Add a grace period between detecting a change and triggering generati…

…on in live preview

* This will prevent some of the "useless" generations, e.g. from the very start of
  the brush stroke
* Period is configurable in settings; setting the default to 0 to
  preserve the existing behaviour

This at least partially addresses/follows the discussions in Acly#628 and Acly#1248

ai_diffusion/model.py

@@ -297,7 +297,7 @@ def estimate_cost(self, kind=JobKind.diffusion):
     def generate_live(self):
         eventloop.run(_report_errors(self, self._generate_live()))
 
-    async def _generate_live(self, last_input: WorkflowInput | None = None):
+    def _prepare_live_job_params(self):
         strength = self.live.strength
         workflow_kind = WorkflowKind.generate if strength == 1.0 else WorkflowKind.refine
         client = self._connection.client
@@ -346,12 +346,15 @@ async def _generate_live(self, last_input: WorkflowInput | None = None):
             inpaint=inpaint if mask else None,
             is_live=True,
         )
+        params = JobParams(bounds, conditioning.positive, regions=job_regions)
+        return input, params
+
+    async def _generate_live(self, last_input: WorkflowInput | None = None):
+        input, job_params = self._prepare_live_job_params()
         if input != last_input:
             self.clear_error()
-            params = JobParams(bounds, conditioning.positive, regions=job_regions)
-            await self.enqueue_jobs(input, JobKind.live_preview, params)
+            await self.enqueue_jobs(input, JobKind.live_preview, job_params)
             return input
-
         return None
 
     async def _generate_custom(self, previous_input: WorkflowInput | None):
@@ -872,12 +875,21 @@ def handle_job_finished(self, job: Job):
             eventloop.run(_report_errors(self._model, self._continue_generating()))
 
     async def _continue_generating(self):
+        just_got_here = True
         while self.is_active and self._model.document.is_active:
-            new_input = await self._model._generate_live(self._last_input)
-            if new_input is not None:  # frame was scheduled
-                self._last_input = new_input
-                return
+            new_input, _ = self._model._prepare_live_job_params()
+            if self._last_input != new_input:
+                if settings.live_redraw_grace_period > 0 and not just_got_here:
+                    # only use grace period if this isn't our first frame of polling
+                    # if it is, and there are changes in the input, it's likely that we have some changes we ignored
+                    # previously due to the generation process running, and we need to update the preview asap
+                    await asyncio.sleep(settings.live_redraw_grace_period)
+                new_input = await self._model._generate_live(self._last_input)
+                if new_input is not None:
+                    self._last_input = new_input
+                    return
             # no changes in input data
+            just_got_here = False
             await asyncio.sleep(self._poll_rate)
 
     def apply_result(self, layer_only=False):

ai_diffusion/settings.py

@@ -155,6 +155,13 @@ class Settings(QObject):
         _("Pick a new seed after copying the result to the canvas in Live mode"),
     )
 
+    live_redraw_grace_period: float
+    _live_redraw_grace_period = Setting(
+        _("Live: Redraw grace period"),
+        0.0,
+        _("How long to delay scheduling the live preview job for after a change is made"),
+    )
+
     prompt_translation: str
     _prompt_translation = Setting(
         _("Prompt Translation"),

ai_diffusion/ui/settings.py

@@ -439,6 +439,10 @@ def __init__(self):
         self.add("auto_preview", SwitchSetting(S._auto_preview, parent=self))
         self.add("show_steps", SwitchSetting(S._show_steps, parent=self))
         self.add("new_seed_after_apply", SwitchSetting(S._new_seed_after_apply, parent=self))
+        self.add(
+            "live_redraw_grace_period",
+            SliderSetting(S._live_redraw_grace_period, self, 0.0, 3.0, "{} s"),
+        )
         self.add("debug_dump_workflow", SwitchSetting(S._debug_dump_workflow, parent=self))
 
         languages = [(lang.name, lang.id) for lang in Localization.available]