make SingleAttributes public and improve README.md for attributes

Signed-off-by: Stefan Niederhauser <[email protected]>

Author: nidi3

README.md

@@ -101,21 +101,26 @@ The basic usage is as follows (assuming `import static guru.nidi.graphviz.model.
 ```java
 Graph g = graph("example1").directed()
         .graphAttr().with(Rank.dir(LEFT_TO_RIGHT))
+        .nodeAttr().with(Font.name("arial"))
+        .linkAttr().with("class", "link-class")
         .with(
                 node("a").with(Color.RED).link(node("b")),
-                node("b").link(to(node("c")).with(Style.DASHED))
+                node("b").link(
+                        to(node("c")).with(attr("weight", 5), Style.DASHED)
+                )
         );
 Graphviz.fromGraph(g).height(100).render(Format.PNG).toFile(new File("example/ex1.png"));
 ```
 [//]: # (end)
 <img src="https://rawgit.com/nidi3/graphviz-java/master/graphviz-java/example/ex1.png" height="100">
 
-Global attributes are set using the `graphAttr`, `linkAttr` and `nodeAttr` methods.
-Nodes are styled using the `with` method. 
-To style edges, use the static method `to` which returns a `Link` that also has a `with` method.
-The `with` method accepts predefined attributes like `Style`, `Arrow` or `Shape` 
+- Global attributes are set using the `graphAttr`, `linkAttr` and `nodeAttr` methods.
+- Nodes are styled using the `with` method. 
+- To style edges, use the static method `to` which returns a `Link` that also has a `with` method.
+- The `with` method accepts predefined attributes like `Style`, `Arrow` or `Shape` 
 as well as everything defined in the [Graphviz reference](https://graphviz.gitlab.io/_pages/doc/info/attrs.html)
-e.g. `with("weight", 5)`
+e.g. `with("weight", 5)` or even arbitrary custom attributes.
+- Custom attribute classes can be defined by extending `SingleAttributes` or `MapAttributes`.
 
 **Attention:** `Node a = node("a"); a.with(Color.RED);` Is not working as it might be expected. 
 All "mutating" methods like `with` on nodes, links and graphs create new objects and leave the original object unchanged.
@@ -132,6 +137,11 @@ Graphviz.fromGraph(g).width(200).render(Format.PNG).toFile(new File("example/ex1
 [//]: # (end)
 <img src="https://rawgit.com/nidi3/graphviz-java/master/graphviz-java/example/ex1m.png" width="100">
 
+The mutable API provides similar functions as the immutable one with slightly different syntax:
+- `mutGraph` instead of `graph`, `mutNode` instead of `node`
+- use setters: `setDirected` instead of `directed`
+- `add` instead of `width`  
+
 ### Imperative
 There is a third possibility to use the API, based on the mutable version.
 Its form is closer to the way dot files are written.
@@ -380,7 +390,7 @@ Graphviz g = Graphviz.fromGraph(graph)
                         SvgElementFinder.use(svg, finder -> {
                             finder.findNode("unicorn").setAttribute("class", "pink");
                         })));
-g.basedir(new File("example")).render(Format.PNG).toFile(new File("example/ex9.png"));
+g.render(Format.PNG).toFile(new File("example/ex9.png"));
 ```
 [//]: # (end)
 <img src="https://rawgit.com/nidi3/graphviz-java/master/graphviz-java/example/ex9.png" width="200">

graphviz-java/example/ex1.png

@@ -18,7 +18,7 @@
 import java.lang.reflect.Constructor;
 import java.lang.reflect.ParameterizedType;
 
-class SingleAttributes<T, F extends For> implements Attributes<F> {
+public class SingleAttributes<T, F extends For> implements Attributes<F> {
     protected final String key;
     public final T value;
 

graphviz-java/example/ex9.png

@@ -24,6 +24,7 @@
 import java.awt.image.BufferedImage;
 import java.io.*;
 
+import static guru.nidi.graphviz.attribute.Attributes.attr;
 import static guru.nidi.graphviz.attribute.Label.Justification.LEFT;
 import static guru.nidi.graphviz.attribute.Rank.RankDir.LEFT_TO_RIGHT;
 import static guru.nidi.graphviz.attribute.Records.rec;
@@ -48,12 +49,16 @@ void ex1() throws IOException {
         //## basic
         Graph g = graph("example1").directed()
                 .graphAttr().with(Rank.dir(LEFT_TO_RIGHT))
+                .nodeAttr().with(Font.name("arial"))
+                .linkAttr().with("class", "link-class")
                 .with(
                         node("a").with(Color.RED).link(node("b")),
-                        node("b").link(to(node("c")).with(Style.DASHED))
+                        node("b").link(
+                                to(node("c")).with(attr("weight", 5), Style.DASHED)
+                        )
                 );
         Graphviz.fromGraph(g).height(100).render(Format.PNG).toFile(new File("example/ex1.png"));
-        //## end
+        //##
     }
 
     @Test
@@ -62,7 +67,7 @@ void ex1m() throws IOException {
         MutableGraph g = mutGraph("example1").setDirected(true).add(
                 mutNode("a").add(Color.RED).addLink(mutNode("b")));
         Graphviz.fromGraph(g).width(200).render(Format.PNG).toFile(new File("example/ex1m.png"));
-        //## end
+        //##
     }
 
     @Test
@@ -74,7 +79,7 @@ void ex1i() throws IOException {
             mutNode("a").addLink(mutNode("b"));
         });
         Graphviz.fromGraph(g).width(200).render(Format.PNG).toFile(new File("example/ex1i.png"));
-        //## end
+        //##
     }
 
     @Test
@@ -100,7 +105,7 @@ void ex2() throws IOException {
                 init.link(mkString));
 
         Graphviz.fromGraph(g).width(900).render(Format.PNG).toFile(new File("example/ex2.png"));
-        //## end
+        //##
     }
 
     @Test
@@ -127,7 +132,7 @@ void ex3() throws IOException {
                         node2.link(between(port("p"), node6.port(NORTH_WEST))),
                         node4.link(between(port("p"), node7.port(SOUTH_WEST))));
         Graphviz.fromGraph(g).width(900).render(Format.PNG).toFile(new File("example/ex3.png"));
-        //## end
+        //##
     }
 
     @Test
@@ -146,7 +151,7 @@ void ex4() throws IOException {
                             Style.lineWidth(4).and(Style.FILLED)));
             Graphviz.fromGraph(g).width(700).render(Format.PNG).toFile(new File("example/ex4-2.png"));
         }
-        //## end
+        //##
     }
 
     @Test
@@ -163,7 +168,7 @@ void ex5() throws IOException {
         String dot = viz.render(Format.DOT).toString();
         String json = viz.engine(Engine.NEATO).render(Format.JSON).toString();
         BufferedImage image = viz.render(Format.PNG).toImage();
-        //## end
+        //##
         end();
         init();
     }
@@ -176,7 +181,7 @@ void ex7() throws IOException {
         Graphviz g = Graphviz.fromGraph(graph()
                 .with(node(Label.html("<table border='0'><tr><td><img src='graphviz.png' /></td></tr></table>"))));
         g.basedir(new File("example")).render(Format.PNG).toFile(new File("example/ex7.png"));
-        //## img
+        //##
     }
 
     @Test
@@ -185,7 +190,7 @@ void ex8() throws IOException {
         Graphviz g = Graphviz.fromGraph(graph()
                 .with(node(" ").with(Size.std().margin(.8, .7), Image.of("graphviz.png"))));
         g.basedir(new File("example")).render(Format.PNG).toFile(new File("example/ex8.png"));
-        //## image
+        //##
     }
 
     @Test
@@ -199,7 +204,7 @@ void ex9() throws IOException {
                                 SvgElementFinder.use(svg, finder -> {
                                     finder.findNode("unicorn").setAttribute("class", "pink");
                                 })));
-        g.basedir(new File("example")).render(Format.PNG).toFile(new File("example/ex9.png"));
-        //## image
+        g.render(Format.PNG).toFile(new File("example/ex9.png"));
+        //##
     }
 }