infobox manager: keep infoboxes in order of insertion

Collections.binarySearch() does not guarantee which element is found if
there are multiple that compare equal, leaving the order of infoboxes
not necessarily in insertion order. This was an unintended side effect of
ba9ffb1d60 and
406c2bc7db.

runelite-client/src/main/java/net/runelite/client/ui/overlay/infobox/InfoBoxManager.java

@@ -29,6 +29,7 @@ import com.google.common.collect.ComparisonChain;
 import java.awt.Graphics;
 import java.awt.image.BufferedImage;
 import java.util.Collections;
+import java.util.Comparator;
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.function.Predicate;
@@ -71,12 +72,12 @@ public class InfoBoxManager
 
 		synchronized (this)
 		{
-			int idx = Collections.binarySearch(infoBoxes, infoBox, (b1, b2) -> ComparisonChain
+			int idx = findInsertionIndex(infoBoxes, infoBox, (b1, b2) -> ComparisonChain
 				.start()
 				.compare(b1.getPriority(), b2.getPriority())
 				.compare(b1.getPlugin().getName(), b2.getPlugin().getName())
 				.result());
-			infoBoxes.add(idx < 0 ? -idx - 1 : idx, infoBox);
+			infoBoxes.add(idx, infoBox);
 		}
 
 		BufferedImage image = infoBox.getImage();
@@ -150,4 +151,38 @@ public class InfoBoxManager
 
 		infoBox.setScaledImage(resultImage);
 	}
+
+	/**
+	 * Find insertion point for the given key into the given sorted list. If key already exists in the list,
+	 * return the index after the last occurrence.
+	 * @param list
+	 * @param key
+	 * @param c
+	 * @param <T>
+	 * @return
+	 */
+	private static <T> int findInsertionIndex(List<? extends T> list, T key, Comparator<? super T> c)
+	{
+		int idx = Collections.binarySearch(list, key, c);
+
+		if (idx < 0)
+		{
+			// key isn't found in the list
+			return -idx - 1;
+		}
+
+		// list(idx) is equal to key, so it is not necessary to recheck it
+		for (int i = idx + 1; i < list.size(); ++i)
+		{
+			T cur = list.get(i);
+			int cmp = c.compare(cur, key);
+			if (cmp > 0)
+			{
+				// this is the first element which is greater
+				return i;
+			}
+		}
+
+		return list.size();
+	}
 }

runelite-client/src/test/java/net/runelite/client/ui/overlay/infobox/InfoBoxManagerTest.java

@@ -114,5 +114,8 @@ public class InfoBoxManagerTest
 		infoBoxManager.addInfoBox(new TestInfobox(InfoBoxPriority.MED, "three"));
 
 		assertEquals(3, infoBoxManager.getInfoBoxes().size());
+		assertEquals("one", infoBoxManager.getInfoBoxes().get(0).getText());
+		assertEquals("two", infoBoxManager.getInfoBoxes().get(1).getText());
+		assertEquals("three", infoBoxManager.getInfoBoxes().get(2).getText());
 	}
 }