I would love an answer to this as well.

As a work-around, before I click the update themes button, open the theme builder for my custom themes, change a value and change it back again, and save it. Then it won’t be included in the update process, as far as I can tell.

Hi John,

The process of updating themes involves reconciling the existing CSS in the theme with the changes that were made in your org’s recently updated Skuid Package. Since custom themes are based on the base Skuid themes, they are updated as well. When you update your org’s Skuid package to a new release, the core Skuid components (table, field editor, etc.) will see changes that involve the HTML structure, as well as the underlying CSS classes and unique Ids that the themes tie into. This is a natural part of the process of improving Skuid. If you forego updating the out of date themes, the themes’ CSS will have some discrepancies that often cause visual aberrations. For example, components may use a new CSS class in the latest release, and if your theme doesn’t have a set of style rules for it, defaults will be applied, or Salesforce styles will be applied if they exist. 

Skuid recommends always updating out of date themes after Skuid is updated in an org, but the theme update is not done automatically. 

If you would like to compare versions of a theme pre & post-update, you can export the theme before and after updating Skuid. To be able to open it, give the downloaded theme an extension of .zip. These are actually zip files, but they use the .sktheme extension for the purposes of storage in static resources in Salesforce.

You can explore the files inside the zip, and even use a diff checker if you’re interested. There is not any documentation on what’s inside these though, so you will probably be able to make more sense of it if you’ve got a Skuid page open in your browser and can inspect the HTML and CSS of the various elements in runtime.

Excellent, thank you for a quick and complete response.