Grid

Introduction

Gum supports adding children to a Panel in a grid layout. Unlike wrapped children in a stack, each cell in a grid is always the same size.

Panels and Grids

Panels have the following behavior by default:

• Sized automatically according to their children (WidthUnits and HeightUnits both set to RelativeToChildren)

• No stacking or grid layout (ChildrenLayout set to Regular)

We can change this default behavior to create a grid as shown in the following code:

var panel = new Panel();
panel.AddToRoot();
panel.Anchor(Gum.Wireframe.Anchor.Center);
panel.Height = 400;
panel.HeightUnits = Gum.DataTypes.DimensionUnitType.Absolute;
panel.Width = 400;
panel.WidthUnits = Gum.DataTypes.DimensionUnitType.Absolute;

var panelVisual = panel.Visual;
panelVisual.ChildrenLayout = Gum.Managers.ChildrenLayout.AutoGridHorizontal;
panelVisual.AutoGridHorizontalCells = 3;
panelVisual.AutoGridVerticalCells = 3;

for(int i = 0; i < 9; i++)
{
    var button = new Button();
    panel.AddChild(button);
    button.Text = $"Button {i}";
}

Buttons in a grid

Grid Cells as Parents

Children in a grid treat their cell as their direct parent. This means that Dock and Anchor calls are performed relative to the cell rather than the entire panel as shown in the following code:

var panel = new Panel();
panel.AddToRoot();
panel.Anchor(Gum.Wireframe.Anchor.Center);
panel.Height = 400;
panel.HeightUnits = Gum.DataTypes.DimensionUnitType.Absolute;
panel.Width = 400;
panel.WidthUnits = Gum.DataTypes.DimensionUnitType.Absolute;

var panelVisual = panel.Visual;
panelVisual.ChildrenLayout = Gum.Managers.ChildrenLayout.AutoGridHorizontal;
panelVisual.AutoGridHorizontalCells = 3;
panelVisual.AutoGridVerticalCells = 3;

for(int i = 0; i < 9; i++)
{
    var button = new Button();
    panel.AddChild(button);
    button.Dock(Gum.Wireframe.Dock.Fill);
    button.Text = $"Button {i}";
}

Grid Overflow

The AutoGridHorizontalCells and AutoGridVerticalCells properties determine the number of rows and columns in the grid. For example, the following code creates a grid with eight (8) cells:

var panel = new Panel();
panel.AddToRoot();
panel.Anchor(Gum.Wireframe.Anchor.Center);
panel.Height = 200;
panel.HeightUnits = Gum.DataTypes.DimensionUnitType.Absolute;
panel.Width = 400;
panel.WidthUnits = Gum.DataTypes.DimensionUnitType.Absolute;

var panelVisual = panel.Visual;
panelVisual.ChildrenLayout = Gum.Managers.ChildrenLayout.AutoGridHorizontal;
panelVisual.AutoGridHorizontalCells = 4;
panelVisual.AutoGridVerticalCells = 2;

for(int i = 0; i < 8; i++)
{
    var button = new Button();
    panel.AddChild(button);
    button.Dock(Gum.Wireframe.Dock.Fill);
    button.Text = $"Button {i}";
}

Buttons in a grid with eight cells

If additional buttons are added, they overflow the grid. Notice that the grid's size is not modified by the additional cells so, so additional rows do not shift the grid up.

var panel = new Panel();
panel.AddToRoot();
panel.Anchor(Gum.Wireframe.Anchor.Center);
panel.Height = 200;
panel.HeightUnits = Gum.DataTypes.DimensionUnitType.Absolute;
panel.Width = 400;
panel.WidthUnits = Gum.DataTypes.DimensionUnitType.Absolute;

var panelVisual = panel.Visual;
panelVisual.ChildrenLayout = Gum.Managers.ChildrenLayout.AutoGridHorizontal;
panelVisual.AutoGridHorizontalCells = 4;
panelVisual.AutoGridVerticalCells = 2;

for(int i = 0; i < 14; i++)
{
    var button = new Button();
    panel.AddChild(button);
    button.Dock(Gum.Wireframe.Dock.Fill);
    button.Text = $"Button {i}";
}

Grid with 8 cells with overflow

Grid Sized to Children

If a Panel is sized to its children, then the size of the grid is based on the largest cell. The following code creates a grid with nine (9) cells. The largest button decides the size of the cell. All cells in the grid match the largest size.

var panel = new Panel();
panel.AddToRoot();
panel.Anchor(Gum.Wireframe.Anchor.Center);
panel.Dock(Gum.Wireframe.Dock.SizeToChildren);

var panelVisual = panel.Visual;
panelVisual.ChildrenLayout = Gum.Managers.ChildrenLayout.AutoGridHorizontal;
panelVisual.AutoGridHorizontalCells = 3;
panelVisual.AutoGridVerticalCells = 3;

for(int i = 0; i < 9; i++)
{
    var button = new Button();
    panel.AddChild(button);
    button.Width = 50 + (float)Random.Shared.NextDouble() * 50;
    button.WidthUnits = Gum.DataTypes.DimensionUnitType.Absolute;
    button.Height = 50 + (float)Random.Shared.NextDouble() * 50;
    button.HeightUnits = Gum.DataTypes.DimensionUnitType.Absolute;
    button.Text = $"Button {i}";
}

Buttons sized randomly. The largest width and height determine the grid size