[Lightbox media viewer] Layout updates

[kirbyevans]

The problem

There are inconsistencies between the current implementation of the Lightbox media viewer and its design specs. There are issues with the margin/padding and the image scrolling with the supporting image copy.

The solution

We hope by simplifying the layout within the Lightbox media viewer that these issues will be resolved. Attached are the updated design specs for the Lightbox media viewer. These specs should address alignment of the image and supporting copy, as well as, how to accommodate supporting copy when it isn't able to fit within the Lightbox media viewer's visible area.

Additional information

Design specs for the proposed solution can be found here:

PDF
Sketch file

Preview of specs for Lightbox media viewer

• Functional specs: https://github.com/carbon-design-system/carbon-for-ibm-dotcom-website/wiki/Lightbox-media-viewer#2-viewer

[shixiedesign]

To be turned into Epic: design spec done. Need func spec, dev issue, QA issues. We need 1 website issue for all the lightbox changes coming from AEM (6328, 6329, 6314)