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|
package widget
import (
"fmt"
"image"
)
type Direction int
const (
UP Direction = iota
DOWN
LEFT
RIGHT
)
type FocusSlave struct {
gain <-chan bool
lose <-chan Direction // forward to yield if widget accepts focus loss
yield chan<- Direction
}
type focusSlave struct {
gain chan bool
lose chan Direction
}
func (fs focusSlave) close() {
close(fs.gain)
close(fs.lose)
}
type FocusMaster struct {
slaves [][]focusSlave
yield chan Direction
focused image.Point // coordinates of focused slave
}
func NewFocusMaster(rows []int) *FocusMaster {
fm := &FocusMaster{
slaves: make([][]focusSlave, len(rows)),
yield: make(chan Direction),
focused: image.Point{0, 0},
}
for y := range fm.slaves {
fm.slaves[y] = make([]focusSlave, rows[y])
for x := range fm.slaves[y] {
fm.slaves[y][x] = focusSlave{make(chan bool), make(chan Direction)}
}
}
go func() {
fm.slaves[0][0].gain <- true
for dir := range fm.yield {
fm.focused = fm.neighborPos(fm.focused, dir)
fm.slaves[fm.focused.Y][fm.focused.X].gain <- true
}
}()
return fm
}
func (fm FocusMaster) Slave(y, x int) FocusSlave {
return FocusSlave{
gain: fm.slaves[y][x].gain,
lose: fm.slaves[y][x].lose,
yield: fm.yield,
}
}
func (fm FocusMaster) Close() {
for y := range fm.slaves {
for x := range fm.slaves[y] {
fm.slaves[y][x].close()
}
}
close(fm.yield)
}
func (fm FocusMaster) Shift(dir Direction) {
fm.slaves[fm.focused.Y][fm.focused.X].lose <- dir
}
func (fm FocusMaster) neighborPos(pos image.Point, dir Direction) image.Point {
switch dir {
case UP:
return fm.upNeighborPos(pos)
case DOWN:
return fm.downNeighborPos(pos)
case LEFT:
return fm.leftNeighborPos(pos)
case RIGHT:
return fm.rightNeighborPos(pos)
default:
panic(fmt.Sprintf("invalid Direction: %v", dir))
}
}
func (fm FocusMaster) upNeighborPos(pos image.Point) image.Point {
if pos.Y <= 0 {
pos.Y = len(fm.slaves) - 1
} else {
pos.Y--
}
pos.X = min(pos.X, len(fm.slaves[pos.Y])-1)
return pos
}
func (fm FocusMaster) downNeighborPos(pos image.Point) image.Point {
if pos.Y >= len(fm.slaves)-1 {
pos.Y = 0
} else {
pos.Y++
}
pos.X = min(pos.X, len(fm.slaves[pos.Y])-1)
return pos
}
func (fm FocusMaster) leftNeighborPos(pos image.Point) image.Point {
if pos.X <= 0 {
pos.X = len(fm.slaves[pos.Y]) - 1
} else {
pos.X--
}
return pos
}
func (fm FocusMaster) rightNeighborPos(pos image.Point) image.Point {
if pos.X >= len(fm.slaves[pos.Y])-1 {
pos.X = 0
} else {
pos.X++
}
return pos
}
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