fix layout of image when either width or height is bounded, but not the other

[JAicewizard]

This PR fixes #1184 with a more considerate layout function never taking +infinite in size.

[ForLoveOfCats]

I'm not qualified to review the unit test but the logic seems sound 👍

[ForLoveOfCats]

cc @cmyr I think you're the master of the rendering test system, can you take a look at the unit test here?

[jneem]

Given that the pixel interpolation and scaling has already been tested, probably it would be enough to just test the image's layout rect? You can look at the layout tests for an example.

[JAicewizard]

I made the tests test just the layout, it works well. I tested that the old implementation would indeed fail.

[JAicewizard]

@jneem can you remove the waiting-on-author label? I think I addressed all the issues raised.

[jneem]

Right, sorry for letting this sit. There's a conflict in the CHANGELOG now, but otherwise it looks good to go.

I think the changes were made, right?

[ForLoveOfCats]

Yeppers! My nits have been addressed :)

[JAicewizard]

This took a bit longer than expected, I fixed some bugs with the renaming and behavior changes around the scrollbar and image buffer.
The mechanisms are the same, and I guess we have now already seen the tests actually work in practice :)
github seems to have broken again so I cant tag anyone.
Would be nice to get this merged to be done with it.

[jneem]

Thanks for your patience on this! I just see a merge conflict on the changelog, but otherwise I'm ready to merge.

[JAicewizard]

oops! I should find a way to make vscode not auto-format .MD files, or highlight merge conflicts in vim.
I'm off to bed but I think its safe to say this wont trip one of the tests (fingers crossed).

It was very nice to work on this, I might try to fix more small things once I have time.

[ForLoveOfCats]

At some point the number for the PR in the changelog link became incorrect. Later tonight I'm going to take the liberty of fixing that then merge this. This message mostly serves as a note to any other collaborators that this change needs to be made real quick before merging

[ForLoveOfCats]

Well nevermind lol, the allow edits box was unchecked. Very very minor change here and then we can merge I promise

Changes made