🐛 Bug Report

When taking a screenshot with the soon to be added fit_to_data functionality #6730 it was noticed that when the canvas size changes, the size of the scale bar does not change. This causes the scale bar to be potentially very small compared to the data.

💡 Steps to Reproduce

import napari
from skimage.data import cells3d

import matplotlib.pyplot as plt

viewer = napari.Viewer()
data = cells3d()

viewer.add_image(data, channel_axis=1, contrast_limits=[[938,24180], [2382, 49151]])
viewer.scale_bar.visible = True
img=viewer.screenshot(canvas_only=True, fit_to_data=True, scale=10)
plt.imshow(img)
plt.show()

The result is an image like this:

💡 Expected Behavior

A screenshot image is generated with a scale bar that is visible.

🌎 Environment

na

💡 Additional Context

No response