PathEffectRenderer doesn't call close_group?

sherlockdoyle · February 29, 2024, 7:56pm

I am in the process of developing a custom Renderer for matplotlib. This task relies on the use of open_group and close_group functions. During testing, I noticed an inconsistency in the number of calls to these two functions while working on the example of Contouring the solution space of optimizations. This issue seems to be linked to the use of patheffects. After some investigation, it appears that in Collection.draw, if any path effects are present, the renderer is updated to PathEffectRenderer. Subsequently, close_group is called on this updated renderer, but this call does not reach the original renderer. I am uncertain if this is the intended behavior or a bug.

QuLogic · March 12, 2024, 2:04am

This was reported as

github.com/matplotlib/matplotlib

[Bug]: close_group is not called when using patheffects

opened 08:44PM - 01 Mar 24 UTC

closed 02:57PM - 11 Mar 24 UTC

sherlockdoyle

topic: path handling

### Bug summary I am in the process of developing a custom `Renderer` for matpl…otlib. My understanding is that every `Renderer.open_group` call will have a corresponding `Renderer.close_group` call. However, when patheffects are used (at least), the `close_group` never gets called. ### Code for reproduction ```Python from matplotlib import patheffects from matplotlib.backend_bases import FigureCanvasBase, GraphicsContextBase, RendererBase from matplotlib.figure import Figure from matplotlib.path import Path from matplotlib.transforms import Transform from matplotlib.typing import ColorType class Renderer(RendererBase): def __init__(self) -> None: super().__init__() self.indent = '' def open_group(self, s: str, gid: str | None = None) -> None: print(self.indent + 'open ' + s) self.indent += ' ' return super().open_group(s, gid) def close_group(self, s: str) -> None: self.indent = self.indent[:-2] print(self.indent + 'close ' + s) return super().close_group(s) def draw_path( self, gc: GraphicsContextBase, path: Path, transform: Transform, rgbFace: ColorType | None = None ) -> None: pass class Canvas(FigureCanvasBase): def draw(self): self.figure.draw(Renderer()) figure = Figure() canvas = Canvas(figure) ax = figure.gca() ax.set_axis_off() cg1 = ax.contour([[0, 1], [2, 3]]) cg1.set(path_effects=[patheffects.withTickedStroke(angle=135)]) canvas.draw() ``` ### Actual outcome open figure open patch close patch open axes open QuadContourSet close axes close figure ### Expected outcome `QuadContourSet` is closed. open figure open patch close patch open axes open QuadContourSet close QuadContourSet close axes close figure ### Additional information After some investigation, it appears that in `Collection.draw`, [if any path effects are present](https://github.com/matplotlib/matplotlib/blob/76eaa9669471b86a2569885adf760dc388585783/lib/matplotlib/collections.py#L367), the renderer is updated to `PathEffectRenderer`. Subsequently, `close_group` is called on this updated renderer, but this call does not reach the original renderer. ### Operating system Ubuntu ### Matplotlib Version 3.8.3 ### Matplotlib Backend Custom ### Python version Python 3.10.12 ### Jupyter version _No response_ ### Installation pip

and should be fixed by

github.com/matplotlib/matplotlib

Override open_group, close_group methods in PathEffectRenderer

matplotlib:main ← chaoyihu:patheffectrenderer-override-renderbase-methods

opened 04:26AM - 11 Mar 24 UTC

chaoyihu

+25 -0

## PR summary This code change is to ensure that methods like `open_group` an…d `close_group` are overridden in `PathEffectRenderer`. This pull request addresses and hopefully closes #27843. ## PR checklist - [ ] "closes #0000" is in the body of the PR description to [link the related issue](https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue) - [ ] new and changed code is [tested](https://matplotlib.org/devdocs/devel/testing.html) - [ ] *Plotting related* features are demonstrated in an [example](https://matplotlib.org/devdocs/devel/document.html#write-examples-and-tutorials) - [ ] *New Features* and *API Changes* are noted with a [directive and release note](https://matplotlib.org/devdocs/devel/api_changes.html#announce-changes-deprecations-and-new-features) - [ ] Documentation complies with [general](https://matplotlib.org/devdocs/devel/document.html#write-rest-pages) and [docstring](https://matplotlib.org/devdocs/devel/document.html#write-docstrings) guidelines