FIX: pull the unscaled dashes from the line collection

tacaswell · tacaswell · commit 9893d4fa2e84 · 2017-01-14T21:25:41.000-05:00
To prevent double-scaling of the pattern in the legend Closes matplotlib#7814
diff --git a/lib/matplotlib/legend_handler.py b/lib/matplotlib/legend_handler.py
@@ -266,12 +266,11 @@ def get_numpoints(self, legend):
 
     def _default_update_prop(self, legend_handle, orig_handle):
         lw = orig_handle.get_linewidths()[0]
-        dashes = orig_handle.get_dashes()[0]
+        dashes = orig_handle._us_linestyles[0]
         color = orig_handle.get_colors()[0]
         legend_handle.set_color(color)
+        legend_handle.set_linestyle(dashes)
         legend_handle.set_linewidth(lw)
-        if dashes[0] is not None: # dashed line
-            legend_handle.set_dashes(dashes[1])
 
     def create_artists(self, legend, orig_handle,
                        xdescent, ydescent, width, height, fontsize, trans):
diff --git a/lib/matplotlib/tests/test_legend.py b/lib/matplotlib/tests/test_legend.py
@@ -17,7 +17,7 @@
 import matplotlib as mpl
 import matplotlib.patches as mpatches
 import matplotlib.transforms as mtrans
-
+import matplotlib.collections as mc
 
 @image_comparison(baseline_images=['legend_auto1'], remove_text=True)
 def test_legend_auto1():
@@ -296,7 +296,28 @@ def test_not_covering_scatter_transform():
     plt.legend(['foo', 'bar'], loc='best')
 
 
+@cleanup
+def test_linecollection_scaled_dashes():
+    lines1 = [[(0, .5), (.5, 1)], [(.3, .6), (.2, .2)]]
+    lines2 = [[[0.7, .2], [.8, .4]], [[.5, .7], [.6, .1]]]
+    lines3 = [[[0.6, .2], [.8, .4]], [[.5, .7], [.1, .1]]]
+    lc1 = mc.LineCollection(lines1, linestyles="--", lw=3)
+    lc2 = mc.LineCollection(lines2, linestyles="-.")
+    lc3 = mc.LineCollection(lines3, linestyles=":", lw=.5)
+
+    fig, ax = plt.subplots()
+    ax.add_collection(lc1)
+    ax.add_collection(lc2)
+    ax.add_collection(lc3)
+
+    leg = ax.legend([lc1, lc2, lc3], ["line1", "line2", 'line 3'])
+    h1, h2, h3 = leg.legendHandles
+
+    for oh, lh in zip((lc1, lc2, lc3), (h1, h2, h3)):
+        assert oh.get_linestyles()[0][1] == lh._dashSeq
+        assert oh.get_linestyles()[0][0] == lh._dashOffset
+
+
 if __name__ == '__main__':
     import nose
     nose.runmodule(argv=['-s', '--with-doctest'], exit=False)
-
