From 24f64ae1a8d4aeae9d79f608b2d33e8b22c9810d Mon Sep 17 00:00:00 2001
From: Paul Chote <pchote@users.noreply.github.com>
Date: Sun, 25 Jul 2021 18:11:25 +0100
Subject: [PATCH] Fix an edge case where the wrong sheet may be mapped to a
 depth sprite.

---
 OpenRA.Game/Graphics/SpriteRenderer.cs | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/OpenRA.Game/Graphics/SpriteRenderer.cs b/OpenRA.Game/Graphics/SpriteRenderer.cs
index 90146b0990..b07f70da5e 100644
--- a/OpenRA.Game/Graphics/SpriteRenderer.cs
+++ b/OpenRA.Game/Graphics/SpriteRenderer.cs
@@ -82,28 +82,32 @@ namespace OpenRA.Graphics
 				for (; secondarySheetIndex < ns; secondarySheetIndex++)
 					if (sheets[secondarySheetIndex] == secondarySheet)
 						break;
+
+				// If neither sheet has been mapped both index values will be set to ns.
+				// This is fine if they both reference the same texture, but if they don't
+				// we must increment the secondary sheet index to the next free sampler.
+				if (secondarySheetIndex == sheetIndex && secondarySheet != sheet)
+					secondarySheetIndex++;
 			}
 
 			// Make sure that we have enough free samplers to map both if needed, otherwise flush
-			var needSamplers = (sheetIndex == ns ? 1 : 0) + (secondarySheetIndex == ns ? 1 : 0);
-			if (ns + needSamplers >= sheets.Length)
+			if (Math.Max(sheetIndex, secondarySheetIndex) >= sheets.Length)
 			{
 				Flush();
 				sheetIndex = 0;
-				if (ss != null)
-					secondarySheetIndex = 1;
+				secondarySheetIndex = ss != null && ss.SecondarySheet != sheet ? 1 : 0;
 			}
 
 			if (sheetIndex >= ns)
 			{
 				sheets[sheetIndex] = sheet;
-				ns += 1;
+				ns++;
 			}
 
 			if (secondarySheetIndex >= ns && ss != null)
 			{
 				sheets[secondarySheetIndex] = ss.SecondarySheet;
-				ns += 1;
+				ns++;
 			}
 
 			return new int2(sheetIndex, secondarySheetIndex);