Grid Layout

GridNode provides true 2D layout with consistent column widths and row heights across all cells. Unlike nesting HorizontalLayout inside VerticalLayout (where each row calculates widths independently), GridNode ensures uniform cell sizing across the entire grid.

When to Use GridNode

Use Case	Why GridNode
Data tables	Consistent column alignment across rows
Dashboards	Multi-panel layouts with precise sizing
Forms	Aligned labels and inputs
Metrics displays	Uniform cell sizes for visual consistency

Basic Usage

Create a grid with explicit dimensions or build it dynamically:

// Explicit dimensions
var grid = new GridNode(rows: 3, cols: 2);

// Or build dynamically with AddRow
var grid = new GridNode()
    .WithColumns(SizeConstraint.Exactly(15), SizeConstraint.FillRemaining())
    .AddRow(new TextNode("Name:"), new TextNode("John Doe"))
    .AddRow(new TextNode("Email:"), new TextNode("[email protected]"))
    .AddRow(new TextNode("Role:"), new TextNode("Developer"));

Column and Row Constraints

Define column widths and row heights using the same constraint types as other layouts:

var grid = new GridNode()
    .WithColumns(
        SizeConstraint.Exactly(10),      // Fixed 10 columns
        SizeConstraint.FillRemaining(),  // Take remaining space
        SizeConstraint.Exactly(8))       // Fixed 8 columns
    .WithRows(
        SizeConstraint.Exactly(1),       // Header row: 1 line
        SizeConstraint.FillRemaining()); // Content: remaining space

Available constraints:

Constraint	Description
Exactly(n)	Fixed size in columns/rows
FillRemaining()	Take remaining space after fixed/auto
Auto()	Size to content
Percentage(n)	Percentage of available space

Setting Cell Content

Use SetCell() for explicit positioning or AddRow() for sequential building:

// Explicit positioning (row, col, content)
grid.SetCell(0, 0, new TextNode("Header").Bold());
grid.SetCell(1, 0, new TextNode("Cell 1,0"));
grid.SetCell(1, 1, new TextNode("Cell 1,1"));

// Sequential row building
grid.AddRow(
    new TextNode("Label"),
    new TextNode("Value"));

Cell Spanning

Cells can span multiple columns and/or rows:

// Header spanning 3 columns
grid.SetCell(0, 0,
    new TextNode("Dashboard Title").AlignCenter().Bold(),
    colSpan: 3);

// Tall cell spanning 2 rows
grid.SetCell(1, 0,
    new TextNode("Sidebar\nContent"),
    rowSpan: 2);

Grid Lines

Add borders between cells using WithGridLines():

var grid = new GridNode()
    .WithColumns(SizeConstraint.Exactly(10), SizeConstraint.FillRemaining())
    .AddRow(new TextNode("Name"), new TextNode("Value"))
    .AddRow(new TextNode("CPU"), new TextNode("45%"))
    .WithGridLines(BorderStyle.Single)
    .WithGridLineColor(Color.Blue);

Available border styles:

• BorderStyle.None - No grid lines (default)
• BorderStyle.Single - Single line (─│┌┐└┘├┤┬┴┼)
• BorderStyle.Double - Double line (═║╔╗╚╝╠╣╦╩╬)
• BorderStyle.Rounded - Rounded corners (─│╭╮╰╯├┤┬┴┼)
• BorderStyle.Ascii - ASCII characters (-|+)

Nested Grids

Grids can contain other grids for complex layouts:

// Metrics panel with its own grid
var metricsGrid = new GridNode()
    .WithColumns(SizeConstraint.Exactly(10), SizeConstraint.FillRemaining())
    .AddRow(new TextNode("CPU:"), new TextNode("45%"))
    .AddRow(new TextNode("Memory:"), new TextNode("62%"));

// Main dashboard grid
var dashboard = new GridNode()
    .WithColumns(SizeConstraint.Exactly(30), SizeConstraint.FillRemaining())
    .WithRows(SizeConstraint.Exactly(1), SizeConstraint.FillRemaining())
    .WithGridLines(BorderStyle.Double);

dashboard.SetCell(0, 0, new TextNode("System Dashboard").AlignCenter(), colSpan: 2);
dashboard.SetCell(1, 0, new PanelNode().WithTitle("Metrics").WithContent(metricsGrid));
dashboard.SetCell(1, 1, new PanelNode().WithTitle("Logs").WithContent(logsContent));

Focus Navigation

Enable keyboard navigation for interactive grids:

var grid = new GridNode()
    .WithNavigationMode(GridNavigationMode.CellNavigation)
    .WithFocusHighlight(Color.Blue, Color.White);

Navigation modes:

Mode	Behavior
None	Display only, no keyboard navigation
CellNavigation	Arrow keys move between cells, Enter activates
ChildFocusRouting	Tab routes to focusable children in cells

Observables

// React to focus changes
grid.FocusedCellChanged.Subscribe(pos =>
    Console.WriteLine($"Focused: row {pos.Row}, col {pos.Col}"));

// React to cell activation (Enter key)
grid.CellActivated.Subscribe(info =>
    HandleCellActivated(info.Row, info.Col, info.Cell));

Complete Example: Dashboard

public class DashboardPage : ReactivePage<DashboardViewModel>
{
    public override ILayoutNode BuildLayout()
    {
        return BuildDashboard().Fill();
    }

    private GridNode BuildDashboard()
    {
        var dashboard = new GridNode()
            .WithColumns(
                SizeConstraint.Exactly(35),
                SizeConstraint.FillRemaining())
            .WithRows(
                SizeConstraint.Exactly(3),
                SizeConstraint.FillRemaining())
            .WithGridLines(BorderStyle.Double)
            .WithGridLineColor(Color.Blue);

        // Header spanning both columns
        dashboard.SetCell(0, 0,
            new TextNode("System Dashboard")
                .AlignCenter()
                .Bold()
                .WithForeground(Color.Cyan),
            colSpan: 2);

        // Left column: Metrics
        dashboard.SetCell(1, 0, BuildMetricsPanel());

        // Right column: Event log
        dashboard.SetCell(1, 1, BuildLogsPanel());

        return dashboard;
    }

    private ILayoutNode BuildMetricsPanel()
    {
        var grid = new GridNode()
            .WithColumns(
                SizeConstraint.Exactly(10),
                SizeConstraint.FillRemaining());

        grid.AddRow(
            new TextNode("CPU:"),
            ViewModel.CpuUsageChanged
                .Select(cpu => BuildProgressBar(cpu))
                .AsLayout());

        grid.AddRow(
            new TextNode("Memory:"),
            ViewModel.MemoryUsageChanged
                .Select(mem => BuildProgressBar(mem))
                .AsLayout());

        return new PanelNode()
            .WithTitle("Metrics")
            .WithContent(grid);
    }

    private static TextNode BuildProgressBar(int percentage)
    {
        var filled = (int)(percentage / 100.0 * 12);
        var bar = new string('█', filled) + new string('░', 12 - filled);
        return new TextNode($"{bar} {percentage,3}%")
            .WithForeground(percentage >= 80 ? Color.Red : Color.Green);
    }
}

GridNode vs. Nested Layouts

Feature	GridNode	Nested Horizontal/Vertical
Column width consistency	All rows share same widths	Each row independent
Grid lines	Built-in border rendering	Manual with PanelNode
Cell spanning	Native colspan/rowspan	Complex workarounds
2D navigation	Built-in arrow key nav	Not available
Best for	Tables, dashboards, forms	Simple stacking

API Reference

Properties

Property	Type	Description
RowCount	int	Number of rows
ColumnCount	int	Number of columns
GridLines	BorderStyle	Border style for grid lines
GridLineColor	Color?	Color for grid lines
CellPadding	int	Padding inside cells
NavigationMode	GridNavigationMode	Keyboard navigation mode
FocusedRow	int	Currently focused row
FocusedColumn	int	Currently focused column

Methods

Method	Description
WithColumns(...)	Set column constraints
WithRows(...)	Set row constraints
SetCell(row, col, content, colSpan?, rowSpan?)	Set cell content
AddRow(...)	Add a row with cells
WithGridLines(style)	Set grid line style
WithGridLineColor(color)	Set grid line color
WithCellPadding(padding)	Set cell padding
WithNavigationMode(mode)	Set navigation mode
WithFocusHighlight(bg, fg)	Set focus highlight colors

Observables

Observable	Type	Description
Invalidated	IObservable<Unit>	Grid needs re-render
FocusedCellChanged	IObservable<(int Row, int Col)>	Focus moved
CellActivated	IObservable<(int Row, int Col, ILayoutNode? Cell)>	Cell activated