Made event handlers more robust.

redo/uitask.go

@@ -39,6 +39,7 @@ func uitask() {
 var stall = make(chan struct{})
 
 // This is the common code for running an event.
+// It runs on the main thread without a message pump; it provides its own.
 // TODO
 // - define event
 // - figure out how to return values from event handlers
@@ -50,7 +51,26 @@ func doevent(e event) {
 		close(c)
 	}()
 	for req := range c {
-		issue(req)
+		// note: this is perform, not issue!
+		// doevent runs on the main thread without a message pump!
+		perform(req)
 	}
-	stall <- struct{}{}		// leave event handler
+	// leave the event handler; leave it only after returning from an event handler so we must issue it like a normal Request
+	issue(&Request{
+		op:		func() {
+			stall <- struct{}{}
+		},
+		// unfortunately, closing a nil channel causes a panic
+		// therefore, we have to make a dummy channel
+		// TODO add conditional checks to the request handler instead?
+		resp:		make(chan interface{}),
+	})
+}
+
+// Common code for performing a Request.
+// This should run on the main thread.
+// Implementations of issue() should call this.
+func perform(req *Request) {
+	req.op()
+	close(req.resp)
 }

redo/uitask_unix.go

@@ -28,7 +28,6 @@ func issue(req *Request) {
 //export doissue
 func doissue(data C.gpointer) C.gboolean {
 	req := (*Request)(unsafe.Pointer(data))
-	req.op()
-	close(req.resp)
+	perform(req)
 	return C.FALSE		// don't repeat
 }