120 lines
2.6 KiB
Go
120 lines
2.6 KiB
Go
// 6 july 2014
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package ui
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import (
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"runtime"
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"sync"
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"unsafe"
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)
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// Go initializes package ui.
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// TODO write this bit
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func Go() error {
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runtime.LockOSThread()
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if err := uiinit(); err != nil {
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return err
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}
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go uiissueloop()
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uimsgloop()
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return nil
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}
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// To ensure that Do() and Stop() only do things after Go() has been called, this channel accepts the requests to issue. The issuing is done by uiissueloop() below.
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// Notice that this is a pointer ot a function. See Do() below for details.
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var issuer = make(chan *func())
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// Do performs f on the main loop, as if it were an event handler.
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// It waits for f to execute before returning.
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// Do cannot be called within event handlers or within Do itself.
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func Do(f func()) {
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done := make(chan struct{})
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defer close(done)
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// THIS MUST BE A POINTER.
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// Previously, the pointer was constructed within issue().
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// This meant that if the Do() was stalled, the garbage collector came in and reused the pointer value too soon!
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call := func() {
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f()
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done <- struct{}{}
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}
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issuer <- &call
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<-done
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}
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// Stop informs package ui that it should stop.
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// Stop then returns immediately.
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// Some time after this request is received, Go() will return without performing any final cleanup.
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// Stop will not have an effect until any event handlers or dialog boxes presently active return.
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// (TODO make sure this is the case for dialog boxes)
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func Stop() {
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// can't send this directly across issuer
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go func() {
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Do(uistop)
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}()
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}
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func uiissueloop() {
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for f := range issuer {
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issue(f)
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}
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}
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type event struct {
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// All events internally return bool; those that don't will be wrapped around to return a dummy value.
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do func() bool
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lock sync.Mutex
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}
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// do should never be nil
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// TODO when writing doc.go, document that setting nil to an event handler ignores the event; if it returns a boolean value, false is returned
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func newEvent() *event {
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return &event{
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do: func() bool {
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return false
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},
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}
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}
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func (e *event) set(f func()) {
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e.lock.Lock()
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defer e.lock.Unlock()
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if f == nil {
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f = func() {}
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}
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e.do = func() bool {
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f()
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return false
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}
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}
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func (e *event) setbool(f func() bool) {
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e.lock.Lock()
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defer e.lock.Unlock()
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if f == nil {
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f = func() bool {
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return false
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}
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}
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e.do = f
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}
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// This is the common code for running an event.
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// It runs on the main thread without a message pump; it provides its own.
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func (e *event) fire() bool {
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e.lock.Lock()
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defer e.lock.Unlock()
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return e.do()
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}
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// Common code for performing a requested action (ui.Do() or ui.Stop()).
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// This should run on the main thread.
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// Implementations of issue() should call this.
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func perform(fp unsafe.Pointer) {
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f := (*func())(fp)
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(*f)()
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}
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