A fade frame repaints an entry's lines; it no longer renders the entry again

src/toad/block_navigation.py

@@ -360,7 +360,7 @@ def starts_agent_activity(self, boundary: AgentActivityBoundary) -> bool:
     def repaint(self) -> None:
         # The widgets inside the entry draw its rows.
         for widget in cast(Widget, self).walk_children(with_self=True):
-            widget.refresh()
+            widget.refresh_lines()
 
     def notification_targets(self):
         return ()

src/toad/frame_presentation.py

@@ -311,11 +311,11 @@ async def on_unmount(self) -> None:
     def on_hide(self) -> None:
         for effect in tuple(self.effects):
             self.effects.pop(effect).stop()
-        self.refresh()
+        self.repaint()
 
     def on_show(self) -> None:
         self.start_wanted()
-        self.refresh()
+        self.repaint()
 
     def paint_effects(self, strip: Strip, *frames: Mix) -> Strip:
         # Background-origin text rises from the widget's tone; accent flashes
@@ -345,6 +345,16 @@ def animation_visible(self) -> bool:
             return False
         return screen is current and self in screen._compositor.visible_widgets
 
+    def repaint(self) -> None:
+        """A frame paints over the lines (paint_effects in render_line); the content they
+        show is unchanged, so it is not rendered again."""
+        self.refresh_lines()
+
+
+class EffectInContent:
+    """A widget whose content itself reads the effect frame (in render or its strips), so each
+    frame renders the content again instead of repainting the same lines."""
+
     def repaint(self) -> None:
         self.refresh()
 

src/toad/widgets/future_text.py

@@ -11,11 +11,11 @@
 from ui_theme.effects import Wipe, Band
 from ui_theme.scheme import AccentColour, PrimaryColour
 
-from toad.frame_presentation import Animated
+from toad.frame_presentation import Animated, EffectInContent
 from toad.native_style import AutoWidth, NoWrap, OneRow
 
 
-class FutureText(AutoWidth, OneRow, NoWrap, Animated[Band], Static):
+class FutureText(EffectInContent, AutoWidth, OneRow, NoWrap, Animated[Band], Static):
     """Reveal one text from elapsed time, then leave it still."""
 
     native_theme = (NativeDeclaration.of(Styles.color, Variable(PrimaryColour.name)),)

src/toad/widgets/message_divider.py

@@ -17,7 +17,7 @@
 
 from toad.block_content import BlockContent
 from toad.block_navigation import CategorizedBlock, ConversationBlock
-from toad.frame_presentation import Animated
+from toad.frame_presentation import Animated, EffectInContent
 from toad.line_blocks import Divider, Gap, LineBlock
 from toad.native_style import (
     AutoHeight,
@@ -121,7 +121,7 @@ def pin(self, pinned: PinnedHeader) -> None:
         self.display = bool(pinned.headers)
 
 
-class MessageDivider(SpacedAbove, Animated[Mix], ConversationLineBlock):
+class MessageDivider(EffectInContent, SpacedAbove, Animated[Mix], ConversationLineBlock):
     """The rule above a live message: the same `Divider` block saved history draws.
 
     A message that has just arrived fades in from the accent colour.

src/toad/widgets/session_tabs.py

@@ -34,7 +34,7 @@
 from toad.core import session_requests
 from toad.core.events import SessionChangedEvent
 from toad.core_event_carrier import CoreEventReceiver
-from toad.frame_presentation import Animated
+from toad.frame_presentation import Animated, EffectInContent
 from toad.session_tracker import OpenTab
 from toad.app_node import ToadNode
 from toad.widgets.selection import ChangingText, ViewLabel
@@ -136,7 +136,7 @@ def close_tab(self) -> None:
 TAB_SLIDE = Transition(Amount, 0.0, 1.0, duration=0.18, frames_per_second=60)
 
 
-class Underline(WidgetView, Animated[Amount]):
+class Underline(EffectInContent, WidgetView, Animated[Amount]):
     """The track under the tab cells, marking the selected tab's cells.
 
     It is laid out under the cells themselves (TabCells), so it spans every

src/toad/widgets/splash_text.py

@@ -8,7 +8,7 @@
 from ui_theme.scheme import ColourScheme
 from ui_theme.splash import loading_splash
 
-from toad.frame_presentation import Animated
+from toad.frame_presentation import Animated, EffectInContent
 from toad.block_navigation import ConversationBlock
 from toad.native_style import (
     AutoHeight,
@@ -20,7 +20,7 @@
 )
 
 
-class SplashText(Animated[TextFrame], Static):
+class SplashText(EffectInContent, Animated[TextFrame], Static):
     """Shows ``TEXT`` plainly until its effect's frames arrive, then plays them.
 
     The frames are built in a render worker, once per colour scheme. A

src/toad/widgets/switch_toast.py

@@ -196,7 +196,7 @@ def on_show(self) -> None:
     def repaint(self) -> None:
         """The clock's paint request: the toast leaves the layout once its swell ends."""
         self.display = self.effect_phase(TAB_TOAST).in_motion
-        self.refresh()
+        self.refresh_lines()
 
     def render_line(self, y: int, paint: PaintState) -> Strip:
         colours = self.app.colours

src/toad/widgets/throbber.py

@@ -15,7 +15,7 @@
 from ui_theme.effects import ACTIVITY_SWEEP, Ribbon
 from ui_theme.scheme import TurnBandColour
 
-from toad.frame_presentation import Animated
+from toad.frame_presentation import Animated, EffectInContent
 from toad.native_style import FullWidth, OneRow
 from toad.textual_colours import BlockInk, BottomInk
 
@@ -45,7 +45,7 @@ def get_height(self, rules: TextFormat, width: int) -> int:
         return 1
 
 
-class Throbber(FullWidth, OneRow, Animated[Ribbon]):
+class Throbber(EffectInContent, FullWidth, OneRow, Animated[Ribbon]):
     _paint_only_render = True
     tone = TurnBandColour
     # The row is always reserved; only its paint and animation change.

tests/textual/test_fade_frames_keep_content.py

@@ -0,0 +1,27 @@
+"""A fade paints over the lines an entry already rendered: each frame re-paints them, and the
+content (Markdown blocks, rows, a new rich Style per segment) is rendered once, not per frame.
+The live profile had rich Style construction at 19% of the main thread from exactly this."""
+
+from textual.widget import Widget
+
+from toad.widgets.agent_response import AgentResponse
+
+
+async def test_an_arrival_fade_renders_its_entry_once(workspace, monkeypatch):
+    rendered: list[Widget] = []
+    render = Widget._render_content
+
+    def counting(self, paint):
+        rendered.append(self)
+        return render(self, paint)
+
+    monkeypatch.setattr(Widget, "_render_content", counting)
+    async with workspace.app(size=(120, 40)) as ui:
+        block = await ui.conversation.post(AgentResponse(""))
+        await block.append_fragment("Streamed agent text that fades in as it arrives")
+        await ui.step()
+        rendered.clear()
+        for _ in range(20):
+            await ui.pilot.pause(0.025)
+
+    assert sum(isinstance(widget, AgentResponse) for widget in rendered) <= 1