fyne-widgets/pkg/vumeter/bind_helper.go

79 lines
2.3 KiB
Go

package vumeter
import (
"sync"
"fyne.io/fyne/v2/data/binding"
)
// basicBinder stores a DataItem and a function to be called when it changes.
// It provides a convenient way to replace data and callback independently.
type basicBinder struct {
callbackLock sync.RWMutex
callback func(binding.DataItem) // access guarded by callbackLock
dataListenerPairLock sync.RWMutex
dataListenerPair annotatedListener // access guarded by dataListenerPairLock
}
// Bind replaces the data item whose changes are tracked by the callback function.
func (binder *basicBinder) Bind(data binding.DataItem) {
listener := binding.NewDataListener(func() { // NB: listener captures `data` but always calls the up-to-date callback
binder.callbackLock.RLock()
f := binder.callback
binder.callbackLock.RUnlock()
if f != nil {
f(data)
}
})
data.AddListener(listener)
listenerInfo := annotatedListener{
data: data,
listener: listener,
}
binder.dataListenerPairLock.Lock()
binder.unbindLocked()
binder.dataListenerPair = listenerInfo
binder.dataListenerPairLock.Unlock()
}
// CallWithData passes the currently bound data item as an argument to the
// provided function.
func (binder *basicBinder) CallWithData(f func(data binding.DataItem)) {
binder.dataListenerPairLock.RLock()
data := binder.dataListenerPair.data
binder.dataListenerPairLock.RUnlock()
f(data)
}
// SetCallback replaces the function to be called when the data changes.
func (binder *basicBinder) SetCallback(f func(data binding.DataItem)) {
binder.callbackLock.Lock()
binder.callback = f
binder.callbackLock.Unlock()
}
// Unbind requests the callback to be no longer called when the previously bound
// data item changes.
func (binder *basicBinder) Unbind() {
binder.dataListenerPairLock.Lock()
binder.unbindLocked()
binder.dataListenerPairLock.Unlock()
}
// unbindLocked expects the caller to hold dataListenerPairLock.
func (binder *basicBinder) unbindLocked() {
previousListener := binder.dataListenerPair
binder.dataListenerPair = annotatedListener{nil, nil}
if previousListener.listener == nil || previousListener.data == nil {
return
}
previousListener.data.RemoveListener(previousListener.listener)
}
type annotatedListener struct {
data binding.DataItem
listener binding.DataListener
}