compiler/rustc_graphviz/src/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<'b>(&'b self, n: &Nd) -> dot::LabelText<'b> {
 168 //!         dot::LabelText::LabelStr(self.nodes[*n].into())
 169 //!     }
 170 //!     fn edge_label<'b>(&'b self, _: &Ed) -> dot::LabelText<'b> {
 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<'b>(&'b self, n: &Nd<'b>) -> dot::LabelText<'b> {
 230 //!         let &(i, _) = n;
 231 //!         dot::LabelText::LabelStr(self.nodes[i].into())
 232 //!     }
 233 //!     fn edge_label<'b>(&'b self, _: &Ed<'b>) -> dot::LabelText<'b> {
 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 #![doc(
 273     html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/",
 274     test(attr(allow(unused_variables), deny(warnings)))
 275 )]
 276
 277 use LabelText::*;
 278
 279 use std::borrow::Cow;
 280 use std::io;
 281 use std::io::prelude::*;
 282
 283 /// The text for a graphviz label on a node or edge.
 284 pub enum LabelText<'a> {
 285     /// This kind of label preserves the text directly as is.
 286     ///
 287     /// Occurrences of backslashes (`\`) are escaped, and thus appear
 288     /// as backslashes in the rendered label.
 289     LabelStr(Cow<'a, str>),
 290
 291     /// This kind of label uses the graphviz label escString type:
 292     /// <https://www.graphviz.org/docs/attr-types/escString>
 293     ///
 294     /// Occurrences of backslashes (`\`) are not escaped; instead they
 295     /// are interpreted as initiating an escString escape sequence.
 296     ///
 297     /// Escape sequences of particular interest: in addition to `\n`
 298     /// to break a line (centering the line preceding the `\n`), there
 299     /// are also the escape sequences `\l` which left-justifies the
 300     /// preceding line and `\r` which right-justifies it.
 301     EscStr(Cow<'a, str>),
 302
 303     /// This uses a graphviz [HTML string label][html]. The string is
 304     /// printed exactly as given, but between `<` and `>`. **No
 305     /// escaping is performed.**
 306     ///
 307     /// [html]: https://www.graphviz.org/doc/info/shapes.html#html
 308     HtmlStr(Cow<'a, str>),
 309 }
 310
 311 /// The style for a node or edge.
 312 /// See <https://www.graphviz.org/docs/attr-types/style/> for descriptions.
 313 /// Note that some of these are not valid for edges.
 314 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 315 pub enum Style {
 316     None,
 317     Solid,
 318     Dashed,
 319     Dotted,
 320     Bold,
 321     Rounded,
 322     Diagonals,
 323     Filled,
 324     Striped,
 325     Wedged,
 326 }
 327
 328 impl Style {
 329     pub fn as_slice(self) -> &'static str {
 330         match self {
 331             Style::None => "",
 332             Style::Solid => "solid",
 333             Style::Dashed => "dashed",
 334             Style::Dotted => "dotted",
 335             Style::Bold => "bold",
 336             Style::Rounded => "rounded",
 337             Style::Diagonals => "diagonals",
 338             Style::Filled => "filled",
 339             Style::Striped => "striped",
 340             Style::Wedged => "wedged",
 341         }
 342     }
 343 }
 344
 345 // There is a tension in the design of the labelling API.
 346 //
 347 // For example, I considered making a `Labeller<T>` trait that
 348 // provides labels for `T`, and then making the graph type `G`
 349 // implement `Labeller<Node>` and `Labeller<Edge>`. However, this is
 350 // not possible without functional dependencies. (One could work
 351 // around that, but I did not explore that avenue heavily.)
 352 //
 353 // Another approach that I actually used for a while was to make a
 354 // `Label<Context>` trait that is implemented by the client-specific
 355 // Node and Edge types (as well as an implementation on Graph itself
 356 // for the overall name for the graph). The main disadvantage of this
 357 // second approach (compared to having the `G` type parameter
 358 // implement a Labelling service) that I have encountered is that it
 359 // makes it impossible to use types outside of the current crate
 360 // directly as Nodes/Edges; you need to wrap them in newtype'd
 361 // structs. See e.g., the `No` and `Ed` structs in the examples. (In
 362 // practice clients using a graph in some other crate would need to
 363 // provide some sort of adapter shim over the graph anyway to
 364 // interface with this library).
 365 //
 366 // Another approach would be to make a single `Labeller<N,E>` trait
 367 // that provides three methods (graph_label, node_label, edge_label),
 368 // and then make `G` implement `Labeller<N,E>`. At first this did not
 369 // appeal to me, since I had thought I would need separate methods on
 370 // each data variant for dot-internal identifiers versus user-visible
 371 // labels. However, the identifier/label distinction only arises for
 372 // nodes; graphs themselves only have identifiers, and edges only have
 373 // labels.
 374 //
 375 // So in the end I decided to use the third approach described above.
 376
 377 /// `Id` is a Graphviz `ID`.
 378 pub struct Id<'a> {
 379     name: Cow<'a, str>,
 380 }
 381
 382 impl<'a> Id<'a> {
 383     /// Creates an `Id` named `name`.
 384     ///
 385     /// The caller must ensure that the input conforms to an
 386     /// identifier format: it must be a non-empty string made up of
 387     /// alphanumeric or underscore characters, not beginning with a
 388     /// digit (i.e., the regular expression `[a-zA-Z_][a-zA-Z_0-9]*`).
 389     ///
 390     /// (Note: this format is a strict subset of the `ID` format
 391     /// defined by the DOT language. This function may change in the
 392     /// future to accept a broader subset, or the entirety, of DOT's
 393     /// `ID` format.)
 394     ///
 395     /// Passing an invalid string (containing spaces, brackets,
 396     /// quotes, ...) will return an empty `Err` value.
 397     pub fn new<Name: Into<Cow<'a, str>>>(name: Name) -> Result<Id<'a>, ()> {
 398         let name = name.into();
 399         match name.chars().next() {
 400             Some(c) if c.is_ascii_alphabetic() || c == '_' => {}
 401             _ => return Err(()),
 402         }
 403         if !name.chars().all(|c| c.is_ascii_alphanumeric() || c == '_') {
 404             return Err(());
 405         }
 406
 407         Ok(Id { name })
 408     }
 409
 410     pub fn as_slice(&'a self) -> &'a str {
 411         &*self.name
 412     }
 413 }
 414
 415 /// Each instance of a type that implements `Label<C>` maps to a
 416 /// unique identifier with respect to `C`, which is used to identify
 417 /// it in the generated .dot file. They can also provide more
 418 /// elaborate (and non-unique) label text that is used in the graphviz
 419 /// rendered output.
 420
 421 /// The graph instance is responsible for providing the DOT compatible
 422 /// identifiers for the nodes and (optionally) rendered labels for the nodes and
 423 /// edges, as well as an identifier for the graph itself.
 424 pub trait Labeller<'a> {
 425     type Node;
 426     type Edge;
 427
 428     /// Must return a DOT compatible identifier naming the graph.
 429     fn graph_id(&'a self) -> Id<'a>;
 430
 431     /// Maps `n` to a unique identifier with respect to `self`. The
 432     /// implementor is responsible for ensuring that the returned name
 433     /// is a valid DOT identifier.
 434     fn node_id(&'a self, n: &Self::Node) -> Id<'a>;
 435
 436     /// Maps `n` to one of the [graphviz `shape` names][1]. If `None`
 437     /// is returned, no `shape` attribute is specified.
 438     ///
 439     /// [1]: https://www.graphviz.org/doc/info/shapes.html
 440     fn node_shape(&'a self, _node: &Self::Node) -> Option<LabelText<'a>> {
 441         None
 442     }
 443
 444     /// Maps `n` to a label that will be used in the rendered output.
 445     /// The label need not be unique, and may be the empty string; the
 446     /// default is just the output from `node_id`.
 447     fn node_label(&'a self, n: &Self::Node) -> LabelText<'a> {
 448         LabelStr(self.node_id(n).name)
 449     }
 450
 451     /// Maps `e` to a label that will be used in the rendered output.
 452     /// The label need not be unique, and may be the empty string; the
 453     /// default is in fact the empty string.
 454     fn edge_label(&'a self, _e: &Self::Edge) -> LabelText<'a> {
 455         LabelStr("".into())
 456     }
 457
 458     /// Maps `n` to a style that will be used in the rendered output.
 459     fn node_style(&'a self, _n: &Self::Node) -> Style {
 460         Style::None
 461     }
 462
 463     /// Maps `e` to a style that will be used in the rendered output.
 464     fn edge_style(&'a self, _e: &Self::Edge) -> Style {
 465         Style::None
 466     }
 467 }
 468
 469 /// Escape tags in such a way that it is suitable for inclusion in a
 470 /// Graphviz HTML label.
 471 pub fn escape_html(s: &str) -> String {
 472     s.replace('&', "&amp;").replace('\"', "&quot;").replace('<', "&lt;").replace('>', "&gt;")
 473 }
 474
 475 impl<'a> LabelText<'a> {
 476     pub fn label<S: Into<Cow<'a, str>>>(s: S) -> LabelText<'a> {
 477         LabelStr(s.into())
 478     }
 479
 480     pub fn html<S: Into<Cow<'a, str>>>(s: S) -> LabelText<'a> {
 481         HtmlStr(s.into())
 482     }
 483
 484     fn escape_char<F>(c: char, mut f: F)
 485     where
 486         F: FnMut(char),
 487     {
 488         match c {
 489             // not escaping \\, since Graphviz escString needs to
 490             // interpret backslashes; see EscStr above.
 491             '\\' => f(c),
 492             _ => {
 493                 for c in c.escape_default() {
 494                     f(c)
 495                 }
 496             }
 497         }
 498     }
 499     fn escape_str(s: &str) -> String {
 500         let mut out = String::with_capacity(s.len());
 501         for c in s.chars() {
 502             LabelText::escape_char(c, |c| out.push(c));
 503         }
 504         out
 505     }
 506
 507     /// Renders text as string suitable for a label in a .dot file.
 508     /// This includes quotes or suitable delimiters.
 509     pub fn to_dot_string(&self) -> String {
 510         match *self {
 511             LabelStr(ref s) => format!("\"{}\"", s.escape_default()),
 512             EscStr(ref s) => format!("\"{}\"", LabelText::escape_str(&s)),
 513             HtmlStr(ref s) => format!("<{}>", s),
 514         }
 515     }
 516
 517     /// Decomposes content into string suitable for making EscStr that
 518     /// yields same content as self. The result obeys the law
 519     /// render(`lt`) == render(`EscStr(lt.pre_escaped_content())`) for
 520     /// all `lt: LabelText`.
 521     fn pre_escaped_content(self) -> Cow<'a, str> {
 522         match self {
 523             EscStr(s) => s,
 524             LabelStr(s) => {
 525                 if s.contains('\\') {
 526                     (&*s).escape_default().to_string().into()
 527                 } else {
 528                     s
 529                 }
 530             }
 531             HtmlStr(s) => s,
 532         }
 533     }
 534
 535     /// Puts `suffix` on a line below this label, with a blank line separator.
 536     pub fn suffix_line(self, suffix: LabelText<'_>) -> LabelText<'static> {
 537         let mut prefix = self.pre_escaped_content().into_owned();
 538         let suffix = suffix.pre_escaped_content();
 539         prefix.push_str(r"\n\n");
 540         prefix.push_str(&suffix);
 541         EscStr(prefix.into())
 542     }
 543 }
 544
 545 pub type Nodes<'a, N> = Cow<'a, [N]>;
 546 pub type Edges<'a, E> = Cow<'a, [E]>;
 547
 548 // (The type parameters in GraphWalk should be associated items,
 549 // when/if Rust supports such.)
 550
 551 /// GraphWalk is an abstraction over a directed graph = (nodes,edges)
 552 /// made up of node handles `N` and edge handles `E`, where each `E`
 553 /// can be mapped to its source and target nodes.
 554 ///
 555 /// The lifetime parameter `'a` is exposed in this trait (rather than
 556 /// introduced as a generic parameter on each method declaration) so
 557 /// that a client impl can choose `N` and `E` that have substructure
 558 /// that is bound by the self lifetime `'a`.
 559 ///
 560 /// The `nodes` and `edges` method each return instantiations of
 561 /// `Cow<[T]>` to leave implementors the freedom to create
 562 /// entirely new vectors or to pass back slices into internally owned
 563 /// vectors.
 564 pub trait GraphWalk<'a> {
 565     type Node: Clone;
 566     type Edge: Clone;
 567
 568     /// Returns all the nodes in this graph.
 569     fn nodes(&'a self) -> Nodes<'a, Self::Node>;
 570     /// Returns all of the edges in this graph.
 571     fn edges(&'a self) -> Edges<'a, Self::Edge>;
 572     /// The source node for `edge`.
 573     fn source(&'a self, edge: &Self::Edge) -> Self::Node;
 574     /// The target node for `edge`.
 575     fn target(&'a self, edge: &Self::Edge) -> Self::Node;
 576 }
 577
 578 #[derive(Clone, PartialEq, Eq, Debug)]
 579 pub enum RenderOption {
 580     NoEdgeLabels,
 581     NoNodeLabels,
 582     NoEdgeStyles,
 583     NoNodeStyles,
 584
 585     Fontname(String),
 586     DarkTheme,
 587 }
 588
 589 /// Renders directed graph `g` into the writer `w` in DOT syntax.
 590 /// (Simple wrapper around `render_opts` that passes a default set of options.)
 591 pub fn render<'a, N, E, G, W>(g: &'a G, w: &mut W) -> io::Result<()>
 592 where
 593     N: Clone + 'a,
 594     E: Clone + 'a,
 595     G: Labeller<'a, Node = N, Edge = E> + GraphWalk<'a, Node = N, Edge = E>,
 596     W: Write,
 597 {
 598     render_opts(g, w, &[])
 599 }
 600
 601 /// Renders directed graph `g` into the writer `w` in DOT syntax.
 602 /// (Main entry point for the library.)
 603 pub fn render_opts<'a, N, E, G, W>(g: &'a G, w: &mut W, options: &[RenderOption]) -> io::Result<()>
 604 where
 605     N: Clone + 'a,
 606     E: Clone + 'a,
 607     G: Labeller<'a, Node = N, Edge = E> + GraphWalk<'a, Node = N, Edge = E>,
 608     W: Write,
 609 {
 610     writeln!(w, "digraph {} {{", g.graph_id().as_slice())?;
 611
 612     // Global graph properties
 613     let mut graph_attrs = Vec::new();
 614     let mut content_attrs = Vec::new();
 615     let font;
 616     if let Some(fontname) = options.iter().find_map(|option| {
 617         if let RenderOption::Fontname(fontname) = option { Some(fontname) } else { None }
 618     }) {
 619         font = format!(r#"fontname="{}""#, fontname);
 620         graph_attrs.push(&font[..]);
 621         content_attrs.push(&font[..]);
 622     }
 623     if options.contains(&RenderOption::DarkTheme) {
 624         graph_attrs.push(r#"bgcolor="black""#);
 625         graph_attrs.push(r#"fontcolor="white""#);
 626         content_attrs.push(r#"color="white""#);
 627         content_attrs.push(r#"fontcolor="white""#);
 628     }
 629     if !(graph_attrs.is_empty() && content_attrs.is_empty()) {
 630         writeln!(w, r#"    graph[{}];"#, graph_attrs.join(" "))?;
 631         let content_attrs_str = content_attrs.join(" ");
 632         writeln!(w, r#"    node[{}];"#, content_attrs_str)?;
 633         writeln!(w, r#"    edge[{}];"#, content_attrs_str)?;
 634     }
 635
 636     let mut text = Vec::new();
 637     for n in g.nodes().iter() {
 638         write!(w, "    ")?;
 639         let id = g.node_id(n);
 640
 641         let escaped = &g.node_label(n).to_dot_string();
 642
 643         write!(text, "{}", id.as_slice()).unwrap();
 644
 645         if !options.contains(&RenderOption::NoNodeLabels) {
 646             write!(text, "[label={}]", escaped).unwrap();
 647         }
 648
 649         let style = g.node_style(n);
 650         if !options.contains(&RenderOption::NoNodeStyles) && style != Style::None {
 651             write!(text, "[style=\"{}\"]", style.as_slice()).unwrap();
 652         }
 653
 654         if let Some(s) = g.node_shape(n) {
 655             write!(text, "[shape={}]", &s.to_dot_string()).unwrap();
 656         }
 657
 658         writeln!(text, ";").unwrap();
 659         w.write_all(&text)?;
 660
 661         text.clear();
 662     }
 663
 664     for e in g.edges().iter() {
 665         let escaped_label = &g.edge_label(e).to_dot_string();
 666         write!(w, "    ")?;
 667         let source = g.source(e);
 668         let target = g.target(e);
 669         let source_id = g.node_id(&source);
 670         let target_id = g.node_id(&target);
 671
 672         write!(text, "{} -> {}", source_id.as_slice(), target_id.as_slice()).unwrap();
 673
 674         if !options.contains(&RenderOption::NoEdgeLabels) {
 675             write!(text, "[label={}]", escaped_label).unwrap();
 676         }
 677
 678         let style = g.edge_style(e);
 679         if !options.contains(&RenderOption::NoEdgeStyles) && style != Style::None {
 680             write!(text, "[style=\"{}\"]", style.as_slice()).unwrap();
 681         }
 682
 683         writeln!(text, ";").unwrap();
 684         w.write_all(&text)?;
 685
 686         text.clear();
 687     }
 688
 689     writeln!(w, "}}")
 690 }
 691
 692 #[cfg(test)]
 693 mod tests;