matplotlib · mdboom · Aug 29, 2011 · Aug 23, 2011 · Aug 23, 2011 · Aug 23, 2011
diff --git a/examples/user_interfaces/svg_histogram.py b/examples/user_interfaces/svg_histogram.py
@@ -0,0 +1,131 @@
+#!/usr/bin/env python
+#-*- encoding:utf-8 -*-
+
+"""
+Demonstrate how to create an interactive histogram, in which bars
+are hidden or shown by cliking on legend markers. 
+
+The interactivity is encoded in ecmascript and inserted in the SVG code
+in a post-processing step. To render the image, open it in a web
+browser. SVG is supported in most web browsers used by Linux and OSX 
+users. Windows IE9 supports SVG, but earlier versions do not. 
+
+__author__="david.huard@gmail.com"
+
+"""
+
+import numpy as np
+import matplotlib.pyplot as plt
+import xml.etree.ElementTree as ET
+from StringIO import StringIO
+
+plt.rcParams['svg.embed_char_paths'] = 'none'
+
+# Apparently, this `register_namespace` method works only with 
+# python 2.7 and up and is necessary to avoid garbling the XML name
+# space with ns0.
+ET.register_namespace("","http://www.w3.org/2000/svg")
+
+
+def python2js(d):
+    """Return a string representation of a python dictionary in 
+    ecmascript object syntax."""
+
+    objs = []
+    for key, value in d.items():
+        objs.append( key + ':' + str(value) )
+
+    return '{' + ', '.join(objs) + '}'
+
+
+# --- Create histogram, legend and title ---
+plt.figure()
+r = np.random.randn(100)
+r1 = r + 1
+labels = ['Rabbits', 'Frogs']
+H = plt.hist([r,r1], label=labels)
+containers = H[-1]
+leg = plt.legend(frameon=False)
+plt.title("""From a web browser, click on the legend 
+marker to toggle the corresponding histogram.""")
+
+
+# --- Add ids to the svg objects we'll modify 
+
+hist_patches = {}
+for ic, c in enumerate(containers):
+    hist_patches['hist_%d'%ic] = []
+    for il, element in enumerate(c):
+        element.set_gid('hist_%d_patch_%d'%(ic, il))
+        hist_patches['hist_%d'%ic].append('hist_%d_patch_%d'%(ic,il))    
+
+# Set ids for the legend patches    
+for i, t in enumerate(leg.get_patches()):
+    t.set_gid('leg_patch_%d'%i)
+
+# Save SVG in a fake file object.
+f = StringIO()
+plt.savefig(f, format="svg")
+
+# Create XML tree from the SVG file.
+tree, xmlid = ET.XMLID(f.getvalue())
+
+
+# --- Add interactivity ---
+
+# Add attributes to the patch objects.    
+for i, t in enumerate(leg.get_patches()):
+    el = xmlid['leg_patch_%d'%i]
+    el.set('cursor', 'pointer')
+    el.set('opacity', '1.0')
+    el.set('onclick', "toggle_element(evt, 'hist_%d')"%i)
+
+# Create script defining the function `toggle_element`. 
+# We create a global variable `container` that stores the patches id 
+# belonging to each histogram. Then a function "toggle_element" sets the 
+# visibility attribute of all patches of each histogram and the opacity
+# of the marker itself. 
+
+script = """
+<script type="text/ecmascript">
+<![CDATA[
+var container = %s 
+
+function toggle_element(evt, element) {
+
+    var names = container[element]
+    var el, state;
+
+    state = evt.target.getAttribute("opacity") == 1.0 || 
+                evt.target.getAttribute("opacity") == null;
+
+    if (state) {
+        evt.target.setAttribute("opacity", 0.5);
+
+        for (var i=0; i < names.length; i++) {
+            el = document.getElementById(names[i]);    
+            el.setAttribute("visibility","hidden");
+            }
+        }
+
+    else {
+        evt.target.setAttribute("opacity", 1);
+
+        for (var i=0; i < names.length; i++) {
+            el = document.getElementById(names[i]);    
+            el.setAttribute("visibility","visible");
+            }
+
+        };
+    };
+]]>
+</script>
+"""%python2js(hist_patches)
+
+# Insert the script and save to file.
+tree.insert(0, ET.XML(script))
+
+ET.ElementTree(tree).write("svg_histogram.svg")
+
+
+
diff --git a/lib/matplotlib/backends/backend_svg.py b/lib/matplotlib/backends/backend_svg.py
@@ -279,6 +279,8 @@ def __init__(self, width, height, svgwriter, basename=None):
         self._write_default_style()
 
     def finalize(self):
+        self._write_clips()
+        self._write_hatches()
         self._write_svgfonts()
         self.writer.close(self._start_id)
 
@@ -321,26 +323,35 @@ def _get_hatch(self, gc, rgbFace):
         """
         Create a new hatch pattern
         """
-        writer = self.writer
-        HATCH_SIZE = 72
         dictkey = (gc.get_hatch(), rgbFace, gc.get_rgb())
         oid = self._hatchd.get(dictkey)
         if oid is None:
             oid = self._make_id('h', dictkey)
-            writer.start('defs')
+            self._hatchd[dictkey] = ((gc.get_hatch_path(), rgbFace, gc.get_rgb()), oid)
+        else:
+            _, oid = oid
+        return oid
+
+    def _write_hatches(self):
+        if not len(self._hatchd):
+            return
+        HATCH_SIZE = 72
+        writer = self.writer
+        writer.start('defs')
+        for ((path, face, stroke), oid) in self._hatchd.values():
             writer.start(
                 'pattern',
                 id=oid,
                 patternUnits="userSpaceOnUse",
                 x="0", y="0", width=str(HATCH_SIZE), height=str(HATCH_SIZE))
             path_data = self._convert_path(
-                gc.get_hatch_path(),
+                path,
                 Affine2D().scale(HATCH_SIZE).scale(1.0, -1.0).translate(0, HATCH_SIZE),
                 simplify=False)
-            if rgbFace is None:
+            if face is None:
                 fill = 'none'
             else:
-                fill = rgb2hex(rgbFace)
+                fill = rgb2hex(face)
             writer.element(
                 'rect',
                 x="0", y="0", width=str(HATCH_SIZE+1), height=str(HATCH_SIZE+1),
@@ -349,17 +360,15 @@ def _get_hatch(self, gc, rgbFace):
                 'path',
                 d=path_data,
                 style=generate_css({
-                    'fill': rgb2hex(gc.get_rgb()),
-                    'stroke': rgb2hex(gc.get_rgb()),
+                    'fill': rgb2hex(stroke),
+                    'stroke': rgb2hex(stroke),
                     'stroke-width': str(1.0),
                     'stroke-linecap': 'butt',
                     'stroke-linejoin': 'miter'
                     })
                 )
             writer.end('pattern')
-            writer.end('defs')
-            self._hatchd[dictkey] = oid
-        return oid
+        writer.end('defs')
 
     def _get_style(self, gc, rgbFace):
         """
@@ -409,22 +418,34 @@ def _get_clip(self, gc):
         else:
             return None
 
-        oid = self._clipd.get(dictkey)
-        if oid is None:
-            writer = self.writer
+        clip = self._clipd.get(dictkey)
+        if clip is None:
             oid = self._make_id('p', dictkey)
-            writer.start('defs')
-            writer.start('clipPath', id=oid)
             if clippath is not None:
+                self._clipd[dictkey] = ((clippath, clippath_trans), oid)
+            else:
+                self._clipd[dictkey] = (dictkey, oid)
+        else:
+            clip, oid = clip
+        return oid
+
+    def _write_clips(self):
+        if not len(self._clipd):
+            return
+        writer = self.writer
+        writer.start('defs')
+        for clip, oid in self._clipd.values():
+            writer.start('clipPath', id=oid)
+            if len(clip) == 2:
+                clippath, clippath_trans = clip
                 path_data = self._convert_path(clippath, clippath_trans, simplify=False)
                 writer.element('path', d=path_data)
             else:
+                x, y, w, h = clip
                 writer.element('rect', x=str(x), y=str(y), width=str(w), height=str(h))
             writer.end('clipPath')
-            writer.end('defs')
-            self._clipd[dictkey] = oid
-        return oid
-
+        writer.end('defs')
+
     def _write_svgfonts(self):
         if not rcParams['svg.fonttype'] == 'svgfont':
             return