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

	colors := ps.ColorScheme
	if colors == (tabview.TabColorScheme{}) {
		colors = p.resolveColors()
	}

	// Segmented control background (pill shape).
	canvas.DrawRoundRect(ps.Bounds, colors.Background, cupTabSegmentRadius)

	// Draw selected segment indicator first (behind text).
	if ps.SelectedIdx >= 0 && ps.SelectedIdx < len(ps.Tabs) {
		selected := &ps.Tabs[ps.SelectedIdx]
		if !selected.Bounds.IsEmpty() {
			segInset := cupTabSegmentInset
			segBounds := geometry.NewRect(
				selected.Bounds.Min.X+segInset,
				selected.Bounds.Min.Y+segInset,
				selected.Bounds.Width()-segInset*2,
				selected.Bounds.Height()-segInset*2,
			)
			canvas.DrawRoundRect(segBounds, colors.Indicator, cupTabSelectedRadius)
		}
	}

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

	// Focus ring around entire segmented control.
	if ps.Focused {
		ringBounds := ps.Bounds.Expand(cupTabFocusRingOffset)
		canvas.StrokeRoundRect(ringBounds, colors.FocusRing, cupTabSegmentRadius+cupTabFocusRingOffset, cupTabFocusRingStroke)
	}
}

type TabViewPainter struct {
	Theme *Theme	// nil uses default system blue fallback
}