fix(chat): clamp text selection menu Y position to the viewport (#2257)

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/ui/src/components/chat/message/TextSelectionMenu.tsx

@@ -16,6 +16,12 @@ import { useEffectiveDirectory } from '@/hooks/useEffectiveDirectory';
 import { isVSCodeRuntime } from '@/lib/desktop';
 import { useI18n } from '@/lib/i18n';
 import { rangeToMarkdown, trimSelectionValue, wrapMarkdownSelectionForChat } from './selectionMarkdown';
+import {
+  DESKTOP_MENU_FALLBACK_HEIGHT_PX,
+  DESKTOP_MENU_FALLBACK_WIDTH_PX,
+  getDesktopClampedX,
+  getDesktopClampedY,
+} from './selectionMenuPosition';
 import { focusChatInput } from '@/components/chat/composer/editor/dom';
 
 interface TextSelectionMenuProps {
@@ -44,8 +50,6 @@ const appendDistilledInsightToNotes = (existingNotes: string, insight: string):
   return trimmedNotes ? `${trimmedNotes}\n${trimmedInsight}` : trimmedInsight;
 };
 
-const DESKTOP_MENU_SIDE_MARGIN_PX = 8;
-const DESKTOP_MENU_FALLBACK_WIDTH_PX = 280;
 export const TextSelectionMenu: React.FC<TextSelectionMenuProps> = ({ containerRef }) => {
   const { t } = useI18n();
   const [position, setPosition] = React.useState<MenuPosition>({ x: 0, y: 0, show: false });
@@ -56,6 +60,7 @@ export const TextSelectionMenu: React.FC<TextSelectionMenuProps> = ({ containerR
   const [isAddingToNotes, setIsAddingToNotes] = React.useState(false);
   const menuRef = React.useRef<HTMLDivElement>(null);
   const menuWidthRef = React.useRef(DESKTOP_MENU_FALLBACK_WIDTH_PX);
+  const menuHeightRef = React.useRef(DESKTOP_MENU_FALLBACK_HEIGHT_PX);
   const pendingSelectionRef = React.useRef<SelectionPayload | null>(null);
   const openRafRef = React.useRef<number | null>(null);
   const mouseUpTimeoutRef = React.useRef<number | null>(null);
@@ -105,22 +110,20 @@ export const TextSelectionMenu: React.FC<TextSelectionMenuProps> = ({ containerR
     isMenuVisibleRef.current = false;
   }, []);
 
-  const getDesktopClampedX = React.useCallback((anchorX: number) => {
+  const clampDesktopX = React.useCallback((anchorX: number) => {
     if (typeof window === 'undefined') {
       return anchorX;
     }
 
-    const viewportWidth = window.innerWidth;
+    return getDesktopClampedX(anchorX, window.innerWidth, menuWidthRef.current);
-    const menuWidth = menuWidthRef.current;
+  }, []);
-    const halfWidth = menuWidth / 2;
-    const minX = DESKTOP_MENU_SIDE_MARGIN_PX + halfWidth;
-    const maxX = viewportWidth - DESKTOP_MENU_SIDE_MARGIN_PX - halfWidth;
 
-    if (minX > maxX) {
+  const clampDesktopY = React.useCallback((anchorY: number) => {
-      return viewportWidth / 2;
+    if (typeof window === 'undefined') {
+      return anchorY;
     }
 
-    return Math.min(Math.max(anchorX, minX), maxX);
+    return getDesktopClampedY(anchorY, window.innerHeight, menuHeightRef.current);
   }, []);
 
   const showMenu = React.useCallback(() => {
@@ -132,8 +135,10 @@ export const TextSelectionMenu: React.FC<TextSelectionMenuProps> = ({ containerR
     // Position menu above the selection
     const menuX = isMobile
       ? rect.left + rect.width / 2
-      : getDesktopClampedX(rect.left + rect.width / 2);
+      : clampDesktopX(rect.left + rect.width / 2);
-    const menuY = rect.top - 10;
+    const menuY = isMobile
+      ? rect.top - 10
+      : clampDesktopY(rect.top - 10);
 
     setSelectedText(plainText);
     setSelectedTextMarkdown(markdownText);
@@ -154,7 +159,7 @@ export const TextSelectionMenu: React.FC<TextSelectionMenuProps> = ({ containerR
         openRafRef.current = null;
       });
     }
-  }, [getDesktopClampedX, isMobile, position.show]);
+  }, [clampDesktopX, clampDesktopY, isMobile, position.show]);
 
   React.useLayoutEffect(() => {
     if (!position.show || isMobile || !menuRef.current) {
@@ -162,16 +167,25 @@ export const TextSelectionMenu: React.FC<TextSelectionMenuProps> = ({ containerR
     }
 
     const measuredWidth = menuRef.current.offsetWidth;
-    if (!Number.isFinite(measuredWidth) || measuredWidth <= 0 || measuredWidth === menuWidthRef.current) {
+    const measuredHeight = menuRef.current.offsetHeight;
+    const widthChanged = Number.isFinite(measuredWidth) && measuredWidth > 0 && measuredWidth !== menuWidthRef.current;
+    const heightChanged = Number.isFinite(measuredHeight) && measuredHeight > 0 && measuredHeight !== menuHeightRef.current;
+    if (!widthChanged && !heightChanged) {
       return;
     }
 
-    menuWidthRef.current = measuredWidth;
+    if (widthChanged) {
+      menuWidthRef.current = measuredWidth;
+    }
+    if (heightChanged) {
+      menuHeightRef.current = measuredHeight;
+    }
     setPosition((prev) => ({
       ...prev,
-      x: getDesktopClampedX(prev.x),
+      x: clampDesktopX(prev.x),
+      y: clampDesktopY(prev.y),
     }));
-  }, [getDesktopClampedX, isMobile, position.show]);
+  }, [clampDesktopX, clampDesktopY, isMobile, position.show]);
 
   React.useEffect(() => {
     if (!position.show || isMobile) {
@@ -181,7 +195,8 @@ export const TextSelectionMenu: React.FC<TextSelectionMenuProps> = ({ containerR
     const handleViewportResize = () => {
       setPosition((prev) => ({
         ...prev,
-        x: getDesktopClampedX(prev.x),
+        x: clampDesktopX(prev.x),
+        y: clampDesktopY(prev.y),
       }));
     };
 
@@ -189,7 +204,7 @@ export const TextSelectionMenu: React.FC<TextSelectionMenuProps> = ({ containerR
     return () => {
       window.removeEventListener('resize', handleViewportResize);
     };
-  }, [getDesktopClampedX, isMobile, position.show]);
+  }, [clampDesktopX, clampDesktopY, isMobile, position.show]);
 
   const handleSelectionChange = React.useCallback(() => {
     const selection = window.getSelection();

packages/ui/src/components/chat/message/__tests__/selectionMenuPosition.test.ts

@@ -0,0 +1,67 @@
+import { describe, expect, test } from 'bun:test';
+import {
+  DESKTOP_MENU_FALLBACK_HEIGHT_PX,
+  DESKTOP_MENU_FALLBACK_WIDTH_PX,
+  DESKTOP_MENU_SIDE_MARGIN_PX,
+  getDesktopClampedX,
+  getDesktopClampedY,
+} from '../selectionMenuPosition';
+
+const VIEWPORT_WIDTH = 1024;
+const VIEWPORT_HEIGHT = 768;
+const MENU_WIDTH = DESKTOP_MENU_FALLBACK_WIDTH_PX;
+const MENU_HEIGHT = DESKTOP_MENU_FALLBACK_HEIGHT_PX;
+
+// Regression coverage for issue #2257: selecting a long assistant response
+// across a scroll boundary makes range.getBoundingClientRect().top negative,
+// and the unclamped anchor (rect.top - 10) placed the menu above the viewport.
+describe('getDesktopClampedY (issue #2257)', () => {
+  test('keeps the menu on screen when the selection starts above the viewport', () => {
+    const clamped = getDesktopClampedY(-210, VIEWPORT_HEIGHT, MENU_HEIGHT);
+    expect(clamped).toBe(DESKTOP_MENU_SIDE_MARGIN_PX + MENU_HEIGHT);
+  });
+
+  test('keeps the menu fully visible for selections near the top edge', () => {
+    // The menu renders with translate(-50%, -100%), so it extends upward from
+    // the anchor; anchors smaller than margin + menu height clip the menu.
+    const clamped = getDesktopClampedY(5, VIEWPORT_HEIGHT, MENU_HEIGHT);
+    expect(clamped).toBe(DESKTOP_MENU_SIDE_MARGIN_PX + MENU_HEIGHT);
+  });
+
+  test('clamps anchors below the viewport back to the bottom margin', () => {
+    const clamped = getDesktopClampedY(VIEWPORT_HEIGHT + 500, VIEWPORT_HEIGHT, MENU_HEIGHT);
+    expect(clamped).toBe(VIEWPORT_HEIGHT - DESKTOP_MENU_SIDE_MARGIN_PX);
+  });
+
+  test('leaves in-viewport anchors unchanged', () => {
+    expect(getDesktopClampedY(300, VIEWPORT_HEIGHT, MENU_HEIGHT)).toBe(300);
+    expect(getDesktopClampedY(MENU_HEIGHT + DESKTOP_MENU_SIDE_MARGIN_PX, VIEWPORT_HEIGHT, MENU_HEIGHT))
+      .toBe(MENU_HEIGHT + DESKTOP_MENU_SIDE_MARGIN_PX);
+  });
+
+  test('falls back to the viewport middle when the viewport is shorter than the menu', () => {
+    const tinyViewportHeight = MENU_HEIGHT;
+    expect(getDesktopClampedY(10, tinyViewportHeight, MENU_HEIGHT)).toBe(tinyViewportHeight / 2);
+  });
+});
+
+describe('getDesktopClampedX', () => {
+  test('clamps anchors past the left edge to the left margin', () => {
+    const clamped = getDesktopClampedX(-500, VIEWPORT_WIDTH, MENU_WIDTH);
+    expect(clamped).toBe(DESKTOP_MENU_SIDE_MARGIN_PX + MENU_WIDTH / 2);
+  });
+
+  test('clamps anchors past the right edge to the right margin', () => {
+    const clamped = getDesktopClampedX(VIEWPORT_WIDTH + 500, VIEWPORT_WIDTH, MENU_WIDTH);
+    expect(clamped).toBe(VIEWPORT_WIDTH - DESKTOP_MENU_SIDE_MARGIN_PX - MENU_WIDTH / 2);
+  });
+
+  test('leaves in-viewport anchors unchanged', () => {
+    expect(getDesktopClampedX(VIEWPORT_WIDTH / 2, VIEWPORT_WIDTH, MENU_WIDTH)).toBe(VIEWPORT_WIDTH / 2);
+  });
+
+  test('falls back to the viewport middle when the viewport is narrower than the menu', () => {
+    const tinyViewportWidth = MENU_WIDTH / 2;
+    expect(getDesktopClampedX(10, tinyViewportWidth, MENU_WIDTH)).toBe(tinyViewportWidth / 2);
+  });
+});

packages/ui/src/components/chat/message/selectionMenuPosition.ts

@@ -0,0 +1,29 @@
+export const DESKTOP_MENU_SIDE_MARGIN_PX = 8;
+export const DESKTOP_MENU_FALLBACK_WIDTH_PX = 280;
+export const DESKTOP_MENU_FALLBACK_HEIGHT_PX = 38;
+
+export const getDesktopClampedX = (anchorX: number, viewportWidth: number, menuWidth: number): number => {
+  const halfWidth = menuWidth / 2;
+  const minX = DESKTOP_MENU_SIDE_MARGIN_PX + halfWidth;
+  const maxX = viewportWidth - DESKTOP_MENU_SIDE_MARGIN_PX - halfWidth;
+
+  if (minX > maxX) {
+    return viewportWidth / 2;
+  }
+
+  return Math.min(Math.max(anchorX, minX), maxX);
+};
+
+// The desktop menu renders with `transform: translate(-50%, -100%)`, so the
+// anchor Y marks the menu's bottom edge and the menu extends `menuHeight`
+// upward from it. The minimum keeps the whole menu below the top margin.
+export const getDesktopClampedY = (anchorY: number, viewportHeight: number, menuHeight: number): number => {
+  const minY = DESKTOP_MENU_SIDE_MARGIN_PX + menuHeight;
+  const maxY = viewportHeight - DESKTOP_MENU_SIDE_MARGIN_PX;
+
+  if (minY > maxY) {
+    return viewportHeight / 2;
+  }
+
+  return Math.min(Math.max(anchorY, minY), maxY);
+};