github.com/gogpu/ui - core/tabview/painter.go

func PaintTabBar

PaintTabBar renders a minimal tab bar with basic styling.

func (p DefaultPainter) PaintTabBar(canvas widget.Canvas, ps PaintState) {
	if ps.Bounds.IsEmpty() {
		return
	}

	hasScheme := ps.ColorScheme != (TabColorScheme{})

	// Tab bar background.
	bg := defaultTabBarBg
	if hasScheme {
		bg = ps.ColorScheme.Background
	}
	canvas.DrawRect(ps.Bounds, bg)

	// Draw each tab.
	for i := range ps.Tabs {
		ts := &ps.Tabs[i]
		paintDefaultTab(canvas, ts, hasScheme, ps.ColorScheme)
	}

	// Draw indicator under selected tab.
	if ps.SelectedIdx >= 0 && ps.SelectedIdx < len(ps.Tabs) {
		selected := &ps.Tabs[ps.SelectedIdx]
		indicatorColor := defaultIndicatorColor
		if hasScheme {
			indicatorColor = ps.ColorScheme.Indicator
		}
		tabW := selected.Bounds.Width()
		indicatorBounds := geometry.NewRect(
			selected.Bounds.Min.X,
			selected.Bounds.Max.Y-indicatorHeight,
			tabW,
			indicatorHeight,
		)
		if ps.Position == Bottom {
			indicatorBounds = geometry.NewRect(
				selected.Bounds.Min.X,
				selected.Bounds.Min.Y,
				tabW,
				indicatorHeight,
			)
		}
		canvas.DrawRect(indicatorBounds, indicatorColor)
	}

	// Focus ring.
	if ps.Focused {
		ringColor := defaultFocusRingColor
		if hasScheme {
			ringColor = ps.ColorScheme.FocusRing
		}
		canvas.StrokeRect(ps.Bounds, ringColor, defaultFocusRingStroke)
	}
}

type PaintState struct

PaintState provides the current tab bar state to the painter.

type PaintState struct {
	// Bounds is the tab bar area.
	Bounds	geometry.Rect

	// Tabs contains the state of each tab.
	Tabs	[]TabState

	// SelectedIdx is the index of the currently selected tab.
	SelectedIdx	int

	// Position is the tab bar position (top or bottom).
	Position	TabPosition

	// Focused is true when the tab bar has keyboard focus.
	Focused	bool

	// ColorScheme provides theme-derived colors for tab bar painting.
	// Zero value means the painter should use its built-in defaults.
	ColorScheme	TabColorScheme
}

type TabState struct

TabState provides the state of a single tab to the painter.

type TabState struct {
	// Label is the display text.
	Label	string

	// Bounds is the tab's clickable area within the tab bar.
	Bounds	geometry.Rect

	// Selected is true when this tab is the active tab.
	Selected	bool

	// Hovered is true when the mouse is over this tab.
	Hovered	bool

	// Disabled is true when this tab cannot be selected.
	Disabled	bool

	// Closeable is true when this tab shows a close button.
	Closeable	bool

	// CloseButtonBounds is the clickable area for the close button.
	// Empty if not closeable.
	CloseButtonBounds	geometry.Rect
}

type TabColorScheme struct

TabColorScheme provides theme-derived colors for tab bar painting.

Zero value means the painter should use its built-in defaults.

type TabColorScheme struct {
	Background	widget.Color
	SelectedText	widget.Color
	UnselectedText	widget.Color
	Indicator	widget.Color
	HoverBackground	widget.Color
	CloseButton	widget.Color
	FocusRing	widget.Color
}

type DefaultPainter struct

DefaultPainter provides a minimal fallback painter with no design system styling.

It draws a simple tab bar useful for testing and prototyping.

type DefaultPainter struct{}

type Painter interface

Painter draws the visual representation of a tab bar.

Each design system (Material 3, Fluent, Cupertino) provides its own

Painter implementation to render the tab bar in its visual style.

If no Painter is set, the tabview uses [DefaultPainter].

type Painter interface {
	PaintTabBar(canvas widget.Canvas, state PaintState)
}

core/tabview/painter.go

Functions