For developers

Filters, actions and a small JavaScript object let you extend the designer without changing the plugin's files. The full reference is the file docs/hooks.md in the plugin's source repository.

All hooks start with vst_. The constant VST_API_VERSION (currently 1) goes up when the hook set or the PHP API changes in a way that breaks add-ons. Option and meta keys with the prefixes vsticker_, _vsticker_ and _vst_ belong to the plugin; an add-on uses its own prefix.

Start an add-on

add_action('vst_loaded', function () {
    if (!defined('VST_API_VERSION') || VST_API_VERSION < 1) {
        return; // too old: show your own admin notice
    }
    My_Addon::init();
});

vst_loaded fires at the end of the plugin's plugins_loaded callback. It does not fire when WooCommerce or the required PHP version is missing.

Pricing

The price a customer pays is always computed on the server. The designer shows the same formula in JavaScript. An add-on that changes the price registers both the PHP filter and the JavaScript filter, with the same logic, so the customer sees the price they pay.

Hook	Type	Purpose
`vst_calculated_price`	filter	Adjust the price per piece after discount, minimum, extra colours and rush, before rounding.
`VSTPricing.addFilter('price', fn)`	JS	The same adjustment in the browser, with an optional label for the breakdown line.
`VSTPricing.addFilter('lines', fn)`	JS	Change the price breakdown lines. Lines never change the price.

Cart and order

Hook	Type	Purpose
`vst_cart_item_data`	filter	Add your own data to the cart item.
`vst_order_item_meta`	action	Add meta to a new designer order item at checkout.
`vst_order_item_actions`	filter	Add your own buttons next to the download buttons in the admin.
`vst_order_item_after`	action	Print your own block after the design block of an item in the admin.

Designer

Hook	Type	Purpose
`vst_designer_allowed`	filter	Return false to switch the designer off for a product; WooCommerce then shows its normal price and add-to-cart button.
`vst_designer_config`	filter	Adjust the designer configuration.
`vst_enqueue_designer`	action	Enqueue your script after the designer's own.
`vst_designer_panels`	filter	Add your own panel to the designer.
`vst_designer_toolbar`	action	Print buttons in the canvas toolbar.
`vst_feature_enabled`, `vst_feature_toggles`	filter	Turn a customer-facing switch on or off on top of the saved setting, or pass extra switches to the browser.
`vst_available_fonts`, `vst_allow_external_fonts`	filter	Add fonts to the designer; allow an external font stylesheet in the template editor.
`vst_start_presets`, `vst_scenes`, `vst_shape_library`, `vst_material_library`, `vst_install_kit_products`	filter	Extend the start presets, the scenes, the shape library, the material presets and the install kit.

JavaScript: window.VSTDesigner

The object exists as soon as the designer script has run, so load your script with vst-frontend-js as a dependency (and vst-pricing for the price filter).

Member	What it does
`on(event, fn)` / `off(event, fn)`	Subscribe or unsubscribe. Events: `ready`, `change`, `beforeAddToCart`, `export`.
`getDesign()` / `applyDesign(doc)`	Read the current design document or load one.
`refresh()`	Re-render and recalculate the price, for example after your own panel changed.
`getCutSVG()`	A promise with the cut file as the order would receive it.

A beforeAddToCart handler may return a promise; if it rejects, the item is not added and the reason is shown to the customer. All handlers together get 10 seconds.

VSTDesigner.on('beforeAddToCart', function (doc) {
    if (!document.querySelector('[name="myaddon_date"]').value) {
        return Promise.reject(new Error('Please choose a mounting date.'));
    }
});

REST and PHP API

The plugin has a REST namespace vst/v1; the vst_rest_init action lets you add routes (give each its own permission_callback). A short list of PHP functions is public API for add-ons, among them vst_get_settings(), vst_feature_enabled(), vst_is_enabled(), vst_designer_active(), vst_get_product_sticker_types() and vst_get_available_fonts(). Anything else is internal.

Pro uses the same API

Pro is itself an add-on built on this public API: it reads the free plugin's order items and design files and adds its own screens and e-mails.