Merge pull request #786 from AvaloniaUI/fixes/785-dialog-text-input

Call SetFocus in ShowWindow.

src/Windows/Avalonia.Win32/WindowImpl.cs

@@ -682,6 +682,7 @@ namespace Avalonia.Win32
             }
 
             UnmanagedMethods.ShowWindow(_hwnd, command);
+            UnmanagedMethods.SetFocus(_hwnd);
         }
 
         public void SetIcon(IWindowIconImpl icon)