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# TRows

> Grid band class that paints multiple rows of column cells

## Overview

`TRows` is a grid band class that paints multiple rows of column cells. It includes support for hierarchical "rows-inside-rows" through the `Children` property, enabling master-detail row structures.

## Key Properties

<ParamField path="Height" type="TCoordinate">
  Default height for all rows in pixels. Individual row heights can be overridden using the `Heights` property.

  ```pascal theme={null}
  Grid.Rows.Height.Value := 25; // 25 pixels per row
  ```
</ParamField>

<ParamField path="Heights[Index]" type="Single">
  Individual height for a specific row. Allows different rows to have different heights.

  ```pascal theme={null}
  Grid.Rows.Heights[0] := 30;  // First row 30 pixels
  Grid.Rows.Heights[1] := 20;  // Second row 20 pixels
  ```
</ParamField>

<ParamField path="Spacing" type="TCoordinate">
  Vertical spacing between rows in pixels.

  ```pascal theme={null}
  Grid.Rows.Spacing.Value := 2; // 2 pixels between rows
  ```
</ParamField>

<ParamField path="Back" type="TFormat">
  Background formatting for all rows. Defines the default background color, gradient, and other visual properties.

  ```pascal theme={null}
  Grid.Rows.Back.Brush.Color := clWhite;
  ```
</ParamField>

<ParamField path="Alternate" type="TAlternateFormat">
  Formatting properties for odd-numbered rows. Enables alternating row colors for better readability.

  ```pascal theme={null}
  Grid.Rows.Alternate.Visible := True;
  Grid.Rows.Alternate.Brush.Color := clSilver;
  ```
</ParamField>

<ParamField path="RowLines" type="TStroke">
  Stroke properties for horizontal lines between rows.

  ```pascal theme={null}
  Grid.Rows.RowLines.Visible := True;
  Grid.Rows.RowLines.Color := clGray;
  Grid.Rows.RowLines.Width := 1;
  ```
</ParamField>

<ParamField path="Hover" type="TCellHover">
  Selection and formatting properties for the cell under the mouse cursor.

  ```pascal theme={null}
  Grid.Rows.Hover.Visible := True;
  Grid.Rows.Hover.Format.Brush.Color := clYellow;
  ```
</ParamField>

<ParamField path="Data" type="TVirtualData">
  The data source for the rows. Must be assigned to display data in the grid.

  ```pascal theme={null}
  Grid.Rows.Data := MyVirtualData;
  ```
</ParamField>

<ParamField path="Children" type="TRowsBands">
  Collection of optional sub-rows for each row. Enables hierarchical row structures.

  ```pascal theme={null}
  var
    SubRow: TGridBand;
  begin
    SubRow := Grid.Rows.Children.Add;
    // Configure sub-row
  end;
  ```
</ParamField>

<ParamField path="SubBands" type="TRowsBands">
  Collection of additional bands that can be displayed for each row.
</ParamField>

<ParamField path="VisibleColumns" type="TVisibleColumns">
  Internal property containing an array of all visible columns. Used for rendering.
</ParamField>

<ParamField path="YSpacing" type="Single">
  Calculated vertical spacing value used internally for rendering.
</ParamField>

## Key Methods

<ParamField path="HeightOf(ARow)" type="Single">
  Returns the height of the specified row, taking into account custom heights or the default height.

  ```pascal theme={null}
  var
    H: Single;
  begin
    H := Grid.Rows.HeightOf(5); // Height of row 5
  end;
  ```
</ParamField>

<ParamField path="TopOf(ARow)" type="Single">
  Returns the Y coordinate of the top edge of the specified row.

  ```pascal theme={null}
  var
    Y: Single;
  begin
    Y := Grid.Rows.TopOf(10); // Top position of row 10
  end;
  ```
</ParamField>

<ParamField path="BottomOf(ARow)" type="Single">
  Returns the Y coordinate of the bottom edge of the specified row.

  ```pascal theme={null}
  var
    Y: Single;
  begin
    Y := Grid.Rows.BottomOf(10); // Bottom position of row 10
  end;
  ```
</ParamField>

<ParamField path="RowAt(Y, AvailableHeight)" type="Integer">
  Returns the row index at the specified Y coordinate, or -1 if no row is found.

  ```pascal theme={null}
  var
    RowIndex: Integer;
  begin
    RowIndex := Grid.Rows.RowAt(100, Grid.Height);
  end;
  ```
</ParamField>

<ParamField path="FirstVisible(AOffset)" type="Integer">
  Returns the index of the first visible row, optionally offset by the specified amount.

  ```pascal theme={null}
  var
    FirstRow: Integer;
  begin
    FirstRow := Grid.Rows.FirstVisible(Grid.Rows.Scroll.Y);
  end;
  ```
</ParamField>

<ParamField path="AutoHeight(ARow)" type="Single">
  Calculates the automatic height for the specified row based on cell content.

  ```pascal theme={null}
  var
    H: Single;
  begin
    H := Grid.Rows.AutoHeight(5);
    Grid.Rows.Heights[5] := H;
  end;
  ```
</ParamField>

<ParamField path="AllHeightsEqual" type="Boolean">
  Returns `true` if all rows have the same height.
</ParamField>

<ParamField path="Empty" type="Boolean">
  Returns `true` if there are no rows to display (data is empty).
</ParamField>

<ParamField path="MaxBottom" type="Single">
  Returns the Y coordinate of the bottom of the last row.
</ParamField>

<ParamField path="CalcDefaultHeight">
  Calculates and sets the default row height based on font size and cell formatting.

  ```pascal theme={null}
  Grid.Rows.CalcDefaultHeight;
  ```
</ParamField>

<ParamField path="Clear">
  Clears all row-specific data and resets to initial state.

  ```pascal theme={null}
  Grid.Rows.Clear;
  ```
</ParamField>

<ParamField path="Swap(A, B)">
  Swaps two rows at the specified indices.

  ```pascal theme={null}
  Grid.Rows.Swap(0, 5); // Swap first and sixth rows
  ```
</ParamField>

## Usage Examples

### Basic Row Configuration

```pascal theme={null}
begin
  // Set default row height
  Grid.Rows.Height.Value := 30;
  
  // Configure row spacing
  Grid.Rows.Spacing.Value := 1;
  
  // Enable row lines
  Grid.Rows.RowLines.Visible := True;
  Grid.Rows.RowLines.Color := clSilver;
end;
```

### Alternating Row Colors

```pascal theme={null}
begin
  // Set default row background
  Grid.Rows.Back.Brush.Color := clWhite;
  
  // Configure alternate row formatting
  Grid.Rows.Alternate.Visible := True;
  Grid.Rows.Alternate.Brush.Color := RGB(240, 240, 240);
end;
```

### Custom Row Heights

```pascal theme={null}
var
  i: Integer;
begin
  // Set individual row heights
  for i := 0 to Grid.Rows.Data.Count - 1 do
  begin
    if i mod 3 = 0 then
      Grid.Rows.Heights[i] := 40  // Every third row is taller
    else
      Grid.Rows.Heights[i] := 25;
  end;
end;
```

### Auto-Height Rows

```pascal theme={null}
var
  i: Integer;
  H: Single;
begin
  // Calculate automatic height for each row
  for i := 0 to Grid.Rows.Data.Count - 1 do
  begin
    H := Grid.Rows.AutoHeight(i);
    Grid.Rows.Heights[i] := H;
  end;
end;
```

### Row Hover Effect

```pascal theme={null}
begin
  // Enable hover highlighting
  Grid.Rows.Hover.Visible := True;
  Grid.Rows.Hover.Format.Brush.Color := clYellow;
  Grid.Rows.Hover.Format.Transparency := 128; // Semi-transparent
end;
```

### Finding Rows

```pascal theme={null}
var
  RowIndex: Integer;
  Y: Single;
begin
  // Find row at mouse position
  RowIndex := Grid.Rows.RowAt(Mouse.Y, Grid.Height);
  if RowIndex >= 0 then
  begin
    // Get row position
    Y := Grid.Rows.TopOf(RowIndex);
    ShowMessage(Format('Row %d at Y=%g', [RowIndex, Y]));
  end;
end;
```

### Hierarchical Rows

```pascal theme={null}
var
  DetailBand: TGridBand;
begin
  // Add sub-rows (detail rows)
  DetailBand := Grid.Rows.Children.Add;
  DetailBand.Height.Value := 20;
  
  // Check if children are visible for a specific row
  if Grid.Rows.IsChildrenVisible(nil, 5) then
    ShowMessage('Row 5 has visible children');
end;
```

## Scrolling

The `TRows` class includes scroll support:

```pascal theme={null}
begin
  // Access scroll position
  ShowMessage('Vertical scroll: ' + FloatToStr(Grid.Rows.Scroll.Y));
  
  // Get first visible row after scrolling
  var FirstRow := Grid.Rows.FirstVisible(Grid.Rows.Scroll.Y);
end;
```

## Related Classes

* [TColumn](/api/tcolumn) - Column class
* [TColumns](/api/tcolumns) - Columns collection
* [TRowGroup](/api/trowgroup) - Row group with headers and footers