Widgets

Every default scene creates a GUI root at scene.root on the hud layer. Add widgets to that tree to build interfaces.

class MyScene(bf.Scene):
    def do_when_added(self):
        button = bf.gui.Button("Click me", callback=lambda: print("hi"))
        self.root.add(button)

Core concepts

Widget tree

Widgets form a parent/child tree under Root. Common operations:

• add(*children) / remove(*children)
• visit(func) — walk the subtree
• top_at(x, y) — pick the topmost widget at a point
• get_root() — climb to the scene root

Layouts

Containers arrange children with a layout. See Layouts.

panel = bf.gui.Container(bf.gui.Column(gap=8))
panel.add(
    bf.gui.Label("Settings"),
    bf.gui.Button("Apply"),
)
self.root.add(panel)

Constraints

See Constraints.

from batFramework.gui.constraints import constraints as c

widget.add_constraints(
    c.Width(200),
    c.Height(40),
    c.Center(),
)

Focus

Root manages hover, focus, tab navigation, and tooltips.

Common widgets

Widget	Role
Label / RichLabel	Text display
Button	Clickable label with callback
Toggle / RadioButton	On/off and exclusive choices
Slider	Numeric value with handle and meter
Selector	Cycle through options
TextInput	Editable text field
AnimatedLabel	Typewriter-style text
Image	Displays a surface/image
Container	Layout host for children
ScrollingContainer	Container with scrollbars
CollapseContainer	Expand/collapse content
SyncedVar	Reactive value shared by widgets

Slider example

volume = bf.gui.SyncedVar(0.8)
slider = (
    bf.gui.Slider("Volume", default_value=0.8, synced_var=volume)
    .set_range(0, 1)
    .set_step(0.05)
)
self.root.add(slider)

HUD camera

GUI lives on the hud layer with its own camera, so it stays screen-fixed while the world camera moves.