docs: Update Code_Overview.md with removal of printer_state() callback

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 21 insertions, 11 deletions

diff --git a/docs/Code_Overview.md b/docs/Code_Overview.md
index 2b5fa621..5266fd1e 100644
--- a/docs/Code_Overview.md
+++ b/docs/Code_Overview.md
@@ -262,16 +262,26 @@ The following may also be useful:
   will have been instantiated. The "gcode" and "pins" modules will
   always be available, but for other modules it is a good idea to
   defer the lookup.
-* Define a `printer_state()` method if the code needs to be called
-  during printer setup and/or shutdown. This method is called twice
-  during setup (with "connect" and then "ready") and may also be
-  called at run-time (with "shutdown" or "disconnect"). It is common
-  to perform "printer object" lookup during the "connect" and "ready"
-  phases.
+* Register event handlers using the `printer.register_event_handler()`
+  method if the code needs to be called during "events" raised by
+  other printer objects. Each event name is a string, and by
+  convention it is the name of the main source module that raises the
+  event along with a short name for the action that is occurring (eg,
+  "klippy:connect"). The parameters passed to each event handler are
+  specific to the given event (as are exception handling and execution
+  context). Two common startup events are:
+  * klippy:connect - This event is generated after all printer objects
+    are instantiated. It is commonly used to lookup other printer
+    objects, to verify config settings, and to perform an initial
+    "handshake" with printer hardware.
+  * klippy:ready - This event is generated after all connect handlers
+    have completed successfully. It indicates the printer is
+    transitioning to a state ready to handle normal operations. Do not
+    raise an error in this callback.
 * If there is an error in the user's config, be sure to raise it
-  during the `load_config()` or `printer_state("connect")` phases. Use
-  either `raise config.error("my error")` or `raise
-  printer.config_error("my error")` to report the error.
+  during the `load_config()` or "connect event" phases. Use either
+  `raise config.error("my error")` or `raise printer.config_error("my
+  error")` to report the error.
 * Use the "pins" module to configure a pin on a micro-controller. This
   is typically done with something similar to
   `printer.lookup_object("pins").setup_pin("pwm",
@@ -286,8 +296,8 @@ The following may also be useful:
   printer object returned from the `load_config()` function. This is
   important as otherwise the RESTART command may not perform as
   expected. Also, for similar reasons, if any external files (or
-  sockets) are opened then be sure to close them from the
-  `printer_state("disconnect")` callback.
+  sockets) are opened then be sure to register a "klippy:disconnect"
+  event handler and close them from that callback.
 * Avoid accessing the internal member variables (or calling methods
   that start with an underscore) of other printer objects. Observing
   this convention makes it easier to manage future changes.