From 414dd4bf127caa0729ce4ee73ce4a67bd3cd964e Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@kdab.com>
Date: Sun, 5 Apr 2015 21:01:54 +0200
Subject: [PATCH] QErrorMessage: replace inefficient QQueue with std::queue

QQueue is-a QList, so it inherits the trait that types larger than
a void* cause a heap-allocation when inserted, which is horribly
inefficient.

Use a std::queue instead, which, by default, is backed by std::deque.

Requires rewriting the API calls, since QQueue uses non-standard
function names.

Text and data size increase negligibly (23 and 8 bytes, respectively),
even though we're instantiating a completely new type (std::deque)
instead of QList<QPair<QString, QString>>, which is probably still
used, despite the inefficiency.

Change-Id: I9bb04a2ec32bb1b9fa2eb83780f0aaa26e872d49
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
---
 src/widgets/dialogs/qerrormessage.cpp | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/widgets/dialogs/qerrormessage.cpp b/src/widgets/dialogs/qerrormessage.cpp
index 7c185ed068..280ce4f44f 100644
--- a/src/widgets/dialogs/qerrormessage.cpp
+++ b/src/widgets/dialogs/qerrormessage.cpp
@@ -47,9 +47,10 @@
 #include "qpixmap.h"
 #include "qmetaobject.h"
 #include "qthread.h"
-#include "qqueue.h"
 #include "qset.h"
 
+#include <queue>
+
 #include <stdio.h>
 #include <stdlib.h>
 
@@ -68,7 +69,7 @@ public:
     QCheckBox * again;
     QTextEdit * errors;
     QLabel * icon;
-    QQueue<QPair<QString, QString> > pending;
+    std::queue<QPair<QString, QString> > pending;
     QSet<QString> doNotShow;
     QSet<QString> doNotShowType;
     QString currentMessage;
@@ -305,10 +306,11 @@ QErrorMessage * QErrorMessage::qtHandler()
 
 bool QErrorMessagePrivate::nextPending()
 {
-    while (!pending.isEmpty()) {
-        QPair<QString,QString> pendingMessage = pending.dequeue();
+    while (!pending.empty()) {
+        const QPair<QString,QString> &pendingMessage = pending.front();
         QString message = pendingMessage.first;
         QString type = pendingMessage.second;
+        pending.pop();
         if (!message.isEmpty() && ((type.isEmpty() && !doNotShow.contains(message)) || (!type.isEmpty() && !doNotShowType.contains(type)))) {
 #ifndef QT_NO_TEXTHTMLPARSER
             errors->setHtml(message);
@@ -338,7 +340,7 @@ void QErrorMessage::showMessage(const QString &message)
     Q_D(QErrorMessage);
     if (d->doNotShow.contains(message))
         return;
-    d->pending.enqueue(qMakePair(message,QString()));
+    d->pending.push(qMakePair(message,QString()));
     if (!isVisible() && d->nextPending())
         show();
 }
@@ -362,7 +364,7 @@ void QErrorMessage::showMessage(const QString &message, const QString &type)
     Q_D(QErrorMessage);
     if (d->doNotShow.contains(message) && d->doNotShowType.contains(type))
         return;
-     d->pending.push_back(qMakePair(message,type));
+    d->pending.push(qMakePair(message,type));
     if (!isVisible() && d->nextPending())
         show();
 }