Reset Label's cached size hint on Resize

label.go

@@ -29,6 +29,14 @@ func NewLabel(text string) *Label {
 	}
 }
 
+// Resize changes the size of the Widget.
+func (l *Label) Resize(size image.Point) {
+	if l.Size() != size {
+		l.cacheSizeHint = nil
+	}
+	l.WidgetBase.Resize(size)
+}
+
 // Draw draws the label.
 func (l *Label) Draw(p *Painter) {
 	lines := strings.Split(l.text, "\n")

label_sizehint_test.go

@@ -0,0 +1,151 @@
+package tui
+
+import (
+	"image"
+	"testing"
+)
+
+var TailBoxTests = []struct {
+	Test string
+	Setup func() Widget
+	Want string
+} {
+	{
+		Test: "draw small labels",
+		Setup: func() Widget {
+			return NewTailBox(
+				NewLabel("hello mom"),
+				NewLabel("hello dad"),
+			)
+		},
+		Want: `
+
+
+
+hello mom 
+hello dad 
+`,
+	},
+	{
+		Test: "draw unwrapped labels",
+		Setup: func() Widget {
+			l1, l2 := NewLabel("hello muddah"), NewLabel("hello faddah")
+			return NewTailBox(l1, l2)
+		},
+		Want: `
+
+
+
+hello mudd
+hello fadd
+`,
+	},
+	{
+		Test: "draw wrapped labels",
+		Setup: func() Widget {
+			l1, l2 := NewLabel("hello muddah"), NewLabel("hello faddah")
+			l1.SetWordWrap(true)
+			l2.SetWordWrap(true)
+			return NewTailBox(l1, l2)
+		},
+		Want: `
+
+hello     
+muddah    
+hello     
+faddah    
+`,
+	},
+
+
+}
+
+func TestTailBox(t *testing.T) {
+	for _, tt := range TailBoxTests {
+		tt := tt
+		t.Run(tt.Test, func(t *testing.T) {
+			surface := NewTestSurface(10, 5)
+			p := NewPainter(surface, NewTheme())
+			p.Repaint(tt.Setup())
+
+			if surface.String() != tt.Want {
+				t.Errorf("unexpected contents: got = \n%s\nwant = \n%s", surface.String(), tt.Want)
+			}
+		})
+	}
+}
+
+
+// TailBox is a container Widget that may not show all its 
+// While Box attempts to show every contained Widget - sometimes shrinking
+// those Widgets to do so- TailBox prioritizes completely displaying its last
+// Widget, then the next-to-last widget, etc.
+// It is vertically-aligned, i.e. all the contained Widgets have the same width.
+type TailBox struct {
+	WidgetBase
+	sz image.Point
+	contents []Widget
+}
+
+var _ Widget = &TailBox{}
+
+func NewTailBox(w ...Widget) *TailBox {
+	return &TailBox{
+		contents: w,
+	}
+}
+
+func (t *TailBox) Append(w Widget) {
+	t.contents = append(t.contents, w)
+	t.doLayout(t.Size())
+}
+
+func (t *TailBox) SetContents(w ...Widget) {
+	t.contents = w
+	t.doLayout(t.Size())
+}
+
+func (t *TailBox) Draw(p *Painter) {
+	p.WithMask(image.Rect(0, 0, t.sz.X, t.sz.Y), func(p *Painter) {
+		// Draw background
+		p.FillRect(0, 0, t.sz.X, t.sz.Y)
+
+		// Draw from the bottom up.
+		space := t.sz.Y
+		p.Translate(0, space)
+		defer p.Restore()
+		for i := len(t.contents) - 1; i >= 0 && space > 0; i-- {
+			w := t.contents[i]
+			space -= w.Size().Y
+			p.Translate(0, -w.Size().Y)
+			defer p.Restore()
+			w.Draw(p)
+		}
+	})
+}
+
+// Resize recalculates the layout of the box's contents.
+func (t *TailBox) Resize(size image.Point) {
+	t.WidgetBase.Resize(size)
+	defer func() {
+		t.sz = size
+	}()
+
+	// If it's just a height change, Draw should do the right thing already.
+	if size.X != t.sz.X {
+		t.doLayout(size)
+	}
+}
+
+func (t *TailBox) doLayout(size image.Point) {
+	for _, w := range t.contents {
+		hint := w.SizeHint()
+		// Set the width to the container width, and height to the requested height
+		w.Resize(image.Pt(size.X, hint.Y))
+		// ...and then resize again, now that the Y-hint has been refreshed by the X-value.
+		hint = w.SizeHint()
+		w.Resize(image.Pt(size.X, hint.Y))
+	}
+}
+
+