Sticky add-to-cart

Keeps the add-to-cart action within reach on product pages after the main buy buttons scroll out of view. It's two surfaces driven by one section:

• Mobile bar — a persistent bar at the bottom of small screens (under 750px wide) with the product thumbnail, title, live price, an optional quantity stepper, and the add-to-cart button.
• Desktop dock — a floating side dock on very wide screens (1400px and up) with thumbnail, title, price and the button. The dock has its own close control, so a shopper can dismiss it.

Both appear only once the product page's primary buy buttons have scrolled off screen, and both step aside while the cart drawer is open. The button mirrors the primary form: on a sold-out variant it disables and relabels to "Sold out", and preorder products keep their preorder label.

This section only exists on the product template, and it renders nothing at all when Enable sticky bar is off.

Settings

Setting	What it does
Color scheme	Which of your theme's color schemes the bar and dock use.
Enable sticky bar	Turns the whole section on or off. On by default.
Show quantity selector	Adds a −/+ quantity stepper to the mobile bar. On by default; the desktop dock never shows a stepper.
Primary section ID	The section ID of the main product section being observed (default: main). Leave it alone unless you've built a custom product template.

This section does not use blocks.

Notes

• Adding through the bar or dock adds the variant currently selected on the page through the theme's cart API — the bar at its stepper's quantity, the dock always at a quantity of one. It does not submit the main product form — a selling-plan (subscription) choice or other extras filled in there are not carried over, so shoppers buying a subscription should use the main buy buttons.
• The price shown in the bar and dock updates as the shopper switches variants on the page.