add auto_scroll

reflex/components/core/__init__.py

@@ -48,6 +48,7 @@ _SUBMOD_ATTRS: dict[str, list[str]] = {
         "get_upload_url",
         "selected_files",
     ],
+    "auto_scroll": ["auto_scroll"],
 }
 
 __getattr__, __dir__, __all__ = lazy_loader.attach(

reflex/components/core/__init__.pyi

@@ -4,6 +4,7 @@
 # ------------------------------------------------------
 
 from . import layout as layout
+from .auto_scroll import auto_scroll as auto_scroll
 from .banner import ConnectionBanner as ConnectionBanner
 from .banner import ConnectionModal as ConnectionModal
 from .banner import ConnectionPulser as ConnectionPulser

reflex/components/core/auto_scroll.py

@@ -0,0 +1,110 @@
+"""A component that automatically scrolls to the bottom when new content is added."""
+
+from __future__ import annotations
+
+from reflex.components.el.elements.typography import Div
+from reflex.constants.compiler import MemoizationDisposition, MemoizationMode
+from reflex.utils.imports import ImportDict
+from reflex.vars.base import Var
+
+
+class AutoScroll(Div):
+    """A div that automatically scrolls to the bottom when new content is added."""
+
+    _memoization_mode = MemoizationMode(disposition=MemoizationDisposition.ALWAYS)
+
+    @classmethod
+    def create(cls, *children, **props):
+        """Create an AutoScroll component.
+
+        Args:
+            *children: The children of the component.
+            **props: The props of the component.
+
+        Returns:
+            An AutoScroll component.
+        """
+        props.setdefault("overflow", "auto")
+        custom_attrs = props.pop("custom_attrs", {})
+        custom_attrs["ref"] = Var("containerRef")
+        return super().create(*children, **props, custom_attrs=custom_attrs)
+
+    def add_imports(self) -> ImportDict | list[ImportDict]:
+        """Add imports required for the component.
+
+        Returns:
+            The imports required for the component.
+        """
+        return {"react": ["useEffect", "useRef"]}
+
+    def add_hooks(self) -> list[str | Var]:
+        """Add hooks required for the component.
+
+        Returns:
+            The hooks required for the component.
+        """
+        return [
+            "const containerRef = useRef(null);",
+            "const wasNearBottom = useRef(false);",
+            "const hadScrollbar = useRef(false);",
+            """
+const checkIfNearBottom = () => {
+    if (!containerRef.current) return;
+
+    const container = containerRef.current;
+    const nearBottomThreshold = 50; // pixels from bottom to trigger auto-scroll
+
+    const distanceFromBottom = container.scrollHeight - container.scrollTop - container.clientHeight;
+
+    wasNearBottom.current = distanceFromBottom <= nearBottomThreshold;
+
+    // Track if container had a scrollbar
+    hadScrollbar.current = container.scrollHeight > container.clientHeight;
+};
+""",
+            """
+const scrollToBottomIfNeeded = () => {
+    if (!containerRef.current) return;
+
+    const container = containerRef.current;
+    const hasScrollbarNow = container.scrollHeight > container.clientHeight;
+
+    // Scroll if:
+    // 1. User was near bottom, OR
+    // 2. Container didn't have scrollbar before but does now
+    if (wasNearBottom.current || (!hadScrollbar.current && hasScrollbarNow)) {
+      container.scrollTop = container.scrollHeight;
+    }
+
+    // Update scrollbar state for next check
+    hadScrollbar.current = hasScrollbarNow;};
+""",
+            """
+  useEffect(() => {
+    const container = containerRef.current;
+    if (!container) return;
+
+    // Create ResizeObserver to detect height changes
+    const resizeObserver = new ResizeObserver(() => {
+      scrollToBottomIfNeeded();
+    });
+
+    // Track scroll position before height changes
+    container.addEventListener('scroll', checkIfNearBottom);
+
+    // Initial check
+    checkIfNearBottom();
+
+    // Observe container for size changes
+    resizeObserver.observe(container);
+
+    return () => {
+      container.removeEventListener('scroll', checkIfNearBottom);
+      resizeObserver.disconnect();
+    };
+  });
+""",
+        ]
+
+
+auto_scroll = AutoScroll.create