GKS: Viewport is not within the NDC unit square in routine SET_VIEWPORT

[songbin6280]

I have run into an issue with gr as backend for matplotlib. Without gr the same python script run without issue. The figure (topo.png) generated is correct. When I turn on gr as the backend with "export MPLBACKEND="module://gr.matplotlib.backend_gr"", the complaint shown in the title appeared multiple times. The figure (topo-gr.png) generated is also wrong. Can you give me some hints how to modify the script to make it work with gr? Sorry that the script is messy. The plotting related part is marked towards the end of the script. The two files referenced are in this google drive folder:
https://drive.google.com/drive/folders/1pXxzYaXTr56HUSbVATegPEGGWLjWjEk-?usp=drive_link.

Thank you.
Bin

plot.py

[jheinen]

Could you pls provide the terrain.vtk file or do you have another MWE which does not require any data files?

[songbin6280]

Thanks for reaching out. The terrain.vtk is in the google drive. The link is https://drive.google.com/drive/folders/1pXxzYaXTr56HUSbVATegPEGGWLjWjEk-?usp=drive_link. After I posted this yesterday, I tried running it again. But this time I did with python plot.py -dmodule://gr.matplotlib.backend_gr. And the figure was correct. I am using anaconda with Python 3.13.0, matplotlib 3.10 and gr 1.30.0. Of course plot.py is only set up to illustrate the issue. The actual script deals with much more vtk files and has argparse to handle arguments. I could not find ways to run the real workflow with -dmodule://gr.matplotlib.backend_gr. The real workflow is still plagued with the issue above: the warnings and the false figures.

[songbin6280]

Never mind my previous comment about using python plot.py -dmodule://gr.matplotlib.backend_gr. I added print(matplotlib.rcParams['backend']) to the script. It turns out that it did not change the backend with python plot.py -dmodule://gr.matplotlib.backend_gr. The export MPLBACKEND="module://gr.matplotlib.backend_gr" option did change the backend to gr. But the figure was not still wrong.

[jheinen]

Unfortunately, the internal structure of Matplotlib has changed with regard to the backends. We need to fundamentally revise the GR backend again. Therefore, we cannot offer a workaround in the short term. We are staying on top of the issue ...

[songbin6280]

Thank you for looking into it. Hopefully this can be resolved. Feel free to close this issue as it is nontrivial.