X improve `xbtree topoview`

good viewer is spawned; the picture is not changed when another topoview
is run in parallel.

wcfs/internal/xbtree.py

@@ -980,7 +980,7 @@ def zcheck(ztree):
 
 # ----------------------------------------
 
-import sys
+import sys, tempfile, shutil, subprocess
 
 # graphviz returns tree graph representation in dot language.
 @func(Tree)
@@ -1072,6 +1072,7 @@ def graphviz(t, clustername=''):
 
 
 # topoview display topologies provided in argv.
+@func
 def topoview(argv):
     if len(argv) == 0:
         raise RuntimeError('E: empty argument')
@@ -1095,8 +1096,17 @@ def topoview(argv):
     import graphviz as gv
     g = gv.Source('\n'.join(outv))
 
-    g.view()
-    #g.render('x', format='svg')
+    tmpd = tempfile.mkdtemp('', 'xbtree')
+    def _():
+        shutil.rmtree(tmpd)
+    defer(_)
+
+    # set filename so that it shows in window title.
+    filename = ' '.join([_.replace('/', '\\') for _ in argv]) # no / in filename
+    g.render(filename, tmpd, format='svg')
+
+    # XXX g.view spawns viewer, but does not wait for it to stop
+    subprocess.check_call(["inkview", "%s/%s.svg" % (tmpd, filename)])
 
 
 if __name__ == '__main__':