Fix scrollbar thumb/arrow overlap and clamp issues across all controls

- Reserve arrow slots in geometry so thumb never overlaps arrows
- Always show arrows with thumb color regardless of scroll position
- Clamp thumb size to track bounds (Math.Clamp) in all controls
- Clamp thumb position with Math.Min to prevent rounding overshoot
- Fix MultilineEdit vertical helper formula mismatch with inline code

Author: nickprotop

SharpConsoleUI/Controls/MultilineEdit/MultilineEditControl.Rendering.cs

@@ -174,12 +174,13 @@ public override void PaintDOM(CharacterBuffer buffer, LayoutRect bounds, LayoutR
 				// Reserve arrow positions so thumb never overlaps them
 				int arrowSlots = effectiveViewport >= 3 ? 2 : 0;
 				int thumbTrackHeight = effectiveViewport - arrowSlots;
-				vThumbHeight = Math.Max(1, (int)(thumbTrackHeight * ((double)effectiveViewport / Math.Max(1, totalWrappedLineCount))));
+				vThumbHeight = Math.Clamp((int)(thumbTrackHeight * ((double)effectiveViewport / Math.Max(1, totalWrappedLineCount))), 1, thumbTrackHeight);
 				vThumbPos = arrowSlots > 0 ? 1 : 0; // start after top arrow
 				if (totalWrappedLineCount > effectiveViewport)
 				{
+					int maxThumbPos = thumbTrackHeight - vThumbHeight;
 					double scrollRatio = (double)_verticalScrollOffset / (totalWrappedLineCount - effectiveViewport);
-					vThumbPos += (int)Math.Round((thumbTrackHeight - vThumbHeight) * scrollRatio);
+					vThumbPos += Math.Min((int)Math.Round(maxThumbPos * scrollRatio), maxThumbPos);
 				}
 			}
 
@@ -509,12 +510,12 @@ public override void PaintDOM(CharacterBuffer buffer, LayoutRect bounds, LayoutR
 					// Reserve arrow positions so thumb never overlaps them
 					int hArrowSlots = effectiveWidth >= 3 ? 2 : 0;
 					int hThumbTrackWidth = effectiveWidth - hArrowSlots;
-					int thumbWidth = Math.Max(1, (hThumbTrackWidth * hThumbTrackWidth) / Math.Max(1, maxLineLength));
+					int thumbWidth = Math.Clamp((hThumbTrackWidth * hThumbTrackWidth) / Math.Max(1, maxLineLength), 1, hThumbTrackWidth);
 					int thumbPos = hArrowSlots > 0 ? 1 : 0;
 					if (maxLineLength > effectiveWidth)
 					{
 						int maxThumbPos = hThumbTrackWidth - thumbWidth;
-						thumbPos += (int)Math.Round((double)_horizontalScrollOffset / (maxLineLength - effectiveWidth) * maxThumbPos);
+						thumbPos += Math.Min((int)Math.Round((double)_horizontalScrollOffset / (maxLineLength - effectiveWidth) * maxThumbPos), maxThumbPos);
 					}
 
 					for (int x = 0; x < effectiveWidth; x++)
@@ -616,12 +617,12 @@ private int GetGutterWidth()
 			// Reserve arrow positions so thumb never overlaps them
 			int arrowSlots = effectiveViewport >= 3 ? 2 : 0;
 			int thumbTrackHeight = effectiveViewport - arrowSlots;
-			int thumbHeight = Math.Max(1, (thumbTrackHeight * thumbTrackHeight) / Math.Max(1, totalLines));
+			int thumbHeight = Math.Clamp((int)(thumbTrackHeight * ((double)effectiveViewport / Math.Max(1, totalLines))), 1, thumbTrackHeight);
 			int thumbY = arrowSlots > 0 ? 1 : 0;
 			if (totalLines > effectiveViewport)
 			{
 				int maxThumbPos = thumbTrackHeight - thumbHeight;
-				thumbY += (int)Math.Round((double)_verticalScrollOffset / (totalLines - effectiveViewport) * maxThumbPos);
+				thumbY += Math.Min((int)Math.Round((double)_verticalScrollOffset / (totalLines - effectiveViewport) * maxThumbPos), maxThumbPos);
 			}
 			return (effectiveViewport, thumbY, thumbHeight);
 		}
@@ -636,12 +637,12 @@ private int GetGutterWidth()
 			// Reserve arrow positions so thumb never overlaps them
 			int arrowSlots = _effectiveWidth >= 3 ? 2 : 0;
 			int thumbTrackWidth = _effectiveWidth - arrowSlots;
-			int thumbWidth = Math.Max(1, (thumbTrackWidth * thumbTrackWidth) / Math.Max(1, maxLineLength));
+			int thumbWidth = Math.Clamp((thumbTrackWidth * thumbTrackWidth) / Math.Max(1, maxLineLength), 1, thumbTrackWidth);
 			int thumbX = arrowSlots > 0 ? 1 : 0;
 			if (maxLineLength > _effectiveWidth)
 			{
 				int maxThumbPos = thumbTrackWidth - thumbWidth;
-				thumbX += (int)Math.Round((double)_horizontalScrollOffset / (maxLineLength - _effectiveWidth) * maxThumbPos);
+				thumbX += Math.Min((int)Math.Round((double)_horizontalScrollOffset / (maxLineLength - _effectiveWidth) * maxThumbPos), maxThumbPos);
 			}
 			return (_effectiveWidth, thumbX, thumbWidth);
 		}

SharpConsoleUI/Controls/ScrollablePanelControl/ScrollablePanelControl.Rendering.cs

@@ -201,13 +201,13 @@ public override void PaintDOM(CharacterBuffer buffer, LayoutRect bounds, LayoutR
 			int arrowSlots = scrollbarHeight >= 3 ? 2 : 0;
 			int thumbTrackHeight = scrollbarHeight - arrowSlots;
 			double viewportRatio = (double)_viewportHeight / _contentHeight;
-			int thumbHeight = Math.Max(1, (int)(thumbTrackHeight * viewportRatio));
+			int thumbHeight = Math.Clamp((int)(thumbTrackHeight * viewportRatio), 1, thumbTrackHeight);
 			int thumbY = arrowSlots > 0 ? 1 : 0;
 			if (_contentHeight > _viewportHeight)
 			{
 				double scrollRatio = (double)_verticalScrollOffset / (_contentHeight - _viewportHeight);
 				int maxThumbPos = thumbTrackHeight - thumbHeight;
-				thumbY += (int)Math.Round(maxThumbPos * scrollRatio);
+				thumbY += Math.Min((int)Math.Round(maxThumbPos * scrollRatio), maxThumbPos);
 			}
 
 			return (scrollbarRelX, scrollbarTop, scrollbarHeight, thumbY, thumbHeight);

SharpConsoleUI/Controls/TableControl/TableControl.Scrolling.cs

@@ -192,10 +192,11 @@ internal bool ShouldShowHorizontalScrollbar(int totalColumnsWidth, int viewportW
 		if (thumbTrackHeight <= 0) return (trackTop, trackHeight, 0, trackHeight);
 
 		double viewportRatio = (double)visibleRows / totalRows;
-		int thumbHeight = Math.Max(1, (int)(thumbTrackHeight * viewportRatio));
+		int thumbHeight = Math.Clamp((int)(thumbTrackHeight * viewportRatio), 1, thumbTrackHeight);
 		double scrollRatio = (double)_scrollOffset / Math.Max(1, totalRows - visibleRows);
 		int thumbY = arrowSlots > 0 ? 1 : 0; // start after top arrow
-		thumbY += (int)((thumbTrackHeight - thumbHeight) * scrollRatio);
+		int maxThumbPos = thumbTrackHeight - thumbHeight;
+		thumbY += Math.Min((int)(maxThumbPos * scrollRatio), maxThumbPos);
 
 		return (trackTop, trackHeight, thumbY, thumbHeight);
 	}
@@ -216,11 +217,12 @@ internal bool ShouldShowHorizontalScrollbar(int totalColumnsWidth, int viewportW
 		if (thumbTrackWidth <= 0) return (trackLeft, trackWidth, 0, trackWidth);
 
 		double viewportRatio = (double)contentAreaWidth / totalColumnsWidth;
-		int thumbWidth = Math.Max(1, (int)(thumbTrackWidth * viewportRatio));
+		int thumbWidth = Math.Clamp((int)(thumbTrackWidth * viewportRatio), 1, thumbTrackWidth);
 		int maxHScroll = totalColumnsWidth - contentAreaWidth;
 		double scrollRatio = maxHScroll > 0 ? (double)_horizontalScrollOffset / maxHScroll : 0;
 		int thumbX = arrowSlots > 0 ? 1 : 0; // start after left arrow
-		thumbX += (int)((thumbTrackWidth - thumbWidth) * scrollRatio);
+		int maxThumbPos = thumbTrackWidth - thumbWidth;
+		thumbX += Math.Min((int)(maxThumbPos * scrollRatio), maxThumbPos);
 
 		return (trackLeft, trackWidth, thumbX, thumbWidth);
 	}

SharpConsoleUI/Helpers/ScrollbarHelper.cs

@@ -59,10 +59,11 @@ public static (int trackTop, int trackHeight, int thumbY, int thumbHeight)
 			if (thumbTrackHeight <= 0) return (trackTop, trackHeight, 0, trackHeight);
 
 			double viewportRatio = (double)visibleItems / totalItems;
-			int thumbHeight = Math.Max(1, (int)(thumbTrackHeight * viewportRatio));
+			int thumbHeight = Math.Clamp((int)(thumbTrackHeight * viewportRatio), 1, thumbTrackHeight);
 			double scrollRatio = (double)scrollOffset / Math.Max(1, totalItems - visibleItems);
 			int thumbY = arrowSlots > 0 ? 1 : 0; // start after top arrow
-			thumbY += (int)((thumbTrackHeight - thumbHeight) * scrollRatio);
+			int maxThumbPos = thumbTrackHeight - thumbHeight;
+			thumbY += Math.Min((int)(maxThumbPos * scrollRatio), maxThumbPos);
 
 			return (trackTop, trackHeight, thumbY, thumbHeight);
 		}