Zoom level should reset for each page

[seanaery]

This appears to be a regression/bug introduced between Mirador 3 & 4. For multi-image items, by default Mirador should reset the Zoom level when navigating from one page to another (so each image is displayed optimally for its resolution/dimensions).

As it is right now in 4, the presently-viewed page's zoom level is being retained when navigating between pages. This might not be very noticeable to a user under the condition that all of the images in the item are similar dimensions (as referenced in #742 ), but it is problematic when they are not.

Here are two example manifests showing a mix of images, where some are portrait vs. some are landscape; likewise some are higher resolution vs. some are lower.

https://repository.duke.edu/iiif/36e0d1db-c773-4f0b-8927-a8da7769b4be/manifest
https://repository.duke.edu/iiif/948cfd89-deaf-4f89-9583-1b5f97e496b0/manifest

[seanaery]

Looking further at this issue, I don't know for sure whether this behavior actually changed between Mirador 3 and 4 or rather my team/stakeholders only just noticed the issue after we upgraded to 4. I do see why it is happening now, and have identified a workaround.

There is long-standing Mirador code in settings.js that specifies i.e.:

osdConfig: { // Default config used for OpenSeadragon
   ...
    preserveViewport: true,
    ...
  },

Note that OSD defaults to preserveViewport: false. Per OSD docs on options:

If sequenceMode is true, then normally navigating through each image resets the viewport to 'home' position. If preserveViewport is set to true, then the viewport position is preserved when navigating between images in the sequence.

So a workable fix for my institution is to change that back to false in our osdConfig when we instantiate Mirador. So I'm OK with this issue being considered closed if the community deems it so. Though it does seem like false would be the more sensible default, since it's common to have multi-image items comprising images that are not the exact same dimensions.