在Graphviz中创建直边 [英] Creating Straight Edges in Graphviz

问题描述

我想使用Graphviz创建流程图(类似于Visio).这是一个有向图示例.

I want to create a flowchart (similar to Visio) using Graphviz. Here is a sample digraph.

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中渲染此行时，该行由"USB\nCommand\nArrived" -> "USB\nCommand\nArrived" [label="No" tailport=w headport=n];创建 看起来很丑.我不介意弯曲的线，但是这条线看起来变形了.您可以在此处查看Graphviz创建的内容

The problem is when I render this in Graphviz the line created by "USB\nCommand\nArrived" -> "USB\nCommand\nArrived" [label="No" tailport=w headport=n]; looks pretty ugly. I wouldn't mind curved lines, but this line looks deformed. You can see what Graphviz creates here

有没有办法使它看起来更好?

Is there a way to make this look better?

推荐答案

我认为最好通过示例学习点.只需阅读我的评论，如果有任何不清楚的地方，我将很乐意回答.

I think it's best to learn dot by example. Just read my comments and I'll be glad to answer if anything is unclear.

作为副节点: 虽然graphviz非常适合为大型数据集生成图，但对于创建诸如ER图，流程图和序列图之类的工具而言，它却不那么令人敬畏.这是可能的，而且相对简单，但是为使某件事变得正确而必须付出的时间通常是不合理的，因为使用Wsywig-GUI建模工具可以在短时间内实现同一件事.但是，您花费的时间将帮助您学习该语言的语法和属性，这在您需要可视化一些大的或复杂的问题(GUI建模工具将无用)时非常有用.

As a side node: While graphviz is great for generating graphs for large datasets, it is less awesome for creating things like ER diagrams, flow-chars and sequence diagrams. It's possible and relatively straight forward, but the amount of time you have to put down to make something come out right is often unjustified because you could achieve the same thing with a Wsywig-GUI modeling tool in a fraction of the time. However, the time you spend doing that will help you towards learning the syntax and properties of the language which really comes in handy when you need to visualize some large or complex problem (where GUI modeling tools would be useless).

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;
}

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