Graph View: make font color adapt to node background

Fixes #11957

Author: prculley

GraphView/graphview.gpr.py

@@ -32,7 +32,7 @@
         name  = _("Graph View"),
         category = ("Ancestry", _("Charts")),
         description =  _("Dynamic and interactive graph of relations"),
-        version = '1.0.116',
+        version = '1.0.117',
         gramps_target_version = "5.1",
         status = STABLE,
         fname = 'graphview.py',

GraphView/graphview.py

@@ -73,7 +73,8 @@
 from gramps.gui.dialog import OptionDialog, ErrorDialog, QuestionDialog2
 from gramps.gui.display import display_url
 from gramps.gui.editors import EditPerson, EditFamily, EditTagList
-from gramps.gui.utils import color_graph_box, color_graph_family, rgb_to_hex
+from gramps.gui.utils import (color_graph_box, color_graph_family,
+                              rgb_to_hex, hex_to_rgb_float)
 from gramps.gui.views.navigationview import NavigationView
 from gramps.gui.views.bookmarks import PersonBookmarks
 from gramps.gui.views.tags import OrganizeTagsDialog
@@ -3030,8 +3031,10 @@ def add_node(self, node_id, label, shape="", color="",
             text += ' color="%s"' % color
 
         if fillcolor:
-            text += ' fillcolor="%s"' % fillcolor
-
+            color = hex_to_rgb_float(fillcolor)
+            yiq = (color[0] * 299 + color[1] * 587 + color[2] * 114)
+            fontcolor = "white" if yiq < 500 else "black"
+            text += ' fillcolor="%s" fontcolor="%s"' % (fillcolor, fontcolor)
         if style:
             text += ' style="%s"' % style