Avoid TransformedBbox where unneeded.

transform_bbox is much faster when one does not need a TransformedBbox,
i.e. something that keeps track of later changes in the transform:
```
In [1]: from pylab import *
   ...: from matplotlib.transforms import *
   ...: tr = plt.gca().transAxes
   ...: bb = Bbox([[0, 0], [1, 1]])
   ...: %timeit TransformedBbox(bb, tr).x0
   ...: %timeit tr.transform_bbox(bb).x0
   ...: %timeit TransformedBbox(bb, tr).width
   ...: %timeit tr.transform_bbox(bb).width
11.8 µs ± 145 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
2.72 µs ± 31.5 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
11.9 µs ± 183 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
2.83 µs ± 16.6 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
```

Author: anntzer

lib/matplotlib/tight_bbox.py

@@ -57,11 +57,9 @@ def restore_bbox():
     tr = Affine2D().scale(fixed_dpi)
     dpi_scale = fixed_dpi / fig.dpi
 
-    _bbox = TransformedBbox(bbox_inches, tr)
-
     fig.bbox_inches = Bbox.from_bounds(0, 0,
                                        bbox_inches.width, bbox_inches.height)
-    x0, y0 = _bbox.x0, _bbox.y0
+    x0, y0 = tr.transform(bbox_inches.p0)
     w1, h1 = fig.bbox.width * dpi_scale, fig.bbox.height * dpi_scale
     fig.transFigure._boxout = Bbox.from_bounds(-x0, -y0, w1, h1)
     fig.transFigure.invalidate()

lib/matplotlib/tight_layout.py

@@ -13,7 +13,7 @@
 
 from matplotlib import _api, rcParams
 from matplotlib.font_manager import FontProperties
-from matplotlib.transforms import TransformedBbox, Bbox
+from matplotlib.transforms import Bbox
 
 
 def _auto_adjust_subplotpars(
@@ -84,8 +84,7 @@ def _auto_adjust_subplotpars(
                     bb += [ax.get_tightbbox(renderer)]
 
         tight_bbox_raw = Bbox.union(bb)
-        tight_bbox = TransformedBbox(tight_bbox_raw,
-                                     fig.transFigure.inverted())
+        tight_bbox = fig.transFigure.inverted().transform_bbox(tight_bbox_raw)
 
         hspaces[rowspan, colspan.start] += ax_bbox.xmin - tight_bbox.xmin  # l
         hspaces[rowspan, colspan.stop] += tight_bbox.xmax - ax_bbox.xmax  # r

lib/mpl_toolkits/axes_grid1/inset_locator.py

@@ -126,7 +126,7 @@ def __init__(self, parent_axes, zoom, loc,
             bbox_transform=bbox_transform)
 
     def get_extent(self, renderer):
-        bb = TransformedBbox(self.axes.viewLim, self.parent_axes.transData)
+        bb = self.parent_axes.transData.transform_bbox(self.axes.viewLim)
         fontsize = renderer.points_to_pixels(self.prop.get_size_in_points())
         pad = self.pad * fontsize
         return (abs(bb.width * self.zoom) + 2 * pad,