Avoid implying that _show always uses xv

[radarhere]

This code in Image.py implies that _show always uses xv.

Pillow/src/PIL/Image.py

Lines 3143 to 3151 in 41a7521

	def _show(image, **options):
	# override me, as necessary
	_showxv(image, **options)
	def _showxv(image, title=None, **options):
	from . import ImageShow
	ImageShow.show(image, title, **options)

This PR rearranges the code into the following to avoid that implication.

def _show(image, **options):
    # override me, as necessary
    from . import ImageShow

    ImageShow.show(image, **options)


_showxv = _show

title still has a default value of None because

Pillow/src/PIL/ImageShow.py

Line 38 in 41a7521

def show(image, title=None, **options):

[nulano]

This change would mean that users replacing Image._showxv with custom code would no longer have an effect. I'm not sure how common that is, just wanted to note this change.

[radarhere]

That's true. As you seem to be aware though. I really don't know why you would do that. If you were going to customise this functionality, _show is the more likely target than _showxv. If someone is replacing Pillow functions with their own code though, unless it is common, my instinct would be that it's on them to keep their code working.

This is a minor cleanup, so it can be dropped if there is debate over it.

[nulano]

I'm just commenting on the comment above the function: # Simple display support. User code may override this.

I think this change is fine, perhaps it should just be noted somewhere. Also note that this makes it into an unused internal function, although it seems to be used quite often from other projects, so I wonder whether it should also be deprecated.

[radarhere]

Oh. I didn't actually notice that comment. I only saw # override me, as necessary.

[hugovk]

Both _show and _showxv begin with underscores indicating they're internal and private, but # Simple display support. User code may override this. suggests otherwise!

A quick search has "9 available code results" for Image._showxv:

• https://github.com/search?l=Python&q=%22Image._showxv%22&type=Code

Compared with 16,074 for Image._show:

• https://github.com/search?l=Python&q=%22Image._show%22&type=Code

Idea: shall we put a deprecation warning on _showxv to remove it in the future, and remove that comment?

[radarhere]

Sure. See #4713 and #4714