Fix FlexLayout Grow causes measured child sizes to be ignored

src/Controls/tests/Core.UnitTests/Layouts/FlexLayoutTests.cs

@@ -33,6 +33,23 @@ protected override Size MeasureOverride(double widthConstraint, double heightCon
 			}
 		}
 
+		class FixedSizeLabel : Label
+		{
+			readonly double _width;
+			readonly double _height;
+
+			public FixedSizeLabel(double width, double height)
+			{
+				_width = width;
+				_height = height;
+			}
+
+			protected override Size MeasureOverride(double widthConstraint, double heightConstraint)
+			{
+				return new Size(_width, _height);
+			}
+		}
+
 		[Fact]
 		public void FlexLayoutMeasuresImagesUnconstrained()
 		{
@@ -344,5 +361,43 @@ public void ArrangeOnlyPassFallsBackToDesiredSizeWhenWidthRequestCleared()
 			var clearedFrame = (flexLayout as IFlexLayout).GetFlexFrame(view as IView);
 			Assert.Equal(100, clearedFrame.Width);
 		}
+
+    [Fact]
+		public void GrowItemsPreserveNaturalSizeAndDistributeFreeSpaceEqually_Issue34464()
+		{
+			// Items with different natural widths but equal Grow values should each receive
+			// an equal share of the available free space added on top of their natural width.
+			// Before the fix, the natural size was zeroed and the inflated flex_dim was
+			// distributed proportionally, causing items with larger natural sizes to receive
+			// less growth than smaller items (violating the flex-grow spec).
+			var root = new Grid();
+			var controlsFlexLayout = new FlexLayout();
+			var flexLayout = controlsFlexLayout as IFlexLayout;
+
+			// item1 is narrower (50px), item2 is wider (100px); both have equal Grow
+			var item1 = new FixedSizeLabel(50, 50);
+			var item2 = new FixedSizeLabel(100, 50);
+
+			FlexLayout.SetGrow(item1, 1);
+			FlexLayout.SetShrink(item1, 0);
+			FlexLayout.SetGrow(item2, 1);
+			FlexLayout.SetShrink(item2, 0);
+
+			root.Add(controlsFlexLayout);
+			flexLayout.Add(item1 as IView);
+			flexLayout.Add(item2 as IView);
+
+			// Container = 300px; total natural width = 150px; free space = 150px.
+			// With Grow=1 on both items each should receive 75px of extra space:
+			//   item1 expected: 50 + 75 = 125
+			//   item2 expected: 100 + 75 = 175
+			_ = flexLayout.CrossPlatformMeasure(300, 200);
+
+			var frame1 = flexLayout.GetFlexFrame(item1 as IView);
+			var frame2 = flexLayout.GetFlexFrame(item2 as IView);
+
+			Assert.Equal(125, frame1.Width);
+			Assert.Equal(175, frame2.Width);
+		}
 	}
 }

src/Controls/tests/TestCases.HostApp/Issues/Issue34464.cs

@@ -0,0 +1,82 @@
+using System.Collections.Generic;
+using Microsoft.Maui;
+using Microsoft.Maui.Controls;
+using Microsoft.Maui.Graphics;
+
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 34464, "FlexLayout with BindableLayout and Label text display", PlatformAffected.All)]
+public class Issue34464 : ContentPage
+{
+	public Issue34464()
+	{
+		var items = new List<string>
+		{
+			"Some Medium Text",
+			"Shorter Text",
+			"Slightly More Text",
+			"One - Two",
+			"Two - Four",
+			"Two - Three",
+			"One - Eleven",
+		};
+
+		var flexLayout = new FlexLayout
+		{
+			Wrap = Microsoft.Maui.Layouts.FlexWrap.Wrap,
+			AutomationId = "TestFlexLayout"
+		};
+
+		BindableLayout.SetItemsSource(flexLayout, items);
+		BindableLayout.SetItemTemplate(flexLayout, new DataTemplate(() =>
+		{
+			var border = new Border
+			{
+				BackgroundColor = Color.FromArgb("#ffcccccc"),
+				Stroke = Color.FromArgb("#ffb8b8b8"),
+				Padding = new Thickness(12)
+			};
+
+			FlexLayout.SetGrow(border, 1);
+			FlexLayout.SetShrink(border, 0);
+
+			var backgroundBorder = new Border
+			{
+				BackgroundColor = Color.FromArgb("#44ff0000")
+			};
+
+			var label = new Label
+			{
+				LineBreakMode = LineBreakMode.NoWrap,
+				FontSize = 20,
+				HorizontalTextAlignment = TextAlignment.Center,
+				VerticalTextAlignment = TextAlignment.Center,
+				TextColor = Color.FromArgb("#ff000000")
+			};
+
+			label.SetBinding(Label.TextProperty, ".");
+
+			var grid = new Grid
+			{
+				Children = { backgroundBorder, label }
+			};
+
+			border.Content = grid;
+
+			return border;
+		}));
+
+		var headerLabel = new Label
+		{
+			Text = "FlexLayout with BindableLayout Items:",
+			FontSize = 16,
+			Margin = new Thickness(10),
+			AutomationId = "HeaderLabel"
+		};
+
+		Content = new VerticalStackLayout
+		{
+			Children = { headerLabel, flexLayout }
+		};
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue34464.cs

@@ -0,0 +1,20 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue34464 : _IssuesUITest
+{
+	public Issue34464(TestDevice device) : base(device) { }
+
+	public override string Issue => "FlexLayout with BindableLayout and Label text display";
+
+	[Test]
+	[Category(UITestCategories.Layout)]
+	public void FlexLayoutWithBindableLayoutDisplaysLabels()
+	{
+		App.WaitForElement("HeaderLabel");
+		VerifyScreenshot();
+	}
+}

src/Core/src/Layouts/Flex.cs

@@ -783,10 +783,15 @@ static void layout_items(Item item, int child_begin, int child_end, int children
 				float flex_size = 0;
 				if (layout.flex_dim > 0)
 				{
+					// Only the free space is distributed proportionally,
+					// not the total container space. layout.flex_dim was inflated by extra_flex_dim
+					// (the sum of measured sizes of growing items), so we recover the actual free
+					// space by subtracting it back. The item's measured size is preserved and the
+					// proportional share of free space is added on top.
+					float freeSpace = Math.Max(0, layout.flex_dim - layout.extra_flex_dim);
 					if (child.Grow != 0)
 					{
-						child.Frame[layout.frame_size_i] = 0; // Ignore previous size when growing.
-						flex_size = (layout.flex_dim / layout.flex_grows) * child.Grow;
+						flex_size = (freeSpace / layout.flex_grows) * child.Grow;
 					}
 				}
 				else if (layout.flex_dim < 0)