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|
package ui
import (
"fmt"
)
// A container which arranges its children in a list.
type List struct {
Items []*ListItem
itemHeight int
onInvalidate func(d Drawable)
selected int
}
type ListItem struct {
Content Drawable
invalid bool
}
type SelectableDrawable interface {
Drawable
DrawWithSelected(ctx *Context, selected bool)
}
func NewList() *List {
return &List{itemHeight: 1, selected: -1}
}
func (list *List) OnInvalidate(onInvalidate func(d Drawable)) {
list.onInvalidate = onInvalidate
}
func (list *List) Invalidate() {
for _, item := range list.Items {
item.Content.Invalidate()
}
if list.onInvalidate != nil {
list.onInvalidate(list)
}
}
func (list *List) Draw(ctx *Context) {
for i, item := range list.Items {
if !item.invalid {
continue
}
subctx := ctx.Subcontext(0, i, ctx.Width(), list.itemHeight)
if content, ok := item.Content.(SelectableDrawable); ok {
content.DrawWithSelected(subctx, i == list.selected)
} else {
item.Content.Draw(subctx)
}
}
}
func (list *List) Add(child Drawable) {
list.Items = append(list.Items, &ListItem{Content: child, invalid: true})
child.OnInvalidate(list.childInvalidated)
list.Invalidate()
}
func (list *List) Remove(child Drawable) {
for i, item := range list.Items {
if item.Content == child {
list.Items = append(list.Items[:i], list.Items[i+1:]...)
child.OnInvalidate(nil)
list.Invalidate()
return
}
}
panic(fmt.Errorf("Attempted to remove unknown child"))
}
func (list *List) Set(items []Drawable) {
for _, item := range list.Items {
item.Content.OnInvalidate(nil)
}
list.Items = make([]*ListItem, len(items))
for i, item := range items {
list.Items[i] = &ListItem{Content: item, invalid: true}
item.OnInvalidate(list.childInvalidated)
}
list.Invalidate()
}
func (list *List) Select(index int) {
if index >= len(list.Items) || index < 0 {
panic(fmt.Errorf("Attempted to select unknown child"))
}
list.selected = index
list.Invalidate()
}
func (list *List) ItemHeight(height int) {
list.itemHeight = height
list.Invalidate()
}
func (list *List) childInvalidated(child Drawable) {
for _, item := range list.Items {
if item.Content == child {
item.invalid = true
if list.onInvalidate != nil {
list.onInvalidate(list)
}
return
}
}
panic(fmt.Errorf("Attempted to invalidate unknown child"))
}
|
