diff --git a/src/cascadia/WpfTerminalControl/TerminalContainer.cs b/src/cascadia/WpfTerminalControl/TerminalContainer.cs
index 25b6746dab4..be212ef7995 100644
--- a/src/cascadia/WpfTerminalControl/TerminalContainer.cs
+++ b/src/cascadia/WpfTerminalControl/TerminalContainer.cs
@@ -166,12 +166,16 @@ internal string GetSelectedText()
             var dpiScale = VisualTreeHelper.GetDpi(this);
 
             NativeMethods.COORD dimensions;
-            NativeMethods.TerminalTriggerResize(this.terminal, renderSize.Width * dpiScale.DpiScaleX, renderSize.Height * dpiScale.DpiScaleY, out dimensions);
+            NativeMethods.TerminalTriggerResize(
+                this.terminal,
+                Convert.ToInt16(renderSize.Width * dpiScale.DpiScaleX),
+                Convert.ToInt16(renderSize.Height * dpiScale.DpiScaleY),
+                out dimensions);
 
             this.Rows = dimensions.Y;
             this.Columns = dimensions.X;
 
-            this.connection?.Resize((uint)dimensions.Y, (uint)dimensions.X);
+            this.Connection?.Resize((uint)dimensions.Y, (uint)dimensions.X);
             return (dimensions.Y, dimensions.X);
         }
 
@@ -180,15 +184,17 @@ internal string GetSelectedText()
         /// </summary>
         /// <param name="rows">Number of rows to show.</param>
         /// <param name="columns">Number of columns to show.</param>
-        internal void Resize(uint rows, uint columns)
+        /// <returns><see cref="long"/> pair with the new width and height size in pixels for the renderer.</returns>
+        internal (int width, int height) Resize(uint rows, uint columns)
         {
+            NativeMethods.SIZE dimensionsInPixels;
             NativeMethods.COORD dimensions = new NativeMethods.COORD
             {
                 X = (short)columns,
                 Y = (short)rows,
             };
 
-            NativeMethods.TerminalResize(this.terminal, dimensions);
+            NativeMethods.TerminalTriggerResizeWithDimension(this.terminal, dimensions, out dimensionsInPixels);
 
             // If AutoFill is true, keep Rows and Columns in sync with MaxRows and MaxColumns.
             // Otherwise, MaxRows and MaxColumns will be set on startup and on control resize by the user.
@@ -201,7 +207,9 @@ internal void Resize(uint rows, uint columns)
             this.Columns = dimensions.X;
             this.Rows = dimensions.Y;
 
-            this.connection?.Resize((uint)dimensions.Y, (uint)dimensions.X);
+            this.Connection?.Resize((uint)dimensions.Y, (uint)dimensions.X);
+
+            return (dimensionsInPixels.cx, dimensionsInPixels.cy);
         }
 
         /// <inheritdoc/>
@@ -330,7 +338,7 @@ private IntPtr TerminalContainer_MessageHook(IntPtr hwnd, int msg, IntPtr wParam
                         // We only trigger a resize if we want to autofill to maximum size.
                         if (this.AutoFill)
                         {
-                            NativeMethods.TerminalTriggerResize(this.terminal, windowpos.cx, windowpos.cy, out dimensions);
+                            NativeMethods.TerminalTriggerResize(this.terminal, (short)windowpos.cx, (short)windowpos.cy, out dimensions);
 
                             this.Columns = dimensions.X;
                             this.Rows = dimensions.Y;
@@ -344,7 +352,7 @@ private IntPtr TerminalContainer_MessageHook(IntPtr hwnd, int msg, IntPtr wParam
                             this.MaxRows = dimensions.Y;
                         }
 
-                        this.connection?.Resize((uint)dimensions.Y, (uint)dimensions.X);
+                        this.Connection?.Resize((uint)dimensions.Y, (uint)dimensions.X);
                         break;
 
                     case NativeMethods.WindowMessage.WM_MOUSEWHEEL:
@@ -401,7 +409,7 @@ private void OnScroll(int viewTop, int viewHeight, int bufferSize)
 
         private void OnWrite(string data)
         {
-            this.connection?.WriteInput(data);
+            this.Connection?.WriteInput(data);
         }
     }
 }
diff --git a/src/cascadia/WpfTerminalControl/TerminalControl.xaml b/src/cascadia/WpfTerminalControl/TerminalControl.xaml
index b820e73df71..90a1c89205a 100644
--- a/src/cascadia/WpfTerminalControl/TerminalControl.xaml
+++ b/src/cascadia/WpfTerminalControl/TerminalControl.xaml
@@ -6,8 +6,9 @@
              xmlns:local="clr-namespace:Microsoft.Terminal.Wpf"
              mc:Ignorable="d" 
              d:DesignHeight="450" d:DesignWidth="800"
-             Focusable="True">
-    <Grid>
+             Focusable="True"
+             x:Name="terminalUserControl">
+    <Grid x:Name="terminalGrid">
         <Grid.ColumnDefinitions>
             <ColumnDefinition />
             <ColumnDefinition Width="Auto"/>
diff --git a/src/cascadia/WpfTerminalControl/TerminalControl.xaml.cs b/src/cascadia/WpfTerminalControl/TerminalControl.xaml.cs
index 1b31c573308..6700ec2c011 100644
--- a/src/cascadia/WpfTerminalControl/TerminalControl.xaml.cs
+++ b/src/cascadia/WpfTerminalControl/TerminalControl.xaml.cs
@@ -5,6 +5,7 @@
 
 namespace Microsoft.Terminal.Wpf
 {
+    using System;
     using System.Windows;
     using System.Windows.Controls;
     using System.Windows.Input;
@@ -17,6 +18,8 @@ public partial class TerminalControl : UserControl
     {
         private int accumulatedDelta = 0;
 
+        private (int width, int height) terminalRendererSize;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="TerminalControl"/> class.
         /// </summary>
@@ -88,6 +91,13 @@ public void SetTheme(TerminalTheme theme, string fontFamily, short fontSize)
             }
 
             this.termContainer.SetTheme(theme, fontFamily, fontSize);
+
+            // DefaultBackground uses Win32 COLORREF syntax which is BGR instead of RGB.
+            byte b = Convert.ToByte((theme.DefaultBackground >> 16) & 0xff);
+            byte g = Convert.ToByte((theme.DefaultBackground >> 8) & 0xff);
+            byte r = Convert.ToByte(theme.DefaultBackground & 0xff);
+
+            this.terminalGrid.Background = new SolidColorBrush(Color.FromRgb(r, g, b));
         }
 
         /// <summary>
@@ -106,7 +116,18 @@ public string GetSelectedText()
         /// <param name="columns">Number of columns to display.</param>
         public void Resize(uint rows, uint columns)
         {
-            this.termContainer.Resize(rows, columns);
+            var dpiScale = VisualTreeHelper.GetDpi(this);
+
+            this.terminalRendererSize = this.termContainer.Resize(rows, columns);
+
+            double width = ((this.terminalUserControl.RenderSize.Width * dpiScale.DpiScaleX) - this.terminalRendererSize.width) / dpiScale.DpiScaleX;
+            double height = ((this.terminalUserControl.RenderSize.Height * dpiScale.DpiScaleY) - this.terminalRendererSize.height) / dpiScale.DpiScaleY;
+
+            // Prevent negative margin size.
+            width = width < 0 ? 0 : width;
+            height = height < 0 ? 0 : height;
+
+            this.terminalGrid.Margin = new Thickness(0, 0, width, height);
         }
 
         /// <summary>
@@ -119,6 +140,27 @@ public void Resize(uint rows, uint columns)
             return this.termContainer.TriggerResize(rendersize);
         }
 
+        /// <inheritdoc/>
+        protected override void OnRenderSizeChanged(SizeChangedInfo sizeInfo)
+        {
+            // Renderer will not resize on control resize. We have to manually recalculate the margin to fill in the space.
+            if (this.AutoFill == false && this.terminalRendererSize.width != 0 && this.terminalRendererSize.height != 0)
+            {
+                var dpiScale = VisualTreeHelper.GetDpi(this);
+
+                double width = ((sizeInfo.NewSize.Width * dpiScale.DpiScaleX) - this.terminalRendererSize.width) / dpiScale.DpiScaleX;
+                double height = ((sizeInfo.NewSize.Height * dpiScale.DpiScaleY) - this.terminalRendererSize.height) / dpiScale.DpiScaleY;
+
+                // Prevent negative margin size.
+                width = width < 0 ? 0 : width;
+                height = height < 0 ? 0 : height;
+
+                this.terminalGrid.Margin = new Thickness(0, 0, width, height);
+            }
+
+            base.OnRenderSizeChanged(sizeInfo);
+        }
+
         private void TerminalControl_GotFocus(object sender, RoutedEventArgs e)
         {
             e.Handled = true;