ui/input/system: introduce package for system events

And add ProfileOp and ProfileEvent for registering and receiving
profile data.

Remove the Profiling field and Timings method from app.Window.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

ui/input/system/system.go

@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+// Package system contain ops and types for
+// system events.
+package system
+
+import (
+	"gioui.org/ui"
+	"gioui.org/ui/input"
+	"gioui.org/ui/internal/ops"
+)
+
+// ProfileOp registers a handler for receiving
+// ProfileEvents.
+type ProfileOp struct {
+	Key input.Key
+}
+
+// ProfileEvent contain profile data from a single
+// rendered frame.
+type ProfileEvent struct {
+	// String with timings. Very likely to change.
+	Timings string
+}
+
+func (p ProfileOp) Add(o *ui.Ops) {
+	data := make([]byte, ops.TypeProfileLen)
+	data[0] = byte(ops.TypeProfile)
+	o.Write(data, p.Key)
+}
+
+func (p *ProfileOp) Decode(d []byte, refs []interface{}) {
+	if ops.OpType(d[0]) != ops.TypeProfile {
+		panic("invalid op")
+	}
+	*p = ProfileOp{
+		Key: refs[0].(input.Key),
+	}
+}
+
+func (p ProfileEvent) ImplementsInputEvent() {}