matplotlib · timhoffm · Dec 18, 2021 · Oct 6, 2021 · tacaswell · Dec 16, 2021
diff --git a/doc/api/next_api_changes/deprecations/21981-AL.rst b/doc/api/next_api_changes/deprecations/21981-AL.rst
@@ -0,0 +1,4 @@
+``RendererGTK3Cairo`` and ``RendererGTK4Cairo``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+... have been deprecated.  Use ``RendererCairo`` instead, which has gained the
+``set_context`` method.
diff --git a/lib/matplotlib/backends/backend_cairo.py b/lib/matplotlib/backends/backend_cairo.py
@@ -133,6 +133,9 @@ def __init__(self, dpi):
            cairo.ImageSurface(cairo.FORMAT_ARGB32, 1, 1))
         super().__init__()
 
+    def set_context(self, ctx):
+        self.gc.ctx = _to_context(ctx)
+
     def set_ctx_from_surface(self, surface):
         self.gc.ctx = cairo.Context(surface)
         # Although it may appear natural to automatically call
@@ -414,6 +417,15 @@ def __init__(self, slices, data):
 
 
 class FigureCanvasCairo(FigureCanvasBase):
+    @property
+    def _renderer(self):
+        # In theory, _renderer should be set in __init__, but GUI canvas
+        # subclasses (FigureCanvasFooCairo) don't always interact well with
+        # multiple inheritance (FigureCanvasFoo inits but doesn't super-init
+        # FigureCanvasCairo), so initialize it in the getter instead.
+        if not hasattr(self, "_cached_renderer"):
+            self._cached_renderer = RendererCairo(self.figure.dpi)
+        return self._cached_renderer
 
     def copy_from_bbox(self, bbox):
         surface = self._renderer.gc.ctx.get_target()
@@ -462,12 +474,12 @@ def print_rgba(self, fobj):
     print_raw = print_rgba
 
     def _get_printed_image_surface(self):
+        self._renderer.dpi = self.figure.dpi
         width, height = self.get_width_height()
-        renderer = RendererCairo(self.figure.dpi)
-        renderer.set_width_height(width, height)
+        self._renderer.set_width_height(width, height)
         surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, width, height)
-        renderer.set_ctx_from_surface(surface)
-        self.figure.draw(renderer)
+        self._renderer.set_ctx_from_surface(surface)
+        self.figure.draw(self._renderer)
         return surface
 
     @_check_savefig_extra_args
@@ -506,18 +518,17 @@ def _save(self, fmt, fobj, *, orientation='portrait'):
         else:
             raise ValueError("Unknown format: {!r}".format(fmt))
 
-        # surface.set_dpi() can be used
-        renderer = RendererCairo(self.figure.dpi)
-        renderer.set_width_height(width_in_points, height_in_points)
-        renderer.set_ctx_from_surface(surface)
-        ctx = renderer.gc.ctx
+        self._renderer.dpi = self.figure.dpi
+        self._renderer.set_width_height(width_in_points, height_in_points)
+        self._renderer.set_ctx_from_surface(surface)
+        ctx = self._renderer.gc.ctx
 
         if orientation == 'landscape':
             ctx.rotate(np.pi / 2)
             ctx.translate(0, -height_in_points)
             # Perhaps add an '%%Orientation: Landscape' comment?
 
-        self.figure.draw(renderer)
+        self.figure.draw(self._renderer)
 
         ctx.show_page()
         surface.finish()

diff --git a/lib/matplotlib/backends/backend_gtk3cairo.py b/lib/matplotlib/backends/backend_gtk3cairo.py
@@ -1,9 +1,11 @@
 from contextlib import nullcontext
 
+from .. import _api
 from . import backend_cairo, backend_gtk3
 from .backend_gtk3 import Gtk, _BackendGTK3
 
 
+@_api.deprecated("3.6")
 class RendererGTK3Cairo(backend_cairo.RendererCairo):
     def set_context(self, ctx):
         self.gc.ctx = backend_cairo._to_context(ctx)
@@ -12,10 +14,6 @@ def set_context(self, ctx):
 class FigureCanvasGTK3Cairo(backend_gtk3.FigureCanvasGTK3,
                             backend_cairo.FigureCanvasCairo):
 
-    def __init__(self, figure):
-        super().__init__(figure)
-        self._renderer = RendererGTK3Cairo(self.figure.dpi)
-
     def on_draw_event(self, widget, ctx):
         with (self.toolbar._wait_cursor_for_draw_cm() if self.toolbar
               else nullcontext()):

diff --git a/lib/matplotlib/backends/backend_gtk4cairo.py b/lib/matplotlib/backends/backend_gtk4cairo.py
@@ -1,9 +1,11 @@
 from contextlib import nullcontext
 
+from .. import _api
 from . import backend_cairo, backend_gtk4
 from .backend_gtk4 import Gtk, _BackendGTK4
 
 
+@_api.deprecated("3.6")
 class RendererGTK4Cairo(backend_cairo.RendererCairo):
     def set_context(self, ctx):
         self.gc.ctx = backend_cairo._to_context(ctx)
@@ -13,10 +15,6 @@ class FigureCanvasGTK4Cairo(backend_gtk4.FigureCanvasGTK4,
                             backend_cairo.FigureCanvasCairo):
     _context_is_scaled = True
 
-    def __init__(self, figure):
-        super().__init__(figure)
-        self._renderer = RendererGTK4Cairo(self.figure.dpi)
-
     def on_draw_event(self, widget, ctx):
         with (self.toolbar._wait_cursor_for_draw_cm() if self.toolbar
               else nullcontext()):

diff --git a/lib/matplotlib/backends/backend_qt5cairo.py b/lib/matplotlib/backends/backend_qt5cairo.py
@@ -1,8 +1,5 @@
 from .backend_qtcairo import (
-    _BackendQTCairo, FigureCanvasQTCairo,
-    FigureCanvasCairo, FigureCanvasQT,
-    RendererCairo
-)
+    _BackendQTCairo, FigureCanvasQTCairo, FigureCanvasCairo, FigureCanvasQT)
 
 
 @_BackendQTCairo.export

diff --git a/lib/matplotlib/backends/backend_qtcairo.py b/lib/matplotlib/backends/backend_qtcairo.py
@@ -1,14 +1,13 @@
 import ctypes
 
-from .backend_cairo import cairo, FigureCanvasCairo, RendererCairo
+from .backend_cairo import cairo, FigureCanvasCairo
 from .backend_qt import QtCore, QtGui, _BackendQT, FigureCanvasQT
 from .qt_compat import QT_API, _enum, _setDevicePixelRatio
 
 
 class FigureCanvasQTCairo(FigureCanvasQT, FigureCanvasCairo):
     def __init__(self, figure=None):
         super().__init__(figure=figure)
-        self._renderer = RendererCairo(self.figure.dpi)
         self._renderer.set_width_height(-1, -1)  # Invalid values.
 
     def draw(self):

diff --git a/lib/matplotlib/backends/backend_tkcairo.py b/lib/matplotlib/backends/backend_tkcairo.py
@@ -3,15 +3,11 @@
 import numpy as np
 
 from . import _backend_tk
-from .backend_cairo import cairo, FigureCanvasCairo, RendererCairo
+from .backend_cairo import cairo, FigureCanvasCairo
 from ._backend_tk import _BackendTk, FigureCanvasTk
 
 
 class FigureCanvasTkCairo(FigureCanvasCairo, FigureCanvasTk):
-    def __init__(self, *args, **kwargs):
-        super().__init__(*args, **kwargs)
-        self._renderer = RendererCairo(self.figure.dpi)
-
     def draw(self):
         width = int(self.figure.bbox.width)
         height = int(self.figure.bbox.height)

diff --git a/lib/matplotlib/backends/backend_wxcairo.py b/lib/matplotlib/backends/backend_wxcairo.py
@@ -1,6 +1,6 @@
 import wx.lib.wxcairo as wxcairo
 
-from .backend_cairo import cairo, FigureCanvasCairo, RendererCairo
+from .backend_cairo import cairo, FigureCanvasCairo
 from .backend_wx import (
     _BackendWx, _FigureCanvasWxBase, FigureFrameWx,
     NavigationToolbar2Wx as NavigationToolbar2WxCairo)
@@ -21,14 +21,6 @@ class FigureCanvasWxCairo(_FigureCanvasWxBase, FigureCanvasCairo):
     we give a hint as to our preferred minimum size.
     """
 
-    def __init__(self, parent, id, figure):
-        # _FigureCanvasWxBase should be fixed to have the same signature as
-        # every other FigureCanvas and use cooperative inheritance, but in the
-        # meantime the following will make do.
-        _FigureCanvasWxBase.__init__(self, parent, id, figure)
-        FigureCanvasCairo.__init__(self, figure)
-        self._renderer = RendererCairo(self.figure.dpi)
-
     def draw(self, drawDC=None):
         size = self.figure.bbox.size.astype(int)
         surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, *size)