Fix some KeepContentInAllViewport bugs.

Terminal.Gui/Views/Scroll/Scroll.cs

@@ -54,22 +54,27 @@ public class Scroll : View
                 _keepContentInAllViewport = value;
                 var pos = 0;
 
-                if (value && Orientation == Orientation.Horizontal && _position + SuperViewAsScrollBar!.Viewport.Width > Size)
+                if (value
+                    && Orientation == Orientation.Horizontal
+                    && _position + (SuperViewAsScrollBar is { } ? SuperViewAsScrollBar.Viewport.Width : Viewport.Width) > Size)
                 {
-                    pos = Size - SuperViewAsScrollBar.Viewport.Width;
+                    pos = Size - (SuperViewAsScrollBar is { } ? SuperViewAsScrollBar.Viewport.Width : Viewport.Width);
                 }
 
-                if (value && Orientation == Orientation.Vertical && _position + SuperViewAsScrollBar!.Viewport.Height > Size)
+                if (value
+                    && Orientation == Orientation.Vertical
+                    && _position + (SuperViewAsScrollBar is { } ? SuperViewAsScrollBar.Viewport.Height : Viewport.Height) > Size)
                 {
-                    pos = _size - SuperViewAsScrollBar.Viewport.Height;
+                    pos = _size - (SuperViewAsScrollBar is { } ? SuperViewAsScrollBar.Viewport.Height : Viewport.Height);
                 }
 
                 if (pos != 0)
                 {
                     Position = pos;
-                    SetNeedsDisplay ();
-                    AdjustScroll ();
                 }
+
+                SetNeedsDisplay ();
+                AdjustScroll ();
             }
         }
     }
@@ -175,12 +180,12 @@ public class Scroll : View
         }
         else if (mouseEvent.Flags.HasFlag (MouseFlags.Button1Pressed) && location > sliderPos.end)
         {
-            Position = Math.Min (Position + barSize, Size - barSize);
+            Position = Math.Min (Position + barSize, Size - barSize + (KeepContentInAllViewport ? 0 : barSize));
         }
         else if ((mouseEvent.Flags == MouseFlags.WheeledDown && Orientation == Orientation.Vertical)
                  || (mouseEvent.Flags == MouseFlags.WheeledRight && Orientation == Orientation.Horizontal))
         {
-            Position = Math.Min (Position + 1, Size - barSize);
+            Position = Math.Min (Position + 1, Size - barSize + (KeepContentInAllViewport ? 0 : barSize));
         }
         else if ((mouseEvent.Flags == MouseFlags.WheeledUp && Orientation == Orientation.Vertical)
                  || (mouseEvent.Flags == MouseFlags.WheeledLeft && Orientation == Orientation.Horizontal))

Terminal.Gui/Views/Scroll/ScrollSlider.cs

@@ -89,8 +89,13 @@ internal class ScrollSlider : View
         {
             if (SuperViewAsScroll.Orientation == Orientation.Vertical)
             {
-                Y = Frame.Y + offset < 0 ? 0 :
-                    Frame.Y + offset + Frame.Height > barSize ? Math.Max (barSize - Frame.Height, 0) : Frame.Y + offset;
+                Y = Frame.Y + offset < 0
+                        ? 0
+                        :
+                        Frame.Y + offset + Frame.Height > barSize + (SuperViewAsScroll.KeepContentInAllViewport ? 0 : barSize)
+                            ?
+                            Math.Max (barSize - Frame.Height, 0)
+                            : Frame.Y + offset;
 
                 SuperViewAsScroll.Position = GetPositionFromSliderLocation (Frame.Y);
             }
@@ -157,7 +162,7 @@ internal class ScrollSlider : View
         if ((SuperViewAsScroll.Orientation == Orientation.Vertical && location + Frame.Height >= scrollSize)
             || (SuperViewAsScroll.Orientation == Orientation.Horizontal && location + Frame.Width >= scrollSize))
         {
-            return SuperViewAsScroll.Size - scrollSize;
+            return SuperViewAsScroll.Size - scrollSize + (SuperViewAsScroll.KeepContentInAllViewport ? 0 : scrollSize);
         }
 
         return (int)Math.Min (Math.Round ((double)(location * SuperViewAsScroll.Size + location) / scrollSize), SuperViewAsScroll.Size - scrollSize);

UICatalog/Scenarios/ScrollBarDemo.cs

@@ -182,14 +182,27 @@ public class ScrollBarDemo : Scenario
                                             }
                                         };
 
-        var ckbAutoHideScrollBar = new CheckBox { Y = Pos.Bottom (scrollPosition), Text = "AutoHideScrollBar" };
-        ckbAutoHideScrollBar.CheckedStateChanging += (s, e) => scrollBar.AutoHide = e.NewValue == CheckState.Checked;
-        view.Add (ckbAutoHideScrollBar);
+        var ckbAutoHide = new CheckBox
+            { Y = Pos.Bottom (scrollPosition), Text = "AutoHideScrollBar", CheckedState = scrollBar.AutoHide ? CheckState.Checked : CheckState.UnChecked };
+        ckbAutoHide.CheckedStateChanging += (s, e) => scrollBar.AutoHide = e.NewValue == CheckState.Checked;
+        view.Add (ckbAutoHide);
 
-        var ckbShowScrollIndicator = new CheckBox { X = Pos.Right (ckbAutoHideScrollBar) + 1, Y = Pos.Bottom (scrollPosition), Text = "ShowScrollIndicator" };
+        var ckbShowScrollIndicator = new CheckBox
+        {
+            X = Pos.Right (ckbAutoHide) + 1, Y = Pos.Bottom (scrollPosition), Text = "ShowScrollIndicator",
+            CheckedState = scrollBar.ShowScrollIndicator ? CheckState.Checked : CheckState.UnChecked
+        };
         ckbShowScrollIndicator.CheckedStateChanging += (s, e) => scrollBar.ShowScrollIndicator = e.NewValue == CheckState.Checked;
         view.Add (ckbShowScrollIndicator);
 
+        var ckbKeepContentInAllViewport = new CheckBox
+        {
+            X = Pos.Right (ckbShowScrollIndicator) + 1, Y = Pos.Bottom (scrollPosition), Text = "KeepContentInAllViewport",
+            CheckedState = scrollBar.KeepContentInAllViewport ? CheckState.Checked : CheckState.UnChecked
+        };
+        ckbKeepContentInAllViewport.CheckedStateChanging += (s, e) => scrollBar.KeepContentInAllViewport = e.NewValue == CheckState.Checked;
+        view.Add (ckbKeepContentInAllViewport);
+
         var lblSizeChanged = new Label
         {
             Y = Pos.Bottom (ckbShowScrollIndicator) + 1

UICatalog/Scenarios/ScrollDemo.cs

@@ -182,9 +182,17 @@ public class ScrollDemo : Scenario
                                             }
                                         };
 
+        var ckbKeepContentInAllViewport = new CheckBox
+        {
+            Y = Pos.Bottom (scrollPosition), Text = "KeepContentInAllViewport",
+            CheckedState = scroll.KeepContentInAllViewport ? CheckState.Checked : CheckState.UnChecked
+        };
+        ckbKeepContentInAllViewport.CheckedStateChanging += (s, e) => scroll.KeepContentInAllViewport = e.NewValue == CheckState.Checked;
+        view.Add (ckbKeepContentInAllViewport);
+
         var lblSizeChanged = new Label
         {
-            Y = Pos.Bottom (lblPosition) + 1
+            Y = Pos.Bottom (ckbKeepContentInAllViewport) + 1
         };
         view.Add (lblSizeChanged);