Added 'double arrow' (DArrow) to patches.BoxStyle.

lkilcher · lkilcher · commit 1aa2e584ec33 · 2014-07-23T15:28:14.000-06:00
diff --git a/doc/users/annotations_guide.rst b/doc/users/annotations_guide.rst
@@ -48,6 +48,7 @@ keyword arguments. Currently, following box styles are implemented.
   ==========   ==============   ==========================
   LArrow       ``larrow``       pad=0.3
   RArrow       ``rarrow``       pad=0.3
+  DArrow       ``darrow``       pad=0.3
   Round        ``round``        pad=0.3,rounding_size=None
   Round4       ``round4``       pad=0.3,rounding_size=None
   Roundtooth   ``roundtooth``   pad=0.3,tooth_size=None
diff --git a/lib/matplotlib/patches.py b/lib/matplotlib/patches.py
@@ -2003,6 +2003,57 @@ def transmute(self, x0, y0, width, height, mutation_size):
 
     _style_list["rarrow"] = RArrow
 
+    class DArrow(_Base):
+        """
+        (Double) Arrow Box
+        """
+        # This source is copied from LArrow,
+        # modified to add a right arrow to the bbox.
+
+        def __init__(self, pad=0.3):
+            self.pad = pad
+            super(BoxStyle.DArrow, self).__init__()
+
+        def transmute(self, x0, y0, width, height, mutation_size):
+
+            # padding
+            pad = mutation_size * self.pad
+
+            # width and height with padding added.
+            # The width is padded by the arrows, so we don't need to pad it.
+            height = height + 2. * pad
+
+            # boundary of the padded box
+            x0, y0 = x0 - pad, y0 - pad
+            x1, y1 = x0 + width, y0 + height
+
+            dx = (y1 - y0)/2.
+            dxx = dx * .5
+            # adjust x0.  1.4 <- sqrt(2)
+            x0 = x0 + pad / 1.4
+
+            cp = [(x0 + dxx, y0), (x1, y0),  # bot-segment
+                  (x1, y0 - dxx), (x1 + dx + dxx, y0 + dx),
+                  (x1, y1 + dxx),  # right-arrow
+                  (x1, y1), (x0 + dxx, y1),  # top-segment
+                  (x0 + dxx, y1 + dxx), (x0 - dx, y0 + dx),
+                  (x0 + dxx, y0 - dxx),  # left-arrow
+                  (x0 + dxx, y0), (x0 + dxx, y0)]  # close-poly
+
+            com = [Path.MOVETO, Path.LINETO,
+                   Path.LINETO, Path.LINETO,
+                   Path.LINETO,
+                   Path.LINETO, Path.LINETO,
+                   Path.LINETO, Path.LINETO,
+                   Path.LINETO,
+                   Path.LINETO, Path.CLOSEPOLY]
+
+            path = Path(cp, com)
+
+            return path
+
+    _style_list['darrow'] = DArrow
+
     class Round(_Base):
         """
         A box with round corners.
