theme/material: add the material theme

Signed-off-by: Elias Naur <mail@eliasnaur.com>

widget/button.go

@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package widget
+
+import (
+	"time"
+
+	"gioui.org/f32"
+	"gioui.org/gesture"
+	"gioui.org/layout"
+	"gioui.org/op"
+)
+
+type Button struct {
+	click   gesture.Click
+	clicks  int
+	history []Click
+}
+
+// Click represents a historic click.
+type Click struct {
+	Position f32.Point
+	Time     time.Time
+}
+
+func (b *Button) Clicked(gtx *layout.Context) bool {
+	for _, e := range b.click.Events(gtx) {
+		switch e.Type {
+		case gesture.TypeClick:
+			b.clicks++
+		case gesture.TypePress:
+			b.history = append(b.history, Click{
+				Position: e.Position,
+				Time:     gtx.Now(),
+			})
+		}
+	}
+	if b.clicks > 0 {
+		b.clicks--
+		if b.clicks > 0 {
+			// Ensure timely delivery of remaining clicks.
+			op.InvalidateOp{}.Add(gtx.Ops)
+		}
+		return true
+	}
+	return false
+}
+
+func (b *Button) Active() bool {
+	return b.click.Active()
+}
+
+func (b *Button) History() []Click {
+	return b.history
+}
+
+func (b *Button) Layout(gtx *layout.Context) {
+	b.click.Add(gtx.Ops)
+	if !b.Active() {
+		b.clicks = 0
+	}
+	for len(b.history) > 0 {
+		c := b.history[0]
+		if gtx.Now().Sub(c.Time) < 1*time.Second {
+			break
+		}
+		copy(b.history, b.history[1:])
+		b.history = b.history[:len(b.history)-1]
+	}
+}