Improve header and cell text alignment in grid

Refactored header height calculation into a dedicated method and adjusted text alignment logic for both headers and cells in Skia rendering. These changes improve visual consistency, especially for centered text in headers without child elements, and clarify padding calculations. Minor code cleanup and comments added for maintainability.

Author: CyLuGh

src/HierarchyGrid.Avalonia/Grid.axaml.cs

@@ -6,6 +6,7 @@
 using Avalonia.Controls.Shapes;
 using Avalonia.Data;
 using Avalonia.Input;
+using Avalonia.Layout;
 using Avalonia.Media;
 using Avalonia.ReactiveUI;
 using Avalonia.VisualTree;
@@ -22,7 +23,7 @@ namespace HierarchyGrid.Avalonia;
 public partial class Grid : ReactiveUserControl<HierarchyGridViewModel>
 {
     private readonly Flyout _tooltip;
-    private Rectangle _tooltipRectangle;
+    private readonly Rectangle _tooltipRectangle;
     private ContextMenu? _contextMenu;
 
     public Grid()
@@ -328,6 +329,11 @@ private void ShowTooltip(PositionedCell pCell)
         Canvas.SetLeft(_tooltipRectangle, pCell.Left + 3);
         Canvas.SetTop(_tooltipRectangle, pCell.Top + 3);
 
+        // var border = new Border() { HorizontalAlignment = HorizontalAlignment.Stretch };
+        // border.Background = Brushes.Wheat;
+        // border.Child = new TextBlock() { Text = text.Trim() };
+        // _tooltip.Content = border;
+
         _tooltip.Content = text.Trim();
         _tooltip.Placement = PlacementMode.Bottom;
         _tooltip.ShowAt(_tooltipRectangle);

src/HierarchyGrid.Skia/CanvasExtensions.cs

@@ -280,15 +280,11 @@ private static void DrawColumnHeader(
             int column,
             HierarchyDefinition hdef,
             double width,
-            double screenScale
+            double screenScale,
+            bool lastColumn = false
         )
         {
-            var height = hdef is { IsExpanded: true, HasChild: true }
-                ? viewModel.ColumnsHeadersHeight[hdef.Level]
-                : Enumerable
-                    .Range(hdef.Level, viewModel.ColumnsHeadersHeight.Length - hdef.Level)
-                    .Select(x => viewModel.ColumnsHeadersHeight[x])
-                    .Sum();
+            double height = ComputeHeaderHeight(viewModel, hdef);
 
             var top = Enumerable
                 .Range(0, hdef.Level)
@@ -320,6 +316,25 @@ double screenScale
             currentPosition += width;
         }
 
+        /// <summary>
+        /// If the definition is expanded and has any child element,
+        /// it should span on only one row, using the height of its level.
+        /// Otherwise, it should span until the end of the headers display.
+        /// </summary>
+        private static double ComputeHeaderHeight(
+            HierarchyGridViewModel viewModel,
+            HierarchyDefinition hdef
+        )
+        {
+            var height = hdef is { IsExpanded: true, HasChild: true }
+                ? viewModel.ColumnsHeadersHeight[hdef.Level]
+                : Enumerable
+                    .Range(hdef.Level, viewModel.ColumnsHeadersHeight.Length - hdef.Level)
+                    .Select(x => viewModel.ColumnsHeadersHeight[x])
+                    .Sum();
+            return height;
+        }
+
         private static void DrawParentColumnHeader(
             this SKCanvas canvas,
             HierarchyGridViewModel viewModel,
@@ -613,7 +628,7 @@ private static void RenderHeaderText(
             double screenScale,
             RenderInfo renderInfo,
             string fontFamily = "",
-            float headerTextSize = 16f
+            float headerFontSize = 16f
         )
         {
             TextDrawer.Clear();
@@ -622,20 +637,30 @@ private static void RenderHeaderText(
                 hdef.Content?.ToString() ?? string.Empty,
                 new Style
                 {
-                    FontSize = headerTextSize,
+                    FontSize = headerFontSize,
                     TextColor = renderInfo.ForegroundColor,
                     FontWeight = 600,
                     FontFamily = !string.IsNullOrEmpty(fontFamily) ? fontFamily : "Sans Serif",
                 }
             );
-            TextDrawer.MaxHeight = (float)((height - 10) * screenScale);
-            TextDrawer.MaxWidth = (float)((width - 24) * screenScale);
 
-            TextDrawer.Paint(
-                canvas,
-                new SKPoint((float)((left + 22) * screenScale), (float)((top + 6) * screenScale)),
-                TextPaintOptions
-            );
+            float textVPadding = (float)(height - (headerFontSize * screenScale));
+            float textHPadding = 22f;
+
+            TextDrawer.MaxHeight = (float)(height * screenScale);
+            TextDrawer.MaxWidth = (float)((width - textHPadding) * screenScale);
+
+            /* We can center elements that have no child elements,
+             otherwise the text might be out of drawn screen */
+            float x = hdef.HasChild
+                ? (float)((left + 22) * screenScale)
+                : (float)((left + ((width - TextDrawer.MeasuredWidth) / 2)) * screenScale);
+
+            float y = hdef.HasChild
+                ? (float)((top + 6) * screenScale)
+                : (float)((top + (textVPadding / 2)) * screenScale);
+
+            TextDrawer.Paint(canvas, new SKPoint(x, y), TextPaintOptions);
         }
 
         private static Option<SKPath> GetHeaderDecorator(
@@ -928,10 +953,10 @@ private static void RenderCellText(
             RenderInfo renderInfo
         )
         {
-            var fontSize = viewModel.CellFontSize;
+            float fontSize = viewModel.CellFontSize;
 
             float textHPadding = (float)((6f + theme.SelectionBorderThickness) * screenScale);
-            var textVPadding = (float)(cell.Height - (fontSize * screenScale));
+            float textVPadding = (float)(cell.Height - (fontSize * screenScale));
 
             var rightDecorPadding = (
                 from rd in cell.ResultSet.RightDecor
@@ -968,8 +993,8 @@ select svg.Picture.CullRect.Width * screenScale
             TextDrawer.Paint(
                 canvas,
                 new SKPoint(
-                    (float)(cell.Left * screenScale) + (textHPadding / 2) + leftDecorPadding,
-                    (float)(cell.Top * screenScale) + (textVPadding / 2)
+                    (float)((cell.Left + (textHPadding / 2) + leftDecorPadding) * screenScale),
+                    (float)((cell.Top + (textVPadding / 2)) * screenScale)
                 ),
                 TextPaintOptions
             );

src/HierarchyGrid.Skia/HierarchyGridDrawer.cs

@@ -32,18 +32,18 @@ public static async Task Draw(
                 var previousGlobalCoordinates = viewModel
                     .GlobalHeadersCoordinates.Select(t => (t.Coord, t.Guid))
                     .ToList();
-                
+
                 viewModel.ClearCoordinates();
 
                 canvas.DrawGlobalHeaders(viewModel, theme, previousGlobalCoordinates, screenScale);
-                
+
                 canvas.DrawCells(
                     viewModel,
                     theme,
                     viewModel.GetDrawnCells(width, height, invalidate),
                     screenScale
                 );
-                
+
                 canvas.DrawColumnHeaders(
                     viewModel,
                     theme,
@@ -52,7 +52,7 @@ public static async Task Draw(
                     ref headerCount,
                     screenScale
                 );
-                
+
                 canvas.DrawRowHeaders(
                     viewModel,
                     theme,
@@ -71,7 +71,6 @@ public static async Task Draw(
                 paint.IsAntialias = true;
                 paint.Color = theme.ForegroundColor;
 
-                // TODO: Check under MacOS
                 canvas.DrawText(
                     viewModel.StatusMessage ?? "NO MESSAGE",
                     (float)screenScale * width / 2,