Scroll Containers

Scroll Containers are specialized widgets that act as a viewport. They render content that is larger than their own bounds and allow the user to pan around using scrollbars or mouse drag.

ScrollContainerWidget

The standard container. Supports Vertical Scrolling only.

Constructor:

// width, height, contentSpacing
new ScrollContainerWidget(int width, int height, int contentSpacing);

How to use

1. Add Components: You add IComponent objects to it.
2. Automatic Layout: The container stacks these components vertically based on their height and the contentSpacing.
3. Scroll: If the total height exceeds the container height, a scrollbar appears.

ScrollContainerWidget list = new ScrollContainerWidget(200, 100, 5);

for (int i = 0; i < 20; i++) {
    // Add components at (0, 0). The container handles the Y offset automatically.
    list.addComponent(new TextComponent(0, 0, Component.literal("Item " + i)));
}

this.addWidget(list);

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ScrollContainer2DWidget

An advanced container that supports Bidirectional Scrolling (Vertical and Horizontal). This is ideal for node editors, skill trees, or large map displays.

Constructor:

// width, height, contentSpacing
new ScrollContainer2DWidget(int width, int height, int contentSpacing);

Features

• Dual Scrollbars: Renders horizontal and vertical scrollbars only when needed.
• Mouse Drag: Users can click and drag the background to pan (if components inside capture the click, dragging won't start).
• Mouse Wheel: Scrolls vertically by default. (Shift+Scroll for horizontal is not standard behavior here, usually handled via drag).

Adding Content

Unlike the vertical container, the 2D container does not automatically stack items. You must define the X/Y coordinates of your components relative to the container's origin (0,0).

ScrollContainer2DWidget map = new ScrollContainer2DWidget(300, 200);

// Add a component at a specific position on the virtual canvas
TextComponent label = new TextComponent(0, 0, Component.literal("Start"));
label.setX(500); // Far to the right
label.setY(500); // Far down

map.addComponent(label);

The container calculates the "Content Width" and "Content Height" by finding the furthest component edge.

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Technical Constraints

Do not add Widgets directly!

You generally cannot add an IWidget (like a Button) directly to a Scroll Container via addWidget().

Why? Scroll Containers rely on the IComponent.setY(...) method to move elements up and down during rendering. Widgets do not have this relative positioning logic exposed in the same way.

The Solution: Wrap your widgets inside an AbstractComponent.

The Wrapper Pattern

If you need a list of buttons, create a Component that holds the button.

public class ButtonWrapper extends AbstractComponent {
    public ButtonWrapper(Component label, OnPress action) {
        super(0, 0, 100, 20); // Define size
        
        // Add the widget to this component
        ButtonWidget btn = new ButtonWidget(0, 0, 100, 20, label, action);
        this.addWidget(btn);
    }
    
    @Override
    public void render(GuiGraphics guiGraphics, int mouseX, int mouseY, float partialTick, int parentWidth, int parentHeight) {
        // We don't need to render anything ourselves, the button widget handles it.
        // But we MUST override this to ensure children render.
        super.render(guiGraphics, mouseX, mouseY, partialTick, parentWidth, parentHeight);
    }
}

// Usage
scrollContainer.addComponent(new ButtonWrapper(Component.literal("Click Me"), ...));