gnu: python-matplotlib: Fix running under Wayland with GTK3.

* gnu/packages/python-xyz.scm (python-matplotlib)[source]: Add patch.
* gnu/packages/patches/python-matplotlib-run-under-wayland-gtk3.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.

gnu/local.mk

@@ -1539,6 +1539,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/python-pyfakefs-remove-bad-test.patch	\
   %D%/packages/patches/python-flint-includes.patch		\
   %D%/packages/patches/python-libxml2-utf8.patch		\
+  %D%/packages/patches/python-matplotlib-run-under-wayland-gtk3.patch	\
   %D%/packages/patches/python-mediafile-wavpack.patch		\
   %D%/packages/patches/python-memcached-syntax-warnings.patch	\
   %D%/packages/patches/python-mox3-python3.6-compat.patch	\

gnu/packages/patches/python-matplotlib-run-under-wayland-gtk3.patch

@@ -0,0 +1,31 @@
+From: Tobias Geerinckx-Rice <me@tobias.gr>
+Date: Tue, 02 Mar 2021 18:04:33 +0100
+Subject: [PATCH] gnu: python-matplotlib: Run under Wayland with GTK3.
+
+Adopted from upstream's fix[0] for
+<https://github.com/matplotlib/matplotlib/issues/19405>.
+
+[0]: https://github.com/liuyun88/matplotlib/commit/3d5000463bd23cb046681220f5511f07743f7d82
+
+---
+diff -Naur a/lib/matplotlib/backends/backend_gtk3.py b/lib/matplotlib/backends/backend_gtk3.py
+--- a/lib/matplotlib/backends/backend_gtk3.py	2019-11-21 23:47:05.000000000 +0100
++++ b/lib/matplotlib/backends/backend_gtk3.py	2021-03-02 18:00:57.479929766 +0100
+@@ -42,11 +42,12 @@
+ 
+ try:
++    _display = Gdk.Display.get_default()
+     cursord = {
+-        cursors.MOVE          : Gdk.Cursor.new(Gdk.CursorType.FLEUR),
+-        cursors.HAND          : Gdk.Cursor.new(Gdk.CursorType.HAND2),
+-        cursors.POINTER       : Gdk.Cursor.new(Gdk.CursorType.LEFT_PTR),
+-        cursors.SELECT_REGION : Gdk.Cursor.new(Gdk.CursorType.TCROSS),
+-        cursors.WAIT          : Gdk.Cursor.new(Gdk.CursorType.WATCH),
++        cursors.MOVE          : Gdk.Cursor.new_from_name(_display, "move"),
++        cursors.HAND          : Gdk.Cursor.new_from_name(_display, "pointer"),
++        cursors.POINTER       : Gdk.Cursor.new_from_name(_display, "default"),
++        cursors.SELECT_REGION : Gdk.Cursor.new_from_name(_display, "crosshair"),
++        cursors.WAIT          : Gdk.Cursor.new_from_name(_display, "wait"),
+     }
+ except TypeError as exc:
+     # Happens when running headless.  Convert to ImportError to cooperate with

gnu/packages/python-xyz.scm

@@ -5131,8 +5131,9 @@ convert between colorspaces like sRGB, XYZ, CIEL*a*b*, CIECAM02, CAM02-UCS, etc.
        (method url-fetch)
        (uri (pypi-uri "matplotlib" version))
        (sha256
-        (base32
+        (base32 "1nmshfqh7wyg15i16hx1yiylcvzkws29ivn66n3i0wyqwcpjr3lf"))
-         "1nmshfqh7wyg15i16hx1yiylcvzkws29ivn66n3i0wyqwcpjr3lf"))))
+       (patches
+        (search-patches "python-matplotlib-run-under-wayland-gtk3.patch"))))
     (build-system python-build-system)
     (propagated-inputs ; the following packages are all needed at run time
      `(("python-cycler" ,python-cycler)