From 9e6b0a42ec4795eb3878e47946370d900aa8d453 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Tue, 27 Oct 2020 16:28:50 +0900
Subject: [PATCH] Allow FrameStabilityContainer to handle waiting-for-data
 state better (and pause outwards)

---
 .../Replays/FramedReplayInputHandler.cs       | 28 +++++++++++++++++--
 .../Rulesets/UI/FrameStabilityContainer.cs    |  3 +-
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/osu.Game/Rulesets/Replays/FramedReplayInputHandler.cs b/osu.Game/Rulesets/Replays/FramedReplayInputHandler.cs
index 62b24f6b55..ddf85b7300 100644
--- a/osu.Game/Rulesets/Replays/FramedReplayInputHandler.cs
+++ b/osu.Game/Rulesets/Replays/FramedReplayInputHandler.cs
@@ -124,20 +124,42 @@ namespace osu.Game.Rulesets.Replays
 
             if (HasFrames)
             {
+                var next = NextFrame;
+
                 // check if the next frame is valid for the current playback direction.
                 // validity is if the next frame is equal or "earlier"
-                var compare = time.CompareTo(NextFrame?.Time);
+                var compare = time.CompareTo(next?.Time);
 
-                if (compare == 0 || compare == currentDirection)
+                if (next != null && (compare == 0 || compare == currentDirection))
                 {
                     if (advanceFrame())
                         return CurrentTime = CurrentFrame.Time;
                 }
                 else
                 {
-                    // if we didn't change frames, we need to ensure we are allowed to run frames in between, else return null.
+                    // this is the case where the frame can't be advanced (in the replay).
+                    // even so, we may be able to move the clock forward due to being at the end of the replay or
+                    // in a section where replay accuracy doesn't matter.
+
+                    // important section is always respected to block the update loop.
                     if (inImportantSection)
                         return null;
+
+                    if (next == null)
+                    {
+                        // in the case we have no more frames and haven't received the full replay, block.
+                        if (!replay.HasReceivedAllFrames)
+                            return null;
+
+                        // else allow play to end.
+                    }
+                    else if (next.Time.CompareTo(time) != currentDirection)
+                    {
+                        // in the case we have more frames, block if the next frame's time is less than the current time.
+                        return null;
+                    }
+
+                    // if we didn't change frames, we need to ensure we are allowed to run frames in between, else return null.
                 }
             }
 
diff --git a/osu.Game/Rulesets/UI/FrameStabilityContainer.cs b/osu.Game/Rulesets/UI/FrameStabilityContainer.cs
index 28b7975a89..fb6c7d4c17 100644
--- a/osu.Game/Rulesets/UI/FrameStabilityContainer.cs
+++ b/osu.Game/Rulesets/UI/FrameStabilityContainer.cs
@@ -96,6 +96,7 @@ namespace osu.Game.Rulesets.UI
         public override bool UpdateSubTree()
         {
             requireMoreUpdateLoops = true;
+
             validState = !frameStableClock.IsPaused.Value;
 
             int loops = 0;
@@ -191,7 +192,7 @@ namespace osu.Game.Rulesets.UI
             finally
             {
                 if (newProposedTime != manualClock.CurrentTime)
-                    direction = newProposedTime > manualClock.CurrentTime ? 1 : -1;
+                    direction = newProposedTime >= manualClock.CurrentTime ? 1 : -1;
 
                 manualClock.CurrentTime = newProposedTime;
                 manualClock.Rate = Math.Abs(parentGameplayClock.Rate) * direction;