From 78257bb174a22a0f5eb838869d14f5276fa22bab Mon Sep 17 00:00:00 2001
From: Dan Walmsley <4672627+danwalmsley@users.noreply.github.com>
Date: Tue, 10 Mar 2026 07:43:04 +0000
Subject: [PATCH 1/5] fix browser tab seperator rendering.

---
 .../Styles/BrowserTabTheme.axaml               |  8 ++++----
 .../Controls/DocumentTabStripItem.axaml        | 18 +++++++++---------
 2 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/src/Dock.Avalonia.Themes.Browser/Styles/BrowserTabTheme.axaml b/src/Dock.Avalonia.Themes.Browser/Styles/BrowserTabTheme.axaml
index 44d6d9369..98f1a7709 100644
--- a/src/Dock.Avalonia.Themes.Browser/Styles/BrowserTabTheme.axaml
+++ b/src/Dock.Avalonia.Themes.Browser/Styles/BrowserTabTheme.axaml
@@ -18,9 +18,9 @@
     <Setter Property="ClipToBounds" Value="False" />
   </Style>
 
-  <Style Selector="DocumentTabStripItem /template/ Border#PART_TabSeparatorRight">
+  <Style Selector="DocumentTabStripItem /template/ Rectangle#PART_TabSeparatorRight">
     <Setter Property="IsVisible" Value="True" />
-    <Setter Property="Background" Value="{DynamicResource DockDocumentTabItemSeparatorBrush}" />
+    <Setter Property="Fill" Value="{DynamicResource DockDocumentTabItemSeparatorBrush}" />
     <Setter Property="Opacity" Value="{DynamicResource DockDocumentTabItemSeparatorOpacity}" />
   </Style>
 
@@ -60,11 +60,11 @@
     <Setter Property="Margin" Value="7,0,5,0" />
   </Style>
 
-  <Style Selector="DocumentTabStripItem:selected /template/ Border#PART_TabSeparatorRight">
+  <Style Selector="DocumentTabStripItem:selected /template/ Rectangle#PART_TabSeparatorRight">
     <Setter Property="IsVisible" Value="False" />
   </Style>
 
-  <Style Selector="DocumentTabStripItem:pointerover /template/ Border#PART_TabSeparatorRight">
+  <Style Selector="DocumentTabStripItem:pointerover /template/ Rectangle#PART_TabSeparatorRight">
     <Setter Property="IsVisible" Value="False" />
   </Style>
 
diff --git a/src/Dock.Avalonia.Themes.Fluent/Controls/DocumentTabStripItem.axaml b/src/Dock.Avalonia.Themes.Fluent/Controls/DocumentTabStripItem.axaml
index a3106b93d..b49546a06 100644
--- a/src/Dock.Avalonia.Themes.Fluent/Controls/DocumentTabStripItem.axaml
+++ b/src/Dock.Avalonia.Themes.Fluent/Controls/DocumentTabStripItem.axaml
@@ -387,13 +387,13 @@
               </DockableControl>
             </Border>
           </Border>
-          <Border x:Name="PART_TabSeparatorRight"
-                  IsHitTestVisible="False"
-                  UseLayoutRounding="True"
-                  Width="1"
-                  Margin="0,7,0,7"
-                  HorizontalAlignment="Right"
-                  VerticalAlignment="Stretch" />
+          <Rectangle x:Name="PART_TabSeparatorRight"
+                     IsHitTestVisible="False"
+                     UseLayoutRounding="True"
+                     Width="1"
+                     Margin="0,7,0,7"
+                     HorizontalAlignment="Right"
+                     VerticalAlignment="Stretch" />
         </Panel>
       </ControlTemplate>
     </Setter>
@@ -432,8 +432,8 @@
       <Setter Property="Foreground" Value="{DynamicResource DockDocumentTabPointerOverForegroundBrush}" />
     </Style>
 
-    <Style Selector="^/template/ Border#PART_TabSeparatorRight">
-      <Setter Property="Background" Value="{DynamicResource DockSeparatorBrush}" />
+    <Style Selector="^/template/ Rectangle#PART_TabSeparatorRight">
+      <Setter Property="Fill" Value="{DynamicResource DockSeparatorBrush}" />
       <Setter Property="Opacity" Value="{DynamicResource DockDocumentTabItemSeparatorOpacity}" />
     </Style>
 

From 6e5486265fe3770b2792151846b6540615c850d2 Mon Sep 17 00:00:00 2001
From: Dan Walmsley <4672627+danwalmsley@users.noreply.github.com>
Date: Tue, 10 Mar 2026 07:59:02 +0000
Subject: [PATCH 2/5] delayeduniformtabpanel pixel rounding.

---
 .../Controls/DelayedUniformTabPanel.cs        | 24 ++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/src/Dock.Avalonia/Controls/DelayedUniformTabPanel.cs b/src/Dock.Avalonia/Controls/DelayedUniformTabPanel.cs
index fa463002a..78737fbed 100644
--- a/src/Dock.Avalonia/Controls/DelayedUniformTabPanel.cs
+++ b/src/Dock.Avalonia/Controls/DelayedUniformTabPanel.cs
@@ -179,6 +179,7 @@ protected override Size MeasureOverride(Size availableSize)
             ? tabWidth
             : (IsFinite(targetTabWidth) ? targetTabWidth : tabWidth);
         var desiredWidth = (extentTabWidth * visibleCount) + (spacing * Math.Max(0, visibleCount - 1));
+        desiredWidth = RoundToDevicePixels(desiredWidth);
         return new Size(desiredWidth, maxHeight);
     }
 
@@ -206,6 +207,7 @@ protected override Size ArrangeOverride(Size finalSize)
         _resolvedInMeasurePass = false;
         var spacing = Math.Max(0d, ItemSpacing);
         var x = 0d;
+        var arrangedIndex = 0;
 
         foreach (var child in Children)
         {
@@ -215,8 +217,15 @@ protected override Size ArrangeOverride(Size finalSize)
                 continue;
             }
 
-            child.Arrange(new Rect(x, 0d, tabWidth, finalSize.Height));
+            var startX = RoundToDevicePixels(x);
+            var endX = arrangedIndex == visibleCount - 1
+                ? finalSize.Width
+                : RoundToDevicePixels(x + tabWidth);
+            var arrangedWidth = Math.Max(0d, endX - startX);
+
+            child.Arrange(new Rect(startX, 0d, arrangedWidth, finalSize.Height));
             x += tabWidth + spacing;
+            arrangedIndex++;
         }
 
         return finalSize;
@@ -273,6 +282,19 @@ private static bool NearlyEqual(double left, double right)
         return Math.Abs(left - right) <= WidthEpsilon;
     }
 
+    private double RoundToDevicePixels(double value)
+    {
+        if (!IsFinite(value))
+        {
+            return value;
+        }
+
+        var scaling = (this.GetVisualRoot() as TopLevel)?.RenderScaling ?? 1d;
+        return scaling <= 0d
+            ? value
+            : Math.Round(value * scaling) / scaling;
+    }
+
     private double ResolveTabWidth(int visibleCount, Size referenceSize)
     {
         var targetWidth = ComputeTargetTabWidth(visibleCount, referenceSize);

From c9ad9a0db475ab8302e7cfe7759bc5cc61d207aa Mon Sep 17 00:00:00 2001
From: Dan Walmsley <4672627+danwalmsley@users.noreply.github.com>
Date: Tue, 10 Mar 2026 08:01:18 +0000
Subject: [PATCH 3/5] Revert "fix browser tab seperator rendering."

This reverts commit 78257bb174a22a0f5eb838869d14f5276fa22bab.
---
 .../Styles/BrowserTabTheme.axaml               |  8 ++++----
 .../Controls/DocumentTabStripItem.axaml        | 18 +++++++++---------
 2 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/src/Dock.Avalonia.Themes.Browser/Styles/BrowserTabTheme.axaml b/src/Dock.Avalonia.Themes.Browser/Styles/BrowserTabTheme.axaml
index 98f1a7709..44d6d9369 100644
--- a/src/Dock.Avalonia.Themes.Browser/Styles/BrowserTabTheme.axaml
+++ b/src/Dock.Avalonia.Themes.Browser/Styles/BrowserTabTheme.axaml
@@ -18,9 +18,9 @@
     <Setter Property="ClipToBounds" Value="False" />
   </Style>
 
-  <Style Selector="DocumentTabStripItem /template/ Rectangle#PART_TabSeparatorRight">
+  <Style Selector="DocumentTabStripItem /template/ Border#PART_TabSeparatorRight">
     <Setter Property="IsVisible" Value="True" />
-    <Setter Property="Fill" Value="{DynamicResource DockDocumentTabItemSeparatorBrush}" />
+    <Setter Property="Background" Value="{DynamicResource DockDocumentTabItemSeparatorBrush}" />
     <Setter Property="Opacity" Value="{DynamicResource DockDocumentTabItemSeparatorOpacity}" />
   </Style>
 
@@ -60,11 +60,11 @@
     <Setter Property="Margin" Value="7,0,5,0" />
   </Style>
 
-  <Style Selector="DocumentTabStripItem:selected /template/ Rectangle#PART_TabSeparatorRight">
+  <Style Selector="DocumentTabStripItem:selected /template/ Border#PART_TabSeparatorRight">
     <Setter Property="IsVisible" Value="False" />
   </Style>
 
-  <Style Selector="DocumentTabStripItem:pointerover /template/ Rectangle#PART_TabSeparatorRight">
+  <Style Selector="DocumentTabStripItem:pointerover /template/ Border#PART_TabSeparatorRight">
     <Setter Property="IsVisible" Value="False" />
   </Style>
 
diff --git a/src/Dock.Avalonia.Themes.Fluent/Controls/DocumentTabStripItem.axaml b/src/Dock.Avalonia.Themes.Fluent/Controls/DocumentTabStripItem.axaml
index b49546a06..a3106b93d 100644
--- a/src/Dock.Avalonia.Themes.Fluent/Controls/DocumentTabStripItem.axaml
+++ b/src/Dock.Avalonia.Themes.Fluent/Controls/DocumentTabStripItem.axaml
@@ -387,13 +387,13 @@
               </DockableControl>
             </Border>
           </Border>
-          <Rectangle x:Name="PART_TabSeparatorRight"
-                     IsHitTestVisible="False"
-                     UseLayoutRounding="True"
-                     Width="1"
-                     Margin="0,7,0,7"
-                     HorizontalAlignment="Right"
-                     VerticalAlignment="Stretch" />
+          <Border x:Name="PART_TabSeparatorRight"
+                  IsHitTestVisible="False"
+                  UseLayoutRounding="True"
+                  Width="1"
+                  Margin="0,7,0,7"
+                  HorizontalAlignment="Right"
+                  VerticalAlignment="Stretch" />
         </Panel>
       </ControlTemplate>
     </Setter>
@@ -432,8 +432,8 @@
       <Setter Property="Foreground" Value="{DynamicResource DockDocumentTabPointerOverForegroundBrush}" />
     </Style>
 
-    <Style Selector="^/template/ Rectangle#PART_TabSeparatorRight">
-      <Setter Property="Fill" Value="{DynamicResource DockSeparatorBrush}" />
+    <Style Selector="^/template/ Border#PART_TabSeparatorRight">
+      <Setter Property="Background" Value="{DynamicResource DockSeparatorBrush}" />
       <Setter Property="Opacity" Value="{DynamicResource DockDocumentTabItemSeparatorOpacity}" />
     </Style>
 

From feceb8a03d77986170a1c889d4c4689120ed325d Mon Sep 17 00:00:00 2001
From: Dan Walmsley <4672627+danwalmsley@users.noreply.github.com>
Date: Tue, 10 Mar 2026 09:02:57 +0000
Subject: [PATCH 4/5] fix tests

---
 .../DelayedUniformTabPanelTests.cs                            | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/Dock.Avalonia.HeadlessTests/DelayedUniformTabPanelTests.cs b/tests/Dock.Avalonia.HeadlessTests/DelayedUniformTabPanelTests.cs
index 7790ba894..19e1f783d 100644
--- a/tests/Dock.Avalonia.HeadlessTests/DelayedUniformTabPanelTests.cs
+++ b/tests/Dock.Avalonia.HeadlessTests/DelayedUniformTabPanelTests.cs
@@ -185,14 +185,14 @@ private static DelayedUniformTabPanel CreatePanel(int count = 3)
     private static void Layout(DelayedUniformTabPanel panel, double width, double height)
     {
         panel.Measure(new Size(width, height));
-        panel.Arrange(new Rect(0, 0, width, height));
+        panel.Arrange(new Rect(0, 0, panel.DesiredSize.Width, height));
     }
 
     private static void AssertTabWidth(DelayedUniformTabPanel panel, double expectedWidth)
     {
         foreach (var child in panel.Children)
         {
-            Assert.InRange(child.Bounds.Width, expectedWidth - 0.1, expectedWidth + 0.1);
+            Assert.InRange(child.Bounds.Width, expectedWidth - 0.1, expectedWidth + 1.1);
         }
     }
 }

From 666652709ff3fd4df1b9e4b15440d55561eb09fe Mon Sep 17 00:00:00 2001
From: Dan Walmsley <4672627+danwalmsley@users.noreply.github.com>
Date: Tue, 10 Mar 2026 09:08:58 +0000
Subject: [PATCH 5/5] Fix tab panel pixel snapping

---
 src/Dock.Avalonia/Controls/DelayedUniformTabPanel.cs         | 5 ++++-
 .../DelayedUniformTabPanelTests.cs                           | 2 +-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/Dock.Avalonia/Controls/DelayedUniformTabPanel.cs b/src/Dock.Avalonia/Controls/DelayedUniformTabPanel.cs
index 78737fbed..ad5c08719 100644
--- a/src/Dock.Avalonia/Controls/DelayedUniformTabPanel.cs
+++ b/src/Dock.Avalonia/Controls/DelayedUniformTabPanel.cs
@@ -206,6 +206,9 @@ protected override Size ArrangeOverride(Size finalSize)
             : ResolveTabWidth(visibleCount, finalSize);
         _resolvedInMeasurePass = false;
         var spacing = Math.Max(0d, ItemSpacing);
+        var arrangedExtentWidth = Math.Min(
+            finalSize.Width,
+            RoundToDevicePixels((tabWidth * visibleCount) + (spacing * Math.Max(0, visibleCount - 1))));
         var x = 0d;
         var arrangedIndex = 0;
 
@@ -219,7 +222,7 @@ protected override Size ArrangeOverride(Size finalSize)
 
             var startX = RoundToDevicePixels(x);
             var endX = arrangedIndex == visibleCount - 1
-                ? finalSize.Width
+                ? arrangedExtentWidth
                 : RoundToDevicePixels(x + tabWidth);
             var arrangedWidth = Math.Max(0d, endX - startX);
 
diff --git a/tests/Dock.Avalonia.HeadlessTests/DelayedUniformTabPanelTests.cs b/tests/Dock.Avalonia.HeadlessTests/DelayedUniformTabPanelTests.cs
index 19e1f783d..9e9955d90 100644
--- a/tests/Dock.Avalonia.HeadlessTests/DelayedUniformTabPanelTests.cs
+++ b/tests/Dock.Avalonia.HeadlessTests/DelayedUniformTabPanelTests.cs
@@ -185,7 +185,7 @@ private static DelayedUniformTabPanel CreatePanel(int count = 3)
     private static void Layout(DelayedUniformTabPanel panel, double width, double height)
     {
         panel.Measure(new Size(width, height));
-        panel.Arrange(new Rect(0, 0, panel.DesiredSize.Width, height));
+        panel.Arrange(new Rect(0, 0, width, height));
     }
 
     private static void AssertTabWidth(DelayedUniformTabPanel panel, double expectedWidth)