feat(preview): add per-queue live preview method override (#11261)

- Add set_preview_method() to override live preview method per queue item
- Read extra_data.preview_method from /prompt request
- Support values: taesd, latent2rgb, none, auto, default
- "default" or unset uses server's CLI --preview-method setting
- Add 44 tests (37 unit + 7 E2E)

Author: ltdrdata

comfy/cli_args.py

@@ -97,6 +97,13 @@ class LatentPreviewMethod(enum.Enum):
     Latent2RGB = "latent2rgb"
     TAESD = "taesd"
 
+    @classmethod
+    def from_string(cls, value: str):
+        for member in cls:
+            if member.value == value:
+                return member
+        return None
+
 parser.add_argument("--preview-method", type=LatentPreviewMethod, default=LatentPreviewMethod.NoPreviews, help="Default preview method for sampler nodes.", action=EnumAction)
 
 parser.add_argument("--preview-size", type=int, default=512, help="Sets the maximum preview size for sampler nodes.")

execution.py

@@ -13,6 +13,7 @@
 import torch
 
 import comfy.model_management
+from latent_preview import set_preview_method
 import nodes
 from comfy_execution.caching import (
     BasicCache,
@@ -669,6 +670,8 @@ def execute(self, prompt, prompt_id, extra_data={}, execute_outputs=[]):
         asyncio.run(self.execute_async(prompt, prompt_id, extra_data, execute_outputs))
 
     async def execute_async(self, prompt, prompt_id, extra_data={}, execute_outputs=[]):
+        set_preview_method(extra_data.get("preview_method"))
+
         nodes.interrupt_processing(False)
 
         if "client_id" in extra_data:

latent_preview.py

@@ -8,6 +8,8 @@
 import comfy.utils
 import logging
 
+default_preview_method = args.preview_method
+
 MAX_PREVIEW_RESOLUTION = args.preview_size
 VIDEO_TAES = ["taehv", "lighttaew2_2", "lighttaew2_1", "lighttaehy1_5"]
 
@@ -125,3 +127,11 @@ def callback(step, x0, x, total_steps):
         pbar.update_absolute(step + 1, total_steps, preview_bytes)
     return callback
 
+def set_preview_method(override: str = None):
+    if override and override != "default":
+        method = LatentPreviewMethod.from_string(override)
+        if method is not None:
+            args.preview_method = method
+            return
+    args.preview_method = default_preview_method
+