fix(ui): remove gaps at rounded window corners

src/OddSnap/App.xaml

@@ -85,7 +85,7 @@
         </Style>
 
         <Style x:Key="OddSnapTitleCloseButton" TargetType="Border" BasedOn="{StaticResource OddSnapTitleButton}">
-            <Setter Property="CornerRadius" Value="0,11,0,0"/>
+            <Setter Property="CornerRadius" Value="0,7,0,0"/>
         </Style>
 
         <Style x:Key="OddSnapTitleButtonIcon" TargetType="Image">

src/OddSnap/UI/Controls/OddSnapTitleBar.xaml

@@ -5,7 +5,7 @@
     <Border x:Name="TitleBarBorder"
             MinHeight="40"
             Padding="14,0,0,0"
-            CornerRadius="11,11,0,0"
+            CornerRadius="7,7,0,0"
             Background="Transparent"
             MouseLeftButtonDown="TitleBar_MouseLeftButtonDown">
         <Grid>

src/OddSnap/UI/OcrResultWindow.xaml

@@ -92,7 +92,7 @@
         </Style>
     </Window.Resources>
 
-    <Border x:Name="RootBorder" CornerRadius="12" ClipToBounds="True">
+    <Border x:Name="RootBorder" CornerRadius="7" ClipToBounds="True">
         <Border.Effect>
             <DropShadowEffect BlurRadius="24" ShadowDepth="2" Opacity="0.4" Color="Black"/>
         </Border.Effect>

src/OddSnap/UI/OddSnapWindowChrome.cs

@@ -7,20 +7,20 @@ namespace OddSnap.UI;
 
 public static class OddSnapWindowChrome
 {
-    private const double DefaultCornerRadius = 12;
+    private const double DefaultCornerRadius = 7;
 
-    public static void Apply(Window window)
+    public static void Apply(Window window, double cornerRadius = DefaultCornerRadius)
     {
         WindowChrome.SetWindowChrome(window, new WindowChrome
         {
             CaptionHeight = 0,
-            CornerRadius = new CornerRadius(DefaultCornerRadius),
+            CornerRadius = new CornerRadius(cornerRadius),
             GlassFrameThickness = new Thickness(0),
             ResizeBorderThickness = new Thickness(8),
             UseAeroCaptionButtons = false
         });
 
-        ApplyRoundedCorners(window, DefaultCornerRadius);
+        ApplyRoundedCorners(window, cornerRadius);
     }
 
     public static void ApplyRoundedCorners(Window window, double radius)
@@ -35,6 +35,10 @@ void ApplyCurrentRegion()
 
             Dwm.TrySetWindowCornerPreference(hwnd, Dwm.DWMWCP_ROUND);
             Dwm.TrySetImmersiveDarkMode(hwnd, Theme.IsDark);
+
+            // On Windows 11 DWM rounds layered windows themselves, so clipping
+            // a region on top of that would leave a crescent wherever the two
+            // roundings disagree. Only Windows 10 needs the manual region.
             if (OperatingSystem.IsWindowsVersionAtLeast(10, 0, 22000))
                 return;
 
@@ -43,8 +47,15 @@ void ApplyCurrentRegion()
 
         window.SourceInitialized += (_, _) => ApplyCurrentRegion();
         window.SizeChanged += (_, _) => ApplyCurrentRegion();
+
+        // On Windows 10 the region must be recomputed when the UI scale
+        // changes, because the content rounding scales with it.
+        void OnUiScaleChanged(double _) => ApplyCurrentRegion();
+        UiScale.Changed += OnUiScaleChanged;
+
         window.Closed += (_, _) =>
         {
+            UiScale.Changed -= OnUiScaleChanged;
             var hwnd = new WindowInteropHelper(window).Handle;
             if (hwnd != IntPtr.Zero)
                 User32.SetWindowRgn(hwnd, IntPtr.Zero, true);
@@ -60,10 +71,17 @@ private static void SetRoundedWindowRegion(Window window, IntPtr hwnd, double ra
         var transform = source?.CompositionTarget?.TransformToDevice ?? System.Windows.Media.Matrix.Identity;
         int width = Math.Max(1, (int)Math.Ceiling(window.ActualWidth * transform.M11));
         int height = Math.Max(1, (int)Math.Ceiling(window.ActualHeight * transform.M22));
-        int diameterX = Math.Max(1, (int)Math.Round(radius * 2 * transform.M11));
-        int diameterY = Math.Max(1, (int)Math.Round(radius * 2 * transform.M22));
 
-        var region = Gdi32.CreateRoundRectRgn(0, 0, width + 1, height + 1, diameterX, diameterY);
+        // The root element is scaled by UiScale via a LayoutTransform, so the
+        // visible corner radius is radius * uiScale in layout units.
+        var effectiveRadius = radius * UiScale.Current;
+
+        // GDI takes the ellipse *diameter*; WPF's CornerRadius is the radius.
+        int diameterX = Math.Max(2, (int)Math.Round(effectiveRadius * 2 * transform.M11));
+        int diameterY = Math.Max(2, (int)Math.Round(effectiveRadius * 2 * transform.M22));
+
+        // Use the exact device bounds so the region lines up with the content.
+        var region = Gdi32.CreateRoundRectRgn(0, 0, width, height, diameterX, diameterY);
         if (region == IntPtr.Zero)
             return;
 

src/OddSnap/UI/SettingsWindow.xaml

@@ -643,8 +643,13 @@
 
     </Window.Resources>
 
-        <Border Margin="1" CornerRadius="12">
-    <Border x:Name="OuterBorder" CornerRadius="12" ClipToBounds="True"
+    <!--
+        The border must reach the window edge. The old wrapper had Margin="1",
+        which inset the content by 1px and left a crescent of desktop visible
+        at each rounded corner. The radius matches
+        OddSnapWindowChrome.DefaultCornerRadius.
+    -->
+    <Border x:Name="OuterBorder" CornerRadius="7" ClipToBounds="True"
             BorderThickness="1">
     <Grid>
         <Grid.RowDefinitions>
@@ -4491,5 +4496,4 @@
     </Grid>
     </Grid>
     </Border>
-    </Border>
 </Window>

src/OddSnap/UI/UpscaleResultWindow.xaml

@@ -22,7 +22,7 @@
         <SolidColorBrush x:Key="LoadingTextBrush" Color="#FFFFFFFF"/>
     </Window.Resources>
 
-    <Border x:Name="RootBorder" CornerRadius="12" ClipToBounds="True">
+    <Border x:Name="RootBorder" CornerRadius="7" ClipToBounds="True">
         <Grid>
             <Grid.RowDefinitions>
                 <RowDefinition Height="40"/>