Fix preview size (#9126)

Author: cinqmilleans

src/Files.Uwp/Views/MainPage.xaml

@@ -19,6 +19,7 @@
     Background="Transparent"
     KeyboardAcceleratorPlacementMode="Hidden"
     Loaded="Page_Loaded"
+    SizeChanged="Page_SizeChanged"
     NavigationCacheMode="Required"
     mc:Ignorable="d">
     <Page.DataContext>
@@ -371,13 +372,13 @@
 
                 <Grid.RowDefinitions>
                     <RowDefinition Height="Auto" />
-                    <RowDefinition Height="*" MinHeight="100" />
+                    <RowDefinition x:Name="ContentRow" Height="*" MinHeight="100" />
                     <RowDefinition Height="Auto" />
                     <RowDefinition x:Name="PaneRow" Height="Auto" />
                     <RowDefinition Height="32" />
                 </Grid.RowDefinitions>
                 <Grid.ColumnDefinitions>
-                    <ColumnDefinition Width="3*" MinWidth="100" />
+                    <ColumnDefinition x:Name="ContentColumn" Width="*" MinWidth="100" />
                     <ColumnDefinition Width="Auto" />
                     <ColumnDefinition x:Name="PaneColumn" Width="Auto" />
                 </Grid.ColumnDefinitions>

src/Files.Uwp/Views/MainPage.xaml.cs

@@ -1,5 +1,6 @@
 using CommunityToolkit.Mvvm.DependencyInjection;
 using CommunityToolkit.Mvvm.Input;
+using Files.Backend.Extensions;
 using Files.Backend.Services.Settings;
 using Files.Shared.Enums;
 using Files.Shared.EventArguments;
@@ -27,7 +28,6 @@
 using Windows.UI.Xaml.Controls;
 using Windows.UI.Xaml.Input;
 using Windows.UI.Xaml.Navigation;
-using Files.Backend.Extensions;
 
 namespace Files.Uwp.Views
 {
@@ -383,6 +383,21 @@ private void Page_Loaded(object sender, RoutedEventArgs e)
             }
         }
 
+        private void Page_SizeChanged(object sender, SizeChangedEventArgs e)
+        {
+            switch (Pane?.Position)
+            {
+                case PanePositions.Right when ContentColumn.ActualWidth == ContentColumn.MinWidth:
+                    UserSettingsService.PaneSettingsService.VerticalSizePx += e.NewSize.Width - e.PreviousSize.Width;
+                    UpdatePositioning();
+                    break;
+                case PanePositions.Bottom when ContentRow.ActualHeight == ContentRow.MinHeight:
+                    UserSettingsService.PaneSettingsService.HorizontalSizePx += e.NewSize.Height - e.PreviousSize.Height;
+                    UpdatePositioning();
+                    break;
+            }
+        }
+
         private void ToggleFullScreenAccelerator(KeyboardAcceleratorInvokedEventArgs e)
         {
             ApplicationView view = ApplicationView.GetForCurrentView();
@@ -474,17 +489,14 @@ private void UpdatePositioning()
 
         private void PaneSplitter_ManipulationCompleted(object sender, ManipulationCompletedRoutedEventArgs e)
         {
-            if (Pane is IPane p)
+            switch (Pane?.Position)
             {
-                switch (p.Position)
-                {
-                    case PanePositions.Right:
-                        UserSettingsService.PaneSettingsService.VerticalSizePx = Pane.ActualWidth;
-                        break;
-                    case PanePositions.Bottom:
-                        UserSettingsService.PaneSettingsService.HorizontalSizePx = Pane.ActualHeight;
-                        break;
-                }
+                case PanePositions.Right:
+                    UserSettingsService.PaneSettingsService.VerticalSizePx = Pane.ActualWidth;
+                    break;
+                case PanePositions.Bottom:
+                    UserSettingsService.PaneSettingsService.HorizontalSizePx = Pane.ActualHeight;
+                    break;
             }
         }