gv(3java)

🌸 NAME 🌸

okay so bestie, this page is all about gv_java — which is, and I quote, graph manipulation in java. that's the whole name. no notes, it does exactly what it says. 💖

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✨ SYNOPSIS ✨

System.loadLibrary("gv");

that's it. that's the whole vibe check. load the library and you're in. 🎀

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💅 USAGE 💅

🦋 INTRODUCTION 🦋

gv_java is a dynamically loaded extension for java that gives you access to the graph facilities of graphviz. literally all of the graph stuff. the whole toolbox. slay. 🫶

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🎀 COMMANDS 🎀

🌱 New graphs 🌱

New empty graph — start from nothing, main character energy:

SWIGTYPE_p_Agraph_t gv.graph (string name);
SWIGTYPE_p_Agraph_t gv.digraph (string name);
SWIGTYPE_p_Agraph_t gv.strictgraph (string name);
SWIGTYPE_p_Agraph_t gv.strictdigraph (string name);

New graph from a dot-syntax string or file — bring your own graph, we love a read:

SWIGTYPE_p_Agraph_t gv.readstring (string string);
SWIGTYPE_p_Agraph_t gv.read (string filename);
SWIGTYPE_p_Agraph_t gv.read (SWIGTYPE_p_FILE f);

Add new subgraph to existing graph — nesting era:

SWIGTYPE_p_Agraph_t gv.graph (SWIGTYPE_p_Agraph_t g, string name);

🌿 New nodes 🌿

Add new node to existing graph — plop a node in there:

SWIGTYPE_p_Agnode_t gv.node (SWIGTYPE_p_Agraph_t g, string name);

🍓 New edges 🍓

Add new edge between existing nodes — both ends already exist, easy:

SWIGTYPE_p_Agedge_t gv.edge (SWIGTYPE_p_Agnode_t t, SWIGTYPE_p_Agnode_t h);

Add a new edge between an existing tail node, and a named head node which will be induced in the graph if it doesn't already exist — the head node gets summoned into existence if it's not already there. manifesting ✨

SWIGTYPE_p_Agedge_t gv.edge (SWIGTYPE_p_Agnode_t t, string hname);

Add a new edge between an existing head node, and a named tail node which will be induced in the graph if it doesn't already exist — same deal but the tail is the one that gets conjured:

SWIGTYPE_p_Agedge_t gv.edge (string tname, SWIGTYPE_p_Agnode_t h);

Add a new edge between named tail and head nodes which will be induced in the graph if they don't already exist — neither end exists yet? doesn't matter, both get induced:

SWIGTYPE_p_Agedge_t gv.edge (SWIGTYPE_p_Agraph_t g, string tname, string hname);

💜 Setting attribute values 💜

Set value of named attribute of graph/node/edge - creating attribute if necessary — if the attribute isn't there yet, it gets created. we love a flexible queen:

string gv.setv (SWIGTYPE_p_Agraph_t g, string attr, string val);
string gv.setv (SWIGTYPE_p_Agnode_t n, string attr, string val);
string gv.setv (SWIGTYPE_p_Agedge_t e, string attr, string val);

Set value of existing attribute of graph/node/edge (using attribute handle) — this flavor wants the attribute handle instead of a name:

string gv.setv (SWIGTYPE_p_Agraph_t g, SWIGTYPE_p_Agsym_t a, string val);
string gv.setv (SWIGTYPE_p_Agnode_t n, SWIGTYPE_p_Agsym_t a, string val);
string gv.setv (SWIGTYPE_p_Agedge_t e, SWIGTYPE_p_Agsym_t a, string val);

🌈 Getting attribute values 🌈

Get value of named attribute of graph/node/edge — ask by name, receive a string:

string gv.getv (SWIGTYPE_p_Agraph_t g, string attr);
string gv.getv (SWIGTYPE_p_Agnode_t n, string attr);
string gv.getv (SWIGTYPE_p_Agedge_t e, string attr);

Get value of attribute of graph/node/edge (using attribute handle) — same energy, handle edition:

string gv.getv (SWIGTYPE_p_Agraph_t g, SWIGTYPE_p_Agsym_t a);
string gv.getv (SWIGTYPE_p_Agnode_t n, SWIGTYPE_p_Agsym_t a);
string gv.getv (SWIGTYPE_p_Agedge_t e, SWIGTYPE_p_Agsym_t a);

🧚 Obtain names from handles 🧚

you got a handle, now you want the name back. iconic round trip:

string gv.nameof (SWIGTYPE_p_Agraph_t g);
string gv.nameof (SWIGTYPE_p_Agnode_t n);
string gv.nameof (SWIGTYPE_p_Agsym_t a);

🦋 Find handles from names 🦋

going the other direction — hand over a name, get a handle:

SWIGTYPE_p_Agraph_t gv.findsubg (SWIGTYPE_p_Agraph_t g, string name);
SWIGTYPE_p_Agnode_t gv.findnode (SWIGTYPE_p_Agraph_t g, string name);
SWIGTYPE_p_Agedge_t gv.findedge (SWIGTYPE_p_Agnode_t t, SWIGTYPE_p_Agnode_t h);
SWIGTYPE_p_Agsym_t gv.findattr (SWIGTYPE_p_Agraph_t g, string name);
SWIGTYPE_p_Agsym_t gv.findattr (SWIGTYPE_p_Agnode_t n, string name);
SWIGTYPE_p_Agsym_t gv.findattr (SWIGTYPE_p_Agedge_t e, string name);

💫 Misc graph navigators returning handles 💫

little wanderers that hand you handles back:

SWIGTYPE_p_Agnode_t gv.headof (SWIGTYPE_p_Agedge_t e);
SWIGTYPE_p_Agnode_t gv.tailof (SWIGTYPE_p_Agedge_t e);
SWIGTYPE_p_Agraph_t gv.graphof (SWIGTYPE_p_Agraph_t g);
SWIGTYPE_p_Agraph_t gv.graphof (SWIGTYPE_p_Agedge_t e);
SWIGTYPE_p_Agraph_t gv.graphof (SWIGTYPE_p_Agnode_t n);
SWIGTYPE_p_Agraph_t gv.rootof (SWIGTYPE_p_Agraph_t g);

⭐ Obtain handles of proto node/edge for setting default attribute values ⭐

get the proto node or proto edge so you can set defaults. the template besties:

SWIGTYPE_p_Agnode_t gv.protonode (SWIGTYPE_p_Agraph_t g);
SWIGTYPE_p_Agedge_t gv.protoedge (SWIGTYPE_p_Agraph_t g);

🔁 Iterators 🔁

Iteration termination tests — the "are we done yet" check:

bool gv.ok (SWIGTYPE_p_Agraph_t g);
bool gv.ok (SWIGTYPE_p_Agnode_t n);
bool gv.ok (SWIGTYPE_p_Agedge_t e);
bool gv.ok (SWIGTYPE_p_Agsym_t a);

Iterate over subgraphs of a graph — walk the subgraphs:

SWIGTYPE_p_Agraph_t gv.firstsubg (SWIGTYPE_p_Agraph_t g);
SWIGTYPE_p_Agraph_t gv.nextsubg (SWIGTYPE_p_Agraph_t g, SWIGTYPE_p_Agraph_t sg);

Iterate over supergraphs of a graph (obscure and rarely useful) — the original page literally calls this one obscure and rarely useful, so. take that as you will 💀

SWIGTYPE_p_Agraph_t gv.firstsupg (SWIGTYPE_p_Agraph_t g);
SWIGTYPE_p_Agraph_t gv.nextsupg (SWIGTYPE_p_Agraph_t g, SWIGTYPE_p_Agraph_t sg);

Iterate over edges of a graph — all the edges, from the graph's perspective:

SWIGTYPE_p_Agedge_t gv.firstedge (SWIGTYPE_p_Agraph_t g);
SWIGTYPE_p_Agedge_t gv.nextedge (SWIGTYPE_p_Agraph_t g, SWIGTYPE_p_Agedge_t e);

Iterate over outedges of a graph — outgoing ones:

SWIGTYPE_p_Agedge_t gv.firstout (SWIGTYPE_p_Agraph_t g);
SWIGTYPE_p_Agedge_t gv.nextout (SWIGTYPE_p_Agraph_t g, SWIGTYPE_p_Agedge_t e);

Iterate over edges of a node — now from a node's perspective:

SWIGTYPE_p_Agedge_t gv.firstedge (SWIGTYPE_p_Agnode_t n);
SWIGTYPE_p_Agedge_t gv.nextedge (SWIGTYPE_p_Agnode_t n, SWIGTYPE_p_Agedge_t e);

Iterate over out-edges of a node — outgoing edges of a node:

SWIGTYPE_p_Agedge_t gv.firstout (SWIGTYPE_p_Agnode_t n);
SWIGTYPE_p_Agedge_t gv.nextout (SWIGTYPE_p_Agnode_t n, SWIGTYPE_p_Agedge_t e);

Iterate over head nodes reachable from out-edges of a node — follow the out-edges to the heads:

SWIGTYPE_p_Agnode_t gv.firsthead (SWIGTYPE_p_Agnode_t n);
SWIGTYPE_p_Agnode_t gv.nexthead (SWIGTYPE_p_Agnode_t n, SWIGTYPE_p_Agnode_t h);

Iterate over in-edges of a graph — incoming edges of a graph. okay this one is written exactly like this on the page, with firstin taking a graph and nextin taking a node, and we are simply passing it along verbatim, no edits, no notes 🙈

SWIGTYPE_p_Agedge_t gv.firstin (SWIGTYPE_p_Agraph_t g);
SWIGTYPE_p_Agedge_t gv.nextin (SWIGTYPE_p_Agnode_t n, SWIGTYPE_p_Agedge_t e);

Iterate over in-edges of a node — incoming edges of a node, written exactly like this too:

SWIGTYPE_p_Agedge_t gv.firstin (SWIGTYPE_p_Agnode_t n);
SWIGTYPE_p_Agedge_t gv.nextin (SWIGTYPE_p_Agraph_t g, SWIGTYPE_p_Agedge_t e);

Iterate over tail nodes reachable from in-edges of a node — follow the in-edges back to the tails:

SWIGTYPE_p_Agnode_t gv.firsttail (SWIGTYPE_p_Agnode_t n);
SWIGTYPE_p_Agnode_t gv.nexttail (SWIGTYPE_p_Agnode_t n, SWIGTYPE_p_Agnode_t t);

Iterate over nodes of a graph — the classic:

SWIGTYPE_p_Agnode_t gv.firstnode (SWIGTYPE_p_Agraph_t g);
SWIGTYPE_p_Agnode_t gv.nextnode (SWIGTYPE_p_Agraph_t g, SWIGTYPE_p_Agnode_t n);

Iterate over nodes of an edge — an edge's two endpoints:

SWIGTYPE_p_Agnode_t gv.firstnode (SWIGTYPE_p_Agedge_t e);
SWIGTYPE_p_Agnode_t gv.nextnode (SWIGTYPE_p_Agedge_t e, SWIGTYPE_p_Agnode_t n);

Iterate over attributes of a graph — the graph's attribute handles:

SWIGTYPE_p_Agsym_t gv.firstattr (SWIGTYPE_p_Agraph_t g);
SWIGTYPE_p_Agsym_t gv.nextattr (SWIGTYPE_p_Agraph_t g, SWIGTYPE_p_Agsym_t a);

Iterate over attributes of an edge — the edge's attribute handles:

SWIGTYPE_p_Agsym_t gv.firstattr (SWIGTYPE_p_Agedge_t e);
SWIGTYPE_p_Agsym_t gv.nextattr (SWIGTYPE_p_Agedge_t e, SWIGTYPE_p_Agsym_t a);

Iterate over attributes of a node — the node's attribute handles:

SWIGTYPE_p_Agsym_t gv.firstattr (SWIGTYPE_p_Agnode_t n);
SWIGTYPE_p_Agsym_t gv.nextattr (SWIGTYPE_p_Agnode_t n, SWIGTYPE_p_Agsym_t a);

Remove graph objects — yeet a graph, a node, or an edge:

bool gv.rm (SWIGTYPE_p_Agraph_t g);
bool gv.rm (SWIGTYPE_p_Agnode_t n);
bool gv.rm (SWIGTYPE_p_Agedge_t e);

👑 Layout 👑

Annotate a graph with layout attributes and values using a specific layout engine — pick your engine and let it cook:

bool gv.layout (SWIGTYPE_p_Agraph_t g, string engine);

🎨 Render 🎨

Render a layout into attributes of the graph — the render goes back into the graph's own attributes:

bool gv.render (SWIGTYPE_p_Agraph_t g);

Render a layout to stdout — straight to the terminal:

bool gv.render (SWIGTYPE_p_Agraph_t g, string format);

Render to an open file — you already have the file open, so here you go:

bool gv.render (SWIGTYPE_p_Agraph_t g, string format, SWIGTYPE_p_FILE fout);

Render a layout to an unopened file by name — just hand it a filename:

bool gv.render (SWIGTYPE_p_Agraph_t g, string format, string filename);

Render to a string result — the page gives you two flavors, exactly as written:

string gv.renderresult (SWIGTYPE_p_Agraph_t ing, string format);
gv.renderresult (SWIGTYPE_p_Agraph_t g, string format, string outdata);

Render to an open channel — channel name in, render out:

bool gv.renderchannel (SWIGTYPE_p_Agraph_t g, string format, string channelname);

Render a layout to a malloc'ed string, to be free'd by the caller

⚠️ deprecated - too easy to leak memory ⚠️

like, the page is begging you. it's giving memory leak. but also:

(still needed for "eval [gv::renderdata $G tk]" )

string gv.renderdata (SWIGTYPE_p_Agraph_t g, string format);

📝 Writing graph back to file 📝

Write it out to a filename, or to a FILE you already have open:

bool gv.write (SWIGTYPE_p_Agraph_t g, string filename);
bool gv.write (SWIGTYPE_p_Agraph_t g, SWIGTYPE_p_FILE f);

🔧 Graph transformation tools 🔧

tred — the transformation tool on this page:

bool gv.tred (SWIGTYPE_p_Agraph_t g);

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🔑 KEYWORDS 🔑

graph, dot, neato, fdp, circo, twopi, java.

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that's the whole page bestie, every last signature, no cap. this was gv(3java), dated 21 March 2026, and honestly? she ate. go build something with nodes in it. 💅✨🦋