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package layout
import (
"image"
"image/color"
"image/draw"
"github.com/faiface/gui"
)
// Region is a layout with a single child Env that occupies a sub-area of its parent.
type Region struct {
events <-chan gui.Event
draw chan<- func(draw.Image) image.Rectangle
}
// NewRegion creates a region layout that occupies part of the parent env's area, as determined by the resize function.
// Resize takes the area of the parent and returns the area of the region.
// It returns the child Env.
func NewRegion(env gui.Env, clr color.Color, resize ResizeFunc) gui.Env {
events := make(chan gui.Event) // to child
draws := make(chan func(draw.Image) image.Rectangle) // from child
go func(events chan<- gui.Event, draws <-chan func(draw.Image) image.Rectangle) {
defer close(env.Draw())
defer close(events)
redraw := func(area, childArea image.Rectangle) {
env.Draw() <- drawSubImage(drawBackground(clr), area)
events <- gui.Resize{childArea}
}
// Draw background and forward first resize event to child
event := (<-env.Events()).(gui.Resize) // first event guaranteed to be Resize
area := event.Rectangle
childArea := resize(area)
go redraw(area, childArea)
for {
select {
case event := <-env.Events(): // event from parent
switch event := event.(type) {
case gui.Resize:
area = event.Rectangle
childArea = resize(area)
go redraw(area, childArea)
default:
go func() { events <- event }() // forward to child
}
case f, ok := <-draws: // draw call from child
if !ok {
return
}
env.Draw() <- drawSubImage(f, childArea)
}
}
}(events, draws)
return Region{events, draws}
}
// Events implements the Env interface.
func (r Region) Events() <-chan gui.Event { return r.events }
// Draw implements the Env interface.
func (r Region) Draw() chan<- func(draw.Image) image.Rectangle { return r.draw }
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