Store dash_pattern as single attribute, not two.

Dash offset and pattern are always used together, so just store them as
single attributes on lines and patches, instead of separate ones.

Author: anntzer

lib/matplotlib/lines.py

@@ -353,14 +353,8 @@ def __init__(self, xdata, ydata,
         self._linestyles = None
         self._drawstyle = None
         self._linewidth = linewidth
-
-        # scaled dash + offset
-        self._dashSeq = None
-        self._dashOffset = 0
-        # unscaled dash + offset
-        # this is needed scaling the dash pattern by linewidth
-        self._us_dashSeq = None
-        self._us_dashOffset = 0
+        self._unscaled_dash_pattern = (0, None)  # offset, dash
+        self._dash_pattern = (0, None)  # offset, dash (scaled by linewidth)
 
         self.set_linewidth(linewidth)
         self.set_linestyle(linestyle)
@@ -775,7 +769,7 @@ def draw(self, renderer):
                 if self.get_sketch_params() is not None:
                     gc.set_sketch_params(*self.get_sketch_params())
 
-                gc.set_dashes(self._dashOffset, self._dashSeq)
+                gc.set_dashes(*self._dash_pattern)
                 renderer.draw_path(gc, tpath, affine.frozen())
                 gc.restore()
 
@@ -1079,13 +1073,10 @@ def set_linewidth(self, w):
             Line width, in points.
         """
         w = float(w)
-
         if self._linewidth != w:
             self.stale = True
         self._linewidth = w
-        # rescale the dashes + offset
-        self._dashOffset, self._dashSeq = _scale_dashes(
-            self._us_dashOffset, self._us_dashSeq, self._linewidth)
+        self._dash_pattern = _scale_dashes(*self._unscaled_dash_pattern, w)
 
     def set_linestyle(self, ls):
         """
@@ -1121,19 +1112,16 @@ def set_linestyle(self, ls):
         if isinstance(ls, str):
             if ls in [' ', '', 'none']:
                 ls = 'None'
-
             _api.check_in_list([*self._lineStyles, *ls_mapper_r], ls=ls)
             if ls not in self._lineStyles:
                 ls = ls_mapper_r[ls]
             self._linestyle = ls
         else:
             self._linestyle = '--'
-
-        # get the unscaled dashes
-        self._us_dashOffset, self._us_dashSeq = _get_dash_pattern(ls)
-        # compute the linewidth scaled dashes
-        self._dashOffset, self._dashSeq = _scale_dashes(
-            self._us_dashOffset, self._us_dashSeq, self._linewidth)
+        self._unscaled_dash_pattern = _get_dash_pattern(ls)
+        self._dash_pattern = _scale_dashes(
+            *self._unscaled_dash_pattern, self._linewidth)
+        self.stale = True
 
     @docstring.interpd
     def set_marker(self, marker):
@@ -1278,10 +1266,8 @@ def update_from(self, other):
         self._markerfacecoloralt = other._markerfacecoloralt
         self._markeredgecolor = other._markeredgecolor
         self._markeredgewidth = other._markeredgewidth
-        self._dashSeq = other._dashSeq
-        self._us_dashSeq = other._us_dashSeq
-        self._dashOffset = other._dashOffset
-        self._us_dashOffset = other._us_dashOffset
+        self._unscaled_dash_pattern = other._unscaled_dash_pattern
+        self._dash_pattern = other._dash_pattern
         self._dashcapstyle = other._dashcapstyle
         self._dashjoinstyle = other._dashjoinstyle
         self._solidcapstyle = other._solidcapstyle

lib/matplotlib/patches.py

@@ -97,9 +97,10 @@ def __init__(self,
         else:
             self.set_edgecolor(edgecolor)
             self.set_facecolor(facecolor)
-        # unscaled dashes.  Needed to scale dash patterns by lw
-        self._us_dashes = None
+
         self._linewidth = 0
+        self._unscaled_dash_pattern = (0, None)  # offset, dash
+        self._dash_pattern = (0, None)  # offset, dash (scaled by linewidth)
 
         self.set_fill(fill)
         self.set_linestyle(linestyle)
@@ -259,9 +260,8 @@ def update_from(self, other):
         self._fill = other._fill
         self._hatch = other._hatch
         self._hatch_color = other._hatch_color
-        # copy the unscaled dash pattern
-        self._us_dashes = other._us_dashes
-        self.set_linewidth(other._linewidth)  # also sets dash properties
+        self._unscaled_dash_pattern = other._unscaled_dash_pattern
+        self.set_linewidth(other._linewidth)  # also sets scaled dashes
         self.set_transform(other.get_data_transform())
         # If the transform of other needs further initialization, then it will
         # be the case for this artist too.
@@ -407,12 +407,9 @@ def set_linewidth(self, w):
             w = mpl.rcParams['patch.linewidth']
             if w is None:
                 w = mpl.rcParams['axes.linewidth']
-
         self._linewidth = float(w)
-        # scale the dash pattern by the linewidth
-        offset, ls = self._us_dashes
-        self._dashoffset, self._dashes = mlines._scale_dashes(
-            offset, ls, self._linewidth)
+        self._dash_pattern = mlines._scale_dashes(
+            *self._unscaled_dash_pattern, w)
         self.stale = True
 
     def set_linestyle(self, ls):
@@ -445,11 +442,9 @@ def set_linestyle(self, ls):
         if ls in [' ', '', 'none']:
             ls = 'None'
         self._linestyle = ls
-        # get the unscaled dash pattern
-        offset, ls = self._us_dashes = mlines._get_dash_pattern(ls)
-        # scale the dash pattern by the linewidth
-        self._dashoffset, self._dashes = mlines._scale_dashes(
-            offset, ls, self._linewidth)
+        self._unscaled_dash_pattern = mlines._get_dash_pattern(ls)
+        self._dash_pattern = mlines._scale_dashes(
+            *self._unscaled_dash_pattern, self._linewidth)
         self.stale = True
 
     def set_fill(self, b):
@@ -565,7 +560,7 @@ def _bind_draw_path_function(self, renderer):
         if self._edgecolor[3] == 0 or self._linestyle == 'None':
             lw = 0
         gc.set_linewidth(lw)
-        gc.set_dashes(self._dashoffset, self._dashes)
+        gc.set_dashes(*self._dash_pattern)
         gc.set_capstyle(self._capstyle)
         gc.set_joinstyle(self._joinstyle)
 
@@ -603,8 +598,9 @@ def draw(self, renderer):
         if not self.get_visible():
             return
         # Patch has traditionally ignored the dashoffset.
-        with cbook._setattr_cm(self, _dashoffset=0), \
-                self._bind_draw_path_function(renderer) as draw_path:
+        with cbook._setattr_cm(
+                 self, _dash_pattern=(0, self._dash_pattern[1])), \
+             self._bind_draw_path_function(renderer) as draw_path:
             path = self.get_path()
             transform = self.get_transform()
             tpath = transform.transform_path_non_affine(path)

lib/matplotlib/tests/test_legend.py

@@ -481,8 +481,7 @@ def test_linecollection_scaled_dashes():
     h1, h2, h3 = leg.legendHandles
 
     for oh, lh in zip((lc1, lc2, lc3), (h1, h2, h3)):
-        assert oh.get_linestyles()[0][1] == lh._dashSeq
-        assert oh.get_linestyles()[0][0] == lh._dashOffset
+        assert oh.get_linestyles()[0] == lh._dash_pattern
 
 
 def test_handler_numpoints():