add before_token_counter callback and use it for prompt comments

modules/script_callbacks.py

@@ -1,3 +1,4 @@
+import dataclasses
 import inspect
 import os
 from collections import namedtuple
@@ -106,6 +107,15 @@ class ImageGridLoopParams:
         self.rows = rows
 
 
+@dataclasses.dataclass
+class BeforeTokenCounterParams:
+    prompt: str
+    steps: int
+    styles: list
+
+    is_positive: bool = True
+
+
 ScriptCallback = namedtuple("ScriptCallback", ["script", "callback"])
 callback_map = dict(
     callbacks_app_started=[],
@@ -128,6 +138,7 @@ callback_map = dict(
     callbacks_on_reload=[],
     callbacks_list_optimizers=[],
     callbacks_list_unets=[],
+    callbacks_before_token_counter=[],
 )
 
 
@@ -309,6 +320,14 @@ def list_unets_callback():
     return res
 
 
+def before_token_counter_callback(params: BeforeTokenCounterParams):
+    for c in callback_map['callbacks_before_token_counter']:
+        try:
+            c.callback(params)
+        except Exception:
+            report_exception(c, 'before_token_counter')
+
+
 def add_callback(callbacks, fun):
     stack = [x for x in inspect.stack() if x.filename != __file__]
     filename = stack[0].filename if stack else 'unknown file'
@@ -483,3 +502,10 @@ def on_list_unets(callback):
     The function will be called with one argument, a list, and shall add objects of type modules.sd_unet.SdUnetOption to it."""
 
     add_callback(callback_map['callbacks_list_unets'], callback)
+
+
+def on_before_token_counter(callback):
+    """register a function to be called when UI is counting tokens for a prompt.
+    The function will be called with one argument of type BeforeTokenCounterParams, and should modify its fields if necessary."""
+
+    add_callback(callback_map['callbacks_before_token_counter'], callback)