Allow the scrollbar to hide if the data fits in the space available.

This is a new option provided to the scrollbar widget. If enabled, the
scrollbar will simply render its data widget if the data available would
fit in the space provided to the scrollbar. Note that this adjusts the
focus path of certain elements in the UI... This is fragile. I really
need a better way e.g. labelling widgets within containers like columns
or piles, rather than using a numeric index.

ui/ui.go

@@ -2825,19 +2825,19 @@ func Build() (*gowid.App, error) {
 	maxViewPath = []interface{}{2, 0} // list, structure or hex - whichever one is selected
 
 	mainviewPaths = [][]interface{}{
-		{2, 0}, // packet list
-		{4},    // packet structure
-		{6},    // packet hex
+		{2}, // packet list
+		{4}, // packet structure
+		{6}, // packet hex
 	}
 
 	altview1Paths = [][]interface{}{
-		{2, 0, 0, 0}, // packet list
-		{2, 0, 2},    // packet structure
-		{2, 2},       // packet hex
+		{2, 0, 0}, // packet list
+		{2, 0, 2}, // packet structure
+		{2, 2},    // packet hex
 	}
 
 	altview2Paths = [][]interface{}{
-		{2, 0, 0}, // packet list
+		{2, 0},    // packet list
 		{2, 2, 0}, // packet structure
 		{2, 2, 2}, // packet hex
 	}

widgets/withscrollbar/withscrollbar.go

@@ -15,31 +15,52 @@ import (
 //======================================================================
 
 type Widget struct {
-	*columns.Widget
+	always   *columns.Widget // use if scrollbar is to be shown
 	w        IScrollSubWidget
 	sb       *vscroll.Widget
 	goUpDown int // positive means down
 	pgUpDown int // positive means down
+	opt      Options
+}
+
+var _ gowid.IWidget = (*Widget)(nil)
+
+type Options struct {
+	HideIfContentFits bool
 }
 
 type IScrollValues interface {
 	ScrollPosition() int
 	ScrollLength() int
 }
 
-type IScrollSubWidget interface {
-	gowid.IWidget
-	IScrollValues
+// Implemented by widgets that can scroll
+type IScrollOneLine interface {
 	Up(lines int, size gowid.IRenderSize, app gowid.IApp)
 	Down(lines int, size gowid.IRenderSize, app gowid.IApp)
+}
+
+type IScrollOnePage interface {
 	UpPage(num int, size gowid.IRenderSize, app gowid.IApp)
 	DownPage(num int, size gowid.IRenderSize, app gowid.IApp)
 }
 
-func New(w IScrollSubWidget) *Widget {
+type IScrollSubWidget interface {
+	gowid.IWidget
+	IScrollValues
+	IScrollOneLine
+	IScrollOnePage
+}
+
+func New(w IScrollSubWidget, opts ...Options) *Widget {
+	var opt Options
+	if len(opts) > 0 {
+		opt = opts[0]
+	}
+
 	sb := vscroll.NewExt(vscroll.VerticalScrollbarUnicodeRunes)
 	res := &Widget{
-		Widget: columns.New([]gowid.IContainerWidget{
+		always: columns.New([]gowid.IContainerWidget{
 			&gowid.ContainerWidget{
 				IWidget: w,
 				D:       gowid.RenderWithWeight{W: 1},
@@ -55,6 +76,7 @@ func New(w IScrollSubWidget) *Widget {
 		sb:       sb,
 		goUpDown: 0,
 		pgUpDown: 0,
+		opt:      opt,
 	}
 	sb.OnClickAbove(gowid.MakeWidgetCallback("cb", res.clickUp))
 	sb.OnClickBelow(gowid.MakeWidgetCallback("cb", res.clickDown))
@@ -84,7 +106,19 @@ func CalculateMenuRows(vals IScrollValues, rows int, focus gowid.Selector, app g
 	return vals.ScrollPosition(), 1, vals.ScrollLength() - (vals.ScrollPosition() + 1)
 }
 
+func (w *Widget) contentFits(size gowid.IRenderSize) bool {
+	res := true
+	if rower, ok := size.(gowid.IRows); ok {
+		res = (w.w.ScrollLength() <= rower.Rows())
+	}
+	return res
+}
+
 func (w *Widget) UserInput(ev interface{}, size gowid.IRenderSize, focus gowid.Selector, app gowid.IApp) bool {
+	if w.opt.HideIfContentFits && w.contentFits(size) {
+		return w.w.UserInput(ev, size, focus, app)
+	}
+
 	box, ok := size.(gowid.IRenderBox)
 	if !ok {
 		panic(gowid.WidgetSizeError{Widget: w, Size: size, Required: "gowid.IRenderBox"})
@@ -96,14 +130,18 @@ func (w *Widget) UserInput(ev interface{}, size gowid.IRenderSize, focus gowid.S
 	w.sb.Middle = y
 	w.sb.Bottom = z
 
-	res := w.Widget.UserInput(ev, size, focus, app)
+	res := w.always.UserInput(ev, size, focus, app)
 	if res {
-		w.Widget.SetFocus(app, 0)
+		w.always.SetFocus(app, 0)
 	}
 	return res
 }
 
 func (w *Widget) Render(size gowid.IRenderSize, focus gowid.Selector, app gowid.IApp) gowid.ICanvas {
+	if w.opt.HideIfContentFits && w.contentFits(size) {
+		return w.w.Render(size, focus, app)
+	}
+
 	box, ok := size.(gowid.IRenderBox)
 	if !ok {
 		panic(gowid.WidgetSizeError{Widget: w, Size: size, Required: "gowid.IRenderBox"})
@@ -136,11 +174,23 @@ func (w *Widget) Render(size gowid.IRenderSize, focus gowid.Selector, app gowid.
 	w.sb.Middle = y
 	w.sb.Bottom = z
 
-	canvas := w.Widget.Render(size, focus, app)
+	canvas := w.always.Render(size, focus, app)
 
 	return canvas
 }
 
+func (w *Widget) RenderSize(size gowid.IRenderSize, focus gowid.Selector, app gowid.IApp) gowid.IRenderBox {
+	if w.opt.HideIfContentFits && w.contentFits(size) {
+		return w.w.RenderSize(size, focus, app)
+	}
+
+	return w.always.RenderSize(size, focus, app)
+}
+
+func (w *Widget) Selectable() bool {
+	return w.w.Selectable()
+}
+
 //======================================================================
 // Local Variables:
 // mode: Go

widgets/withscrollbar/withscrollbar_test.go

@@ -0,0 +1,82 @@
+package withscrollbar
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/gcla/gowid"
+	"github.com/gcla/gowid/gwtest"
+	"github.com/gcla/gowid/widgets/button"
+	"github.com/gcla/gowid/widgets/list"
+	"github.com/gcla/gowid/widgets/text"
+	"github.com/stretchr/testify/assert"
+)
+
+type scrollingListBox struct {
+	*list.Widget
+}
+
+func (t *scrollingListBox) Up(lines int, size gowid.IRenderSize, app gowid.IApp)     {}
+func (t *scrollingListBox) Down(lines int, size gowid.IRenderSize, app gowid.IApp)   {}
+func (t *scrollingListBox) UpPage(num int, size gowid.IRenderSize, app gowid.IApp)   {}
+func (t *scrollingListBox) DownPage(num int, size gowid.IRenderSize, app gowid.IApp) {}
+
+func (t *scrollingListBox) ScrollLength() int {
+	return 8
+}
+
+func (t *scrollingListBox) ScrollPosition() int {
+	return 0
+}
+
+func Test1(t *testing.T) {
+	bws := make([]gowid.IWidget, 8)
+	for i := 0; i < len(bws); i++ {
+		bws[i] = button.NewBare(text.New(fmt.Sprintf("%03d", i)))
+	}
+
+	walker := list.NewSimpleListWalker(bws)
+	lbox := &scrollingListBox{Widget: list.New(walker)}
+	sbox := New(lbox)
+
+	canvas1 := sbox.Render(gowid.MakeRenderBox(4, 8), gowid.NotSelected, gwtest.D)
+	res := strings.Join([]string{
+		"000▲",
+		"001█",
+		"002 ",
+		"003 ",
+		"004 ",
+		"005 ",
+		"006 ",
+		"007▼",
+	}, "\n")
+	assert.Equal(t, res, canvas1.String())
+
+	sbox = New(lbox, Options{
+		HideIfContentFits: true,
+	})
+
+	canvas1 = sbox.Render(gowid.MakeRenderBox(4, 8), gowid.NotSelected, gwtest.D)
+	res = strings.Join([]string{
+		"000 ",
+		"001 ",
+		"002 ",
+		"003 ",
+		"004 ",
+		"005 ",
+		"006 ",
+		"007 ",
+	}, "\n")
+	assert.Equal(t, res, canvas1.String())
+
+	canvas1 = sbox.Render(gowid.MakeRenderBox(4, 5), gowid.NotSelected, gwtest.D)
+	res = strings.Join([]string{
+		"000▲",
+		"001█",
+		"002 ",
+		"003 ",
+		"004▼",
+	}, "\n")
+	assert.Equal(t, res, canvas1.String())
+}