[Bug]: Zoom und pan not working after writing pdf pages.

[Erwin-Wert]

Bug summary

Ladies and Gentlemen,
Zoom und pan is not working after writing pdf pages.
Within matplotlib version 3.7.5 it is working.
In e.g. 3.8.3 it does not react any more.

Code for reproduction

import matplotlib.pyplot as plt
from matplotlib.backends.backend_pdf import PdfPages
fig, ax = plt.subplots()
ax.plot([1, 2, 3], [4, 5, 6])
filename = "test4.pdf"
with PdfPages(filename) as pdf:
    fig.show()
    pdf.savefig() # <== if you comment this line, then zoom is working fine. However it is not getting stored.

Actual outcome

Expected outcome

Additional information

In earlier versions it has been working fine.
It is also not working within jupyterlab.
It was testet in Spyder IDE 5.5.1 and IDLE(Python 3.12 64-bit)
I take the earlier matplotlib version instead.

Operating system

Windows 7,

Matplotlib Version

3.8.3

Matplotlib Backend

QtAgg

Python version

Python 3.12.2 64-bit

Jupyter version

4.1.2

Installation

pip

[Impaler343]

I believe a more appropriate code for reproduction is:

import matplotlib.pyplot as plt
from matplotlib.backends.backend_pdf import PdfPages

filename = "test4.pdf"

with PdfPages(filename) as pdf:
    fig, ax = plt.subplots()
    ax.plot([1, 2, 3], [4, 5, 6])
    pdf.savefig() # <== if you comment this line, then zoom is working fine. However it is not getting stored.

plt.show()

[Impaler343]

To solve this issue, you just need to write plt.show() before saving the figure and pass the figure to the savefig() function. Like:

import matplotlib.pyplot as plt
from matplotlib.backends.backend_pdf import PdfPages
filename = "test4.pdf"

with PdfPages(filename) as pdf:
    fig, ax = plt.subplots()
    ax.plot([1, 2, 3], [4, 5, 6])
    plt.show()
    pdf.savefig(fig) # <== if you comment this line, then zoom is working fine. However it is not getting stored.

But you might have to undo changes that you did while inspecting the figure to save the original figure

[Impaler343]

On another note,

The import statement is slightly incorrect from matplotlib.backends.backend_pgf import PdfPages and needs to be backend_pdf instead of backend_pgf. Is it recommended to open a PR in small changes like this one?

[QuLogic]

This bisects to a6230cc, or #25546, by @anntzer.

[QuLogic]

However, that appears to be exposing an existing different bug. For some reason, this context manager is not restoring the old canvas:

matplotlib/lib/matplotlib/backends/backend_pdf.py

Lines 2758 to 2759 in 9618fc6

	with cbook._setattr_cm(figure, canvas=FigureCanvasPdf(figure)):
	figure.savefig(self, format="pdf", **kwargs)

[QuLogic]

The import statement is slightly incorrect from matplotlib.backends.backend_pgf import PdfPages and needs to be backend_pdf instead of backend_pgf. Is it recommended to open a PR in small changes like this one?

That is not a typo; there are two PdfPages classes, one in the PDF backend and one in the PGF backend. That example uses the PDF backend, and the line is a cross-reference to the PGF backend.

[Erwin-Wert]

To solve this issue, you just need to write plt.show() before saving the figure and pass the figure to the savefig() function. Like:

import matplotlib.pyplot as plt
from matplotlib.backends.backend_pdf import PdfPages
filename = "test4.pdf"

with PdfPages(filename) as pdf:
    fig, ax = plt.subplots()
    ax.plot([1, 2, 3], [4, 5, 6])
    plt.show()
    pdf.savefig(fig) # <== if you comment this line, then zoom is working fine. However it is not getting stored.

But you might have to undo changes that you did while inspecting the figure to save the original figure

The code snippet was just used to reproduce the effect. The real application has multiple figures opened in a tkinter window. Then a function is called to export these figures to the pdf. After that I need the figures to be responsive to zoom and pan. Adding plt.show() opens an extra window with the figure. So this is not an option.

[Impaler343]

To solve this issue, you just need to write plt.show() before saving the figure and pass the figure to the savefig() function. Like:

import matplotlib.pyplot as plt
from matplotlib.backends.backend_pdf import PdfPages
filename = "test4.pdf"

with PdfPages(filename) as pdf:
    fig, ax = plt.subplots()
    ax.plot([1, 2, 3], [4, 5, 6])
    plt.show()
    pdf.savefig(fig) # <== if you comment this line, then zoom is working fine. However it is not getting stored.

But you might have to undo changes that you did while inspecting the figure to save the original figure

The code snippet was just used to reproduce the effect. The real application has multiple figures opened in a tkinter window. Then a function is called to export these figures to the pdf. After that I need the figures to be responsive to zoom and pan. Adding plt.show() opens an extra window with the figure. So this is not an option.

What I collect from this is that the showing functionality must work after saving the figure. The initial code had a fig.show() function before saving the figure due to which I interpreted it in that way