Diaglib: Add class LogWidget.

Add a class to display debug messages, providing convenience functions for
installing and formatting parameters like indentation. It prints a startup
message containing relevant information about Qt.

Change-Id: Id0a19adbb5953a6ded1a8e692f242b63748e7273
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

tests/manual/diaglib/README.txt

@@ -32,6 +32,17 @@ class DebugProxyStyle (debugproxystyle.h)
   the parameters and return values of its function calls, useful
   for debugging QStyle.
 
+class LogWidget (logwidget.h)
+  A Log Widget inheriting QPlainTextEdit with convenience functions
+  to install as a message handler.
+
+class LogFunctionGuard
+   A guard class for use with LogWidget logging messages when a function
+   is entered/left (indenting the log messages).
+   Can be instantiated using:
+   LogFunctionGuard guard(__FUNCTION__) or
+   LogFunctionGuard guard(Q_FUNC_INFO)
+
 function glInfo() (glinfo.h):
   Returns a string describing the Open GL configuration (obtained
   by querying GL_VENDOR and GL_RENDERER). Available only

tests/manual/diaglib/diaglib.pri

@@ -23,17 +23,21 @@ greaterThan(QT_MAJOR_VERSION, 4) {
     QT += gui-private core-private
     contains(QT, widgets) {
         HEADERS += \
-            $$PWD/qwidgetdump.h
+            $$PWD/qwidgetdump.h \
+            $$PWD/logwidget.h
 
         SOURCES += \
-            $$PWD/qwidgetdump.cpp
+            $$PWD/qwidgetdump.cpp \
+            $$PWD/logwidget.cpp
     }
 } else {
     HEADERS += \
-        $$PWD/qwidgetdump.h
+        $$PWD/qwidgetdump.h \
+        $$PWD/logwidget.h
 
     SOURCES += \
-        $$PWD/qwidgetdump.cpp
+        $$PWD/qwidgetdump.cpp \
+        $$PWD/logwidget.cpp
 }
 
 contains(QT, opengl) {

tests/manual/diaglib/logwidget.cpp

@@ -0,0 +1,164 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** As a special exception, The Qt Company gives you certain additional
+** rights. These rights are described in The Qt Company LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "logwidget.h"
+#if QT_VERSION >= 0x050000
+#  include <QtCore/qlogging.h>
+#  include <QtCore/QLibraryInfo>
+#endif
+#include <QApplication>
+#include <QStyle>
+
+#include <QtCore/QDebug>
+#include <QtCore/QVector>
+#include <QtCore/QStringList>
+
+#include <iostream>
+
+LogWidget *LogWidget::m_instance = 0;
+bool LogWidget::m_lineNumberingEnabled = true;
+bool LogWidget::m_showMessageType = true;
+int LogWidget::m_indent = 0;
+
+LogWidget::LogWidget(QWidget *parent)
+    : QPlainTextEdit(parent)
+{
+    LogWidget::m_instance = this;
+    setReadOnly(true);
+}
+
+LogWidget::~LogWidget()
+{
+    LogWidget::m_instance = 0;
+}
+
+QString LogWidget::startupMessage()
+{
+    QString result;
+#if QT_VERSION >= 0x050300
+    result += QLatin1String(QLibraryInfo::build());
+#else
+    result += QLatin1String("Qt ") + QLatin1String(QT_VERSION_STR);
+#endif
+
+    const QCoreApplication *coreApp = QCoreApplication::instance();
+#if QT_VERSION >= 0x050000
+    if (qobject_cast<const QGuiApplication *>(coreApp)) {
+        result += QLatin1Char(' ');
+        result += QGuiApplication::platformName();
+    }
+#endif
+    if (qobject_cast<const QApplication *>(coreApp)) {
+        result += QLatin1Char(' ');
+        result += QApplication::style()->objectName();
+    }
+    if (coreApp) {
+        QStringList arguments = QCoreApplication::arguments();
+        arguments.pop_front();
+        if (!arguments.isEmpty()) {
+            result += QLatin1Char('\n');
+            result += arguments.join(QLatin1String(" "));
+        }
+    }
+    return result;
+}
+
+static const QVector<QString> &messageTypes()
+{
+    static QVector<QString> result;
+    if (result.isEmpty()) {
+        result << QLatin1String("debug") << QLatin1String("warn")
+            << QLatin1String("critical") << QLatin1String("fatal")
+            << QLatin1String("info");
+    }
+    return result;
+}
+
+static void messageHandler(QtMsgType type, const QString &text)
+{
+    static int n = 0;
+    QString message;
+    if (LogWidget::lineNumberingEnabled())
+        message.append(QString::fromLatin1("%1 ").arg(n, 4, 10, QLatin1Char('0')));
+    if (LogWidget::showMessageType()) {
+        message.append(messageTypes().at(type));
+        message.append(QLatin1Char(' '));
+    }
+    for (int i = 0, ie = LogWidget::indent(); i < ie; ++i)
+        message.append(QLatin1Char(' '));
+    message.append(text);
+    if (LogWidget *logWindow = LogWidget::instance())
+        logWindow->appendText(message);
+#ifdef Q_OS_WIN
+    std::wcerr << reinterpret_cast<const wchar_t *>(message.utf16()) << L'\n';
+#else
+    std::cerr << qPrintable(message) << '\n';
+#endif
+    n++;
+}
+
+#if QT_VERSION >= 0x050000
+
+static void qt5MessageHandler(QtMsgType type, const QMessageLogContext &, const QString &text)
+{ messageHandler(type, text); }
+
+void LogWidget::install()
+{
+    qInstallMessageHandler(qt5MessageHandler);
+    qInfo("%s", qPrintable(LogWidget::startupMessage()));
+}
+
+void LogWidget::uninstall() { qInstallMessageHandler(Q_NULLPTR); }
+
+#else // Qt 5
+
+static QtMsgHandler oldHandler = 0;
+
+static void qt4MessageHandler(QtMsgType type, const char *text)
+{ messageHandler(type, QString::fromLocal8Bit(text)); }
+
+void LogWidget::install()
+{
+    oldHandler = qInstallMsgHandler(qt4MessageHandler);
+    qDebug("%s", qPrintable(LogWidget::startupMessage()));
+}
+
+void LogWidget::uninstall() { qInstallMsgHandler(oldHandler); }
+
+#endif // Qt 4
+
+void LogWidget::appendText(const QString &message)
+{
+    appendPlainText(message);
+    ensureCursorVisible();
+}

tests/manual/diaglib/logwidget.h

@@ -0,0 +1,94 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** As a special exception, The Qt Company gives you certain additional
+** rights. These rights are described in The Qt Company LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef LOGWIDGET_H
+#define LOGWIDGET_H
+
+#include <QPlainTextEdit>
+
+// Instantiate as follows: LogFunctionGuard guard(Q_FUNC_INFO)
+class LogFunctionGuard {
+    Q_DISABLE_COPY(LogFunctionGuard)
+public:
+    explicit LogFunctionGuard(const char *name);
+    ~LogFunctionGuard();
+
+private:
+    const char *m_name;
+};
+
+class LogWidget : public QPlainTextEdit
+{
+    Q_OBJECT
+public:
+    explicit LogWidget(QWidget *parent = 0);
+    ~LogWidget();
+
+    static LogWidget *instance() { return m_instance; }
+
+    static QString startupMessage();
+    static void install();
+    static void uninstall();
+
+    static int indent()          { return m_indent; }
+    static void setIndent(int i) { m_indent = i; }
+
+    static bool lineNumberingEnabled()          { return m_lineNumberingEnabled; }
+    static void setLineNumberingEnabled(bool l) { m_lineNumberingEnabled = l; }
+
+    static bool showMessageType()          { return m_showMessageType; }
+    static void setShowMessageType(bool s) { m_showMessageType = s; }
+
+public slots:
+    void appendText(const QString &);
+
+private:
+    static int m_indent;
+    static bool m_lineNumberingEnabled;
+    static bool m_showMessageType;
+    static LogWidget *m_instance;
+};
+
+inline LogFunctionGuard::LogFunctionGuard(const char *name) : m_name(name)
+{
+    qDebug(">%s", m_name);
+    LogWidget::setIndent(LogWidget::indent() + 2);
+}
+
+inline LogFunctionGuard::~LogFunctionGuard()
+{
+    LogWidget::setIndent(LogWidget::indent() - 2);
+    qDebug("<%s", m_name);
+}
+
+#endif // LOGWIDGET_H