Ignore non-draw codes when calculating path extent

dstansby · dstansby · commit da7338684e6b · 2021-01-02T11:37:44.000Z
diff --git a/lib/matplotlib/path.py b/lib/matplotlib/path.py
@@ -95,6 +95,9 @@ class Path:
                              CURVE4: 3,
                              CLOSEPOLY: 1}
 
+    #: A list of the codes that do not draw anything
+    NON_DRAW_CODES = [MOVETO, CLOSEPOLY, STOP]
+
     def __init__(self, vertices, codes=None, _interpolation_steps=1,
                  closed=False, readonly=False):
         """
@@ -620,11 +623,17 @@ def get_extents(self, transform=None, **kwargs):
             self = transform.transform_path(self)
         if self.codes is None:
             xys = self.vertices
+        # Short cut the case with only straight lines
         elif len(np.intersect1d(self.codes, [Path.CURVE3, Path.CURVE4])) == 0:
-            xys = self.vertices[self.codes != Path.CLOSEPOLY]
+            draw_idxs = np.nonzero(self.codes == Path.LINETO)[0]
+            # Include the start and end point of each line
+            draw_idxs = np.union1d(draw_idxs, draw_idxs - 1)
+            xys = self.vertices[draw_idxs]
         else:
             xys = []
             for curve, code in self.iter_bezier(**kwargs):
+                if code in Path.NON_DRAW_CODES:
+                    continue
                 # places where the derivative is zero can be extrema
                 _, dzeros = curve.axis_aligned_extrema()
                 # as can the ends of the curve
