Desktop: decide a titlebar double-click on the press, before the drag can swallow it

tests/DodoSSH.Client.App.Layout.Tests/TitleBarTests.cs

@@ -66,6 +66,52 @@ public sealed class TitleBarTests : IAsyncLifetime
         caches.Dispose();
     }
 
+    /// <remarks>
+    /// A double-click on the bar maximises, and a second one restores. It was a <c>DoubleTapped</c> handler
+    /// beside a press that started a drag, and the drag handed the press to the operating system's move loop,
+    /// which ate the release a double tap is assembled from — so on Windows the click often did nothing. The
+    /// press decides now; see <c>CaptionPresses</c>. A single press must still be a drag and nothing else.
+    /// </remarks>
+    [Fact]
+    public async Task DoubleClickingTheBar_MaximisesAndRestores_AndASinglePressDoesNot()
+    {
+        await LayoutHarness.OnTheUiThreadAsync(
+            () =>
+            {
+                var bar = new TitleBar { DataContext = shell };
+                var window = LayoutHarness.HostAtMinimumSize(
+                    bar, LayoutHarness.MinimumWidth, LayoutHarness.TitleBarHeight);
+
+                try
+                {
+                    // The top edge, past everything the bar draws: the drag surface and nothing else.
+                    var empty = new Point(bar.Bounds.Width * 0.6, 2);
+
+                    window.MouseDown(empty, MouseButton.Left);
+                    window.MouseUp(empty, MouseButton.Left);
+
+                    window.WindowState.ShouldBe(WindowState.Normal, "one press is a drag");
+
+                    window.MouseDown(empty, MouseButton.Left);
+                    window.MouseUp(empty, MouseButton.Left);
+
+                    window.WindowState.ShouldBe(WindowState.Maximized);
+
+                    window.MouseDown(empty, MouseButton.Left);
+                    window.MouseUp(empty, MouseButton.Left);
+                    window.MouseDown(empty, MouseButton.Left);
+                    window.MouseUp(empty, MouseButton.Left);
+
+                    window.WindowState.ShouldBe(WindowState.Normal);
+                }
+                finally
+                {
+                    window.Close();
+                }
+            },
+            Token);
+    }
+
     [Fact]
     public async Task ClickingTheSearchPill_OpensTheQuickConnectPalette()
     {