From be560f00f5ae964fd7c0342390a3fa23c8e7c312 Mon Sep 17 00:00:00 2001
From: Christoph Gohlke <cgohlke@uci.edu>
Date: Sun, 21 Oct 2012 11:01:14 -0500
Subject: [PATCH] py3k: Allow slicing for paths

This is Gohlke's fix for two issues: negative indexes on paths were not
resolved to the correct index, and path slicing didn't work.

His fix for slicing is related to the one found at:

  http://renesd.blogspot.com/2009/07/python3-c-api-simple-slicing-sqslice.html

With this commit, all 79 tests (82 minus the three skipped ones) run
successfully on Python 2.6.8, Python 2.7.3rc2, and Python 3.2.3.
---
 path.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 50 insertions(+), 1 deletion(-)

diff --git a/path.c b/path.c
index af0f4951d..a27b59156 100644
--- a/path.c
+++ b/path.c
@@ -370,6 +370,8 @@ path_getbbox(PyPathObject* self, PyObject* args)
 static PyObject*
 path_getitem(PyPathObject* self, int i)
 {
+    if (i < 0)
+        i = self->count + i;
     if (i < 0 || i >= self->count) {
 	PyErr_SetString(PyExc_IndexError, "path index out of range");
 	return NULL;
@@ -559,6 +561,47 @@ static struct PyGetSetDef getsetters[] = {
     { NULL }
 };
 
+static PyObject*
+path_subscript(PyPathObject* self, PyObject* item) {
+    if (PyIndex_Check(item)) {
+        Py_ssize_t i;
+        i = PyNumber_AsSsize_t(item, PyExc_IndexError);
+        if (i == -1 && PyErr_Occurred())
+            return NULL;
+        return path_getitem(self, i);
+    }
+    if (PySlice_Check(item)) {
+        int len = 4;
+        Py_ssize_t start, stop, step, slicelength;
+
+#if PY_VERSION_HEX >= 0x03000000
+        if (PySlice_GetIndicesEx(item, len, &start, &stop, &step, &slicelength) < 0)
+            return NULL;
+#else
+        if (PySlice_GetIndicesEx((PySliceObject*)item, len, &start, &stop, &step, &slicelength) < 0)
+            return NULL;
+#endif
+
+        if (slicelength <= 0) {
+            double *xy = alloc_array(0);
+            return (PyObject*) path_new(0, xy, 0);
+        }
+        else if (step == 1) {
+            return path_getslice(self, start, stop);
+        }
+        else {
+            PyErr_SetString(PyExc_TypeError, "slice steps not supported");
+            return NULL;
+        }
+    }
+    else {
+        PyErr_Format(PyExc_TypeError,
+                     "Path indices must be integers, not %.200s",
+                     Py_TYPE(&item)->tp_name);
+        return NULL;
+    }
+}
+
 static PySequenceMethods path_as_sequence = {
 	(lenfunc)path_len, /*sq_length*/
 	(binaryfunc)0, /*sq_concat*/
@@ -569,6 +612,12 @@ static PySequenceMethods path_as_sequence = {
 	(ssizessizeobjargproc)0, /*sq_ass_slice*/
 };
 
+static PyMappingMethods path_as_mapping = {
+    (lenfunc)path_len,
+    (binaryfunc)path_subscript,
+    NULL
+};
+
 static PyTypeObject PyPathType = {
 	PyVarObject_HEAD_INIT(NULL, 0)
 	"Path",				/*tp_name*/
@@ -583,7 +632,7 @@ static PyTypeObject PyPathType = {
 	0,				/*tp_repr*/
 	0,                              /*tp_as_number */
 	&path_as_sequence,              /*tp_as_sequence */
-    0,                          /*tp_as_mapping */
+    &path_as_mapping,           /*tp_as_mapping */
     0,                          /*tp_hash*/
     0,                          /*tp_call*/
     0,                          /*tp_str*/