Address u-pr review feedback for UUM-141423

- Collapse the composite-part scan into a single loop. The original two-pass
  scan computed lastPartIndex but did not use it for outer-loop advancement,
  so merging the bounds check into the for-loop condition eliminates the
  redundant first pass without changing behaviour.
- Reword the inline comment to reference the index-based GetBindingDisplayString
  overload by name instead of by line number, which goes stale as the file
  is edited.
- Add Actions_WhenGettingDisplayTextForBindingsOnAction_MixedGroupCompositeIsRenderedAtomicallyWhenAnyPartMatchesBindingMask
  covering a mixed-group 1DAxis composite (Keyboard + Mouse parts) under both
  MaskByGroup("Keyboard") and MaskByGroup("Mouse"). Both masks must render the
  whole composite ("A/Left Button"), exercising the atomic-promotion claim.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: Pauliusd01

Assets/Tests/InputSystem/CoreTests_Actions.cs

@@ -9253,6 +9253,23 @@ public void Actions_WhenGettingDisplayTextForBindingsOnAction_CompositeIsInclude
             Is.EqualTo("A/D"));
     }
 
+    // https://issuetracker.unity3d.com/product/unity/issues/guid/UUM-141423
+    [Test]
+    [Category("Actions")]
+    public void Actions_WhenGettingDisplayTextForBindingsOnAction_MixedGroupCompositeIsRenderedAtomicallyWhenAnyPartMatchesBindingMask()
+    {
+        var action = new InputAction();
+
+        action.AddCompositeBinding("1DAxis")
+            .With("Negative", "<Keyboard>/a", groups: "Keyboard")
+            .With("Positive", "<Mouse>/leftButton", groups: "Mouse");
+
+        Assert.That(action.GetBindingDisplayString(InputBinding.MaskByGroup("Keyboard")),
+            Is.EqualTo("A/Left Button"));
+        Assert.That(action.GetBindingDisplayString(InputBinding.MaskByGroup("Mouse")),
+            Is.EqualTo("A/Left Button"));
+    }
+
     // https://fogbugz.unity3d.com/f/cases/1321175/
     [Test]
     [Category("Actions")]

Packages/com.unity.inputsystem/InputSystem/Runtime/Actions/InputActionRebindingExtensions.cs

@@ -323,16 +323,13 @@ public static string GetBindingDisplayString(this InputAction action, InputBindi
                 if (!bindingMask.Matches(bindings[i]))
                 {
                     // Composites are filtered atomically: any matching part promotes the whole
-                    // composite, consistent with how the integer-index renderer at lines 440-492
-                    // already treats composites as one display unit; per-part filtering would
-                    // require a separate API.
+                    // composite, consistent with how the index-based GetBindingDisplayString
+                    // overload below treats composites as one display unit; per-part filtering
+                    // would require a separate API.
                     if (!bindings[i].isComposite)
                         continue;
-                    var lastPartIndex = i + 1;
-                    while (lastPartIndex < bindings.Count && bindings[lastPartIndex].isPartOfComposite)
-                        ++lastPartIndex;
                     var anyPartMatches = false;
-                    for (var partIndex = i + 1; partIndex < lastPartIndex; ++partIndex)
+                    for (var partIndex = i + 1; partIndex < bindings.Count && bindings[partIndex].isPartOfComposite; ++partIndex)
                     {
                         if (bindingMask.Matches(bindings[partIndex]))
                         {