This PR has flake8 errors like:

./lib/matplotlib/_mathtext.py:1613:9: F824 `nonlocal off_h` is unused: name is never assigned in scope
...

But clearly doesn't touch that file, so I think maybe flake8 is on a new version?

EDIT: ah yes 7.2 was released 4 hours ago.

Sigh. Why does the bot remove tags that I have specifically added?

You are also removing tick labels. Is that ok because they are trivial for the layout, or should they also be repaced with boxes?

Could we just moneypatch Text.draw to draw a rectangle instead of characters?

If you want to be selective we could create a PlaceholderText class deriving from Text but drawing a rectangle instead. We could then switch out the class on an per-instance basis (artist.__class__ = PlaceholderText).

drawing text has a bunch of options (rotation, cantering etc) that seem like a lot of work to implement versus just redefining x/ylabel which does 95% of what we want.

Are there that many relevant options? I assume implementing rotation should be sufficient for 99% of the test use cases. This feels simpler than reimplementing all functions that create text. You start with xlabel/ylabel, but remarked yourself, there are issues with suptitles. Then we may need ticks. Then it would be helpful to use this for legends etc.

But it's just a suggestion. I won't block over this.

I could try monkey patching, but it'd take me a while to sort out how to do it, and maybe not in time for #29827 which this was aimed at. Note that it is not trivial to place rectangles relative to an axes, but have a fixed physical size, and we place x and y labels by avoiding ticks so we would need to make sure the extents are correct for whatever is monkey patched. It may be worth the effort, but it's not trivial.

As a very minimal test

--- a/lib/matplotlib/text.py
+++ b/lib/matplotlib/text.py
@@ -796,6 +796,7 @@ class Text(Artist):
                 mtext = self if len(info) == 1 else None
                 x = x + posx
                 y = y + posy
+                Rectangle((x, y), wh[0], wh[1]).draw(renderer)
                 if renderer.flipy():
                     y = canvash - y
                 clean_line, ismath = self._preprocess_math(line)

marks the text positions well. Rotation must still be added, you'll want to replace the actual sizes with dummy sizes to not depend on the font, and you want to pull this out of the middle of draw. But it looks quite doable.

plt.plot([1, 3, 2])
plt.xlabel("foo")
plt.ylabel("test")
plt.title("title")
plt.show()

This is a good idea, but I do not think we want to block the freetype 2.13.3 adoption on it.

Closed in lieu of #29872