RenderTargetTextureSource

Introduction

The RenderTargetTextureSource property allows a Sprite to render a texture produced by a different ContainerRuntime which is drawing to a render target. This feature allows a render target to be scaled, rotated, positioned, stacked, or to use any other Gum layout functionality.

To set up this same pattern in the Gum tool, see Rotating and Scaling Clipped Contents.

RenderTargetTextureSource Requirements

To use RenderTargetTextureSource, the following must exist:

1. A container which has its IsRenderTarget set to true. This container can contain any number of children.
2. A Sprite which has its RenderTargetTextureSource set to the container

Normally invisible objects are not rendered and do not perform their Layout calls. If a container has its IsRenderTarget set to true, then it will perform layout and rendering calls so even if invisible so that SpriteRuntime instances can reference the resulting texture.

Code Example: Scaling a ListBox

The following code creates a ListBox which is displayed on a render target with wavy scaling:

SpriteRuntime sprite;

protected override void Initialize()
{
    GumUI.Initialize(this);

    var container = new ContainerRuntime();
    container.AddToRoot();
    container.Name = "Render target container";
    container.IsRenderTarget = true;
    container.Dock(Dock.SizeToChildren);
    container.Visible = false;

    var listBox = new ListBox();
    container.AddChild(listBox);
    for (int i = 0; i < 20; i++)
    {
        listBox.Items.Add($"Item {i}");
    }

    sprite = new SpriteRuntime();
    sprite.AddToRoot();
    sprite.Anchor(Anchor.Center);
    sprite.RenderTargetTextureSource = container;

    base.Initialize();
}

protected override void Update(GameTime gameTime)
{
    var gameSeconds = (float)gameTime.TotalGameTime.TotalSeconds;
    sprite.Width = 100 + 50 * MathF.Sin(gameSeconds * 4);
    sprite.Height = 100 + 50 * MathF.Sin(gameSeconds * 3);

    GumUI.Update(gameTime);

    base.Update(gameTime);
}

Currently the ListBox is not interactive because the original ListBox is invisible so it does not receive events from the Cursor. Future versions of Gum may provide a way to interact with invisible controls rendered to a RenderTarget.