Fix window position restore on relaunch (#2129)

* test: cover accessible window frame restore

* fix: preserve accessible window frame on relaunch

Author: austinywang

Sources/AppDelegate.swift

@@ -3066,6 +3066,15 @@ final class AppDelegate: NSObject, NSApplicationDelegate, UNUserNotificationCent
         minHeight: CGFloat
     ) -> CGRect {
         if targetDisplay.visibleFrame.intersects(frame) {
+            // Preserve the user's exact frame when enough of the top of the window
+            // remains reachable on-screen; only clamp when the saved frame would
+            // reopen with an inaccessible titlebar/top strip.
+            if shouldPreserveAccessibleFrame(
+                frame: frame,
+                targetDisplay: targetDisplay
+            ) {
+                return frame
+            }
             return clampFrame(
                 frame,
                 within: targetDisplay.visibleFrame,
@@ -3092,6 +3101,38 @@ final class AppDelegate: NSObject, NSApplicationDelegate, UNUserNotificationCent
         )
     }
 
+    private nonisolated static func shouldPreserveAccessibleFrame(
+        frame: CGRect,
+        targetDisplay: SessionDisplayGeometry,
+        minimumVisibleTopStripWidth: CGFloat = 120,
+        topStripHeight: CGFloat = 64,
+        minimumVisibleTopStripHeight: CGFloat = 24
+    ) -> Bool {
+        let standardizedFrame = frame.standardized
+        guard standardizedFrame.width.isFinite,
+              standardizedFrame.height.isFinite,
+              standardizedFrame.width > 0,
+              standardizedFrame.height > 0,
+              standardizedFrame.intersects(targetDisplay.frame) else {
+            return false
+        }
+
+        let stripHeight = min(topStripHeight, standardizedFrame.height)
+        let topStrip = CGRect(
+            x: standardizedFrame.minX,
+            y: standardizedFrame.maxY - stripHeight,
+            width: standardizedFrame.width,
+            height: stripHeight
+        )
+        let visibleTopStrip = topStrip.intersection(targetDisplay.visibleFrame)
+        guard !visibleTopStrip.isNull else { return false }
+
+        let requiredWidth = min(minimumVisibleTopStripWidth, standardizedFrame.width)
+        let requiredHeight = min(minimumVisibleTopStripHeight, stripHeight)
+        return visibleTopStrip.width >= requiredWidth
+            && visibleTopStrip.height >= requiredHeight
+    }
+
     private nonisolated static func display(
         for snapshot: SessionDisplaySnapshot?,
         in displays: [SessionDisplayGeometry]

cmuxTests/SessionPersistenceTests.swift

@@ -693,6 +693,34 @@ final class SessionPersistenceTests: XCTestCase {
         XCTAssertEqual(restored.height, 1_410, accuracy: 0.001)
     }
 
+    func testResolvedWindowFramePreservesExactGeometryWhenDisplayChangesButWindowRemainsAccessible() {
+        let savedFrame = SessionRectSnapshot(x: 1_100, y: -20, width: 1_280, height: 1_000)
+        let savedDisplay = SessionDisplaySnapshot(
+            displayID: 2,
+            frame: SessionRectSnapshot(x: 0, y: 0, width: 2_560, height: 1_440),
+            visibleFrame: SessionRectSnapshot(x: 0, y: 0, width: 2_560, height: 1_410)
+        )
+        let adjustedDisplay = AppDelegate.SessionDisplayGeometry(
+            displayID: 2,
+            frame: CGRect(x: 0, y: 0, width: 2_560, height: 1_440),
+            visibleFrame: CGRect(x: 0, y: 40, width: 2_560, height: 1_360)
+        )
+
+        let restored = AppDelegate.resolvedWindowFrame(
+            from: savedFrame,
+            display: savedDisplay,
+            availableDisplays: [adjustedDisplay],
+            fallbackDisplay: adjustedDisplay
+        )
+
+        XCTAssertNotNil(restored)
+        guard let restored else { return }
+        XCTAssertEqual(restored.minX, 1_100, accuracy: 0.001)
+        XCTAssertEqual(restored.minY, -20, accuracy: 0.001)
+        XCTAssertEqual(restored.width, 1_280, accuracy: 0.001)
+        XCTAssertEqual(restored.height, 1_000, accuracy: 0.001)
+    }
+
     func testResolvedWindowFrameClampsWhenDisplayGeometryChangesEvenWithSameDisplayID() {
         let savedFrame = SessionRectSnapshot(x: 1_303, y: -90, width: 1_280, height: 1_410)
         let savedDisplay = SessionDisplaySnapshot(