Customizer: Use proper preview URL for Live Preview links

[mattwiebe]

You're doing more work then is needed, since the theme object already has the theme.actions.customize URL built in. Also, it breaks on WordPress.com since our themes are in subdirectories. Using theme.actions.customize is how wp-admin/themes.php does it.

[westonruter]

Good re-use of the data we're already passing to the template.

[ocean90]

In 31911:

Customizer: Use proper preview URL for Live Preview links.

props mattwiebe.
fixes #31782.

[celloexpressions]

Sorry, totally missed this.

This was done so that we can preserve url and return URL parameters, to make the experience smoother (I changed it from using theme.actions.customize for that reason). The page you're previewing shouldn't be changed when you switch themes, which currently works if you don't navigate further in the preview and will be improved westonruter's ticket that adds history and url updating for that.

I'd suggest correcting the bug with assuming that the theme id can be used as the query arg by using either an additional available field or adding a field to wp_prepare_themes_for_js(). Unfortunately the way it currently works, we need to build the URL in PHP with the adding/removing query args, which shouldn't happen in prepare_themes_for_js.

[ocean90]

In 31933:

Customizer: Revert [31911]. We want to preserve url and return URL parameters to make the experience smoother.

see #31782.

[westonruter]

I think we can still preserve the URL and return parameters. We just have to amend them to the URL we get from data.theme.actions.customize.

Related: #31896