Would it be enough to not warn when the existing layout engine isany placeholder layout engine? My understanding is that the warning is aimed at users who set up a figure with compressed/constrained layout and do not realisetight_layout is incompatible (or who copy-pasted some old code and neglected to strip out thetight_layout call).#24528

If you have a placeholder, I think you must already have turned the layout engine off somewhere.

I was worried about the case of

fig=plt.figure(layout='constrained')fig.set_layout_engine('none')fig.tight_layout()# <- should this warn?!

I went with "yes" on reflex but on a bit more consideration, I think "no" may be a better answer as by explicitly clearing the layout engine the user as already opted out of the automatic calls and are doing it "manually".