From 6a04d7d1ba57a323badd211641c7c835dad3ae1c Mon Sep 17 00:00:00 2001
From: martinRenou <martin.renou@gmail.com>
Date: Mon, 8 Feb 2021 18:14:48 +0100
Subject: [PATCH] Plugging system for backends

---
 lib/matplotlib/backend_bases.py               |  2 +-
 .../backends/manifests/GTK3Agg.json           |  5 +++
 .../backends/manifests/GTK3Cairo.json         |  5 +++
 lib/matplotlib/backends/manifests/MacOSX.json |  5 +++
 lib/matplotlib/backends/manifests/Qt4Agg.json |  5 +++
 .../backends/manifests/Qt4Cairo.json          |  5 +++
 lib/matplotlib/backends/manifests/Qt5Agg.json |  5 +++
 .../backends/manifests/Qt5Cairo.json          |  5 +++
 lib/matplotlib/backends/manifests/TkAgg.json  |  5 +++
 .../backends/manifests/TkCairo.json           |  5 +++
 lib/matplotlib/backends/manifests/WX.json     |  5 +++
 lib/matplotlib/backends/manifests/WXAgg.json  |  5 +++
 .../backends/manifests/WXCairo.json           |  5 +++
 lib/matplotlib/backends/manifests/WebAgg.json |  5 +++
 lib/matplotlib/backends/manifests/agg.json    |  5 +++
 lib/matplotlib/backends/manifests/cairo.json  |  5 +++
 lib/matplotlib/backends/manifests/gtk3.json   |  5 +++
 lib/matplotlib/backends/manifests/mixed.json  |  5 +++
 lib/matplotlib/backends/manifests/nbAgg.json  |  5 +++
 lib/matplotlib/backends/manifests/pdf.json    |  5 +++
 lib/matplotlib/backends/manifests/pgf.json    |  5 +++
 lib/matplotlib/backends/manifests/ps.json     |  5 +++
 lib/matplotlib/backends/manifests/qt4.json    |  5 +++
 lib/matplotlib/backends/manifests/qt5.json    |  5 +++
 lib/matplotlib/backends/manifests/svg.json    |  5 +++
 .../backends/manifests/template.json          |  5 +++
 .../backends/manifests/webagg_core.json       |  5 +++
 lib/matplotlib/cbook/__init__.py              | 32 +++++++++++++++----
 lib/matplotlib/pyplot.py                      |  2 +-
 lib/matplotlib/rcsetup.py                     | 16 +++-------
 setup.py                                      | 11 +++++++
 31 files changed, 172 insertions(+), 21 deletions(-)
 create mode 100644 lib/matplotlib/backends/manifests/GTK3Agg.json
 create mode 100644 lib/matplotlib/backends/manifests/GTK3Cairo.json
 create mode 100644 lib/matplotlib/backends/manifests/MacOSX.json
 create mode 100644 lib/matplotlib/backends/manifests/Qt4Agg.json
 create mode 100644 lib/matplotlib/backends/manifests/Qt4Cairo.json
 create mode 100644 lib/matplotlib/backends/manifests/Qt5Agg.json
 create mode 100644 lib/matplotlib/backends/manifests/Qt5Cairo.json
 create mode 100644 lib/matplotlib/backends/manifests/TkAgg.json
 create mode 100644 lib/matplotlib/backends/manifests/TkCairo.json
 create mode 100644 lib/matplotlib/backends/manifests/WX.json
 create mode 100644 lib/matplotlib/backends/manifests/WXAgg.json
 create mode 100644 lib/matplotlib/backends/manifests/WXCairo.json
 create mode 100644 lib/matplotlib/backends/manifests/WebAgg.json
 create mode 100644 lib/matplotlib/backends/manifests/agg.json
 create mode 100644 lib/matplotlib/backends/manifests/cairo.json
 create mode 100644 lib/matplotlib/backends/manifests/gtk3.json
 create mode 100644 lib/matplotlib/backends/manifests/mixed.json
 create mode 100644 lib/matplotlib/backends/manifests/nbAgg.json
 create mode 100644 lib/matplotlib/backends/manifests/pdf.json
 create mode 100644 lib/matplotlib/backends/manifests/pgf.json
 create mode 100644 lib/matplotlib/backends/manifests/ps.json
 create mode 100644 lib/matplotlib/backends/manifests/qt4.json
 create mode 100644 lib/matplotlib/backends/manifests/qt5.json
 create mode 100644 lib/matplotlib/backends/manifests/svg.json
 create mode 100644 lib/matplotlib/backends/manifests/template.json
 create mode 100644 lib/matplotlib/backends/manifests/webagg_core.json

diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
index ac041495a030..6b4837293f48 100644
--- a/lib/matplotlib/backend_bases.py
+++ b/lib/matplotlib/backend_bases.py
@@ -2084,7 +2084,7 @@ def _get_output_canvas(self, backend, fmt):
         if backend is not None:
             # Return a specific canvas class, if requested.
             canvas_class = (
-                importlib.import_module(cbook._backend_module_name(backend))
+                importlib.import_module(cbook.backends[backend]['module'])
                 .FigureCanvas)
             if not hasattr(canvas_class, f"print_{fmt}"):
                 raise ValueError(
diff --git a/lib/matplotlib/backends/manifests/GTK3Agg.json b/lib/matplotlib/backends/manifests/GTK3Agg.json
new file mode 100644
index 000000000000..17d28e5f8744
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/GTK3Agg.json
@@ -0,0 +1,5 @@
+{
+  "name": "GTK3Agg",
+  "module": "matplotlib.backends.backend_gtk3agg",
+  "interactive": true
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/GTK3Cairo.json b/lib/matplotlib/backends/manifests/GTK3Cairo.json
new file mode 100644
index 000000000000..a85630ee3fd0
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/GTK3Cairo.json
@@ -0,0 +1,5 @@
+{
+  "name": "GTK3Cairo",
+  "module": "matplotlib.backends.backend_gtk3cairo",
+  "interactive": true
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/MacOSX.json b/lib/matplotlib/backends/manifests/MacOSX.json
new file mode 100644
index 000000000000..708ecbb39dbb
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/MacOSX.json
@@ -0,0 +1,5 @@
+{
+  "name": "MacOSX",
+  "module": "matplotlib.backends.backend_macosx",
+  "interactive": true
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/Qt4Agg.json b/lib/matplotlib/backends/manifests/Qt4Agg.json
new file mode 100644
index 000000000000..1f920fea7972
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/Qt4Agg.json
@@ -0,0 +1,5 @@
+{
+  "name": "Qt4Agg",
+  "module": "matplotlib.backends.backend_qt4agg",
+  "interactive": true
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/Qt4Cairo.json b/lib/matplotlib/backends/manifests/Qt4Cairo.json
new file mode 100644
index 000000000000..cad78c4f8abc
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/Qt4Cairo.json
@@ -0,0 +1,5 @@
+{
+  "name": "Qt4Cairo",
+  "module": "matplotlib.backends.backend_qt4cairo",
+  "interactive": true
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/Qt5Agg.json b/lib/matplotlib/backends/manifests/Qt5Agg.json
new file mode 100644
index 000000000000..6886cd652f71
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/Qt5Agg.json
@@ -0,0 +1,5 @@
+{
+  "name": "Qt5Agg",
+  "module": "matplotlib.backends.backend_qt5agg",
+  "interactive": true
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/Qt5Cairo.json b/lib/matplotlib/backends/manifests/Qt5Cairo.json
new file mode 100644
index 000000000000..8c8a5081db15
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/Qt5Cairo.json
@@ -0,0 +1,5 @@
+{
+  "name": "Qt5Cairo",
+  "module": "matplotlib.backends.backend_qt5cairo",
+  "interactive": true
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/TkAgg.json b/lib/matplotlib/backends/manifests/TkAgg.json
new file mode 100644
index 000000000000..a48d6ced46b3
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/TkAgg.json
@@ -0,0 +1,5 @@
+{
+  "name": "TkAgg",
+  "module": "matplotlib.backends.backend_tkagg",
+  "interactive": true
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/TkCairo.json b/lib/matplotlib/backends/manifests/TkCairo.json
new file mode 100644
index 000000000000..52254a3ccd16
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/TkCairo.json
@@ -0,0 +1,5 @@
+{
+  "name": "TkCairo",
+  "module": "matplotlib.backends.backend_tkcairo",
+  "interactive": true
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/WX.json b/lib/matplotlib/backends/manifests/WX.json
new file mode 100644
index 000000000000..addef1d363bc
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/WX.json
@@ -0,0 +1,5 @@
+{
+  "name": "WX",
+  "module": "matplotlib.backends.backend_wx",
+  "interactive": true
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/WXAgg.json b/lib/matplotlib/backends/manifests/WXAgg.json
new file mode 100644
index 000000000000..684700737942
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/WXAgg.json
@@ -0,0 +1,5 @@
+{
+  "name": "WXAgg",
+  "module": "matplotlib.backends.backend_wxagg",
+  "interactive": true
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/WXCairo.json b/lib/matplotlib/backends/manifests/WXCairo.json
new file mode 100644
index 000000000000..ff5c86ad2238
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/WXCairo.json
@@ -0,0 +1,5 @@
+{
+  "name": "WXCairo",
+  "module": "matplotlib.backends.backend_wxcairo",
+  "interactive": true
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/WebAgg.json b/lib/matplotlib/backends/manifests/WebAgg.json
new file mode 100644
index 000000000000..c02e94f27804
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/WebAgg.json
@@ -0,0 +1,5 @@
+{
+  "name": "WebAgg",
+  "module": "matplotlib.backends.backend_webagg",
+  "interactive": true
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/agg.json b/lib/matplotlib/backends/manifests/agg.json
new file mode 100644
index 000000000000..e58f287f80bf
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/agg.json
@@ -0,0 +1,5 @@
+{
+  "name": "agg",
+  "module": "matplotlib.backends.backend_agg",
+  "interactive": false
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/cairo.json b/lib/matplotlib/backends/manifests/cairo.json
new file mode 100644
index 000000000000..316b97b6ecdc
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/cairo.json
@@ -0,0 +1,5 @@
+{
+  "name": "cairo",
+  "module": "matplotlib.backends.backend_cairo",
+  "interactive": false
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/gtk3.json b/lib/matplotlib/backends/manifests/gtk3.json
new file mode 100644
index 000000000000..58016dd89052
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/gtk3.json
@@ -0,0 +1,5 @@
+{
+  "name": "gtk3",
+  "module": "matplotlib.backends.backend_gtk3",
+  "interactive": false
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/mixed.json b/lib/matplotlib/backends/manifests/mixed.json
new file mode 100644
index 000000000000..7db3a6459eb0
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/mixed.json
@@ -0,0 +1,5 @@
+{
+  "name": "mixed",
+  "module": "matplotlib.backends.backend_mixed",
+  "interactive": false
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/nbAgg.json b/lib/matplotlib/backends/manifests/nbAgg.json
new file mode 100644
index 000000000000..169df405ccd9
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/nbAgg.json
@@ -0,0 +1,5 @@
+{
+  "name": "nbAgg",
+  "module": "matplotlib.backends.backend_nbagg",
+  "interactive": true
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/pdf.json b/lib/matplotlib/backends/manifests/pdf.json
new file mode 100644
index 000000000000..6643eb582ca0
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/pdf.json
@@ -0,0 +1,5 @@
+{
+  "name": "pdf",
+  "module": "matplotlib.backends.backend_pdf",
+  "interactive": false
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/pgf.json b/lib/matplotlib/backends/manifests/pgf.json
new file mode 100644
index 000000000000..abe3cd91aca3
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/pgf.json
@@ -0,0 +1,5 @@
+{
+  "name": "pgf",
+  "module": "matplotlib.backends.backend_pgf",
+  "interactive": false
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/ps.json b/lib/matplotlib/backends/manifests/ps.json
new file mode 100644
index 000000000000..88ec5f979491
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/ps.json
@@ -0,0 +1,5 @@
+{
+  "name": "ps",
+  "module": "matplotlib.backends.backend_ps",
+  "interactive": false
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/qt4.json b/lib/matplotlib/backends/manifests/qt4.json
new file mode 100644
index 000000000000..7c2d53d251b8
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/qt4.json
@@ -0,0 +1,5 @@
+{
+  "name": "qt4",
+  "module": "matplotlib.backends.backend_qt4",
+  "interactive": false
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/qt5.json b/lib/matplotlib/backends/manifests/qt5.json
new file mode 100644
index 000000000000..73d92775e3ed
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/qt5.json
@@ -0,0 +1,5 @@
+{
+  "name": "qt5",
+  "module": "matplotlib.backends.backend_qt5",
+  "interactive": false
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/svg.json b/lib/matplotlib/backends/manifests/svg.json
new file mode 100644
index 000000000000..8ae035bfd82d
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/svg.json
@@ -0,0 +1,5 @@
+{
+  "name": "svg",
+  "module": "matplotlib.backends.backend_svg",
+  "interactive": false
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/template.json b/lib/matplotlib/backends/manifests/template.json
new file mode 100644
index 000000000000..3a932e440217
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/template.json
@@ -0,0 +1,5 @@
+{
+  "name": "template",
+  "module": "matplotlib.backends.backend_template",
+  "interactive": false
+}
\ No newline at end of file
diff --git a/lib/matplotlib/backends/manifests/webagg_core.json b/lib/matplotlib/backends/manifests/webagg_core.json
new file mode 100644
index 000000000000..a415f9b2c3ab
--- /dev/null
+++ b/lib/matplotlib/backends/manifests/webagg_core.json
@@ -0,0 +1,5 @@
+{
+  "name": "webagg_core",
+  "module": "matplotlib.backends.backend_webagg_core",
+  "interactive": false
+}
\ No newline at end of file
diff --git a/lib/matplotlib/cbook/__init__.py b/lib/matplotlib/cbook/__init__.py
index 31055dcd7990..e7070e0728ca 100644
--- a/lib/matplotlib/cbook/__init__.py
+++ b/lib/matplotlib/cbook/__init__.py
@@ -12,6 +12,8 @@
 import functools
 import gzip
 import itertools
+import json
+import logging
 import operator
 import os
 from pathlib import Path
@@ -33,6 +35,8 @@
     MatplotlibDeprecationWarning, mplDeprecation)
 
 
+_log = logging.getLogger(__name__)
+
 @_api.deprecated("3.4")
 def deprecated(*args, **kwargs):
     return _api.deprecated(*args, **kwargs)
@@ -2245,13 +2249,27 @@ def _check_and_log_subprocess(command, logger, **kwargs):
     return proc.stdout
 
 
-def _backend_module_name(name):
-    """
-    Convert a backend name (either a standard backend -- "Agg", "TkAgg", ... --
-    or a custom backend -- "module://...") to the corresponding module name).
-    """
-    return (name[9:] if name.startswith("module://")
-            else "matplotlib.backends.backend_{}".format(name.lower()))
+def load_backends():
+    backends_dir = Path(sys.prefix) / 'share' / 'matplotlib' / 'backends'
+    manifests = [str(manifest) for manifest in backends_dir.glob('*.json')]
+
+    backends = {}
+    for manifest in manifests:
+        try:
+            with open(manifest, 'r') as fobj:
+                backend = json.load(fobj)
+                backends[backend['name']] = {
+                    'module': backend['module'],
+                    'interactive': backend['interactive']
+                }
+        except:
+            _log.warning('Error while loading {}'.format(manifest))
+
+    return backends
+
+
+# Load backends
+backends = load_backends()
 
 
 def _setup_new_guiapp():
diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
index 39b28ab11346..aa081786f33b 100644
--- a/lib/matplotlib/pyplot.py
+++ b/lib/matplotlib/pyplot.py
@@ -272,7 +272,7 @@ def switch_backend(newbackend):
     # creating a "class" that inherits from backend_bases._Backend and whose
     # body is filled with the module's globals.
 
-    backend_name = cbook._backend_module_name(newbackend)
+    backend_name = cbook.backends[newbackend]['module']
 
     class backend_mod(matplotlib.backend_bases._Backend):
         locals().update(vars(importlib.import_module(backend_name)))
diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
index 535649b03f9f..0090be6ecf04 100644
--- a/lib/matplotlib/rcsetup.py
+++ b/lib/matplotlib/rcsetup.py
@@ -23,7 +23,7 @@
 import numpy as np
 
 from matplotlib import _api, animation, cbook
-from matplotlib.cbook import ls_mapper
+from matplotlib.cbook import ls_mapper, backends
 from matplotlib.colors import Colormap, is_color_like
 from matplotlib.fontconfig_pattern import parse_fontconfig_pattern
 from matplotlib._enums import JoinStyle, CapStyle
@@ -33,17 +33,9 @@
 
 
 _log = logging.getLogger(__name__)
-# The capitalized forms are needed for ipython at present; this may
-# change for later versions.
-interactive_bk = ['GTK3Agg', 'GTK3Cairo',
-                  'MacOSX',
-                  'nbAgg',
-                  'Qt4Agg', 'Qt4Cairo', 'Qt5Agg', 'Qt5Cairo',
-                  'TkAgg', 'TkCairo',
-                  'WebAgg',
-                  'WX', 'WXAgg', 'WXCairo']
-non_interactive_bk = ['agg', 'cairo',
-                      'pdf', 'pgf', 'ps', 'svg', 'template']
+
+interactive_bk = [name for name, backend in backends.items() if backend['interactive']]
+non_interactive_bk = [name for name, backend in backends.items() if not backend['interactive']]
 all_backends = interactive_bk + non_interactive_bk
 
 
diff --git a/setup.py b/setup.py
index b51ae806c2fb..1b35cea1d92a 100644
--- a/setup.py
+++ b/setup.py
@@ -255,6 +255,16 @@ def build_extensions(self):
     with open('lib/matplotlib/mpl-data/matplotlibrc', 'w') as fd:
         fd.write(''.join(template_lines))
 
+
+share_prefix = str(Path('share') / 'matplotlib' / 'backends')
+backends_manifests_dir = Path(__file__).parent / 'lib' / 'matplotlib' / 'backends' / 'manifests'
+data_files = [
+    (
+        str(Path('share') / 'matplotlib' / 'backends'),
+        [str(manifest) for manifest in backends_manifests_dir.glob('*.json')]
+    ),
+]
+
 setup(  # Finally, pass this all along to distutils to do the heavy lifting.
     name="matplotlib",
     version=__version__,
@@ -296,6 +306,7 @@ def build_extensions(self):
     # real extensions that can depend on numpy for the build.
     ext_modules=[Extension("", [])],
     package_data=package_data,
+    data_files=data_files,
 
     python_requires='>={}'.format('.'.join(str(n) for n in py_min_version)),
     setup_requires=[