Merge pull request matplotlib#24484 from leejjoon/draw-prevent-rasterization-by-default

Artist's draw method prevents rasterization by default

Author: tacaswell

doc/api/prev_api_changes/api_changes_3.3.0/deprecations.rst

@@ -273,13 +273,13 @@ mathtext glues
 The *copy* parameter of ``mathtext.Glue`` is deprecated (the underlying glue
 spec is now immutable).  ``mathtext.GlueSpec`` is deprecated.
 
-Signatures of `.Artist.draw` and `.Axes.draw`
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The *inframe* parameter to `.Axes.draw` is deprecated.  Use
+Signatures of `.Artist.draw` and `matplotlib.axes.Axes.draw`
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The *inframe* parameter to `matplotlib.axes.Axes.draw` is deprecated.  Use
 `.Axes.redraw_in_frame` instead.
 
-Not passing the *renderer* parameter to `.Axes.draw` is deprecated.  Use
-``axes.draw_artist(axes)`` instead.
+Not passing the *renderer* parameter to `matplotlib.axes.Axes.draw` is
+deprecated. Use ``axes.draw_artist(axes)`` instead.
 
 These changes make the signature of the ``draw`` (``artist.draw(renderer)``)
 method consistent across all artists; thus, additional parameters to

doc/api/prev_api_changes/api_changes_3.5.0/removals.rst

@@ -260,7 +260,7 @@ Arguments
 
 - The *s* parameter to `.Axes.annotate` and  `.pyplot.annotate` is no longer
   supported; use the new name *text*.
-- The *inframe* parameter to `.Axes.draw` has been removed; use
+- The *inframe* parameter to `matplotlib.axes.Axes.draw` has been removed; use
   `.Axes.redraw_in_frame` instead.
 - The *required*, *forbidden* and *allowed* parameters of
   `.cbook.normalize_kwargs` have been removed.
@@ -312,13 +312,13 @@ Arguments
   warning for keyword arguments that were overridden by the mappable is now
   removed.
 
-- Omitting the *renderer* parameter to `.Axes.draw` is no longer supported; use
-  ``axes.draw_artist(axes)`` instead.
+- Omitting the *renderer* parameter to `matplotlib.axes.Axes.draw` is no longer
+  supported; use ``axes.draw_artist(axes)`` instead.
 - Passing ``ismath="TeX!"`` to `.RendererAgg.get_text_width_height_descent` is
   no longer supported; pass ``ismath="TeX"`` instead,
-- Changes to the signature of the `.Axes.draw` method make it consistent with
-  all other artists; thus additional parameters to `.Artist.draw` have also
-  been removed.
+- Changes to the signature of the `matplotlib.axes.Axes.draw` method make it
+  consistent with all other artists; thus additional parameters to
+  `.Artist.draw` have also been removed.
 
 rcParams
 ~~~~~~~~

lib/matplotlib/artist.py

@@ -21,6 +21,27 @@
 _log = logging.getLogger(__name__)
 
 
+def _prevent_rasterization(draw):
+    # We assume that by default artists are not allowed to rasterize (unless
+    # its draw method is explicitly decorated). If it is being drawn after a
+    # rasterized artist and it has reached a raster_depth of 0, we stop
+    # rasterization so that it does not affect the behavior of normal artist
+    # (e.g., change in dpi).
+
+    @wraps(draw)
+    def draw_wrapper(artist, renderer):
+        if renderer._raster_depth == 0 and renderer._rasterizing:
+            # Only stop when we are not in a rasterized parent
+            # and something has been rasterized since last stop.
+            renderer.stop_rasterizing()
+            renderer._rasterizing = False
+
+        return draw(artist, renderer)
+
+    draw_wrapper._supports_rasterization = False
+    return draw_wrapper
+
+
 def allow_rasterization(draw):
     """
     Decorator for Artist.draw method. Provides routines
@@ -103,6 +124,15 @@ class Artist:
     zorder = 0
 
     def __init_subclass__(cls):
+
+        # Decorate draw() method so that all artists are able to stop
+        # rastrization when necessary. If the artist's draw method is already
+        # decorated (has a `_supports_rasterization` attribute), it won't be
+        # decorated.
+
+        if not hasattr(cls.draw, "_supports_rasterization"):
+            cls.draw = _prevent_rasterization(cls.draw)
+
         # Inject custom set() methods into the subclass with signature and
         # docstring based on the subclasses' properties.
 
@@ -921,7 +951,9 @@ def set_rasterized(self, rasterized):
         ----------
         rasterized : bool
         """
-        if rasterized and not hasattr(self.draw, "_supports_rasterization"):
+        supports_rasterization = getattr(self.draw,
+                                         "_supports_rasterization", False)
+        if rasterized and not supports_rasterization:
             _api.warn_external(f"Rasterization of '{self}' will be ignored")
 
         self._rasterized = rasterized

lib/matplotlib/tests/test_artist.py

@@ -535,3 +535,17 @@ def test_format_cursor_data_BoundaryNorm():
         assert img.format_cursor_data(v) == label
 
     plt.close()
+
+
+def test_auto_no_rasterize():
+    class Gen1(martist.Artist):
+        ...
+
+    assert 'draw' in Gen1.__dict__
+    assert Gen1.__dict__['draw'] is Gen1.draw
+
+    class Gen2(Gen1):
+        ...
+
+    assert 'draw' not in Gen2.__dict__
+    assert Gen2.draw is Gen1.draw

lib/matplotlib/tests/test_backend_svg.py

@@ -122,6 +122,27 @@ def test_rasterized_ordering(fig_test, fig_ref):
     ax_test.plot(x+1, y, "-", c="b", lw=10, rasterized=False, zorder=1.2)
 
 
+@check_figures_equal(tol=5, extensions=['svg', 'pdf'])
+def test_prevent_rasterization(fig_test, fig_ref):
+    loc = [0.05, 0.05]
+
+    ax_ref = fig_ref.subplots()
+
+    ax_ref.plot([loc[0]], [loc[1]], marker="x", c="black", zorder=2)
+
+    b = mpl.offsetbox.TextArea("X")
+    abox = mpl.offsetbox.AnnotationBbox(b, loc, zorder=2.1)
+    ax_ref.add_artist(abox)
+
+    ax_test = fig_test.subplots()
+    ax_test.plot([loc[0]], [loc[1]], marker="x", c="black", zorder=2,
+                 rasterized=True)
+
+    b = mpl.offsetbox.TextArea("X")
+    abox = mpl.offsetbox.AnnotationBbox(b, loc, zorder=2.1)
+    ax_test.add_artist(abox)
+
+
 def test_count_bitmaps():
     def count_tag(fig, tag):
         with BytesIO() as fd: