From 7bccd1e586b653c35343037046e3a05d4e848634 Mon Sep 17 00:00:00 2001
From: Florian Mounier <florian.mounier@kozea.fr>
Date: Fri, 30 Oct 2015 17:56:54 +0100
Subject: [PATCH] Add `dynamic_print_values` to show print_values on legend
 hover. (Fix #279)

---
 demo/moulinrouge/tests.py                 |  3 ++-
 docs/changelog.rst                        |  6 ++++++
 docs/documentation/configuration/data.rst | 14 ++++++++++++++
 pygal/config.py                           |  4 ++++
 pygal/css/graph.css                       |  8 ++++++++
 pygal/graph/graph.py                      |  5 +++--
 6 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/demo/moulinrouge/tests.py b/demo/moulinrouge/tests.py
index 183b007..dbe80b0 100644
--- a/demo/moulinrouge/tests.py
+++ b/demo/moulinrouge/tests.py
@@ -54,6 +54,7 @@ def get_test_routes(app):
         bar.title = 'Wow ! Such Chart !'
         bar.x_title = 'Many x labels'
         bar.y_title = 'Much y labels'
+        bar.dynamic_print_values = True
 
         bar.add('Red serie', [
             {'value': 10,
@@ -343,7 +344,7 @@ def get_test_routes(app):
 
     @app.route('/test/bar')
     def test_bar():
-        bar = Bar()
+        bar = Bar(dynamic_print_values=True)
         bar.add('1', [1, 2, 3])
         bar.add('2', [4, 5, 6])
         bar.x_labels = ['a']
diff --git a/docs/changelog.rst b/docs/changelog.rst
index bafec30..6344d3e 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -2,6 +2,12 @@
 Changelog
 =========
 
+2.0.9 UNRELEASED
+================
+
+* Add `dynamic_print_values` to show print_values on legend hover. (Fix #279)
+
+
 2.0.8
 =====
 
diff --git a/docs/documentation/configuration/data.rst b/docs/documentation/configuration/data.rst
index 6d9fad0..04ec317 100644
--- a/docs/documentation/configuration/data.rst
+++ b/docs/documentation/configuration/data.rst
@@ -39,6 +39,20 @@ When using pygal to display static charts for printing for example you can chose
                     value_colors=('white',)))
   chart.add('line', [0, 12, 31, 8, 28, 0])
 
+dynamic_print_values
+--------------------
+
+Show print_values only on legend hover.
+
+.. pygal-code::
+
+  from pygal.style import DefaultStyle
+  chart = pygal.Bar(dynamic_print_values=True, style=DefaultStyle(
+                    value_font_family='googlefont:Raleway',
+                    value_font_size=30,
+                    value_colors=('white',)))
+  chart.add('line', [0, 12, 31, 8, 28, 0])
+
 
 print_zeroes
 ------------
diff --git a/pygal/config.py b/pygal/config.py
index b56c174..faadb73 100644
--- a/pygal/config.py
+++ b/pygal/config.py
@@ -458,6 +458,10 @@ class Config(CommonConfig):
         False, bool,
         "Text", "Display value labels")
 
+    dynamic_print_values = Key(
+        False, bool,
+        "Text", "Show values only on hover")
+
     truncate_legend = Key(
         None, int, "Text",
         "Legend string length truncation threshold",
diff --git a/pygal/css/graph.css b/pygal/css/graph.css
index 7e93d53..95563c5 100644
--- a/pygal/css/graph.css
+++ b/pygal/css/graph.css
@@ -119,3 +119,11 @@
 {{ id }}.tooltip text {
   fill-opacity: 1;
 }
+
+{{ id }}.showable {
+  visibility: hidden;
+}
+
+{{ id }}.showable.shown {
+  visibility: visible;
+}
diff --git a/pygal/graph/graph.py b/pygal/graph/graph.py
index a381a37..eb5cebc 100644
--- a/pygal/graph/graph.py
+++ b/pygal/graph/graph.py
@@ -472,10 +472,11 @@ class Graph(PublicApi):
             ).text = label
             y += self.style.value_font_size
 
-        if self.print_values:
+        if self.print_values or self.dynamic_print_values:
             self.svg.node(
                 serie_node['text_overlay'], 'text',
-                class_='centered value',
+                class_='centered value%s' % (
+                    ' showable' if self.dynamic_print_values else ''),
                 x=x,
                 y=y + self.style.value_font_size / 3
             ).text = value if self.print_zeroes or value != '0' else ''