Add List widget combinator. Add HScroll and VScroll functions. Add

scroll demo to see a 2-way scrolling field of selectable labels.

.gitignore

@@ -1,3 +1,4 @@
 cmd/hello/hello
 cmd/cal/cal
+cmd/scroll/scroll
 *.apk

cmd/scroll/main.go

@@ -0,0 +1,152 @@
+package main
+
+import (
+	"image/color"
+	"fmt"
+	"log"
+
+	gio "git.wow.st/gmp/giowrap"
+
+	"gioui.org/ui"
+	"gioui.org/ui/app"
+	"gioui.org/ui/layout"
+	"gioui.org/ui/text"
+
+	"golang.org/x/image/font/sfnt"
+	"golang.org/x/image/font/gofont/goregular"
+)
+
+var (
+	face text.Face
+	black color.RGBA = color.RGBA{ A: 0xff, R: 0x00, G: 0x00, B: 0x00 }
+	gray2 color.RGBA = color.RGBA{ A: 0xff, R: 0x70, G: 0x70, B: 0x70 }
+	gray1 color.RGBA = color.RGBA{ A: 0xff, R: 0x50, G: 0x50, B: 0x50 }
+)
+
+type SLabel struct {
+	w gio.Clickable
+	bg *gio.Background
+	active *bool
+}
+
+func NewSLabel(t string, active *bool, lops ...gio.LabelOption) *SLabel {
+	ret := &SLabel{}
+	lops = append([]gio.LabelOption{gio.Face(face)},lops...)
+	lbl := gio.NewLabel(t, lops...)
+	bg := &gio.Background{
+		Color: gray2,
+		Radius: ui.Dp(4),
+		Inset: layout.UniformInset(ui.Dp(4)),
+	}
+	if *active {
+		bg.Color = gray1
+	}
+	l := gio.AsClickable(gio.Enclose(bg,lbl))
+	ret.w = l
+	ret.bg = bg
+	ret.active = active
+	return ret
+}
+
+func (w *SLabel) Layout(ctx *gio.Context) {
+	if *w.active {
+		w.bg.Color = gray1
+	} else {
+		w.bg.Color = gray2
+	}
+	w.w.Layout(ctx)
+	if w.w.Clicked(ctx) {
+		if *w.active {
+			*w.active = false
+		} else {
+			*w.active = true
+		}
+	}
+}
+
+func main() {
+	log.Print("Staring event loop")
+	go eventloop()
+	app.Main()
+	log.Print("App closed")
+}
+
+func diffInsets(x, y app.Insets) bool {
+	return  x.Top != y.Top ||
+		x.Bottom != y.Bottom ||
+		x.Left != y.Left ||
+		x.Right != y.Right
+}
+
+func eventloop() {
+	w := app.NewWindow(
+		app.WithWidth(ui.Dp(200)),
+		app.WithHeight(ui.Dp(400)),
+		app.WithTitle("Tickets"))
+	ctx := gio.NewContext(w)
+
+	regular, err := sfnt.Parse(goregular.TTF)
+	face = ctx.Faces.For(regular, ui.Sp(16))
+	if err != nil { log.Fatal("Cannot parse font.") }
+
+	sysbg := gio.NewBackground(gio.Color(black))
+	bg := gio.NewBackground(gio.Color(gray2))
+
+	margin := gio.NewInset(gio.Size(ui.Dp(10)))
+	sh := gio.HScroll(gio.NewFlex(gio.Axis(layout.Horizontal)))
+	sv := gio.VScroll(gio.NewFlex(gio.Axis(layout.Vertical)))
+	numlabs := 50
+	labs := make([][]gio.Widget, numlabs)
+	sels := make([][]bool, numlabs)
+	for i := 0; i < 16; i++ {
+		labs[i] = make([]gio.Widget, numlabs)
+		sels[i] = make([]bool, numlabs)
+		for j := 0; j < numlabs; j++ {
+			labs[i][j] = NewSLabel(fmt.Sprintf("%03d",i * j), &sels[i][j])
+		}
+	}
+
+	sysinset := gio.NewInset(gio.Size(ui.Dp(0)))
+	resetSysinset := func(x app.Insets) {
+		sysinset = gio.NewInset(gio.Top(x.Top), gio.Bottom(x.Bottom),
+					gio.Left(x.Left), gio.Right(x.Right))
+	}
+
+	var oldInsets app.Insets
+
+	for { select {
+	case e:= <-w.Events():
+		switch e := e.(type) {
+		case app.DestroyEvent:
+			return
+		case app.UpdateEvent:
+			ctx.Reset(e)
+			if diffInsets(e.Insets, oldInsets) {
+				oldInsets = e.Insets
+				resetSysinset(e.Insets)
+			}
+
+			sysbg(sysinset(bg(margin(
+				sh(
+					sv(labs[0]...),
+					sv(labs[1]...),
+					sv(labs[2]...),
+					sv(labs[3]...),
+					sv(labs[4]...),
+					sv(labs[5]...),
+					sv(labs[6]...),
+					sv(labs[7]...),
+					sv(labs[8]...),
+					sv(labs[9]...),
+					sv(labs[10]...),
+					sv(labs[11]...),
+					sv(labs[12]...),
+					sv(labs[13]...),
+					sv(labs[14]...),
+					sv(labs[15]...),
+			))))).Layout(ctx)
+			ctx.Update()
+		}
+	}}
+}
+

main.go

@@ -184,7 +184,42 @@ func NewStack() Stack {
 	}
 }
 
-type Flex WidgetCombinator
+type List = WidgetCombinator
+
+type AxisOpt struct { axis layout.Axis }
+func Axis(x layout.Axis) AxisOpt { return AxisOpt{ x } }
+
+type ListOpts struct {
+	AxisOpt
+}
+type ListOption interface { DoListOption(*ListOpts) }
+func (x AxisOpt) DoListOption(o *ListOpts) { o.axis = x.axis }
+
+func NewList(los ...ListOption) List {
+	opts := &ListOpts{}
+	for _,o := range los { o.DoListOption(opts) }
+	l := layout.List { Axis: opts.axis }
+	return func(ws ...Widget) Widget {
+		return NewfWidget(func(ctx *Context) {
+			for l.Init(ctx.c, ctx.q, ctx.ops, ctx.cs, len(ws)); l.More(); l.Next() {
+				ctx.cs = l.Constraints()
+				ws[l.Index()].Layout(ctx)
+				l.End(ctx.dims)
+			}
+			ctx.dims = l.Layout()
+		})
+	}
+}
+
+func HScroll(c WidgetCombinator) WidgetCombinator {
+	return NewList(Axis(layout.Horizontal))
+}
+
+func VScroll(c WidgetCombinator) WidgetCombinator {
+	return NewList(Axis(layout.Vertical))
+}
+
+type Flex = WidgetCombinator
 
 // This "Widget" does nothing except set the Flexible field of a FlexOpts
 // struct within the Extra data structure
@@ -199,8 +234,6 @@ func Rigid() Widget {
 	})
 }
 
-type AxisOpt struct { axis layout.Axis }
-func Axis(x layout.Axis) AxisOpt { return AxisOpt{ x } }
 type AlignmentOpt struct { alignment layout.Alignment }
 func Alignment(x layout.Alignment) AlignmentOpt { return AlignmentOpt{ x } }