feat: Ribbon.TabRect and Ribbon.ControlRect

ribbon.go

@@ -621,3 +621,32 @@ func (r *Ribbon) bodyRect() Rect {
 	b := r.Bounds()
 	return Rect{X: b.X, Y: b.Y + m.tabH + 1, W: b.W, H: m.bodyH + m.labelH + 1}
 }
+
+// TabRect is where tab i's label is, in surface coordinates; false when there is
+// no such tab. A test harness that drives the page with synthetic events clicks
+// there.
+func (r *Ribbon) TabRect(i int) (Rect, bool) {
+	tabs, _ := r.tabRects(r.metrics())
+	if i < 0 || i >= len(tabs) {
+		return Rect{}, false
+	}
+	return tabs[i], true
+}
+
+// ControlRect is where the control (or folded group) labelled label is, in surface
+// coordinates, among those the ribbon shows now; false when it is not shown (on
+// another tab, hidden, or folded into a group's pop-up).
+func (r *Ribbon) ControlRect(label string) (Rect, bool) {
+	for _, c := range r.cells() {
+		l := ""
+		if c.form == formPopup {
+			l = c.grp.Label
+		} else {
+			l = c.ctrl.label()
+		}
+		if l == label {
+			return c.rect, true
+		}
+	}
+	return Rect{}, false
+}

ribbon_rect_test.go

@@ -0,0 +1,42 @@
+// Copyright (c) 2026 the go-widgets/toolkit authors. All rights reserved.
+// Use of this source code is governed by a BSD-3-Clause license that can be
+// found in the LICENSE file at the root of this repository.
+
+package toolkit
+
+import "testing"
+
+func TestRibbonTabRectAndControlRect(t *testing.T) {
+	r, run := rtRibbon(2000)
+	tab, ok := r.TabRect(1)
+	if !ok || !tab.Contains(tab.X+1, tab.Y+1) {
+		t.Fatalf("TabRect(1) = %v %v", tab, ok)
+	}
+	if _, ok := r.TabRect(-1); ok {
+		t.Error("a negative tab has no rect")
+	}
+	if _, ok := r.TabRect(99); ok {
+		t.Error("a tab past the end has no rect")
+	}
+	// A control's rect is where a click runs it.
+	rc, ok := r.ControlRect("Undo")
+	if !ok {
+		t.Fatal("Undo is shown")
+	}
+	x, y := rtCenter(rc)
+	rtClick(r, x, y)
+	if len(run.ids) != 1 || run.ids[0] != "undo" {
+		t.Errorf("a click at ControlRect ran %v", run.ids)
+	}
+	// Not shown: another tab's control, and a folded group's own control.
+	if _, ok := r.ControlRect("Image"); ok {
+		t.Error("Image is on the Insert tab")
+	}
+	small, _ := rtRibbon(360)
+	if _, ok := small.ControlRect("Kinds"); ok {
+		t.Error("Kinds is folded into the Theme group's pop-up at 360px")
+	}
+	if rc, ok := small.ControlRect("Theme"); !ok || rc.W == 0 {
+		t.Error("the folded group's button is shown under its label")
+	}
+}