b0 := g.Batch(trace.ThreadID(0), 0)
	b0.Event("ProcStatus", trace.ProcID(1), go122.ProcIdle)
	b0.Event("ProcStatus", trace.ProcID(0), go122.ProcRunning)
	b0.Event("GoStatus", trace.GoID(1), trace.ThreadID(0), go122.GoRunning)
	b0.Event("GoSyscallBegin", testgen.Seq(1), testgen.NoStack)
	b0.Event("ProcStart", trace.ProcID(1), testgen.Seq(1))
	b0.Event("GoSyscallEndBlocked")

	// A running goroutine steals proc 0.

	b0.Event("GoStatus", trace.GoID(1), trace.ThreadID(0), go122.GoRunning)
	b0.Event("GoSyscallBegin", testgen.Seq(1), testgen.NoStack)
	b0.Event("GoSyscallEndBlocked")

	// A running goroutine steals proc 0.
	b1 := g.Batch(trace.ThreadID(1), 0)
	b1.Event("ProcStatus", trace.ProcID(2), go122.ProcRunning)
	b1.Event("GoStatus", trace.GoID(2), trace.ThreadID(1), go122.GoRunning)

	// A running goroutine emits a task begin.
	b1 := g1.Batch(trace.ThreadID(0), 0)
	b1.Event("ProcStatus", trace.ProcID(0), go122.ProcRunning)
	b1.Event("GoStatus", trace.GoID(1), trace.ThreadID(0), go122.GoRunning)
	b1.Event("UserTaskBegin", trace.TaskID(2), trace.TaskID(0) /* 0 means no parent, not background */, "my task", testgen.NoStack)

	g2 := t.Generation(2)

	// That same goroutine emits a task end in the following generation.

	// it's P gets stolen.
	b0 := g.Batch(trace.ThreadID(0), 0)
	b0.Event("ProcStatus", trace.ProcID(0), go122.ProcRunning)
	b0.Event("GoStatus", trace.GoID(1), trace.ThreadID(0), go122.GoRunning)
	b0.Event("GoSyscallBegin", testgen.Seq(1), testgen.NoStack)
	b0.Event("GoSyscallEnd")
	b0.Event("GoSyscallBegin", testgen.Seq(2), testgen.NoStack)
	b0.Event("GoSyscallEndBlocked")

	if from == to {
		// Filter out no-op events.
		return
	}
	if from == trace.GoRunning && !to.Executing() {
		if to == trace.GoWaiting {
			// Goroutine started blocking.
			gs.block(ev.Time(), ev.Stack(), st.Reason, ctx)
		} else {
			gs.stop(ev.Time(), ev.Stack(), ctx)
		}
	}
	if !from.Executing() && to == trace.GoRunning {
		start := ev.Time()
		if from == trace.GoUndetermined {

	g := t.Generation(1)

	// One goroutine enters a syscall.
	b0 := g.Batch(trace.ThreadID(0), 0)
	b0.Event("ProcStatus", trace.ProcID(0), go122.ProcRunning)
	b0.Event("GoStatus", trace.GoID(1), trace.ThreadID(0), go122.GoRunning)
	b0.Event("GoSyscallBegin", testgen.Seq(1), testgen.NoStack)
	b0.Event("GoSyscallEndBlocked")

	// A bare M steals the goroutine's P.
	b1 := g.Batch(trace.ThreadID(1), 0)

	b0 := g.Batch(trace.ThreadID(0), 0)
	b0.Event("ProcStatus", trace.ProcID(1), go122.ProcIdle)
	b0.Event("ProcStatus", trace.ProcID(0), go122.ProcRunning)
	b0.Event("GoStatus", trace.GoID(1), trace.ThreadID(0), go122.GoRunning)
	b0.Event("GoSyscallBegin", testgen.Seq(1), testgen.NoStack)
	b0.Event("ProcStart", trace.ProcID(1), testgen.Seq(1))
	b0.Event("GoSyscallEndBlocked")

	// A bare M steals the goroutine's P.

	// A running goroutine stole P0 at the generation boundary.
	b1 := g.Batch(trace.ThreadID(1), 0)
	b1.Event("ProcStatus", trace.ProcID(2), go122.ProcRunning)
	b1.Event("GoStatus", trace.GoID(2), trace.ThreadID(1), go122.GoRunning)
	b1.Event("ProcStatus", trace.ProcID(0), go122.ProcSyscallAbandoned)
	b1.Event("ProcSteal", trace.ProcID(0), testgen.Seq(1), trace.ThreadID(0))

	// on that P.
	b0 := g.Batch(trace.ThreadID(0), 0)
	b0.Event("ProcStatus", trace.ProcID(0), go122.ProcRunning)
	b0.Event("GoStatus", trace.GoID(1), trace.ThreadID(0), go122.GoRunning)
	b0.Event("GoSyscallBegin", testgen.Seq(1), testgen.NoStack)
	b0.Event("ProcSteal", trace.ProcID(0), testgen.Seq(2), trace.ThreadID(0))
	b0.Event("ProcStart", trace.ProcID(0), testgen.Seq(3))
	b0.Event("GoSyscallEndBlocked")

	switch state {
	case trace.GoUndetermined:
		return traceviewer.GDead
	case trace.GoNotExist:
		return traceviewer.GDead
	case trace.GoRunnable:
		return traceviewer.GRunnable
	case trace.GoRunning:
		return traceviewer.GRunning
	case trace.GoWaiting:
		if inMarkAssist {
			return traceviewer.GWaitingGC
		}
		return traceviewer.GWaiting
	case trace.GoSyscall: