UIElement

Namespace:

namespace Lenga\Engine\UI;

abstract class UIElement

Base class for all UI elements — Button, Text, and Image all extend UIElement. It provides the shared API for visibility, hierarchy, layout, and child-element creation.

Obtain an element reference via Canvas::getElement(). You do not instantiate UIElement directly; the canvas creates and manages element instances.

Properties

Property	Type	Access	Description
`$name`	`string`	read	The name of the element as set in the scene.
`$enabled`	`bool`	read/write	Whether the element processes input and updates.
`$visible`	`bool`	read/write	Whether the element is drawn on screen.
`$activeInHierarchy`	`bool`	read	`true` when the element and all of its ancestors are active.
`$sortOrder`	`int`	read/write	Draw order relative to sibling elements. Higher values render on top.
`$rectTransform`	`RectTransform`	read	Layout data (anchors, position, size, pivot).

Methods

getId

public function getId(): int

Returns the native element identifier. Used internally by engine bindings.

getCanvas

public function getCanvas(): ?Canvas

Returns the Canvas this element belongs to.

getParent / setParent

public function getParent(): ?UIElement
public function setParent(?UIElement $parent): bool

Gets or re-parents the element in the UI hierarchy.

getChildren / findDescendantByName

public function getChildren(): list<UIElement>
public function findDescendantByName(string $name): ?UIElement

Traverses child elements. findDescendantByName searches the entire subtree recursively.

createText / createImage / createButton

public function createText(string $name): Text
public function createImage(string $name): Image
public function createButton(string $name): Button

Creates a new child element of the given type, parented to this element. Throws RuntimeException if the element is not attached to a canvas.

Example

use Lenga\Engine\Core\Behaviour;
use Lenga\Engine\UI\Canvas;
use Lenga\Engine\UI\Button;

class InventoryPanel extends Behaviour
{
    private ?Canvas $canvas = null;

    public function start(): void
    {
        $this->canvas = $this->getComponent(Canvas::class);
        $panel = $this->canvas->getElement('InventoryPanel');

        // Toggle panel visibility
        $panel->visible = true;

        // Dynamically create a close button as a child of the panel
        $closeBtn = $panel->createButton('CloseButton');
        $closeBtn->text   = 'Close';
        $closeBtn->visible = true;
    }

    public function update(): void
    {
        $closeBtn = $this->canvas?->getElement('CloseButton');
        if ($closeBtn instanceof Button && $closeBtn->clicked) {
            $this->canvas->getElement('InventoryPanel')->visible = false;
        }
    }
}