
587    N: Clone + 'a,
588    E: Clone + 'a,
589    G: Labeller<'a, Node = N, Edge = E> + GraphWalk<'a, Node = N, Edge = E>,
590    W: Write,
591{
592    writeln!(w, "digraph {} {{", g.graph_id().as_slice())?;
593
594    // Global graph properties
595    let mut graph_attrs = Vec::new();
596    let mut content_attrs = Vec::new();
597    let font;
598    if let Some(fontname) = options.iter().find_map(|option| {
599        if let RenderOption::Fontname(fontname) = option { Some(fontname) } else { None }
600    }) {
601        font = format!(r#"fontname="{fontname}""#);
602        graph_attrs.push(&font[..]);
603        content_attrs.push(&font[..]);
604    }
605    if options.contains(&RenderOption::DarkTheme) {
606        graph_attrs.push(r#"bgcolor="black""#);
607        graph_attrs.push(r#"fontcolor="white""#);
608        content_attrs.push(r#"color="white""#);
609        content_attrs.push(r#"fontcolor="white""#);
610    }
611    if !(graph_attrs.is_empty() && content_attrs.is_empty()) {
612        writeln!(w, r#"    graph[{}];"#, graph_attrs.join(" "))?;
613        let content_attrs_str = content_attrs.join(" ");
614        writeln!(w, r#"    node[{content_attrs_str}];"#)?;
615        writeln!(w, r#"    edge[{content_attrs_str}];"#)?;
616    }
617
618    let mut text = Vec::new();
619    for n in g.nodes().iter() {
620        write!(w, "    ")?;
621        let id = g.node_id(n);
622
623        let escaped = &g.node_label(n).to_dot_string();
624
625        write!(text, "{}", id.as_slice()).unwrap();
626
627        if !options.contains(&RenderOption::NoNodeLabels) {
628            write!(text, "[label={escaped}]").unwrap();
629        }
630
631        let style = g.node_style(n);
632        if !options.contains(&RenderOption::NoNodeStyles) && style != Style::None {
633            write!(text, "[style=\"{}\"]", style.as_slice()).unwrap();
634        }
635
636        if let Some(s) = g.node_shape(n) {
637            write!(text, "[shape={}]", &s.to_dot_string()).unwrap();
638        }
639
640        writeln!(text, ";").unwrap();
641        w.write_all(&text)?;
642
643        text.clear();
644    }
645
646    for e in g.edges().iter() {
647        let escaped_label = &g.edge_label(e).to_dot_string();
648        write!(w, "    ")?;
649        let source = g.source(e);
650        let target = g.target(e);
651        let source_id = g.node_id(&source);
652        let target_id = g.node_id(&target);
653
654        write!(text, "{} -> {}", source_id.as_slice(), target_id.as_slice()).unwrap();
655
656        if !options.contains(&RenderOption::NoEdgeLabels) {
657            write!(text, "[label={escaped_label}]").unwrap();
658        }
659
660        let style = g.edge_style(e);
661        if !options.contains(&RenderOption::NoEdgeStyles) && style != Style::None {
662            write!(text, "[style=\"{}\"]", style.as_slice()).unwrap();
663        }
664
665        writeln!(text, ";").unwrap();
666        w.write_all(&text)?;
667
668        text.clear();
669    }
670
671    writeln!(w, "}}")
672}
673
674#[cfg(test)]
675mod tests;