From 144e10eafbba82d8ac554bbd25afab112482f509 Mon Sep 17 00:00:00 2001
From: Edward Welbourne <edward.welbourne@qt.io>
Date: Mon, 10 Jul 2023 16:27:13 +0200
Subject: [PATCH] Treat simple spaces as equivalent in date-time format
 separators
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The user might not be aware of, or able to see, the difference between
Unicode's assorted horizontal spacing characters, leading them to
expect their input to be accepted for a format despite differences in
spacing. So treat the various horizontal spacing (other than tab)
characters as equivalent when matching the separators in a date-time
format. Add a test-case that failed before this fix.

Fixes: QTBUG-114909
Pick-to: 6.6 6.5
Change-Id: I3e798d3e5b89adb8e86168ebd3954904b258d630
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Ievgenii Meshcheriakov <ievgenii.meshcheriakov@qt.io>
---
 src/corelib/time/qdatetimeparser.cpp          | 26 +++++++++++++++++--
 .../auto/corelib/text/qlocale/tst_qlocale.cpp |  4 +++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/src/corelib/time/qdatetimeparser.cpp b/src/corelib/time/qdatetimeparser.cpp
index f8709f6b71..93ee63207c 100644
--- a/src/corelib/time/qdatetimeparser.cpp
+++ b/src/corelib/time/qdatetimeparser.cpp
@@ -728,11 +728,33 @@ int QDateTimeParser::sectionMaxSize(int index) const
 }
 
 // Separator matching
+//
+// QTBUG-114909: user may be oblivious to difference between visibly
+// indistinguishable spacing characters. For now we only treat horizontal
+// spacing characters, excluding tab, as equivalent.
+
 static int matchesSeparator(QStringView text, QStringView separator)
 {
+    const auto isSimpleSpace = [](char32_t ch) {
+        // Distinguish tab, CR and the vertical spaces from the rest:
+        return ch == u' ' || (ch > 127 && QChar::isSpace(ch));
+    };
     // -1 if not a match, else length of prefix of text that does match.
-    // For now, just check for exact match:
-    return text.startsWith(separator) ? separator.size() : -1;
+    // First check for exact match
+    if (!text.startsWith(separator)) {
+        // Failing that, check for space-identifying match:
+        QStringIterator given(text), sep(separator);
+        while (sep.hasNext()) {
+            if (!given.hasNext())
+                return -1;
+            char32_t s = sep.next(), g = given.next();
+            if (s != g && !(isSimpleSpace(s) && isSimpleSpace(g)))
+                return -1;
+        }
+        // One side may have used a surrogate pair space where the other didn't:
+        return given.index();
+    }
+    return separator.size();
 }
 
 /*!
diff --git a/tests/auto/corelib/text/qlocale/tst_qlocale.cpp b/tests/auto/corelib/text/qlocale/tst_qlocale.cpp
index 5de653138b..97eb99d3a1 100644
--- a/tests/auto/corelib/text/qlocale/tst_qlocale.cpp
+++ b/tests/auto/corelib/text/qlocale/tst_qlocale.cpp
@@ -2431,6 +2431,10 @@ void tst_QLocale::toTime_data()
         << usa << QTime(16, 43, 32) << u"h:mm:ss AP "_s << u"4:43:32 PM "_s << true;
     QTest::newRow("shortFormat-PM")
         << usa << QTime(16, 43) << u"h:mm AP "_s << u"4:43 PM "_s << true;
+    // Some locales use a narrow non-breaking space as separator, but
+    // the user can't see the difference from a space (QTBUG-114909):
+    QTest::newRow("shortFormat-AM-mixspace")
+        << usa << QTime(4, 43) << u"h:mm\u202F" "AP "_s << u"4:43 AM "_s << true;
 
     // Parsing am/pm indicators case-insensitively:
     const QLocale czech{QLocale::Czech, QLocale::Czechia};