matplotlib · QuLogic · Mar 15, 2023 · Nov 21, 2022
diff --git a/doc/api/next_api_changes/behavior/24531-DOS.rst b/doc/api/next_api_changes/behavior/24531-DOS.rst
@@ -0,0 +1,8 @@
+Tk backend respects file format selection when saving figures
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+When saving a figure from a Tkinter GUI to a filename without an
+extension, the file format is now selected based on the value of
+the dropdown menu, rather than defaulting to PNG. When the filename
+contains an extension, or the OS automatically appends one, the
+behavior remains unchanged.
diff --git a/doc/api/next_api_changes/development/24531-DOS.rst b/doc/api/next_api_changes/development/24531-DOS.rst
@@ -0,0 +1,13 @@
+Increase to minimum supported optional dependencies
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+For Matplotlib 3.8, the :ref:`minimum supported versions of optional dependencies
+<optional_dependencies>` are being bumped:
+
++------------+-----------------+---------------+
+| Dependency |  min in mpl3.7  | min in mpl3.8 |
++============+=================+===============+
+|   Tk       |      8.4        |     8.5       |
++------------+-----------------+---------------+
+
+This is consistent with our :ref:`min_deps_policy`
diff --git a/doc/devel/dependencies.rst b/doc/devel/dependencies.rst
@@ -46,7 +46,7 @@ Matplotlib figures can be rendered to various user interfaces. See
 :ref:`what-is-a-backend` for more details on the optional Matplotlib backends
 and the capabilities they provide.
 
-* Tk_ (>= 8.4, != 8.6.0 or 8.6.1): for the Tk-based backends. Tk is part of
+* Tk_ (>= 8.5, != 8.6.0 or 8.6.1): for the Tk-based backends. Tk is part of
   most standard Python installations, but it's not part of Python itself and
   thus may not be present in rare cases.
 * PyQt6_ (>= 6.1), PySide6_, PyQt5_, or PySide2_: for the Qt-based backends.

diff --git a/lib/matplotlib/backends/_backend_tk.py b/lib/matplotlib/backends/_backend_tk.py
@@ -4,6 +4,7 @@
 import logging
 import math
 import os.path
+import pathlib
 import sys
 import tkinter as tk
 import tkinter.filedialog
@@ -499,11 +500,8 @@ def create_with_canvas(cls, canvas_class, figure, num):
                 'images/matplotlib_large.png'))
             icon_img_large = ImageTk.PhotoImage(
                 file=icon_fname_large, master=window)
-            try:
-                window.iconphoto(False, icon_img_large, icon_img)
-            except Exception as exc:
-                # log the failure (due e.g. to Tk version), but carry on
-                _log.info('Could not load matplotlib icon: %s', exc)
+
+            window.iconphoto(False, icon_img_large, icon_img)
 
             canvas = canvas_class(figure, master=window)
             manager = cls(canvas, num, window)
@@ -846,15 +844,15 @@ def _Spacer(self):
         return s
 
     def save_figure(self, *args):
-        filetypes = self.canvas.get_supported_filetypes().copy()
-        default_filetype = self.canvas.get_default_filetype()
+        filetypes = self.canvas.get_supported_filetypes_grouped()
+        tk_filetypes = [
+            (name, " ".join(f"*.{ext}" for ext in exts))
+            for name, exts in sorted(filetypes.items())
+        ]
 
-        # Tk doesn't provide a way to choose a default filetype,
-        # so we just have to put it first
-        default_filetype_name = filetypes.pop(default_filetype)
-        sorted_filetypes = ([(default_filetype, default_filetype_name)]
-                            + sorted(filetypes.items()))
-        tk_filetypes = [(name, '*.%s' % ext) for ext, name in sorted_filetypes]
+        default_extension = self.canvas.get_default_filetype()
+        default_filetype = self.canvas.get_supported_filetypes()[default_extension]
+        filetype_variable = tk.StringVar(self, default_filetype)
 
         # adding a default extension seems to break the
         # asksaveasfilename dialog when you choose various save types
@@ -863,14 +861,18 @@ def save_figure(self, *args):
         # defaultextension = self.canvas.get_default_filetype()
         defaultextension = ''
         initialdir = os.path.expanduser(mpl.rcParams['savefig.directory'])
-        initialfile = self.canvas.get_default_filename()
+        # get_default_filename() contains the default extension. On some platforms,
+        # choosing a different extension from the dropdown does not overwrite it,
+        # so we need to remove it to make the dropdown functional.
+        initialfile = pathlib.Path(self.canvas.get_default_filename()).stem
         fname = tkinter.filedialog.asksaveasfilename(
             master=self.canvas.get_tk_widget().master,
             title='Save the figure',
             filetypes=tk_filetypes,
             defaultextension=defaultextension,
             initialdir=initialdir,
             initialfile=initialfile,
+            typevariable=filetype_variable
             )
 
         if fname in ["", ()]:
@@ -879,9 +881,16 @@ def save_figure(self, *args):
         if initialdir != "":
             mpl.rcParams['savefig.directory'] = (
                 os.path.dirname(str(fname)))
+
+        # If the filename contains an extension, let savefig() infer the file
+        # format from that. If it does not, use the selected dropdown option.
+        if pathlib.Path(fname).suffix[1:] != "":
+            extension = None
+        else:
+            extension = filetypes[filetype_variable.get()][0]
+
         try:
-            # This method will handle the delegation to the correct type
-            self.canvas.figure.savefig(fname)
+            self.canvas.figure.savefig(fname, format=extension)
         except Exception as e:
             tkinter.messagebox.showerror("Error saving file", str(e))