Description

chacabuco

opened on Sep 28, 2023

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Bug summary

with mypy, FigureCanvasWxAgg results in error:

Call to untyped function "FigureCanvasWxAgg" in typed context [no-untyped-call]

Code for reproduction

from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg as FigureCanvas

FigureCanvas(None, -1)
# Then run mypy --strict

Actual outcome

Call to untyped function "FigureCanvasWxAgg" in typed context [no-untyped-call]

Expected outcome

No Mypy error

Additional information

No response

Operating system

Ubuntu

Matplotlib Version

3.8.0

Matplotlib Backend

wxAgg

Python version

3.8.10

Jupyter version

No response

Installation

pip

Activity

1. oscargus

   added

   topic: typing

   on Sep 28, 2023
2. oscargus commented on Sep 28, 2023

   

   oscargus

   on Sep 28, 2023

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   All backends are missing typing (except for the C++-based agg-backend).
3. ksunden commented on Sep 28, 2023

   

   ksunden

   on Sep 28, 2023

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   Backends were left out of the initial round of type hints because they are a bit more advanced and we needed to reign in the scope a bit.

   Even the agg one is an empty file, FYI. (There just to make it so that imports aren't flagged)

   While it doesn't help with the constructor call, you should be able to get a reasonable amount of the benefits of type hinting from matplotlib.backend_bases.FigureCanvasBase, which is the shared base class for all figure canvases. The base class is type hinted.

   If you are interested in adding type hints to backends, that would also be welcome.

   For wxagg, this would include type hinting the agg backend, which defines the following methods not found in FigureCanvasBase:

   >>> set(dir(agg))-set(dir(base))
   {
       'print_jpg',
       'print_jpeg',
       '_print_pil',
       'print_tiff',
       'restore_region',
       'print_to_buffer',
       'tostring_rgb',
       '_lastKey',
       'print_tif',
       'print_raw',
       'print_webp',
       'get_renderer',
       'buffer_rgba',
       'print_rgba',
       'print_png',
       'copy_from_bbox',
       'tostring_argb'
   }

   And the following functions are defined which are not defined for either of the base classes (Filtering out things added by the wx Parent):

   >>> set(filter(lambda x: x[0] == x[0].lower() and x[0] != '_', set(dir(wx))-set(dir(base))-set(dir(agg)))
   {'gui_repaint', 'keyvald'}

   These lists are a starting point/hint at the amount of work for this task, but I'd actually suggest running stubgen to get started.

   Note that a full solution would address not only FigureCanvas, but also Renderer, Toolbar-related things, etc. (essentially all classes defined in backend_wx.py, backend_wxagg.py, and backend_agg.py, and at least their public behaviors)
   Functions which do not modify signatures from the base class may be omitted from the stub file.

   I believe all of these to be reasonably well behaved from a type perspective, though it is quite possible docstrings are lacking parameter information (or missing entirely) for these, so may take some digging for someone who has not worked with backends code before (and I'd count myself in that category).

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