ui/input: move Router and input queues to internal package

Now that only app.Window needs the Router, make it unavailable for
clients.

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

ui/app/internal/input/key.go

@@ -0,0 +1,136 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package input
+
+import (
+	"gioui.org/ui"
+	"gioui.org/ui/input"
+	"gioui.org/ui/internal/ops"
+	"gioui.org/ui/key"
+)
+
+type keyQueue struct {
+	focus    input.Key
+	handlers map[input.Key]*keyHandler
+	reader   ui.OpsReader
+	state    key.TextInputState
+}
+
+type keyHandler struct {
+	active bool
+}
+
+type listenerPriority uint8
+
+const (
+	priNone listenerPriority = iota
+	priDefault
+	priCurrentFocus
+	priNewFocus
+)
+
+// InputState returns the last text input state as
+// determined in Frame.
+func (q *keyQueue) InputState() key.TextInputState {
+	return q.state
+}
+
+func (q *keyQueue) Frame(root *ui.Ops, events handlerEvents) {
+	if q.handlers == nil {
+		q.handlers = make(map[input.Key]*keyHandler)
+	}
+	for _, h := range q.handlers {
+		h.active = false
+	}
+	q.reader.Reset(root)
+	focus, pri, hide := q.resolveFocus(events)
+	for k, h := range q.handlers {
+		if !h.active {
+			delete(q.handlers, k)
+			if q.focus == k {
+				q.focus = nil
+				hide = true
+			}
+		}
+	}
+	changed := focus != nil && focus != q.focus
+	if focus != q.focus {
+		if q.focus != nil {
+			events[q.focus] = append(events[q.focus], key.FocusEvent{Focus: false})
+		}
+		q.focus = focus
+		if q.focus != nil {
+			events[q.focus] = append(events[q.focus], key.FocusEvent{Focus: true})
+		} else {
+			hide = true
+		}
+	}
+	switch {
+	case pri == priNewFocus:
+		q.state = key.TextInputOpen
+	case hide:
+		q.state = key.TextInputClose
+	case changed:
+		q.state = key.TextInputFocus
+	default:
+		q.state = key.TextInputKeep
+	}
+}
+
+func (q *keyQueue) Push(e input.Event, events handlerEvents) {
+	if q.focus == nil {
+		return
+	}
+	events[q.focus] = append(events[q.focus], e)
+}
+
+func (q *keyQueue) resolveFocus(events handlerEvents) (input.Key, listenerPriority, bool) {
+	var k input.Key
+	var pri listenerPriority
+	var hide bool
+loop:
+	for encOp, ok := q.reader.Decode(); ok; encOp, ok = q.reader.Decode() {
+		switch ops.OpType(encOp.Data[0]) {
+		case ops.TypeKeyHandler:
+			var op key.HandlerOp
+			op.Decode(encOp.Data, encOp.Refs)
+			var newPri listenerPriority
+			switch {
+			case op.Focus:
+				newPri = priNewFocus
+			case op.Key == q.focus:
+				newPri = priCurrentFocus
+			default:
+				newPri = priDefault
+			}
+			// Switch focus if higher priority or if focus requested.
+			if newPri.replaces(pri) {
+				k, pri = op.Key, newPri
+			}
+			h, ok := q.handlers[op.Key]
+			if !ok {
+				h = new(keyHandler)
+				q.handlers[op.Key] = h
+				// Reset the handler on (each) first appearance.
+				events[op.Key] = []input.Event{key.FocusEvent{Focus: false}}
+			}
+			h.active = true
+		case ops.TypeHideInput:
+			hide = true
+		case ops.TypePush:
+			newK, newPri, h := q.resolveFocus(events)
+			hide = hide || h
+			if newPri.replaces(pri) {
+				k, pri = newK, newPri
+			}
+		case ops.TypePop:
+			break loop
+		}
+	}
+	return k, pri, hide
+}
+
+func (p listenerPriority) replaces(p2 listenerPriority) bool {
+	// Favor earliest default focus or latest requested focus.
+	return p > p2 || p == p2 && p == priNewFocus
+}