feat(app): highlight sidebar resize handles

packages/app/e2e/sidebar-resize-handle.spec.ts

@@ -0,0 +1,27 @@
+import { expect, test, type Page } from "./fixtures";
+
+test.use({ viewport: { width: 1600, height: 900 } });
+
+async function expectBorderHighlight(page: Page, testID: string) {
+  const handle = page.getByTestId(testID);
+  await expect(handle).toBeVisible();
+  await expect(page.getByTestId(`${testID}-highlight`)).toHaveCount(0);
+
+  await handle.hover();
+  await expect(page.getByTestId(`${testID}-highlight`)).toHaveCount(0);
+
+  const highlight = page.getByTestId(`${testID}-highlight`);
+  await expect(highlight).toBeVisible();
+  await expect(highlight).toHaveCSS("width", "1px");
+  await expect(highlight).not.toHaveCSS("background-color", "rgba(0, 0, 0, 0)");
+}
+
+test("both sidebar borders highlight on hover", async ({ page, withWorkspace }) => {
+  const workspace = await withWorkspace({ prefix: "sidebar-resize-handle-" });
+  await workspace.navigateTo();
+
+  await expectBorderHighlight(page, "left-sidebar-resize-handle");
+
+  await page.getByTestId("workspace-explorer-toggle").first().click();
+  await expectBorderHighlight(page, "explorer-sidebar-resize-handle");
+});

packages/app/src/components/explorer-sidebar.tsx

@@ -8,7 +8,7 @@ import {
 } from "react-native";
 import { useSafeAreaInsets } from "react-native-safe-area-context";
 import Animated, { useAnimatedStyle, useSharedValue, runOnJS } from "react-native-reanimated";
-import { Gesture, GestureDetector } from "react-native-gesture-handler";
+import { Gesture } from "react-native-gesture-handler";
 import { StyleSheet, useUnistyles } from "react-native-unistyles";
 import { X } from "lucide-react-native";
 import { useTranslation } from "react-i18next";
@@ -33,7 +33,7 @@ import { useKeyboardShiftStyle } from "@/hooks/use-keyboard-shift-style";
 import { useHasOwnedWindowChromeObstruction, WindowChromeSafeArea } from "@/utils/desktop-window";
 import { TitlebarDragRegion } from "@/components/desktop/titlebar-drag-region";
 import { RetainedPanelActivity } from "@/components/retained-panel";
-import { isWeb } from "@/constants/platform";
+import { SidebarResizeHandle } from "@/components/sidebar-resize-handle";
 import { buildWorkspaceAttachmentScopeKey } from "@/attachments/workspace-attachments-store";
 import { resolveDesktopExplorerWidth } from "@/components/desktop-sidebar-layout";
 
@@ -212,9 +212,11 @@ export function ExplorerSidebar({
   return (
     <Animated.View style={desktopSidebarStyle}>
       <View style={DESKTOP_SIDEBAR_BORDER_STYLE}>
-        <GestureDetector gesture={resizeGesture}>
+        <SidebarResizeHandle
-          <View style={RESIZE_HANDLE_STYLE} />
+          edge="left"
-        </GestureDetector>
+          gesture={resizeGesture}
+          testID="explorer-sidebar-resize-handle"
+        />
 
         <ExplorerSidebarContent
           activeTab={explorerTab}
@@ -460,14 +462,6 @@ const styles = StyleSheet.create((theme) => ({
     borderLeftColor: theme.colors.border,
     backgroundColor: theme.colors.surfaceSidebar,
   },
-  resizeHandle: {
-    position: "absolute",
-    left: -5,
-    top: 0,
-    bottom: 0,
-    width: 10,
-    zIndex: 10,
-  },
   sidebarContent: {
     flex: 1,
     minHeight: 0,
@@ -524,4 +518,3 @@ const styles = StyleSheet.create((theme) => ({
 }));
 
 const DESKTOP_SIDEBAR_BORDER_STYLE = [styles.desktopSidebarBorder, { flex: 1 }];
-const RESIZE_HANDLE_STYLE = [styles.resizeHandle, isWeb && ({ cursor: "col-resize" } as object)];

packages/app/src/components/left-sidebar.tsx

@@ -20,7 +20,7 @@ import {
   View,
   type PressableStateCallbackType,
 } from "react-native";
-import { Gesture, GestureDetector } from "react-native-gesture-handler";
+import { Gesture } from "react-native-gesture-handler";
 import Animated, { runOnJS, useAnimatedStyle, useSharedValue } from "react-native-reanimated";
 import { useSafeAreaInsets } from "react-native-safe-area-context";
 import { StyleSheet, useUnistyles } from "react-native-unistyles";
@@ -30,10 +30,10 @@ import { HostPicker } from "@/components/hosts/host-picker";
 import { SidebarHeaderRow } from "@/components/sidebar/sidebar-header-row";
 import { SidebarDisplayPreferencesMenu } from "@/components/sidebar/sidebar-display-preferences-menu";
 import { SidebarHelpMenu } from "@/components/sidebar/sidebar-help-menu";
+import { SidebarResizeHandle } from "@/components/sidebar-resize-handle";
 import { Shortcut } from "@/components/ui/shortcut";
 import { Tooltip, TooltipContent, TooltipTrigger } from "@/components/ui/tooltip";
 import { HEADER_INNER_HEIGHT, useIsCompactFormFactor } from "@/constants/layout";
-import { isWeb } from "@/constants/platform";
 import { useOpenAddProject } from "@/hooks/use-open-add-project";
 import { useShortcutKeys } from "@/hooks/use-shortcut-keys";
 import { canCreateWorktreeForProjectKind } from "@/projects/host-projects";
@@ -765,11 +765,6 @@ function DesktopSidebar({
     () => [styles.sidebarHeaderGroup, ownsTopLeft && styles.sidebarHeaderGroupBelowChrome],
     [ownsTopLeft],
   );
-  const resizeHandleStyle = useMemo(
-    () => [styles.resizeHandle, isWeb && ({ cursor: "col-resize" } as object)],
-    [],
-  );
-
   return (
     <Animated.View
       accessibilityElementsHidden={!active}
@@ -844,10 +839,11 @@ function DesktopSidebar({
           handleOpenHostSettings={handleOpenHostSettings}
         />
 
-        {/* Resize handle - absolutely positioned over right border */}
+        <SidebarResizeHandle
-        <GestureDetector gesture={resizeGesture}>
+          edge="right"
-          <View style={resizeHandleStyle} />
+          gesture={resizeGesture}
-        </GestureDetector>
+          testID="left-sidebar-resize-handle"
+        />
       </View>
     </Animated.View>
   );
@@ -998,14 +994,6 @@ const styles = StyleSheet.create((theme) => ({
     borderRightColor: theme.colors.border,
     backgroundColor: theme.colors.surfaceSidebar,
   },
-  resizeHandle: {
-    position: "absolute",
-    right: -5,
-    top: 0,
-    bottom: 0,
-    width: 10,
-    zIndex: 10,
-  },
   sidebarDragArea: {
     position: "relative",
   },

packages/app/src/components/sidebar-resize-handle.tsx

@@ -0,0 +1,89 @@
+import { useCallback, useEffect, useRef, useState } from "react";
+import { Pressable, View } from "react-native";
+import { GestureDetector, type GestureType } from "react-native-gesture-handler";
+import { StyleSheet } from "react-native-unistyles";
+import { isWeb } from "@/constants/platform";
+
+interface SidebarResizeHandleProps {
+  edge: "left" | "right";
+  gesture: GestureType;
+  testID: string;
+}
+
+const HIGHLIGHT_DELAY_MS = 100;
+
+const webResizeCursorStyle = isWeb
+  ? ({
+      cursor: "col-resize",
+    } as object)
+  : null;
+
+export function SidebarResizeHandle({ edge, gesture, testID }: SidebarResizeHandleProps) {
+  const [highlighted, setHighlighted] = useState(false);
+  const highlightTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+  const hitAreaStyle = edge === "left" ? LEFT_HIT_AREA_STYLE : RIGHT_HIT_AREA_STYLE;
+
+  const cancelHighlightTimer = useCallback(() => {
+    if (highlightTimerRef.current === null) return;
+    clearTimeout(highlightTimerRef.current);
+    highlightTimerRef.current = null;
+  }, []);
+
+  const handleHoverIn = useCallback(() => {
+    cancelHighlightTimer();
+    highlightTimerRef.current = setTimeout(() => {
+      highlightTimerRef.current = null;
+      setHighlighted(true);
+    }, HIGHLIGHT_DELAY_MS);
+  }, [cancelHighlightTimer]);
+
+  const handleHoverOut = useCallback(() => {
+    cancelHighlightTimer();
+    setHighlighted(false);
+  }, [cancelHighlightTimer]);
+
+  useEffect(() => cancelHighlightTimer, [cancelHighlightTimer]);
+
+  return (
+    <GestureDetector gesture={gesture}>
+      <Pressable
+        testID={testID}
+        style={hitAreaStyle}
+        onHoverIn={handleHoverIn}
+        onHoverOut={handleHoverOut}
+      >
+        {highlighted ? (
+          <View pointerEvents="none" testID={`${testID}-highlight`} style={styles.highlight} />
+        ) : null}
+      </Pressable>
+    </GestureDetector>
+  );
+}
+
+const styles = StyleSheet.create((theme) => ({
+  hitArea: {
+    position: "absolute",
+    top: 0,
+    bottom: 0,
+    width: 10,
+    zIndex: 10,
+  },
+  leftEdge: {
+    left: -5,
+  },
+  rightEdge: {
+    right: -5,
+  },
+  highlight: {
+    position: "absolute",
+    top: 0,
+    bottom: 0,
+    left: 5,
+    width: 1,
+    backgroundColor: theme.colors.foreground,
+    opacity: 0.25,
+  },
+}));
+
+const LEFT_HIT_AREA_STYLE = [styles.hitArea, styles.leftEdge, webResizeCursorStyle];
+const RIGHT_HIT_AREA_STYLE = [styles.hitArea, styles.rightEdge, webResizeCursorStyle];