From 94a5d323436a4ae6e3d1b8cea62b07115e855d55 Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Tue, 8 Aug 2023 19:12:25 +0200
Subject: [PATCH] tst_QImageReader: it's a rotate^Wadjacent_find!
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Instead of copying a list, sorting it just to check it's sorted, and
making a QSet out of it just to check the size is the same as that of
the list (thereby checking there were no duplicates), simply apply
adjacent_find with greater_equal. If none of the elements is ≥ their
successor, that means all elements are < their successor, and _that_
means the range is sorted and has no duplicates.               q.e.d.

Change-Id: Id73c674ad4e29117370e8fc6af9fdfc690a3fba9
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
(cherry picked from commit 29d07101e5dd7efbb0ffbab1acb5d8d4ef0ed731)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 .../image/qimagereader/tst_qimagereader.cpp   | 47 +++++++------------
 1 file changed, 18 insertions(+), 29 deletions(-)

diff --git a/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp b/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
index c8ef8ff839e..10f3a813c30 100644
--- a/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
+++ b/tests/auto/gui/image/qimagereader/tst_qimagereader.cpp
@@ -11,7 +11,6 @@
 #include <QImageReader>
 #include <QImageWriter>
 #include <QPixmap>
-#include <QSet>
 #include <QScopeGuard>
 #include <QTcpSocket>
 #include <QTcpServer>
@@ -595,41 +594,31 @@ void tst_QImageReader::multiWordNamedColorXPM()
     QCOMPARE(image.pixel(0, 2), qRgb(255, 250, 205)); // lemon chiffon
 }
 
+namespace {
+template <typename ForwardIterator>
+bool is_sorted_unique(ForwardIterator first, ForwardIterator last)
+{
+    // a range is sorted with no dups iff each *i < *(i+1), so check that none are >=:
+    return std::adjacent_find(first, last, std::greater_equal<>{}) == last;
+}
+}
+
 void tst_QImageReader::supportedFormats()
 {
-    QList<QByteArray> formats = QImageReader::supportedImageFormats();
-    QList<QByteArray> sortedFormats = formats;
-    std::sort(sortedFormats.begin(), sortedFormats.end());
-
-    // check that the list is sorted
-    QCOMPARE(formats, sortedFormats);
-
-    QSet<QByteArray> formatSet;
-    foreach (QByteArray format, formats)
-        formatSet << format;
-
-    // check that the list does not contain duplicates
-    QCOMPARE(formatSet.size(), formats.size());
+    const QList<QByteArray> formats = QImageReader::supportedImageFormats();
+    auto printOnFailure = qScopeGuard([&] { qDebug() << formats; });
+    QVERIFY(is_sorted_unique(formats.begin(), formats.end()));
+    printOnFailure.dismiss();
 }
 
 void tst_QImageReader::supportedMimeTypes()
 {
-    QList<QByteArray> mimeTypes = QImageReader::supportedMimeTypes();
-    QList<QByteArray> sortedMimeTypes = mimeTypes;
-    std::sort(sortedMimeTypes.begin(), sortedMimeTypes.end());
-
-    // check that the list is sorted
-    QCOMPARE(mimeTypes, sortedMimeTypes);
-
-    QSet<QByteArray> mimeTypeSet;
-    foreach (QByteArray mimeType, mimeTypes)
-        mimeTypeSet << mimeType;
-
+    const QList<QByteArray> mimeTypes = QImageReader::supportedMimeTypes();
+    auto printOnFailure = qScopeGuard([&] { qDebug() << mimeTypes; });
+    QVERIFY(is_sorted_unique(mimeTypes.begin(), mimeTypes.end()));
     // check the list as a minimum contains image/bmp
-    QVERIFY(mimeTypeSet.contains("image/bmp"));
-
-    // check that the list does not contain duplicates
-    QCOMPARE(mimeTypeSet.size(), mimeTypes.size());
+    QVERIFY(mimeTypes.contains("image/bmp"));
+    printOnFailure.dismiss();
 }
 
 void tst_QImageReader::setBackgroundColor_data()