Added AllowNegativeXWhenWidthGreaterThanContentWidth

Terminal.Gui/View/View.Content.cs

@@ -348,6 +348,14 @@ public partial class View
                 }
             }
 
+            if (!ViewportSettings.HasFlag (ViewportSettings.AllowNegativeXWhenWidthGreaterThanContentWidth))
+            {
+                if (Viewport.Width > GetContentSize ().Width)
+                {
+                    newViewport.X = 0;
+                }
+            }
+
             if (!ViewportSettings.HasFlag (ViewportSettings.AllowYGreaterThanContentHeight))
             {
                 if (newViewport.Y >= GetContentSize ().Height)
@@ -356,6 +364,14 @@ public partial class View
                 }
             }
 
+            if (!ViewportSettings.HasFlag (ViewportSettings.AllowNegativeYWhenHeightGreaterThanContentHeight))
+            {
+                if (Viewport.Height > GetContentSize ().Height)
+                {
+                    newViewport.Y = 0;
+                }
+            }
+
             // IMPORTANT: Check for negative location AFTER checking for location greater than content width
             if (!ViewportSettings.HasFlag (ViewportSettings.AllowNegativeY))
             {

Terminal.Gui/View/ViewportSettings.cs

@@ -76,7 +76,7 @@ public enum ViewportSettings
     AllowYGreaterThanContentHeight = 8,
 
     /// <summary>
-    ///     If set, <see cref="View.Viewport"/><c>.Size</c> can be set values greater than <see cref="View.GetContentSize ()"/>
+    ///     If set, <see cref="View.Viewport"/><c>.Location</c> can be set values greater than <see cref="View.GetContentSize ()"/>
     ///     enabling scrolling beyond the bottom-right
     ///     of the content area.
     ///     <para>
@@ -87,11 +87,42 @@ public enum ViewportSettings
     /// </summary>
     AllowLocationGreaterThanContentSize = AllowXGreaterThanContentWidth | AllowYGreaterThanContentHeight,
 
+    /// <summary>
+    ///     If set and <see cref="View.Viewport"/><c>.Width</c> is greater than <see cref="View.GetContentSize ()"/>
+    ///     <c>.Width</c> <see cref="View.Viewport"/><c>.X</c> can be negative.
+    ///     <para>
+    ///         When not set, <see cref="View.Viewport"/><c>.X</c> will be constrained to non-negative values, preventing
+    ///         scrolling beyond the left of the Viewport.
+    ///     </para>
+    ///     <para>
+    ///         This can be useful in infinite scrolling scenarios.
+    ///     </para>
+    /// </summary>
+    AllowNegativeXWhenWidthGreaterThanContentWidth = 16,
+
+    /// <summary>
+    ///     If set and <see cref="View.Viewport"/><c>.Height</c> is greater than <see cref="View.GetContentSize ()"/>
+    ///     <c>.Height</c> <see cref="View.Viewport"/><c>.Y</c> can be negative.
+    ///     <para>
+    ///         When not set, <see cref="View.Viewport"/><c>.Y</c> will be constrained to non-negative values, preventing
+    ///         scrolling above the top of the Viewport.
+    ///     </para>
+    ///     <para>
+    ///         This can be useful in infinite scrolling scenarios.
+    ///     </para>
+    /// </summary>
+    AllowNegativeYWhenHeightGreaterThanContentHeight = 32,
+
+    /// <summary>
+    ///     The combination of <see cref="AllowNegativeXWhenWidthGreaterThanContentWidth"/> and <see cref="AllowNegativeYWhenHeightGreaterThanContentHeight"/>.
+    /// </summary>
+    AllowNegativeLocationWhenSizeGreaterThanContentSize = AllowNegativeXWhenWidthGreaterThanContentWidth | AllowNegativeYWhenHeightGreaterThanContentHeight,
+
     /// <summary>
     ///     By default, clipping is applied to the <see cref="View.Viewport"/>. Setting this flag will cause clipping to be
     ///     applied to the visible content area.
     /// </summary>
-    ClipContentOnly = 16,
+    ClipContentOnly = 64,
 
     /// <summary>
     ///     If set <see cref="View.ClearViewport"/> will clear only the portion of the content
@@ -100,5 +131,5 @@ public enum ViewportSettings
     ///     <see cref="ClipContentOnly"/> must be set for this setting to work (clipping beyond the visible area must be
     ///     disabled).
     /// </summary>
-    ClearContentOnly = 32,
+    ClearContentOnly = 128,
 }

Terminal.Gui/Views/ScrollBar/ScrollBar.cs

@@ -17,7 +17,8 @@ namespace Terminal.Gui;
 ///         See the <see href="https://gui-cs.github.io/Terminal.GuiV2Docs/docs/scrolling.html">Scrolling Deep Dive</see>.
 ///     </para>
 ///     <para>
-///         By default, the built-in View scrollbars (<see cref="View.VerticalScrollBar"/>/<see cref="View.HorizontalScrollBar"/>) have both <see cref="View.Visible"/> and <see cref="AutoShow"/> set to
+///         By default, the built-in View scrollbars (<see cref="View.VerticalScrollBar"/>/
+///         <see cref="View.HorizontalScrollBar"/>) have both <see cref="View.Visible"/> and <see cref="AutoShow"/> set to
 ///         <see langword="false"/>.
 ///         To enable them, either set <see cref="AutoShow"/> set to <see langword="true"/> or explicitly set
 ///         <see cref="View.Visible"/>
@@ -184,7 +185,8 @@ public class ScrollBar : View, IOrientation, IDesignable
     #endregion
 
     /// <summary>
-    ///     Gets or sets the amount each mouse wheel event, or click on the increment/decrement buttons, will incremenet/decrement the <see cref="Position"/>.
+    ///     Gets or sets the amount each mouse wheel event, or click on the increment/decrement buttons, will
+    ///     incremenet/decrement the <see cref="Position"/>.
     /// </summary>
     /// <remarks>
     ///     The default is 1.

Terminal.Gui/Views/ScrollBar/ScrollSlider.cs

@@ -1,8 +1,6 @@
 #nullable enable
 
 using System.ComponentModel;
-using System.Diagnostics;
-using System.Drawing;
 
 namespace Terminal.Gui;
 
@@ -13,11 +11,6 @@ namespace Terminal.Gui;
 /// </summary>
 /// <remarks>
 ///     <para>
-///         If <see cref="View.Text"/> is set, it will be displayed centered within the slider. Set
-///         <see cref="ShowPercent"/> to automatically have the Text
-///         be show what percent the slider is to the Superview's Viewport size.
-///     </para>
-///     <para>
 ///         Used to represent the proportion of the visible content to the Viewport in a <see cref="Scrolled"/>.
 ///     </para>
 /// </remarks>
@@ -105,7 +98,7 @@ public class ScrollSlider : View, IOrientation, IDesignable
     /// <summary>
     ///     Gets or sets the size of the ScrollSlider. This is a helper that gets or sets Width or Height depending
     ///     on  <see cref="Orientation"/>. The size will be clamped between 1 and the dimension of
-    ///     the <see cref="View.SuperView"/>'s Viewport. 
+    ///     the <see cref="View.SuperView"/>'s Viewport.
     /// </summary>
     /// <remarks>
     ///     <para>

UICatalog/Scenarios/CharacterMap/CharMap.cs

@@ -134,7 +134,6 @@ public class CharMap : View, IDesignable
         KeyBindings.Add (Key.End, Command.End);
 
         MouseClick += Handle_MouseClick;
-        MouseEvent += Handle_MouseEvent;
 
         SetContentSize (new (COLUMN_WIDTH * 16 + RowLabelWidth, MAX_CODE_POINT / 16 * _rowHeight + HEADER_HEIGHT));
 
@@ -468,39 +467,36 @@ public class CharMap : View, IDesignable
     // TODO: Use this to demonstrate using a popover to show glyph info on hover
     public event EventHandler<ListViewItemEventArgs>? Hover;
 
-    private void Handle_MouseEvent (object? sender, MouseEventArgs e)
+    /// <inheritdoc />
+    protected override bool OnMouseEvent (MouseEventArgs mouseEvent)
     {
-        if (e.Flags == MouseFlags.WheeledDown)
+        if (mouseEvent.Flags == MouseFlags.WheeledDown)
         {
             ScrollVertical (1);
-            e.Handled = true;
-
-            return;
+            return mouseEvent.Handled = true;
         }
 
-        if (e.Flags == MouseFlags.WheeledUp)
+        if (mouseEvent.Flags == MouseFlags.WheeledUp)
         {
             ScrollVertical (-1);
-            e.Handled = true;
-
-            return;
+            return mouseEvent.Handled = true;
         }
 
-        if (e.Flags == MouseFlags.WheeledRight)
+        if (mouseEvent.Flags == MouseFlags.WheeledRight)
         {
             ScrollHorizontal (1);
-            e.Handled = true;
-
-            return;
+            return mouseEvent.Handled = true;
         }
 
-        if (e.Flags == MouseFlags.WheeledLeft)
+        if (mouseEvent.Flags == MouseFlags.WheeledLeft)
         {
             ScrollHorizontal (-1);
-            e.Handled = true;
+            return mouseEvent.Handled = true;
         }
-    }
 
+        return false;
+    }
+    
     private void Handle_MouseClick (object? sender, MouseEventArgs me)
     {
         if (me.Flags != MouseFlags.ReportMousePosition && me.Flags != MouseFlags.Button1Clicked && me.Flags != MouseFlags.Button1DoubleClicked)

UICatalog/Scenarios/Scrolling.cs

@@ -29,7 +29,6 @@ public class Scrolling : Scenario
             Width = 60,
             Height = 20
         };
-        demoView.SetContentSize (new (80, 25));
 
         label.Text =
             $"{demoView}\nContentSize: {demoView.GetContentSize ()}\nViewport.Location: {demoView.Viewport.Location}";
@@ -149,6 +148,8 @@ public class DemoView : View
 
     private void OnInitialized (object sender, EventArgs e)
     {
+        SetContentSize (new (80, 25));
+
         var rulerView = new View
         {
             Height = Dim.Fill (),
@@ -161,6 +162,16 @@ public class DemoView : View
 
         Add (rulerView);
 
+        var centeredLabel = new Label ()
+        {
+            X = Pos.Center (),
+            Y = Pos.Center (),
+            TextAlignment = Alignment.Center,
+            VerticalTextAlignment = Alignment.Center,
+            Text = $"This label is centred.\nContentSize is {GetContentSize ()}"
+        };
+        Add (centeredLabel);
+
         var pressMeButton = new Button
         {
             X = 1,
@@ -209,7 +220,7 @@ public class DemoView : View
                  Y = 40,
                  Width = 50,
                  ColorScheme = Colors.ColorSchemes ["Error"],
-                 Text = "Last line"
+                 Text = "Last line - Beyond content area @ Y = 40"
              }
             );
 
@@ -229,4 +240,33 @@ public class DemoView : View
                                   };
         Add (anchorButton);
     }
+
+    protected override bool OnMouseEvent (MouseEventArgs mouseEvent)
+    {
+        if (mouseEvent.Flags == MouseFlags.WheeledDown)
+        {
+            ScrollVertical (1);
+            return mouseEvent.Handled = true;
+        }
+
+        if (mouseEvent.Flags == MouseFlags.WheeledUp)
+        {
+            ScrollVertical (-1);
+            return mouseEvent.Handled = true;
+        }
+
+        if (mouseEvent.Flags == MouseFlags.WheeledRight)
+        {
+            ScrollHorizontal (1);
+            return mouseEvent.Handled = true;
+        }
+
+        if (mouseEvent.Flags == MouseFlags.WheeledLeft)
+        {
+            ScrollHorizontal (-1);
+            return mouseEvent.Handled = true;
+        }
+
+        return false;
+    }
 }