在Graphviz中创建直边

Question

我想使用Graphviz创建一个流程图（类似于Visio）。这是一个示例图。

digraph start_up {
node [style = rounded]; 
node [shape = rect] start end;
node [style = ""];
node [shape = diamond] "USB\nCommand\nArrived";
start -> "Initialize\nCode";
"Initialize\nCode" -> "USB\nCommand\nArrived";
"USB\nCommand\nArrived" -> "USB\nCommand\nArrived" [label="No" tailport=w headport=n];
"USB\nCommand\nArrived" -> "Has USB 3.0\nInterface Been\nSelected" [label = "Yes"];
 "Has USB 3.0\nInterface Been\nSelected" -> end
}

问题是当我在Graphviz中呈现由"USB\nCommand\nArrived" -> "USB\nCommand\nArrived" [label="No" tailport=w headport=n];创建的行时 看起来很难看。我不介意曲线，但这条线看起来变形了。你可以看到Graphviz在这里创建的内容

有没有办法让这个看起来更好？

Answer 1

我认为最好通过例子来学习。请阅读我的评论，如果有任何不清楚的地方我会很乐意回答。

作为辅助节点： 虽然graphviz非常适合生成大型数据集的图形，但创建ER图表，流程图和序列图等功能并不是很棒。这是可能的，而且相对简单，但是你需要花费大量时间来制作出正确的东西通常是不合理的，因为你可以在很短的时间内使用Wsywig-GUI建模工具实现同样的目的。但是，您花在这上面的时间将帮助您学习语言的语法和属性，当您需要可视化某些大型或复杂的问题（GUI建模工具将毫无用处）时，该语言和属性非常有用。

digraph start_up {
    { 
/* fake levels (level0 -> level1) and support nodes
 *
 * graphviz to charts is what latex is to documents, 
 * sometimes you'll have to fight it.
 * This is typically done by defining levels and connection points that
 * don't really have anything to do with your graph, but are used to 
 * force the graph to appear in a certain way.
 */
        node [shape=none, /*label="."*/]; l1a; l2a; l3a; l4a; l5a; l6a;
        node [shape=square label="no"]; l20a; 
    }

    {   /* connectiong point for the no arrow above "arrived" */
        node [width=0 shape=point label=""];
        d1; no;
    }

    node [style = rounded]; 
    node [shape = rect] start end;
    node [style = ""];

    node [shape = diamond]; {
        node [label="USB\nCommand\nArrived"]; arrived; 
        node [label="Has USB 3.0\nInterface Been\nSelected"]; selected;
        node [label="Initialize\nCode"]; init;
    }

    start -> init; 
    /*init -> arrived; */
    init -> d1 [arrowhead=none]; 
            d1 -> arrived;

/* 
 * tricky part:
 * since nodes in a digrap go either from top to bottom or left to right, we 
 * can usually not connect (->) two nodes and have them appear on the same 
 * level unless the connection is specified within a block that has the 
 * parameter `rank' set to `same'
 */
            l20a->no [arrowhead=none];

    {   rank=same; no -> arrived [dir=back arrowtail=none]; }
    {   rank=same; l20a -> d1; }

    /*arrived       -> arrived;*/ /*  [label="No" tailport=w headport=n]; */
    arrived     -> selected [label = "Yes"];
    selected    -> end


    /* just to demonstrate */
    l1a-> l2a-> l3a-> l4a-> l5a-> l6a;
}