Handlers

The MODX events the package subscribes to, and what the framework does on each. Your own class with the same name runs after the framework one — see Events.

Request lifecycle

Event	What the framework does
OnMODXInit	Nothing yet. Registered with priority: 1000 so the component boots before other plugins that may depend on it.
OnHandleRequest	Aliases modUser and modUserProfile to their MODX\Revolution\ counterparts, starts the session, mints the CSRF token if the session has none, switches the locale when the URI carries a language prefix, and hands the request to routing. Skips asset extensions (.css, .js, images, fonts) and, with pageblocks_routing = off, everything outside mgr/.
OnWebPageInit	Front-end setup for the requested page: sends the security headers, registers the style layer through regClientCSS (unless pageblocks_load_styles is off), adds the reCAPTCHA script when a public key is filled in, and — unless pageblocks_load_scripts is off — the web scripts plus their configuration.
OnCacheUpdate	Clears the route cache, the Fenom view cache, the component cache and the menu cache, and drops $_SESSION['pageblocks']. Runs whenever MODX clears its cache.

The one case where the style layer needs a tag in the template

Because OnWebPageInit registers the block styles itself, an ordinary MODX page needs nothing from you — no {pb_styles()}, no manual <link>. But a page rendered by the component's own router never reaches that event: OnHandleRequest sends the response and returns first. In that template, and only there, put {pb_styles()} in the <head>.

Clearing the MODX cache clears ours

OnCacheUpdate means the manager's "Clear cache" button already covers PageBlocks — routes, compiled templates and cached lists. You rarely need to clear anything by hand.

Resource form

Event	What the framework does
OnDocFormPrerender	On an existing resource, loads the component's manager scripts. Skipped in new mode.
OnDocFormRender	Renders the resource's section fields into the form. Skipped in new mode.
OnBeforeDocFormSave	Collects the section field values from the submitted form and writes them into the resource.
OnResourceDuplicate	Copies the resource's PageBlocks content to the copy: blocks, their nested tables and galleries, and rows attached to the resource's section fields. Custom field values ride along inside properties, which MODX copies itself.

User form

Event	What the framework does
OnUserFormPrerender	Loads manager scripts for an existing user. Skipped in new mode.
OnUserFormRender	Renders the user's section fields into the form.
OnUserSave	Writes custom user fields into modx_user_attributes.extended. Runs after the core processor on purpose — otherwise the processor would overwrite extended.
OnUserDuplicate	The user counterpart of OnResourceDuplicate. Accepts several spellings of the processor's parameters, because they differ between MODX builds.
OnUserRemove	No framework handler. Registered so a site can hook it from core/App/Events/OnUserRemove.php.

Manager

Event	What the framework does
OnManagerPageBeforeRender	Loads the base scripts, the data scripts and the rich text editor on every manager page.
OnSiteSettingsRender	Adds modx.combo.js to the system settings page.

Where the code is

Framework handlers live in core/components/pageblocks/src/Events/, one file per event. They are short and readable — when this page is not enough, the class itself usually is.