Include interactive_bst.py demo into repository

doc/demos/interactive_bst.py

+#! /usr/bin/env python
+# -*- coding: utf-8 -*-
+
+# This simple example on how to interactive animations using graph-tool. Here we
+# show the BFS tree of length 3 for the currently selected vertex.
+
+from graph_tool.all import *
+
+# We need some Gtk functions
+from gi.repository import Gtk, Gdk
+import sys
+
+offscreen = sys.argv[1] == "offscreen" if len(sys.argv) > 1 else False
+
+# We will use the network of network scientists, and filter out the largest
+# component
+g = collection.data["netscience"]
+g = GraphView(g, vfilt=label_largest_component(g), directed=False)
+g = Graph(g, prune=True)
+
+pos = g.vp["pos"]  # layout positions
+
+ecolor = g.new_edge_property("vector<double>")
+for e in g.edges():
+    ecolor[e] = [0.6, 0.6, 0.6, 1]
+vcolor = g.new_vertex_property("vector<double>")
+for v in g.vertices():
+    vcolor[v] = [0.6, 0.6, 0.6, 1]
+
+win = GraphWindow(g, pos, geometry=(500, 400),
+                  edge_color=ecolor,
+                  vertex_fill_color=vcolor)
+
+orange = [0.807843137254902, 0.3607843137254902, 0.0, 1.0]
+old_src = None
+count = 0
+def update_bfs(widget, event):
+    global old_src, g, count, win
+    src = widget.picked
+    if src is None:
+        return True
+    if isinstance(src, PropertyMap):
+        src = [v for v in g.vertices() if src[v]]
+        if len(src) == 0:
+            return True
+        src = src[0]
+    if src == old_src:
+        return True
+    old_src = src
+    pred = shortest_distance(g, src, max_dist=3, pred_map=True)[1]
+    for e in g.edges():
+        ecolor[e] = [0.6, 0.6, 0.6, 1]
+    for v in g.vertices():
+        vcolor[v] = [0.6, 0.6, 0.6, 1]
+    for v in g.vertices():
+        w = g.vertex(pred[v])
+        if w < g.num_vertices():
+            e = g.edge(w, v)
+            if e is not None:
+                ecolor[e] = orange
+                vcolor[v] = vcolor[w] = orange
+    widget.regenerate_surface(lazy=False)
+    widget.queue_draw()
+
+    if offscreen:
+        window = widget.get_window()
+        pixbuf = Gdk.pixbuf_get_from_window(window, 0, 0, 500, 400)
+        pixbuf.savev(r'./frames/bfs%06d.png' % count, 'png', [], [])
+        count += 1
+
+# Bind the function above as a montion notify handler
+win.graph.connect("motion_notify_event", update_bfs)
+
+# We will give the user the ability to stop the program by closing the window.
+win.connect("delete_event", Gtk.main_quit)
+
+# Actually show the window, and start the main loop.
+win.show_all()
+Gtk.main()