Refactor printer into own base dir

InvenTree/label/api.py

@@ -156,7 +156,7 @@ class LabelPrintMixin:
 
                 # Offload a background task to print the provided label
                 offload_task(
-                    'plugin.events.print_label',
+                    'plugin.base.label.label.print_label',
                     plugin.plugin_slug(),
                     image,
                     label_instance=label_instance,

InvenTree/plugin/base/event/events.py

@@ -14,8 +14,6 @@ from django.db import transaction
 from django.db.models.signals import post_save, post_delete
 from django.dispatch.dispatcher import receiver
 
-import common.notifications
-
 from InvenTree.ready import canAppAccessDatabase, isImportingData
 from InvenTree.tasks import offload_task
 
@@ -194,46 +192,3 @@ def after_delete(sender, instance, **kwargs):
         f'{table}.deleted',
         model=sender.__name__,
     )
-
-
-def print_label(plugin_slug, label_image, label_instance=None, user=None):
-    """
-    Print label with the provided plugin.
-
-    This task is nominally handled by the background worker.
-
-    If the printing fails (throws an exception) then the user is notified.
-
-    Arguments:
-        plugin_slug: The unique slug (key) of the plugin
-        label_image: A PIL.Image image object to be printed
-    """
-
-    logger.info(f"Plugin '{plugin_slug}' is printing a label")
-
-    plugin = registry.plugins.get(plugin_slug, None)
-
-    if plugin is None:
-        logger.error(f"Could not find matching plugin for '{plugin_slug}'")
-        return
-
-    try:
-        plugin.print_label(label_image, width=label_instance.width, height=label_instance.height)
-    except Exception as e:
-        # Plugin threw an error - notify the user who attempted to print
-
-        ctx = {
-            'name': _('Label printing failed'),
-            'message': str(e),
-        }
-
-        logger.error(f"Label printing failed: Sending notification to user '{user}'")
-
-        # Throw an error against the plugin instance
-        common.notifications.trigger_notifaction(
-            plugin.plugin_config(),
-            'label.printing_failed',
-            targets=[user],
-            context=ctx,
-            delivery_methods=[common.notifications.UIMessageNotification]
-        )

InvenTree/plugin/base/label/label.py

@@ -0,0 +1,52 @@
+"""Functions to print a label to a mixin printer"""
+import logging
+
+from django.utils.translation import gettext_lazy as _
+
+from plugin.registry import registry
+
+
+logger = logging.getLogger('inventree')
+
+
+def print_label(plugin_slug, label_image, label_instance=None, user=None):
+    """
+    Print label with the provided plugin.
+
+    This task is nominally handled by the background worker.
+
+    If the printing fails (throws an exception) then the user is notified.
+
+    Arguments:
+        plugin_slug: The unique slug (key) of the plugin
+        label_image: A PIL.Image image object to be printed
+    """
+
+    logger.info(f"Plugin '{plugin_slug}' is printing a label")
+
+    plugin = registry.plugins.get(plugin_slug, None)
+
+    if plugin is None:
+        logger.error(f"Could not find matching plugin for '{plugin_slug}'")
+        return
+
+    try:
+        plugin.print_label(label_image, width=label_instance.width, height=label_instance.height)
+    except Exception as e:
+        # Plugin threw an error - notify the user who attempted to print
+
+        ctx = {
+            'name': _('Label printing failed'),
+            'message': str(e),
+        }
+
+        logger.error(f"Label printing failed: Sending notification to user '{user}'")
+
+        # Throw an error against the plugin instance
+        common.notifications.trigger_notifaction(
+            plugin.plugin_config(),
+            'label.printing_failed',
+            targets=[user],
+            context=ctx,
+            delivery_methods=[common.notifications.UIMessageNotification]
+        )

InvenTree/plugin/base/label/mixins.py

@@ -0,0 +1,37 @@
+"""Plugin mixin classes for label plugins"""
+
+
+class LabelPrintingMixin:
+    """
+    Mixin which enables direct printing of stock labels.
+
+    Each plugin must provide a NAME attribute, which is used to uniquely identify the printer.
+
+    The plugin must also implement the print_label() function
+    """
+
+    class MixinMeta:
+        """
+        Meta options for this mixin
+        """
+        MIXIN_NAME = 'Label printing'
+
+    def __init__(self):  # pragma: no cover
+        super().__init__()
+        self.add_mixin('labels', True, __class__)
+
+    def print_label(self, label, **kwargs):
+        """
+        Callback to print a single label
+
+        Arguments:
+            label: A black-and-white pillow Image object
+
+        kwargs:
+            length: The length of the label (in mm)
+            width: The width of the label (in mm)
+
+        """
+
+        # Unimplemented (to be implemented by the particular plugin class)
+        ...  # pragma: no cover

InvenTree/plugin/mixins/__init__.py

@@ -2,13 +2,14 @@
 Utility class to enable simpler imports
 """
 
-from ..base.integration.mixins import APICallMixin, AppMixin, LabelPrintingMixin, SettingsMixin, ScheduleMixin, UrlsMixin, NavigationMixin, PanelMixin
+from ..base.integration.mixins import APICallMixin, AppMixin, SettingsMixin, ScheduleMixin, UrlsMixin, NavigationMixin, PanelMixin
 
 from common.notifications import SingleNotificationMethod, BulkNotificationMethod
 
 from ..base.action.mixins import ActionMixin
 from ..base.barcodes.mixins import BarcodeMixin
 from ..base.event.mixins import EventMixin
+from ..base.label.mixins import LabelPrintingMixin
 
 __all__ = [
     'APICallMixin',