From ac65b63a8f74f3ce293c78bdb95a41da1a8e252d Mon Sep 17 00:00:00 2001
From: Jason Ross <jason.ross841@gmail.com>
Date: Tue, 2 Jun 2026 14:01:58 -0500
Subject: [PATCH] Adopt Fluent/Mica look for light mode

Replaces WinUI 2 grey brushes with WinUI 3 equivalents and enables the Mica system backdrop on Windows 11. RootGrid is transparent when Mica is active so the material shows through; falls back to ApplicationPageBackgroundThemeBrush on Win10. Sensor header uses LayerFillColorDefaultBrush; plot pane border uses DividerStrokeColorDefaultBrush. Black theme keeps a solid background and disables Mica.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../MainWindow.cs                             | 40 +++++++++++++++----
 .../MainWindow.xaml                           |  2 +-
 2 files changed, 34 insertions(+), 8 deletions(-)

diff --git a/LibreHardwareMonitor.Windows.WinUI/MainWindow.cs b/LibreHardwareMonitor.Windows.WinUI/MainWindow.cs
index 7a48a37..22eef24 100644
--- a/LibreHardwareMonitor.Windows.WinUI/MainWindow.cs
+++ b/LibreHardwareMonitor.Windows.WinUI/MainWindow.cs
@@ -85,7 +85,7 @@ public sealed partial class MainWindow : Window
         _columnMeasurer.SettleTriggered += (_, _) => UpdateSensorColumnWidths();
 
         MeasureStartup("MainWindow.InitializeComponent", InitializeComponent);
-        RootGrid.Background = new SolidColorBrush(Colors.White);
+        TryApplyMicaBackdrop();
         RootGrid.Loaded += RootGrid_Loaded;
         RootGrid.LayoutUpdated += RootGrid_LayoutUpdated;
         Bind(ContentGrid, UIElement.IsHitTestVisibleProperty, ViewModel, nameof(ViewModel.IsHardwareInteractionEnabled));
@@ -350,7 +350,7 @@ public sealed partial class MainWindow : Window
     {
         Grid header = _columnMeasurer.CreateHeaderGrid();
         header.Padding = new Thickness(8, 5, 8, 5);
-        header.Background = (Brush)Application.Current.Resources["SystemControlBackgroundChromeMediumLowBrush"];
+        header.Background = (Brush)Application.Current.Resources["LayerFillColorDefaultBrush"];
         header.Children.Add(CreateHeaderText("Sensor", 0, Visibility.Visible));
         header.Children.Add(CreateHeaderText("Value", 1, ViewModel.ValueColumnVisibility, nameof(ViewModel.ValueColumnVisibility)));
         header.Children.Add(CreateHeaderText("Min", 2, ViewModel.MinColumnVisibility, nameof(ViewModel.MinColumnVisibility)));
@@ -798,17 +798,43 @@ public sealed partial class MainWindow : Window
             _ => ElementTheme.Default
         };
 
-        RootGrid.Background = ViewModel.ThemeMode switch
+        if (ViewModel.ThemeMode == AppThemeMode.Black)
         {
-            AppThemeMode.Black => new SolidColorBrush(Colors.Black),
-            AppThemeMode.Dark => new SolidColorBrush(global::Windows.UI.Color.FromArgb(255, 30, 30, 30)),
-            _ => (Brush)Application.Current.Resources["ApplicationPageBackgroundThemeBrush"]
-        };
+            SystemBackdrop = null;
+            RootGrid.Background = new SolidColorBrush(Colors.Black);
+        }
+        else if (SystemBackdrop is MicaBackdrop)
+        {
+            RootGrid.Background = new SolidColorBrush(Colors.Transparent);
+        }
+        else
+        {
+            TryApplyMicaBackdrop();
+            RootGrid.Background = SystemBackdrop is MicaBackdrop
+                ? new SolidColorBrush(Colors.Transparent)
+                : (Brush)Application.Current.Resources["ApplicationPageBackgroundThemeBrush"];
+        }
 
         PlotControl.ApplyTheme(ViewModel.ThemeMode);
         _secondaryWindows.ApplyTheme(ViewModel.ThemeMode);
     }
 
+    private void TryApplyMicaBackdrop()
+    {
+        if (SystemBackdrop is MicaBackdrop)
+            return;
+
+        try
+        {
+            if (Microsoft.UI.Composition.SystemBackdrops.MicaController.IsSupported())
+                SystemBackdrop = new MicaBackdrop { Kind = Microsoft.UI.Composition.SystemBackdrops.MicaKind.Base };
+        }
+        catch
+        {
+            // Mica unavailable (e.g. Win10) — fall back to theme brush in ApplyTheme.
+        }
+    }
+
     private void UpdateSensorColumnWidths()
     {
         MeasureStartup("MainWindow.UpdateSensorColumnWidths", _columnMeasurer.UpdateWidths, () => FormattableString.Invariant($"rows={_columnMeasurer.RowCount}, cacheEntries={_columnMeasurer.CacheEntryCount}, deviceWidth={_columnMeasurer.DeviceColumnWidth:F0}, settled={_columnMeasurer.IsSettled}"));
diff --git a/LibreHardwareMonitor.Windows.WinUI/MainWindow.xaml b/LibreHardwareMonitor.Windows.WinUI/MainWindow.xaml
index 4323571..bdfd1c5 100644
--- a/LibreHardwareMonitor.Windows.WinUI/MainWindow.xaml
+++ b/LibreHardwareMonitor.Windows.WinUI/MainWindow.xaml
@@ -111,7 +111,7 @@
                   Grid.Row="0"
                   Padding="8"
                   BorderThickness="1,0,0,0"
-                  BorderBrush="{ThemeResource SystemControlForegroundBaseLowBrush}">
+                  BorderBrush="{ThemeResource DividerStrokeColorDefaultBrush}">
                 <Grid.RowDefinitions>
                     <RowDefinition Height="Auto" />
                     <RowDefinition Height="*" />