From a78f9c6eaa7d3ed305aad37c4e1302bce3299f35 Mon Sep 17 00:00:00 2001
From: Elias Naur <mail@eliasnaur.com>
Date: Fri, 7 Jun 2019 19:35:46 +0200
Subject: [PATCH] ui/pointer: don't drop handlers that whose events haven't
 been read

We're about to merge the pointer and key event streams in a single
input queue. To do that, we need to simplify Queue.For to just returning
events for the given handler.

First step is the handler active flag.

Dropping handlers that haven't had their events read doesn't seem
worth it. Drop that special case and only determine a handler's activeness
from its presence in the ops list.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
---
 ui/pointer/queue.go | 37 +++++++++++++++++--------------------
 1 file changed, 17 insertions(+), 20 deletions(-)

diff --git a/ui/pointer/queue.go b/ui/pointer/queue.go
index 79895487..fa2f3c8c 100644
--- a/ui/pointer/queue.go
+++ b/ui/pointer/queue.go
@@ -81,9 +81,13 @@ func (q *Queue) collectHandlers(r *ui.OpsReader, t ui.Transform, layer int) {
 			q.hitTree = append(q.hitTree, hitNode{level: layer, key: op.Key})
 			h, ok := q.handlers[op.Key]
 			if !ok {
-				h = new(handler)
+				h = &handler{
+					// Reset the handler on (each) first appearance.
+					events: []Event{Event{Type: Cancel}},
+				}
 				q.handlers[op.Key] = h
 			}
+			h.active = true
 			h.area = q.areas.intersection()
 			h.transform = t
 			h.wantsGrab = h.wantsGrab || op.Grab
@@ -126,36 +130,29 @@ func (q *Queue) init() {
 
 func (q *Queue) Frame(root *ui.Ops) {
 	q.init()
-	for k, h := range q.handlers {
-		if !h.active {
-			q.dropHandler(k)
-		} else {
-			// Reset handler.
-			h.events = h.events[:0]
-		}
+	for _, h := range q.handlers {
+		// Reset handler.
+		h.active = false
+		h.events = h.events[:0]
 	}
 	q.hitTree = q.hitTree[:0]
 	q.areas.reset()
 	q.reader.Reset(root)
 	q.collectHandlers(&q.reader, ui.Transform{}, 0)
+	for k, h := range q.handlers {
+		if !h.active {
+			q.dropHandler(k)
+		}
+	}
 }
 
 func (q *Queue) For(k Key) []Event {
 	if k == nil {
 		panic("nil handler")
 	}
-	q.init()
-	h, ok := q.handlers[k]
-	if !ok {
-		h = new(handler)
-		q.handlers[k] = h
-	}
-	if !h.active {
-		h.active = true
-		// Prepend a Cancel.
-		h.events = append(h.events, Event{})
-		copy(h.events[1:], h.events)
-		h.events[0] = Event{Type: Cancel}
+	h := q.handlers[k]
+	if h == nil {
+		return nil
 	}
 	return h.events
 }