matplotlib · mdboom · Aug 21, 2012 · Feb 29, 2012 · Feb 29, 2012 · Feb 29, 2012
diff --git a/doc/api/api_changes.rst b/doc/api/api_changes.rst
@@ -72,6 +72,54 @@ Changes in 1.2.x
   original keyword arguments will override any value provided by
   *capthick*.
 
+* Transform subclassing behaviour is now subtly changed. If your transform
+  implements a non-affine transformation, then it should override the 
+  ``transform_non_affine`` method, rather than the generic ``transform`` method.
+  Previously transforms would define ``transform`` and then copy the
+  method into ``transform_non_affine``:
+
+     class MyTransform(mtrans.Transform):
+         def transform(self, xy):
+             ...
+         transform_non_affine = transform
+
+  This approach will no longer function correctly and should be changed to:
+
+     class MyTransform(mtrans.Transform):
+         def transform_non_affine(self, xy):
+             ...
+
+* Artists no longer have ``x_isdata`` or ``y_isdata`` attributes; instead
+  any artist's transform can be interrogated with
+  ``artist_instance.get_transform().contains_branch(ax.transData)``
+
+* Lines added to an axes now take into account their transform when updating the
+  data and view limits. This means transforms can now be used as a pre-transform.
+  For instance:
+
+      >>> import matplotlib.pyplot as plt
+      >>> import matplotlib.transforms as mtrans
+      >>> ax = plt.axes()
+      >>> ax.plot(range(10), transform=mtrans.Affine2D().scale(10) + ax.transData)
+      >>> print(ax.viewLim)
+      Bbox('array([[  0.,   0.],\n       [ 90.,  90.]])')
+
+* One can now easily get a transform which goes from one transform's coordinate system
+  to another, in an optimized way, using the new subtract method on a transform. For instance,
+  to go from data coordinates to axes coordinates::
+
+      >>> import matplotlib.pyplot as plt
+      >>> ax = plt.axes()
+      >>> data2ax = ax.transData - ax.transAxes
+      >>> print(ax.transData.depth, ax.transAxes.depth)
+      3, 1
+      >>> print(data2ax.depth)
+      2
+
+  for versions before 1.2 this could only be achieved in a sub-optimal way, using 
+  ``ax.transData + ax.transAxes.inverted()`` (depth is a new concept, but had it existed 
+  it would return 4 for this example).      
+
 Changes in 1.1.x
 ================
 

diff --git a/lib/matplotlib/artist.py b/lib/matplotlib/artist.py
@@ -101,8 +101,6 @@ def __init__(self):
         self._remove_method = None
         self._url = None
         self._gid = None
-        self.x_isdata = True  # False to avoid updating Axes.dataLim with x
-        self.y_isdata = True  #                                      with y
         self._snap = None
 
     def remove(self):

diff --git a/lib/matplotlib/axes.py b/lib/matplotlib/axes.py
@@ -1461,17 +1461,52 @@ def add_line(self, line):
 
         self._update_line_limits(line)
         if not line.get_label():
-            line.set_label('_line%d'%len(self.lines))
+            line.set_label('_line%d' % len(self.lines))
         self.lines.append(line)
         line._remove_method = lambda h: self.lines.remove(h)
         return line
 
     def _update_line_limits(self, line):
-        p = line.get_path()
-        if p.vertices.size > 0:
-            self.dataLim.update_from_path(p, self.ignore_existing_data_limits,
-                                            updatex=line.x_isdata,
-                                            updatey=line.y_isdata)
+        """Figures out the data limit of the given line, updating self.dataLim."""
+        path = line.get_path()
+        if path.vertices.size == 0:
+            return
+
+        line_trans = line.get_transform()
+
+        if line_trans == self.transData:
+            data_path = path
+
+        elif any(line_trans.contains_branch_seperately(self.transData)):
+            # identify the transform to go from line's coordinates
+            # to data coordinates
+            trans_to_data = line_trans - self.transData
+
+            # if transData is affine we can use the cached non-affine component
+            # of line's path. (since the non-affine part of line_trans is
+            # entirely encapsulated in trans_to_data).
+            if self.transData.is_affine:
+                line_trans_path = line._get_transformed_path()
+                na_path, _ = line_trans_path.get_transformed_path_and_affine()
+                data_path = trans_to_data.transform_path_affine(na_path)
+            else:
+                data_path = trans_to_data.transform_path(path)
+        else:
+            # for backwards compatibility we update the dataLim with the 
+            # coordinate range of the given path, even though the coordinate 
+            # systems are completely different. This may occur in situations
+            # such as when ax.transAxes is passed through for absolute
+            # positioning.
+            data_path = path
+
+        if data_path.vertices.size > 0:
+            updatex, updatey = line_trans.contains_branch_seperately(
+                                                               self.transData
+                                                                    )
+            self.dataLim.update_from_path(data_path, 
+                                          self.ignore_existing_data_limits,
+                                          updatex=updatex,
+                                          updatey=updatey)
             self.ignore_existing_data_limits = False
 
     def add_patch(self, p):
@@ -1507,11 +1542,14 @@ def _update_patch_limits(self, patch):
         if vertices.size > 0:
             xys = patch.get_patch_transform().transform(vertices)
             if patch.get_data_transform() != self.transData:
-                transform = (patch.get_data_transform() +
-                                    self.transData.inverted())
-                xys = transform.transform(xys)
-            self.update_datalim(xys, updatex=patch.x_isdata,
-                                     updatey=patch.y_isdata)
+                patch_to_data = (patch.get_data_transform() -
+                                    self.transData)
+                xys = patch_to_data.transform(xys)
+
+            updatex, updatey = patch.get_transform().\
+                                    contains_branch_seperately(self.transData)
+            self.update_datalim(xys, updatex=updatex,
+                                     updatey=updatey)
 
 
     def add_table(self, tab):
@@ -1599,13 +1637,13 @@ def _process_unit_info(self, xdata=None, ydata=None, kwargs=None):
         if xdata is not None:
             # we only need to update if there is nothing set yet.
             if not self.xaxis.have_units():
-               self.xaxis.update_units(xdata)
+                self.xaxis.update_units(xdata)
             #print '\tset from xdata', self.xaxis.units
 
         if ydata is not None:
             # we only need to update if there is nothing set yet.
             if not self.yaxis.have_units():
-               self.yaxis.update_units(ydata)
+                self.yaxis.update_units(ydata)
             #print '\tset from ydata', self.yaxis.units
 
         # process kwargs 2nd since these will override default units
@@ -3424,7 +3462,6 @@ def axhline(self, y=0, xmin=0, xmax=1, **kwargs):
         trans = mtransforms.blended_transform_factory(
             self.transAxes, self.transData)
         l = mlines.Line2D([xmin,xmax], [y,y], transform=trans, **kwargs)
-        l.x_isdata = False
         self.add_line(l)
         self.autoscale_view(scalex=False, scaley=scaley)
         return l
@@ -3489,7 +3526,6 @@ def axvline(self, x=0, ymin=0, ymax=1, **kwargs):
         trans = mtransforms.blended_transform_factory(
             self.transData, self.transAxes)
         l = mlines.Line2D([x,x], [ymin,ymax] , transform=trans, **kwargs)
-        l.y_isdata = False
         self.add_line(l)
         self.autoscale_view(scalex=scalex, scaley=False)
         return l
@@ -3546,7 +3582,6 @@ def axhspan(self, ymin, ymax, xmin=0, xmax=1, **kwargs):
         verts = (xmin, ymin), (xmin, ymax), (xmax, ymax), (xmax, ymin)
         p = mpatches.Polygon(verts, **kwargs)
         p.set_transform(trans)
-        p.x_isdata = False
         self.add_patch(p)
         self.autoscale_view(scalex=False)
         return p
@@ -3603,7 +3638,6 @@ def axvspan(self, xmin, xmax, ymin=0, ymax=1, **kwargs):
         verts = [(xmin, ymin), (xmin, ymax), (xmax, ymax), (xmax, ymin)]
         p = mpatches.Polygon(verts, **kwargs)
         p.set_transform(trans)
-        p.y_isdata = False
         self.add_patch(p)
         self.autoscale_view(scaley=False)
         return p
@@ -3909,7 +3943,6 @@ def plot(self, *args, **kwargs):
             self.add_line(line)
             lines.append(line)
 
-
         self.autoscale_view(scalex=scalex, scaley=scaley)
         return lines
 

diff --git a/lib/matplotlib/lines.py b/lib/matplotlib/lines.py
@@ -6,6 +6,8 @@
 # TODO: expose cap and join style attrs
 from __future__ import division, print_function
 
+import warnings
+
 import numpy as np
 from numpy import ma
 from matplotlib import verbose
@@ -249,17 +251,15 @@ def contains(self, mouseevent):
         if len(self._xy)==0: return False,{}
 
         # Convert points to pixels
-        if self._transformed_path is None:
-            self._transform_path()
-        path, affine = self._transformed_path.get_transformed_path_and_affine()
+        path, affine = self._get_transformed_path().get_transformed_path_and_affine()
         path = affine.transform_path(path)
         xy = path.vertices
         xt = xy[:, 0]
         yt = xy[:, 1]
 
         # Convert pick radius from points to pixels
-        if self.figure == None:
-            warning.warn('no figure set when check if mouse is on line')
+        if self.figure is None:
+            warnings.warn('no figure set when check if mouse is on line')
             pixels = self.pickradius
         else:
             pixels = self.figure.dpi/72. * self.pickradius
@@ -446,13 +446,26 @@ def recache(self, always=False):
         self._invalidy = False
 
     def _transform_path(self, subslice=None):
+        """
+        Puts a TransformedPath instance at self._transformed_path,
+        all invalidation of the transform is then handled by the 
+        TransformedPath instance.
+        """
         # Masked arrays are now handled by the Path class itself
         if subslice is not None:
             _path = Path(self._xy[subslice,:])
         else:
             _path = self._path
         self._transformed_path = TransformedPath(_path, self.get_transform())
 
+    def _get_transformed_path(self):
+        """
+        Return the :class:`~matplotlib.transforms.TransformedPath` instance
+        of this line.
+        """
+        if self._transformed_path is None:
+            self._transform_path()
+        return self._transformed_path
 
     def set_transform(self, t):
         """
@@ -482,8 +495,8 @@ def draw(self, renderer):
             subslice = slice(max(i0-1, 0), i1+1)
             self.ind_offset = subslice.start
             self._transform_path(subslice)
-        if self._transformed_path is None:
-            self._transform_path()
+
+        transformed_path = self._get_transformed_path()
 
         if not self.get_visible(): return
 
@@ -507,7 +520,7 @@ def draw(self, renderer):
 
         funcname = self._lineStyles.get(self._linestyle, '_draw_nothing')
         if funcname != '_draw_nothing':
-            tpath, affine = self._transformed_path.get_transformed_path_and_affine()
+            tpath, affine = transformed_path.get_transformed_path_and_affine()
             if len(tpath.vertices):
                 self._lineFunc = getattr(self, funcname)
                 funcname = self.drawStyles.get(self._drawstyle, '_draw_lines')
@@ -528,7 +541,7 @@ def draw(self, renderer):
                 gc.set_linewidth(self._markeredgewidth)
             gc.set_alpha(self._alpha)
             marker = self._marker
-            tpath, affine = self._transformed_path.get_transformed_points_and_affine()
+            tpath, affine = transformed_path.get_transformed_points_and_affine()
             if len(tpath.vertices):
                 # subsample the markers if markevery is not None
                 markevery = self.get_markevery()

diff --git a/lib/matplotlib/patches.py b/lib/matplotlib/patches.py
@@ -167,9 +167,21 @@ def get_transform(self):
         return self.get_patch_transform() + artist.Artist.get_transform(self)
 
     def get_data_transform(self):
+        """
+        Return the :class:`~matplotlib.transforms.Transform` instance which
+        maps data coordinates to physical coordinates.
+        """
         return artist.Artist.get_transform(self)
 
     def get_patch_transform(self):
+        """
+        Return the :class:`~matplotlib.transforms.Transform` instance which
+        takes patch coordinates to data coordinates.
+
+        For example, one may define a patch of a circle which represents a
+        radius of 5 by providing coordinates for a unit circle, and a
+        transform which scales the coordinates (the patch coordinate) by 5.
+        """
         return transforms.IdentityTransform()
 
     def get_antialiased(self):