test: recording drawing context and DataGridRenderer command tests (#26)

.github/instructions/testing.instructions.md

@@ -84,35 +84,27 @@ public class DataGridSourceSortingTests
 
 ---
 
-## `FakeDrawingContext` — test double for renderers
+## `RecordingDrawingContext` — test double for rendering
 
-When testing `ICellRenderer` or `DrawnComponent`, create a no-op `IDrawingContext`:
+Rendering tests run without SkiaSharp against `tests/KumikoUI.Core.Tests/TestHelpers/RecordingDrawingContext.cs`.
+It records every `IDrawingContext` call as a `DrawOp` in call order (so index = z-order), in viewport
+coordinates with the active clip, and measures text monospace (8 px per character, 14 px tall).
+`DrawOp.Visible` is the part of an op its clip lets reach the screen.
+
+For `DataGridRenderer`, use `RenderHarness` (same folder): it builds a four-column grid of people, gives
+every `GridColor` on the style a distinct value (so a recorded colour identifies its style role) and
+renders into a fresh recording context:
 
 ```csharp
-// tests/KumikoUI.Core.Tests/TestHelpers/FakeDrawingContext.cs
-using KumikoUI.Core.Rendering;
+var h = RenderHarness.Create(width: 300);
+h.Column("Name").FreezeMode = ColumnFreezeMode.Left;
+h.Scroll.OffsetX = 50;
 
-namespace KumikoUI.Core.Tests.TestHelpers;
+var ctx = h.Render();
 
-internal sealed class FakeDrawingContext : IDrawingContext
-{
-    public void DrawRect(GridRect r, GridPaint p) { }
-    public void FillRect(GridRect r, GridPaint p) { }
-    public void DrawRoundRect(GridRect r, float cr, GridPaint p) { }
-    public void FillRoundRect(GridRect r, float cr, GridPaint p) { }
-    public void DrawLine(float x1, float y1, float x2, float y2, GridPaint p) { }
-    public void DrawText(string t, float x, float y, GridPaint p) { }
-    public void DrawTextInRect(string t, GridRect r, GridPaint p,
-        GridTextAlignment h = GridTextAlignment.Left,
-        GridVerticalAlignment v = GridVerticalAlignment.Center,
-        bool clip = true) { }
-    public GridSize MeasureText(string t, GridPaint p) => new GridSize(t.Length * 8, 14);
-    public GridFontMetrics GetFontMetrics(GridPaint p) => new GridFontMetrics(14, 0, 2);
-    public void ClipRect(GridRect r) { }
-    public void Save() { }
-    public void Restore() { }
-    public void Translate(float dx, float dy) { }
-    public void DrawImage(object image, GridRect dest) { }
-    public void Dispose() { }
-}
+var cell = ctx.SingleText("P00");
+Assert.Equal(new GridRect(0, 0, 150, 400), cell.Clip);
 ```
+
+Known renderer defects are pinned as `[Fact(Skip = "<finding>, fixed by #<issue>: …")]` tests in
+`tests/KumikoUI.Core.Tests/Rendering/`; the fix removes the `Skip`.

src/KumikoUI.Core/DataGridRenderer.cs

@@ -22,7 +22,7 @@
     private readonly List<(DataGridColumn Column, float X, int OriginalIndex)> _scrollableCols = new();
     private readonly List<(DataGridColumn Column, float X, int OriginalIndex)> _allCols = new();
 
     public DataGridRenderer()
     {
         var textRenderer = new TextCellRenderer();
         _cellRenderers[DataGridColumnType.Text] = textRenderer;
@@ -307,11 +307,6 @@
         popupManager?.DrawPopups(ctx);
     }
 
-    private static float ColumnScreenX(float colContentX, ScrollState scroll, bool isFrozen)
-    {
-        return isFrozen ? colContentX : colContentX - scroll.OffsetX;
-    }
-
     /// <summary>
     /// Returns screen X for a column, handling left-frozen, right-frozen, and scrollable.
     /// For right-frozen columns, the X is already an absolute screen position from GetVisibleRightFrozenColumns.
@@ -326,13 +321,6 @@
         };
     }
 
-    private void DrawFrozenBackground(
-        IDrawingContext ctx, float frozenWidth, ScrollState scroll, DataGridStyle style)
-    {
-        ctx.FillRect(new GridRect(0, 0, frozenWidth, scroll.ViewportHeight),
-            _paintCache.FrozenColumnBackground);
-    }
-
     private void DrawRightFrozenBackground(
         IDrawingContext ctx, float rightFrozenLeft, float rightFrozenWidth, ScrollState scroll, DataGridStyle style)
     {

src/KumikoUI.Core/Rendering/Primitives.cs

@@ -139,6 +139,9 @@ public GridRect Offset(float dx, float dy)
 
     /// <summary>A zero-size rectangle at the origin.</summary>
     public static GridRect Empty => new(0, 0, 0, 0);
+
+    /// <inheritdoc />
+    public override string ToString() => FormattableString.Invariant($"GridRect({X}, {Y}, {Width}, {Height})");
 }
 
 /// <summary>

tests/KumikoUI.Core.Tests/PinnedBottomSummaryTests.cs

@@ -312,14 +312,14 @@ public void Render_PinnedFooter_IsDrawnAfterDragHandleGrips()
         grid.Style.ShowRowDragHandle = true;
         grid.Style.RowDragHandlePosition = DragHandlePosition.Left;
 
-        var fills = grid.Render().Fills;
+        var fills = grid.Render().Fills.ToList();
 
         int footerIndex = fills.FindLastIndex(f =>
             f.Color == grid.Style.SummaryRowBackgroundColor &&
             Math.Abs(f.Rect.Y - grid.FooterTop) < 0.01f &&
             f.Rect.Width >= ViewportWidth);
         int lastGripIndex = fills.FindLastIndex(f =>
-            f.Kind == "FillRoundRect" && f.Color == grid.Style.RowDragHandleColor);
+            f.Kind == DrawOpKind.FillRoundRect && f.Color == grid.Style.RowDragHandleColor);
 
         Assert.True(footerIndex >= 0, "pinned footer background was not drawn");
         Assert.True(lastGripIndex >= 0, "drag handle grips were not drawn");
@@ -332,7 +332,7 @@ public void Render_Unpinned_SummaryIsDrawnAfterLastRow()
         var grid = CreateGrid(rowCount: 3, pinned: false);
         float expectedY = grid.Style.HeaderHeight + 3 * grid.Style.RowHeight;
 
-        var fills = grid.Render().Fills;
+        var fills = grid.Render().Fills.ToList();
 
         Assert.Contains(fills, f => f.Color == grid.Style.SummaryRowBackgroundColor && Math.Abs(f.Rect.Y - expectedY) < 0.01f);
         Assert.DoesNotContain(fills, f => f.Color == grid.Style.SummaryRowBackgroundColor && Math.Abs(f.Rect.Y - grid.FooterTop) < 0.01f);