chore: import upstream snapshot with attribution

python/samples/02-agents/harness/console/components/scroll_panel.py

@@ -0,0 +1,127 @@
+# Copyright (c) Microsoft. All rights reserved.
+
+"""Scrolling panel for conversation history display."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from textual.widgets import RichLog
+
+if TYPE_CHECKING:
+    from ..app_state import OutputEntry
+
+
+class HarnessScrollPanel(RichLog):
+    """Scrolling panel for displaying conversation history.
+
+    Uses Textual's RichLog widget for efficient append-only rendering with
+    Rich text formatting support. Automatically scrolls to the bottom when
+    new entries are added.
+
+    For streaming text, the panel uses a truncate-and-rewrite strategy: it
+    tracks where streaming began in the RichLog lines list, and on each update
+    truncates back to that point and rewrites the full accumulated text as a
+    single write. This ensures consistent rendering without line-break artifacts
+    between streamed chunks.
+    """
+
+    def __init__(self, **kwargs) -> None:
+        """Initialize the scroll panel.
+
+        Args:
+            **kwargs: Additional arguments passed to RichLog.
+        """
+        super().__init__(
+            **kwargs,
+            auto_scroll=True,  # Automatically scroll to bottom
+            wrap=True,  # Wrap long lines instead of horizontal scroll
+            markup=True,  # Enable Rich markup
+            highlight=True,  # Enable syntax highlighting
+        )
+        self._entries: list[OutputEntry] = []
+        self._is_streaming = False
+        self._streaming_line_start: int = 0
+
+    def append_entry(self, entry: OutputEntry) -> None:
+        """Append a new output entry to the conversation history.
+
+        Args:
+            entry: The output entry to append.
+        """
+        self._entries.append(entry)
+        text = self._format_entry(entry)
+        self.write(text)
+
+    def set_streaming_entry(self, entry: OutputEntry) -> None:
+        """Set or update the current streaming entry.
+
+        On each update, truncates the RichLog back to where streaming
+        started, then rewrites the full streaming text as a single block.
+        This ensures no spurious line breaks between chunks while avoiding
+        a full rewrite of all entries.
+
+        Args:
+            entry: The streaming entry (will be mutated externally).
+        """
+        if not self._is_streaming:
+            # First streaming chunk — record where streaming lines begin
+            self._is_streaming = True
+            self._entries.append(entry)
+            self._streaming_line_start = len(self.lines)
+
+        # Truncate lines back to where streaming started
+        if len(self.lines) > self._streaming_line_start:
+            del self.lines[self._streaming_line_start :]
+            from textual.geometry import Size
+
+            self.virtual_size = Size(self._widest_line_width, len(self.lines))
+
+        # Write full streaming text as a single renderable
+        formatted = self._format_text(entry.text, entry.color)
+        self.write(formatted)
+
+    def end_streaming(self) -> None:
+        """End the current streaming mode."""
+        if self._is_streaming:
+            self._is_streaming = False
+            self._streaming_line_start = 0
+
+    def _rewrite_all(self) -> None:
+        """Clear and rewrite all entries from scratch."""
+        self.clear()
+        for entry in self._entries:
+            self.write(self._format_entry(entry))
+
+    def _format_entry(self, entry: OutputEntry) -> str:
+        """Format an output entry with Rich markup.
+
+        Args:
+            entry: The entry to format.
+
+        Returns:
+            Formatted string with Rich markup for color and styling.
+        """
+        return self._format_text(entry.text, entry.color)
+
+    @staticmethod
+    def _format_text(text: str, color: str | None) -> str:
+        """Format text with optional Rich color markup.
+
+        Args:
+            text: The text to format.
+            color: Optional Rich color name.
+
+        Returns:
+            Formatted string.
+        """
+        if color:
+            return f"[{color}]{text}[/{color}]"
+        return text
+
+    def clear_history(self) -> None:
+        """Clear all conversation history from the panel."""
+        self._entries.clear()
+        self._is_streaming = False
+        self._streaming_line_start = 0
+        self.clear()