lemur-ui

Lemur UI Framework

Lemur is the UI framework for building game interfaces. Documentation from official wiki.

Initialization (from Wiki)

// In simpleInitApp() or app initialization
GuiGlobals.initialize(this);

// Load the 'glass' style (requires Groovy dependency)
BaseStyles.loadGlassStyle();

// Set 'glass' as default style
GuiGlobals.getInstance().getStyles().setDefaultStyle("glass");

Positioning and Size (from Wiki)

Important: GUI elements are positioned by their upper left corner and grow down and right. This is a compromise between OpenGL (0,0 at lower left) and traditional UI (0,0 at upper left).

// Put window at upper area - elements grow DOWN from this point
myWindow.setLocalTranslation(300, 300, 0);

Class Hierarchy (from Wiki)

Spatial
  └── Panel (base: background, border, insets, alpha)
        ├── Container (adds layout support)
        └── Label (adds text, icon, font, color)
              └── Button (adds click commands, highlight)

Base GUI Elements

Panel Properties

• background: Background component (QuadComponent)
• border: Border component (underneath background)
• insets: Insets3f - space around element within parent (like CSS margin)
• alpha: Fade in/out entire hierarchy

Container

// Create with default SpringGridLayout
Container myWindow = new Container();
guiNode.attachChild(myWindow);

// Or with specific layout
Container c = new Container(new BorderLayout());

Label Properties

• text: Display text
• icon: Icon component
• font, fontSize: Text rendering
• textVAlignment: VAlignment.Top/Bottom/Center
• textHAlignment: HAlignment.Left/Right/Center
• color: Text color
• shadowColor, shadowOffset: Text shadow

Label label = new Label("Hello, World.");
label.setFontSize(16);
label.setColor(ColorRGBA.White);

Button

Extends Label with click support.

Button clickMe = myWindow.addChild(new Button("Click Me"));
clickMe.addClickCommands(new Command<Button>() {
    @Override
    public void execute(Button source) {
        System.out.println("Clicked!");
    }
});

// Or with lambda
clickMe.addClickCommands(source -> System.out.println("Clicked!"));

Button Actions: ButtonAction.Down, Up, Click, HighlightOn, HighlightOff

TextField Properties

• text: Entered text value
• singleLine: true (default) or false for multiline
• preferredWidth: Width hint for layouts

TextField field = new TextField("default");
String value = field.getText();

Layouts (from Wiki)

SpringGridLayout (default)

Row-major by default. Children added to grid cells.

Container c = new Container();  // SpringGridLayout by default

// Explicit grid positions (row, column)
c.addChild(new Label("Foo"), 0, 0);
c.addChild(new Label("Bar"), 1, 0);

// Shortcut - auto-increments row
c.addChild(new Label("Foo"));
c.addChild(new Label("Bar"));

// Two-column layout - specify column only
c.addChild(new Label("Name:"));
c.addChild(new TextField("value"), 1);  // column 1
c.addChild(new Label("Age:"));
c.addChild(new TextField("25"), 1);     // column 1

BorderLayout

Container c = new Container(new BorderLayout());
c.addChild(new Label("Top"), Position.North);
c.addChild(new Label("Bottom"), Position.South);
c.addChild(new Label("Center"), Position.Center);
c.addChild(new Label("Left"), Position.West);
c.addChild(new Label("Right"), Position.East);

Composite Elements (from Wiki)

Slider

Slider slider = new Slider();  // x-axis default
slider.setDelta(1);  // increment amount
double value = slider.getModel().getValue();

ProgressBar

ProgressBar progress = new ProgressBar();
progress.setProgressPercent(0.5);  // 50%
progress.setMessage("Loading...");

ListBox (proto)

ListBox<String> listBox = new ListBox<>();
listBox.getModel().add("Item 1");
listBox.getModel().add("Item 2");

OptionPanelState (proto)

// Add to state manager once
stateManager.attach(new OptionPanelState());

// Show modal dialogs
getState(OptionPanelState.class).show("Title", "Message");
getState(OptionPanelState.class).showError("Error", "Something went wrong");

Styling (from Wiki)

Element IDs

Define style hierarchy: container.contained.contained

// Create with ElementId
Container window = new Container(new ElementId("mywindow"));
Button btn = new Button("Click", new ElementId("mywindow.button"));

Selectors (Groovy style language)

// Style all elements of 'glass' style
selector('glass') {
    fontSize = 20
}

// Style specific element ID
selector('button', 'glass') {
    color = color(0.5, 0.75, 0.75, 0.85)
    background = new QuadBackgroundComponent(color(0, 1, 0, 1))
}

// Containment selector - only buttons inside sliders
selector('slider', 'button', 'glass') {
    fontSize = 10
}

Style in Code

Styles styles = GuiGlobals.getInstance().getStyles();
Attributes attrs = styles.getSelector("button", "glass");
attrs.set("color", new ColorRGBA(0.5f, 0.75f, 0.75f, 0.85f));
attrs.set("fontSize", 14);

Project-Specific Patterns

ActionButton with CallMethodAction

import com.simsilica.lemur.ActionButton;
import com.simsilica.lemur.CallMethodAction;

ActionButton btn = new ActionButton(
    new CallMethodAction("Button Text", this, "methodName")
);
btn.setInsets(new Insets3f(5, 10, 5, 10));
window.addChild(btn);

// Method called when clicked
protected void methodName() {
    log.info("Button clicked");
}

Menu State Pattern

public class MainMenuState extends BaseAppState {
    private Container mainWindow;

    @Override
    protected void initialize(Application app) {
        mainWindow = new Container();
        // Build UI...
    }

    @Override
    protected void onEnable() {
        ((SimpleApplication) getApplication()).getGuiNode().attachChild(mainWindow);
        GuiGlobals.getInstance().requestCursorEnabled(this);
    }

    @Override
    protected void onDisable() {
        mainWindow.removeFromParent();
        GuiGlobals.getInstance().releaseCursorEnabled(this);
    }
}

Project Assets

• Styles in infinity/assets/Interface/