homing_override: Add basic support for running custom g-code on G28

Allow users to override the behavior of G28 using a new
"homing_override" config section.  This may be used on printers that
require specific steps during the homing process.

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

1 files changed, 28 insertions, 0 deletions

diff --git a/klippy/extras/homing_override.py b/klippy/extras/homing_override.py
new file mode 100644
index 00000000..1e23fb80
--- /dev/null
+++ b/klippy/extras/homing_override.py
@@ -0,0 +1,28 @@
+# Run user defined actions in place of a normal G28 homing command
+#
+# Copyright (C) 2018  Kevin O'Connor <kevin@koconnor.net>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+
+class HomingOverride:
+    def __init__(self, config):
+        printer = config.get_printer()
+        self.script = config.get('gcode')
+        self.in_script = False
+        self.gcode = printer.lookup_object('gcode')
+        self.gcode.register_command("G28", self.cmd_G28)
+    def cmd_G28(self, params):
+        if self.in_script:
+            # Was called recursively - invoke the real G28 command
+            self.gcode.cmd_G28(params)
+            return
+        try:
+            self.in_script = True
+            self.gcode.run_script(self.script)
+        finally:
+            self.in_script = False
+
+def load_config(config):
+    if config.get_name() != 'homing_override':
+        raise config.error("Invalid homing_override config name")
+    return HomingOverride(config)