ENH: pass dash_offset through to gc for Line2D

tacaswell · tacaswell · commit 50aceb5357b0 · 2015-11-24T00:23:36.000-05:00
Previously, the user supplied offset to Line2D set_linestyle
was silently discarded.  This commit makes the value to be passed
through to the underlying GC on draw, but not all of the backends do
anything with the offset (ex Agg does not).
diff --git a/lib/matplotlib/lines.py b/lib/matplotlib/lines.py
@@ -346,6 +346,7 @@ def __init__(self, xdata, ydata,
         self.set_markersize(markersize)
 
         self._dashSeq = None
+        self._dashOffset = 0
 
         self._markeredgecolor = None
         self._markeredgewidth = None
@@ -1028,6 +1029,7 @@ def set_linestyle(self, ls):
                 raise ValueError()
 
             self.set_dashes(ls[1])
+            self._dashOffset = ls[0]
             self._linestyle = "--"
             return
 
@@ -1198,7 +1200,7 @@ def _draw_solid(self, renderer, gc, path, trans):
     def _draw_dashed(self, renderer, gc, path, trans):
         gc.set_linestyle('dashed')
         if self._dashSeq is not None:
-            gc.set_dashes(0, self._dashSeq)
+            gc.set_dashes(self._dashOffset, self._dashSeq)
 
         renderer.draw_path(gc, path, trans)
 
@@ -1222,6 +1224,7 @@ def update_from(self, other):
         self._markeredgecolor = other._markeredgecolor
         self._markeredgewidth = other._markeredgewidth
         self._dashSeq = other._dashSeq
+        self._dashOffset = other._dashOffset
         self._dashcapstyle = other._dashcapstyle
         self._dashjoinstyle = other._dashjoinstyle
         self._solidcapstyle = other._solidcapstyle
