Fixed position of bounding rectangle for ComboBox items when drop dow…

…n shows a scrollbar (#4354)
dotnet · Dec 14, 2020 · cb03d37 · cb03d37
1 parent a4fa8f9
commit cb03d37
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Showing 2 changed files with 22 additions and 3 deletions.
diff --git a/src/System.Windows.Forms/src/System/Windows/Forms/ComboBox.ComboBoxItemAccessibleObject.cs b/src/System.Windows.Forms/src/System/Windows/Forms/ComboBox.ComboBoxItemAccessibleObject.cs
@@ -44,6 +44,13 @@ public override Rectangle Bounds
                 {
                     ChildAccessibleObject listAccessibleObject = _owningComboBox.ChildListAccessibleObject;
                     int currentIndex = GetCurrentIndex();
+                    if (_owningComboBox.IsHandleCreated)
+                    {
+                        int firstVisibleIndex = (int)(long)User32.SendMessageW(_owningComboBox, (User32.WM)User32.CB.GETTOPINDEX);
+
+                        // Using the first visible index, we make an index shift, which helps to draw a rectangle with the correct position
+                        currentIndex -= firstVisibleIndex;
+                    }
 
                     Rectangle parentRect = listAccessibleObject.BoundingRectangle;
                     int left = parentRect.Left;

diff --git a/src/System.Windows.Forms/tests/IntegrationTests/WinformsControlsTest/ComboBoxes.Designer.cs b/src/System.Windows.Forms/tests/IntegrationTests/WinformsControlsTest/ComboBoxes.Designer.cs