Dash styles for line collections (hv)lines etc

This goes together with mpld3/mplexporter#71
it's the mpld3 side of the change.

Again, done together with gpt-5.1-codex but with full review/polish from me,
thoug I think this one's trivial given the other one.

See the other PR for example screenshot of it working.

I would re-generate the compiled js files once you approve.

Also, how shall we do the submodule update commit? Should I include it
in this PR after the mplexplorer got in?

(I find the submodule to be an annoying maintenance burden btw)

Author: lucasb-eyer

mpld3/mpld3renderer.py

@@ -211,7 +211,11 @@ def draw_path_collection(self, paths, path_coordinates, path_transforms,
                              offsets, offset_coordinates, offset_order,
                              styles, mplobj=None):
         if len(paths) != 0:
+            dasharrays = styles.get('dasharray', None)
+            if dasharrays is None:
+                dasharrays = ["none"]
             styles = dict(alphas=[styles['alpha']],
+                          dasharrays=list(dasharrays),
                           edgecolors=[export_color(ec)
                                       for ec in styles['edgecolor']],
                           facecolors=[export_color(fc)

mpld3/tests/test_elements.py

@@ -60,10 +60,12 @@ def test_scatter():
     points = axrep['collections'][0]
 
     assert_equal(list(sorted(points.keys())),
-                 ['alphas', 'edgecolors', 'edgewidths', 'facecolors', 'id',
-                  'offsetcoordinates', 'offsets', 'pathcoordinates', 'paths',
-                  'pathtransforms', 'xindex', 'yindex', 'zorder'])
+                 ['alphas', 'dasharrays', 'edgecolors', 'edgewidths',
+                  'facecolors', 'id', 'offsetcoordinates', 'offsets',
+                  'pathcoordinates', 'paths', 'pathtransforms', 'xindex',
+                  'yindex', 'zorder'])
     assert_equal(points['alphas'], [0.3])
+    assert_equal(points['dasharrays'], ['none'])
     assert_equal(points['zorder'], 10)
     assert_equal(points['edgecolors'], ['rgba(0, 0, 255, 0.3)'])
     assert_equal(points['facecolors'], ['rgba(255, 0, 0, 0.3)'])
@@ -120,6 +122,17 @@ def test_text():
     assert_equal(text['coordinates'], "data")
 
 
+def test_hlines_linestyle():
+    fig, ax = plt.subplots()
+    ax.hlines([0, 1], [0, 0], [1, 2], linestyles='--')
+    rep = fig_to_dict(fig)
+    collection = rep['axes'][0]['collections'][0]
+
+    assert 'dasharrays' in collection
+    assert len(collection['dasharrays']) > 0
+    assert collection['dasharrays'][0] not in (None, 'none')
+
+
 def test_image():
     fig, ax = plt.subplots()
     ax.imshow(np.random.random((20, 20)), cmap=plt.cm.binary,

src/elements/path_collection.js

@@ -17,6 +17,7 @@ mpld3_PathCollection.prototype.defaultProps = {
     edgecolors: ["#000000"],
     drawstyle: "none",
     edgewidths: [1.0],
+    dasharrays: ["none"],
     facecolors: ["#0000FF"],
     alphas: [1.0],
     zorder: 2
@@ -86,6 +87,7 @@ mpld3_PathCollection.prototype.styleFunc = function(d, i) {
     var styles = {
         "stroke": stroke,
         "stroke-width": getMod(this.props.edgewidths, i),
+        "stroke-dasharray": getMod(this.props.dasharrays, i),
         "fill": fill,
     };