Rework the UI framework

Interface is now Driver, and Widget is now a set of interfaces with a
struct per widget type. This should make it easier to add other types.

internal/ui/selectors.go

@@ -0,0 +1,62 @@
+package ui
+
+import (
+	"code.ur.gs/lupine/ordoor/internal/menus"
+)
+
+func init() {
+	registerBuilder(menus.TypeCheckbox, registerCheckbox)
+}
+
+type checkbox struct {
+	button
+
+	valueImpl
+}
+
+// A checkbox has 3 sprites, and 3 states: unchecked, checked, disabled.
+func registerCheckbox(d *Driver, r *menus.Record) error {
+	sprites, err := d.menu.Sprites(r.Share, 3) // unchecked, disabled, checked
+	if err != nil {
+		return err
+	}
+
+	checkbox := &checkbox{
+		button: button{
+			path:      r.Path(),
+			baseSpr:   sprites[0], // unchecked
+			clickSpr:  sprites[2], // checked
+			frozenSpr: sprites[1],
+			hoverImpl: hoverImpl{text: r.Desc},
+		},
+		valueImpl: valueImpl{str: "0"},
+	}
+
+	d.clickables = append(d.clickables, checkbox)
+	d.freezables = append(d.freezables, checkbox)
+	d.hoverables = append(d.hoverables, checkbox)
+	d.paintables = append(d.paintables, checkbox)
+	d.valueables = append(d.valueables, checkbox)
+
+	return nil
+}
+
+func (c *checkbox) registerMouseClick() {
+	if c.value() == "1" { // Click disables
+		c.setValue("0")
+	} else { // Click enables
+		c.setValue("1")
+	}
+}
+
+func (c *checkbox) regions(tick int) []region {
+	if c.isFrozen() {
+		return oneRegion(c.bounds().Min, c.frozenSpr.Image)
+	}
+
+	if c.value() == "1" {
+		return oneRegion(c.bounds().Min, c.clickSpr.Image)
+	}
+
+	return oneRegion(c.bounds().Min, c.baseSpr.Image)
+}