Fixes #1227

Changelog.md

@@ -84,6 +84,7 @@
   - [#1196](../../issues/1196) - GroupName causes the selected ToggleButton to no longer trigger the click event
   - [#1218](../../issues/1218) - Selected tab is lost on screen changes (thanks @cbra-caa)
   - [#1222](../../issues/1222) - Icon property values of controls are translated by the translation tools like catalyst (thanks @avikramaditya)
+  - [#1227](../../issues/1227) - Button events inside split button do not fire when ClosePopupOnMouseDownDelay = 0
   - Value of `HideContextTabs` are now properly restored when `Backstage` is closed
   - `RibbonTitleBar`
     - Fixed rendering when `HideContextTabs` is `true`

Fluent.Ribbon/Controls/DropDownButton.cs

@@ -578,13 +578,20 @@ private void OnDropDownPopupMouseDown(object sender, RoutedEventArgs e)
             // Note: get outside thread to prevent exceptions (it's a dependency property after all)
             var timespan = this.ClosePopupOnMouseDownDelay;
 
-            // Ugly workaround, but use a timer to allow routed event to continue
-            Task.Factory.StartNew(async () =>
+            if (timespan <= 0)
             {
-                await Task.Delay(timespan);
+                this.IsDropDownOpen = false;
+            }
+            else
+            {
+                // Ugly workaround, but use a timer to allow routed event to continue
+                Task.Factory.StartNew(async () =>
+                {
+                    await Task.Delay(timespan);
 
-                this.RunInDispatcherAsync(() => this.IsDropDownOpen = false);
-            });
+                    this.RunInDispatcherAsync(() => this.IsDropDownOpen = false);
+                });
+            }
         }
     }