QCommandLineParser: add word-wrapping algorithm

Rather than breaking at column 79 precisely, break entire words,
to improve readability.

Change-Id: Ie30db00f0e6ed95cce87480c3b91804826c6076b
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

3 files changed, 82 insertions, 27 deletions

diff --git a/src/corelib/tools/qcommandlineparser.cpp b/src/corelib/tools/qcommandlineparser.cpp
index 8054542333..5463e4f0c1 100644
--- a/src/corelib/tools/qcommandlineparser.cpp
+++ b/src/corelib/tools/qcommandlineparser.cpp
@@ -845,11 +845,50 @@ static QString wrapText(const QString &names, int longestOptionNameString, const
 {
     const QLatin1Char nl('\n');
     QString text = QStringLiteral("  ") + names.leftJustified(longestOptionNameString) + QLatin1Char(' ');
-    const int leftColumnWidth = text.length();
-    const int rightColumnWidth = 79 - leftColumnWidth;
-    text += description.left(rightColumnWidth) + nl;
-    for (int n = rightColumnWidth; n < description.length(); n += rightColumnWidth)
-        text += QStringLiteral(" ").repeated(leftColumnWidth) + description.mid(n, rightColumnWidth) + nl;
+    const int indent = text.length();
+    int lineStart = 0;
+    int lastBreakable = -1;
+    const int max = 79 - indent;
+    int x = 0;
+    const int len = description.length();
+
+    for (int i = 0; i < len; ++i) {
+        ++x;
+        const QChar c = description.at(i);
+        if (c.isSpace())
+            lastBreakable = i;
+
+        int breakAt = -1;
+        int nextLineStart = -1;
+        if (x > max && lastBreakable != -1) {
+            // time to break and we know where
+            breakAt = lastBreakable;
+            nextLineStart = lastBreakable + 1;
+        } else if ((x > max - 1 && lastBreakable == -1) || i == len - 1) {
+            // time to break but found nowhere [-> break here], or end of last line
+            breakAt = i + 1;
+            nextLineStart = breakAt;
+        } else if (c == nl) {
+            // forced break
+            breakAt = i;
+            nextLineStart = i + 1;
+        }
+
+        if (breakAt != -1) {
+            const int numChars = breakAt - lineStart;
+            //qDebug() << "breakAt=" << description.at(breakAt) << "breakAtSpace=" << breakAtSpace << lineStart << "to" << breakAt << description.mid(lineStart, numChars);
+            if (lineStart > 0)
+                text += QString(indent, QLatin1Char(' '));
+            text += description.midRef(lineStart, numChars) + nl;
+            x = 0;
+            lastBreakable = -1;
+            lineStart = nextLineStart;
+            if (lineStart < len && description.at(lineStart).isSpace())
+                ++lineStart; // don't start a line with a space
+            i = lineStart;
+        }
+    }
+
     return text;
 }
 
diff --git a/tests/auto/corelib/tools/qcommandlineparser/testhelper/qcommandlineparser_test_helper.cpp b/tests/auto/corelib/tools/qcommandlineparser/testhelper/qcommandlineparser_test_helper.cpp
index 07f8ddfc8e..2b30b0486b 100644
--- a/tests/auto/corelib/tools/qcommandlineparser/testhelper/qcommandlineparser_test_helper.cpp
+++ b/tests/auto/corelib/tools/qcommandlineparser/testhelper/qcommandlineparser_test_helper.cpp
@@ -69,9 +69,18 @@ int main(int argc, char *argv[])
 
     // An option with a longer description, to test wrapping
     QCommandLineOption noImplicitIncludesOption(QStringList() << QStringLiteral("n") << QStringLiteral("no-implicit-includes"));
-    noImplicitIncludesOption.setDescription(QStringLiteral("Disable automatic generation of implicit #include-directives."));
+    noImplicitIncludesOption.setDescription(QStringLiteral("Disable magic generation of implicit #include-directives."));
     parser.addOption(noImplicitIncludesOption);
 
+    QCommandLineOption newlineOption(QStringList() << QStringLiteral("newline"));
+    newlineOption.setDescription(QString::fromLatin1("This is an option with a rather long\n"
+                "description using explicit newline characters "
+                "(but testing automatic wrapping too). In addition, "
+                "here, we test breaking after a comma. Testing -option. "
+                "Long URL: http://qt-project.org/wiki/How_to_create_a_library_with_Qt_and_use_it_in_an_application "
+                "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz"));
+    parser.addOption(newlineOption);
+
     // This program supports different options depending on the "command" (first argument).
     // Call parse() to find out the positional arguments.
     parser.parse(QCoreApplication::arguments());
diff --git a/tests/auto/corelib/tools/qcommandlineparser/tst_qcommandlineparser.cpp b/tests/auto/corelib/tools/qcommandlineparser/tst_qcommandlineparser.cpp
index d8965dee5d..f37e192ad3 100644
--- a/tests/auto/corelib/tools/qcommandlineparser/tst_qcommandlineparser.cpp
+++ b/tests/auto/corelib/tools/qcommandlineparser/tst_qcommandlineparser.cpp
@@ -459,27 +459,40 @@ void tst_QCommandLineParser::testVersionOption()
 #endif // !QT_NO_PROCESS
 }
 
+static const char expectedOptionsHelp[] =
+        "Options:\n"
+        "  -h, --help                  Displays this help.\n"
+        "  -v, --version               Displays version information.\n"
+        "  --load <url>                Load file from URL.\n"
+        "  -o, --output <file>         Set output file.\n"
+        "  -D <key=value>              Define macro.\n"
+        "  -n, --no-implicit-includes  Disable magic generation of implicit\n"
+        "                              #include-directives.\n"
+        "  --newline                   This is an option with a rather long\n"
+        "                              description using explicit newline characters (but\n"
+        "                              testing automatic wrapping too). In addition,\n"
+        "                              here, we test breaking after a comma. Testing\n"
+        "                              -option. Long URL:\n"
+        "                              http://qt-project.org/wiki/How_to_create_a_library\n"
+        "                              _with_Qt_and_use_it_in_an_application\n"
+        "                              abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwx\n"
+        "                              yzabcdefghijklmnopqrstuvwxyz\n";
+
 void tst_QCommandLineParser::testHelpOption_data()
 {
     QTest::addColumn<QCommandLineParser::SingleDashWordOptionMode>("parsingMode");
     QTest::addColumn<QString>("expectedHelpOutput");
 
-    QString expectedOutput =
+    QString expectedOutput = QString::fromLatin1(
         "Usage: testhelper/qcommandlineparser_test_helper [options] parsingMode command\n"
         "Test helper\n"
-        "\n"
-        "Options:\n"
-        "  -h, --help                  Displays this help.\n"
-        "  -v, --version               Displays version information.\n"
-        "  --load <url>                Load file from URL.\n"
-        "  -o, --output <file>         Set output file.\n"
-        "  -D <key=value>              Define macro.\n"
-        "  -n, --no-implicit-includes  Disable automatic generation of implicit #include\n"
-        "                              -directives.\n"
+        "\n")
+        + QString::fromLatin1(expectedOptionsHelp) +
+        QString::fromLatin1(
         "\n"
         "Arguments:\n"
         "  parsingMode                 The parsing mode to test.\n"
-        "  command                     The command to execute.\n";
+        "  command                     The command to execute.\n");
 #ifdef Q_OS_WIN
     expectedOutput.replace("  -h, --help                  Displays this help.\n",
                            "  -?, -h, --help              Displays this help.\n");
@@ -510,6 +523,7 @@ void tst_QCommandLineParser::testHelpOption()
 #ifdef Q_OS_WIN
     output.replace(QStringLiteral("\r\n"), QStringLiteral("\n"));
 #endif
+    QCOMPARE(output.split('\n'), expectedHelpOutput.split('\n')); // easier to debug than the next line, on failure
     QCOMPARE(output, expectedHelpOutput);
 
     process.start("testhelper/qcommandlineparser_test_helper", QStringList() << "0" << "resize" << "--help");
@@ -519,18 +533,11 @@ void tst_QCommandLineParser::testHelpOption()
 #ifdef Q_OS_WIN
     output.replace(QStringLiteral("\r\n"), QStringLiteral("\n"));
 #endif
-    QByteArray expectedResizeHelp =
+    QByteArray expectedResizeHelp = QByteArrayLiteral(
         "Usage: testhelper/qcommandlineparser_test_helper [options] resize [resize_options]\n"
         "Test helper\n"
-        "\n"
-        "Options:\n"
-        "  -h, --help                  Displays this help.\n"
-        "  -v, --version               Displays version information.\n"
-        "  --load <url>                Load file from URL.\n"
-        "  -o, --output <file>         Set output file.\n"
-        "  -D <key=value>              Define macro.\n"
-        "  -n, --no-implicit-includes  Disable automatic generation of implicit #include\n"
-        "                              -directives.\n"
+        "\n")
+        + expectedOptionsHelp +
         "  --size <size>               New size.\n"
         "\n"
         "Arguments:\n"