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Support odd-length dash patterns in Agg. #17444

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Merged
merged 1 commit into from
May 19, 2020
Merged

Support odd-length dash patterns in Agg. #17444

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6 changes: 6 additions & 0 deletions lib/matplotlib/tests/test_lines.py
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Original file line number Diff line number Diff line change
Expand Up @@ -217,3 +217,9 @@ def test_marker_as_markerstyle():

assert_array_equal(line2.get_marker().vertices, triangle1.vertices)
assert_array_equal(line3.get_marker().vertices, triangle1.vertices)


@check_figures_equal()
def test_odd_dashes(fig_test, fig_ref):
fig_test.add_subplot().plot([1, 2], dashes=[1, 2, 3])
fig_ref.add_subplot().plot([1, 2], dashes=[1, 2, 3, 1, 2, 3])
16 changes: 7 additions & 9 deletions src/py_converters.cpp
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Expand Up @@ -226,7 +226,6 @@ int convert_dashes(PyObject *dashobj, void *dashesp)
PyObject *dash_offset_obj = NULL;
double dash_offset = 0.0;
PyObject *dashes_seq = NULL;
Py_ssize_t nentries;

if (!PyArg_ParseTuple(dashobj, "OO:dashes", &dash_offset_obj, &dashes_seq)) {
return 0;
Expand Down Expand Up @@ -256,18 +255,17 @@ int convert_dashes(PyObject *dashobj, void *dashesp)
return 0;
}

nentries = PySequence_Size(dashes_seq);
if (nentries % 2 != 0) {
PyErr_Format(PyExc_ValueError, "dashes sequence must have an even number of elements");
return 0;
}
Py_ssize_t nentries = PySequence_Size(dashes_seq);
// If the dashpattern has odd length, iterate through it twice (in
// accordance with the pdf/ps/svg specs).
Py_ssize_t dash_pattern_length = (nentries % 2) ? 2 * nentries : nentries;
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Can you add a comment what this is doing and why? It's hard to understand if one doesn't know the context.

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done


for (Py_ssize_t i = 0; i < nentries; ++i) {
for (Py_ssize_t i = 0; i < dash_pattern_length; ++i) {
PyObject *item;
double length;
double skip;

item = PySequence_GetItem(dashes_seq, i);
item = PySequence_GetItem(dashes_seq, i % nentries);
if (item == NULL) {
return 0;
}
Expand All @@ -280,7 +278,7 @@ int convert_dashes(PyObject *dashobj, void *dashesp)

++i;

item = PySequence_GetItem(dashes_seq, i);
item = PySequence_GetItem(dashes_seq, i % nentries);
if (item == NULL) {
return 0;
}
Expand Down