From 1ae58f676b7f4757070f86cc2c44abe1cdcc875f Mon Sep 17 00:00:00 2001
From: edde746 <86283021+edde746@users.noreply.github.com>
Date: Sat, 25 Jul 2026 17:37:40 +0200
Subject: [PATCH] fix(windows): recover failed display handoffs

---
 windows/runner/mpv/display_mode_manager.cpp   | 10 +++-
 .../runner/mpv/display_mode_manager_test.cpp  | 59 +++++++++++++++++++
 2 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/windows/runner/mpv/display_mode_manager.cpp b/windows/runner/mpv/display_mode_manager.cpp
index 31f2b44b..8de1c57c 100644
--- a/windows/runner/mpv/display_mode_manager.cpp
+++ b/windows/runner/mpv/display_mode_manager.cpp
@@ -1142,13 +1142,17 @@ bool RecoverRecord(DisplayRecoveryBackend& backend, bool mode_is_live, bool hdr_
     const bool restored =
         backend.IsDevicePresent(mode_device_name) && backend.RestoreMode(mode_device_name, width, height, refresh_rate);
     if (mode_handoff_pending) {
-      // Restore the replacement first and the pre-handoff original last. Both
-      // remain marked until both idempotent restores and cleanup succeed.
+      // Restore the replacement first and the pre-handoff original last. If
+      // either restore or cleanup fails, collapse authority back to the prior
+      // slot so topology retries do not keep forcing the surviving replacement.
       const bool previous_restored =
           backend.IsDevicePresent(previous_mode_device_name) &&
           backend.RestoreMode(previous_mode_device_name, previous_width, previous_height, previous_refresh_rate);
       if (!restored || !previous_restored ||
           !CompleteRecoveryOperation(backend, kRegModeChanged, kRegModeTakeoverEligible, kRegModeHandoffPending)) {
+        RollbackRecoveryHandoff(
+            backend, kRegModeTakeoverEligible, kRegModeRecoverySlot, kRegModePreviousRecoverySlot,
+            kRegModeHandoffPending);
         completed = false;
       }
     } else if (
@@ -1170,6 +1174,8 @@ bool RecoverRecord(DisplayRecoveryBackend& backend, bool mode_is_live, bool hdr_
                                      backend.RestoreHDR(previous_hdr_device_name, previous_original_hdr != 0);
       if (!restored || !previous_restored ||
           !CompleteRecoveryOperation(backend, kRegHDRChanged, kRegHDRTakeoverEligible, kRegHDRHandoffPending)) {
+        RollbackRecoveryHandoff(
+            backend, kRegHDRTakeoverEligible, kRegHDRRecoverySlot, kRegHDRPreviousRecoverySlot, kRegHDRHandoffPending);
         completed = false;
       }
     } else if (
diff --git a/windows/runner/mpv/display_mode_manager_test.cpp b/windows/runner/mpv/display_mode_manager_test.cpp
index 8c565c81..4ff4529d 100644
--- a/windows/runner/mpv/display_mode_manager_test.cpp
+++ b/windows/runner/mpv/display_mode_manager_test.cpp
@@ -699,6 +699,64 @@ void TestCrashDuringTakeoverHandoffRecoversBothOriginals() {
       "HDR handoff recovery must restore replacement then prior and preserve its sibling");
 }
 
+void TestFailedHandoffRecoveryRollsBackForTakeover() {
+  FakeRecoveryBackend mode;
+  mode.SeedBoth();
+  mode.dwords[kModeTakeoverEligible] = 1;
+  mode.dwords[kHDRTakeoverEligible] = 1;
+  Check(
+      DisplayModeManager::PrepareModeRecovery(mode, kReplacementModeDevice, 2560, 1440, 120),
+      "mode takeover preparation must reach its pre-apply handoff");
+  mode.expected_mode_restores = {{kReplacementModeDevice, 2560, 1440, 120}};
+  mode.device_present[kModeDevice] = false;
+  Check(
+      !DisplayModeManager::RecoverIfNeededForTesting(mode, false, true),
+      "a missing prior mode display must leave handoff recovery incomplete");
+  Check(
+      mode.mode_restore_attempts == 1 && mode.dwords[kModeChanged] == 1 && mode.dwords[kModeRecoverySlot] == 0 &&
+          mode.dwords[kModeTakeoverEligible] == 1 && mode.dwords[kModeHandoffPending] == 0,
+      "failed mode handoff recovery must roll authority back to a takeover-eligible prior slot");
+
+  mode.events.clear();
+  Check(
+      !DisplayModeManager::RecoverIfNeededForTesting(mode, false, true),
+      "the absent prior mode display must remain retryable after handoff rollback");
+  Check(
+      EventIndex(mode.events, L"restore:mode") == mode.events.size(),
+      "topology retries must not keep restoring the surviving replacement display");
+  Check(
+      ApplyModeAfterPreparing(mode, kReplacementModeDevice, 2560, 1440, 120),
+      "a later mode request must be able to consume the rolled-back handoff");
+
+  FakeRecoveryBackend hdr;
+  hdr.SeedBoth();
+  hdr.dwords[kModeTakeoverEligible] = 1;
+  hdr.dwords[kHDRTakeoverEligible] = 1;
+  Check(
+      DisplayModeManager::PrepareHDRRecovery(hdr, kReplacementHDRDevice, true),
+      "HDR takeover preparation must reach its pre-apply handoff");
+  hdr.expected_hdr_restores = {{kReplacementHDRDevice, true}};
+  hdr.device_present[kHDRDevice] = false;
+  Check(
+      !DisplayModeManager::RecoverIfNeededForTesting(hdr, true, false),
+      "a missing prior HDR display must leave handoff recovery incomplete");
+  Check(
+      hdr.hdr_restore_attempts == 1 && hdr.dwords[kHDRChanged] == 1 && hdr.dwords[kHDRRecoverySlot] == 0 &&
+          hdr.dwords[kHDRTakeoverEligible] == 1 && hdr.dwords[kHDRHandoffPending] == 0,
+      "failed HDR handoff recovery must roll authority back to a takeover-eligible prior slot");
+
+  hdr.events.clear();
+  Check(
+      !DisplayModeManager::RecoverIfNeededForTesting(hdr, true, false),
+      "the absent prior HDR display must remain retryable after handoff rollback");
+  Check(
+      EventIndex(hdr.events, L"restore:hdr") == hdr.events.size(),
+      "topology retries must not keep restoring the surviving replacement HDR state");
+  Check(
+      ApplyHDRAfterPreparing(hdr, kReplacementHDRDevice, true),
+      "a later HDR request must be able to consume the rolled-back handoff");
+}
+
 void TestHDRReconnectRecoversBeforeTakeover() {
   FakeRecoveryBackend backend;
   backend.SeedBoth();
@@ -1051,6 +1109,7 @@ int main() {
   mpv::TestBadModeHDRRestoreAllowsSameKindTakeover();
   mpv::TestFailedOSApplyRollsBackTakeover();
   mpv::TestCrashDuringTakeoverHandoffRecoversBothOriginals();
+  mpv::TestFailedHandoffRecoveryRollsBackForTakeover();
   mpv::TestHDRReconnectRecoversBeforeTakeover();
   mpv::TestEligibleSameOriginalReuseResetsDisposition();
   mpv::TestRepeatedModeTakeoverStagesOnlyTheInactiveSlot();