widget,widget/material: add CheckBox

widget/checkbox.go

@@ -0,0 +1,25 @@
+package widget
+
+import (
+	"gioui.org/gesture"
+	"gioui.org/layout"
+)
+
+type CheckBox struct {
+	click   gesture.Click
+	checked bool
+}
+
+func (c *CheckBox) Checked(gtx *layout.Context) bool {
+	for _, e := range c.click.Events(gtx) {
+		switch e.Type {
+		case gesture.TypeClick:
+			c.checked = !c.checked
+		}
+	}
+	return c.checked
+}
+
+func (c *CheckBox) Layout(gtx *layout.Context) {
+	c.click.Add(gtx.Ops)
+}