#13469 - selecting one item does select several - circle only select …

Svg.Editor.Core.Tests/SelectionToolTests.cs

@@ -74,6 +74,95 @@ public async Task IfUserTapsCanvas_AndTapPositionDoesNotIntersectWithSelectedEle
             Assert.AreEqual(0, Canvas.SelectedElements.Count);
         }
 
+        [Test]
+        public async Task IfUserTapsOverlappingElements_OnlySelectsTopMostElement()
+        {
+            // Arrange
+            await Canvas.EnsureInitialized();
+            var txtTool = Canvas.Tools.OfType<SelectionTool>().Single();
+            Canvas.ActiveTool = txtTool;
+            Canvas.ScreenWidth = 800;
+            Canvas.ScreenHeight = 500;
+
+            // "bottom" is declared first, so "top" (declared after, hence higher z-order) fully occludes it
+            var bottom = new SvgRectangle
+            {
+                X = new SvgUnit(SvgUnitType.Pixel, 200),
+                Y = new SvgUnit(SvgUnitType.Pixel, 200),
+                Width = new SvgUnit(SvgUnitType.Pixel, 100),
+                Height = new SvgUnit(SvgUnitType.Pixel, 100),
+                Fill = new SvgColourServer(Color.Create(255, 0, 0))
+            };
+            var top = new SvgRectangle
+            {
+                X = new SvgUnit(SvgUnitType.Pixel, 200),
+                Y = new SvgUnit(SvgUnitType.Pixel, 200),
+                Width = new SvgUnit(SvgUnitType.Pixel, 100),
+                Height = new SvgUnit(SvgUnitType.Pixel, 100),
+                Fill = new SvgColourServer(Color.Create(0, 0, 255))
+            };
+            Canvas.Document.Children.Add(bottom);
+            Canvas.Document.Children.Add(top);
+
+            // Preassert
+            Assert.AreEqual(0, Canvas.SelectedElements.Count);
+
+            // Act - tap somewhere in the middle of both fully-overlapping rectangles
+            var pt1 = PointF.Create(250, 250);
+            await Canvas.OnEvent(new PointerEvent(EventType.PointerDown, pt1, pt1, pt1, 1));
+            await Canvas.OnEvent(new PointerEvent(EventType.PointerUp, pt1, pt1, pt1, 1));
+            ((TestScheduler)SchedulerProvider.BackgroundScheduler).AdvanceBy(TimeSpan.FromSeconds(1).Ticks);
+
+            // Assert - only the top-most element is selected, even though both are hit
+            Assert.AreEqual(1, Canvas.SelectedElements.Count);
+            Assert.AreSame(top, Canvas.SelectedElements.Single());
+        }
+
+        [Test]
+        public async Task IfUserDrawsSelectionRectangle_AndOverlappingElementsAreContained_AllOverlappingElementsAreSelected()
+        {
+            // Arrange
+            await Canvas.EnsureInitialized();
+            var txtTool = Canvas.Tools.OfType<SelectionTool>().Single();
+            Canvas.ActiveTool = txtTool;
+            Canvas.ScreenWidth = 800;
+            Canvas.ScreenHeight = 500;
+
+            var bottom = new SvgRectangle
+            {
+                X = new SvgUnit(SvgUnitType.Pixel, 200),
+                Y = new SvgUnit(SvgUnitType.Pixel, 200),
+                Width = new SvgUnit(SvgUnitType.Pixel, 100),
+                Height = new SvgUnit(SvgUnitType.Pixel, 100),
+                Fill = new SvgColourServer(Color.Create(255, 0, 0))
+            };
+            var top = new SvgRectangle
+            {
+                X = new SvgUnit(SvgUnitType.Pixel, 200),
+                Y = new SvgUnit(SvgUnitType.Pixel, 200),
+                Width = new SvgUnit(SvgUnitType.Pixel, 100),
+                Height = new SvgUnit(SvgUnitType.Pixel, 100),
+                Fill = new SvgColourServer(Color.Create(0, 0, 255))
+            };
+            Canvas.Document.Children.Add(bottom);
+            Canvas.Document.Children.Add(top);
+
+            // Preassert
+            Assert.AreEqual(0, Canvas.SelectedElements.Count);
+
+            // Act - drag a selection area that encloses both fully-overlapping rectangles
+            var start = PointF.Create(190, 190);
+            var end = PointF.Create(310, 310);
+            await Canvas.OnEvent(new PointerEvent(EventType.PointerDown, start, start, start, 1));
+            await Canvas.OnEvent(new MoveEvent(start, start, end, end - start, 1));
+            await Canvas.OnEvent(new PointerEvent(EventType.PointerUp, start, end, end, 1));
+
+            // Assert - unlike a tap, an area selection selects every element it contains
+            Assert.AreEqual(2, Canvas.SelectedElements.Count);
+            CollectionAssert.Contains(Canvas.SelectedElements, bottom);
+            CollectionAssert.Contains(Canvas.SelectedElements, top);
+        }
+
         [Test]
         public async Task IfUserDrawsSelectionRectangle_AndElementsAreContained_ElementsAreSelected()
         {

Svg.Editor.Core/Tools/SelectionTool.cs

@@ -260,10 +260,13 @@ private void SelectElementsUnderArea(RectangleF selectionRectangle, ISvgDrawingC
             SelectElementsUnder(selectionRectangle, ws, selectionType, maxItems, 1);
         }
 
-        private void SelectElementsUnderPoint(RectangleF selectionRectangle, ISvgDrawingCanvas ws, SelectionType selectionType, int maxItems = int.MaxValue)
+        private void SelectElementsUnderPoint(RectangleF selectionRectangle, ISvgDrawingCanvas ws, SelectionType selectionType, int maxItems = 1)
         {
             // when selecting by tapping a point, we do want an element to be selected, if the point intersects with ANY child element of it
             // therefore we need "recursionLevel=max"!
+            // a tap is a single point, so it should only ever select the top-most (highest z-order) element under
+            // it, not every overlapping element - that's what dragging out a selection area is for (see SelectElementsUnderArea).
+            // HitTest already returns matches in top-to-bottom z-order, so taking just the first one is correct.
             SelectElementsUnder(selectionRectangle, ws, selectionType, maxItems, int.MaxValue);
         }
 

Svg.Tests.Win/SvgHitTests.cs

@@ -390,5 +390,28 @@ public void Contains_Group_HasTransformations_IsHit(float x, float y, float wh,
                 }
             }
         }
+
+        [Test]
+        public void Intersect_TwoLayeredRectangles_OnlySelectsTopLayerRectangle()
+        {
+            // Arrange
+            // "top" is declared last, so it is rendered on top of (and occludes) "bottom"
+            var rawSvg = @"<svg>
+    <rect id=""bottom"" x=""100"" y=""100"" width=""100"" height=""100"" style=""fill:rgb(255,0,0);stroke:none"" />
+    <rect id=""top"" x=""100"" y=""100"" width=""100"" height=""100"" style=""fill:rgb(0,0,255);stroke:none"" />
+</svg>";
+            var svg = SvgDocument.FromSvg<SvgDocument>(rawSvg);
+            var rect = RectangleF.Create(150f, 150f, 10, 10);
+
+            // Act
+            var result = svg.HitTest<SvgRectangle>(rect, SelectionType.Intersect, HitTestResultMode.ReturnAllMatchingDescendants)
+                .ToArray();
+
+            // Assert
+            // both rectangles are hit, but the top-most (highest z-order) one must be reported first,
+            // so that a caller who only cares about a single selection (e.g. result.First()) selects "top"
+            result.Count().ShouldBe(2);
+            result[0].ID.ShouldBe("top");
+        }
     }
 }