Codecs example: Add a dialog for showing common C++ encodings

Add a dialog where the user can enter a line of text, which is then
displayed in several encodings with special characters converted
suitable for C++/Python string literals.

Task-number: QTBUG-60635
Change-Id: Ibd436f9f76e128c93cbb581235c730d636641d8a
Reviewed-by: Andy Shaw <andy.shaw@qt.io>

examples/widgets/tools/codecs/codecs.pro

@@ -2,10 +2,15 @@ QT += widgets
 requires(qtConfig(filedialog))
 
 HEADERS      += mainwindow.h \
-                previewform.h
+                previewform.h \
+                encodingdialog.h
+
 SOURCES      += main.cpp \
                 mainwindow.cpp \
-                previewform.cpp
+                previewform.cpp \
+                encodingdialog.cpp
+
+RESOURCES    += codecs.qrc
 
 EXAMPLE_FILES = encodedfiles
 

examples/widgets/tools/codecs/codecs.qrc

@@ -0,0 +1,5 @@
+<RCC>
+    <qresource prefix="/" >
+        <file>images/editcopy.png</file>
+    </qresource>
+</RCC>

examples/widgets/tools/codecs/encodingdialog.cpp

@@ -0,0 +1,333 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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 https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "encodingdialog.h"
+
+#if QT_CONFIG(action)
+#  include <QAction>
+#endif
+#include <QDialogButtonBox>
+#include <QFormLayout>
+#include <QLabel>
+#include <QLineEdit>
+#include <QVBoxLayout>
+
+#if QT_CONFIG(clipboard)
+#  include <QGuiApplication>
+#  include <QClipboard>
+#endif
+
+#include <QTextStream>
+
+// Helpers for formatting character sequences
+
+// Format a special character like '\x0a'
+template <class Int>
+static void formatEscapedNumber(QTextStream &str, Int value, int base,
+                                int width = 0,char prefix = 0)
+{
+    str << '\\';
+    if (prefix)
+        str << prefix;
+    const auto oldPadChar = str.padChar();
+    const auto oldFieldWidth = str.fieldWidth();
+    const auto oldFieldAlignment = str.fieldAlignment();
+    const auto oldIntegerBase = str.integerBase();
+    str.setPadChar(QLatin1Char('0'));
+    str.setFieldWidth(width);
+    str.setFieldAlignment(QTextStream::AlignRight);
+    str.setIntegerBase(base);
+    str << value;
+    str.setIntegerBase(oldIntegerBase);
+    str.setFieldAlignment(oldFieldAlignment);
+    str.setFieldWidth(oldFieldWidth);
+    str.setPadChar(oldPadChar);
+}
+
+template <class Int>
+static bool formatSpecialCharacter(QTextStream &str, Int value)
+{
+    bool result = true;
+    switch (value) {
+    case '\\':
+        str << "\\\\";
+        break;
+    case '\"':
+        str << "\\\"";
+        break;
+    case '\n':
+        str << "\\n";
+        break;
+    default:
+        result = false;
+        break;
+    }
+    return result;
+}
+
+// Format a sequence of characters (QChar, ushort (UTF-16), uint (UTF-32)
+// or just char (Latin1, Utf-8)) with the help of traits specifying
+// how to obtain the code for checking the printable-ness and how to
+// stream out the plain ASCII values.
+
+template <EncodingDialog::Encoding>
+struct FormattingTraits
+{
+};
+
+template <>
+struct FormattingTraits<EncodingDialog::Unicode>
+{
+    static ushort code(QChar c) { return c.unicode(); }
+    static char toAscii(QChar c) { return c.toLatin1(); }
+};
+
+template <>
+struct FormattingTraits<EncodingDialog::Utf8>
+{
+    static ushort code(char c) { return uchar(c); }
+    static char toAscii(char c) { return c; }
+};
+
+template <>
+struct FormattingTraits<EncodingDialog::Utf16>
+{
+    static ushort code(ushort c) { return c; }
+    static char toAscii(ushort c) { return char(c); }
+};
+
+template <>
+struct FormattingTraits<EncodingDialog::Utf32>
+{
+    static uint code(uint c) { return c; }
+    static char toAscii(uint c) { return char(c); }
+};
+
+template <>
+struct FormattingTraits<EncodingDialog::Latin1>
+{
+    static uchar code(char c) { return uchar(c); }
+    static char toAscii(char  c) { return c; }
+};
+
+static bool isHexDigit(char c)
+{
+    return (c >= '0' && c <= '9') || (c >= 'a' && c <= 'f')
+        || (c >= 'A' && c <= 'F');
+}
+
+template <EncodingDialog::Encoding encoding, class Iterator>
+static void formatStringSequence(QTextStream &str, Iterator i1, Iterator i2,
+                                 int escapeIntegerBase, int escapeWidth,
+                                 char escapePrefix = 0)
+{
+    str << '"';
+    bool separateHexEscape = false;
+    for (; i1 != i2; ++i1) {
+        const auto code = FormattingTraits<encoding>::code(*i1);
+        if (code >= 0x80) {
+            formatEscapedNumber(str, code, escapeIntegerBase, escapeWidth, escapePrefix);
+            separateHexEscape = escapeIntegerBase == 16 && escapeWidth == 0;
+        } else {
+            if (!formatSpecialCharacter(str, code)) {
+                const char c = FormattingTraits<encoding>::toAscii(*i1);
+                // For variable width/hex: Terminate the literal to stop digit parsing
+                // ("\x12" "34...").
+                if (separateHexEscape && isHexDigit(c))
+                    str << "\" \"";
+                str << c;
+            }
+            separateHexEscape = false;
+        }
+    }
+    str << '"';
+}
+
+static QString encodedString(const QString &value, EncodingDialog::Encoding e)
+{
+    QString result;
+    QTextStream str(&result);
+    switch (e) {
+    case EncodingDialog::Unicode:
+        formatStringSequence<EncodingDialog::Unicode>(str, value.cbegin(), value.cend(),
+                                                      16, 4, 'u');
+        break;
+    case EncodingDialog::Utf8: {
+        const QByteArray utf8 = value.toUtf8();
+        str << "u8";
+        formatStringSequence<EncodingDialog::Utf8>(str, utf8.cbegin(), utf8.cend(),
+                                                   8, 3);
+    }
+        break;
+    case EncodingDialog::Utf16: {
+        auto utf16 = value.utf16();
+        auto utf16End = utf16 + value.size();
+        str << 'u';
+        formatStringSequence<EncodingDialog::Utf16>(str, utf16, utf16End,
+                                                    16, 0, 'x');
+    }
+        break;
+    case EncodingDialog::Utf32: {
+        auto utf32 = value.toUcs4();
+        str << 'U';
+        formatStringSequence<EncodingDialog::Utf32>(str, utf32.cbegin(), utf32.cend(),
+                                                    16, 0, 'x');
+    }
+        break;
+    case EncodingDialog::Latin1: {
+        const QByteArray latin1 = value.toLatin1();
+        formatStringSequence<EncodingDialog::Latin1>(str, latin1.cbegin(), latin1.cend(),
+                                                     16, 0, 'x');
+    }
+        break;
+    case EncodingDialog::EncodingCount:
+        break;
+    }
+    return result;
+}
+
+// Dialog helpers
+
+static const char *encodingLabels[]
+{
+    QT_TRANSLATE_NOOP("EncodingDialog", "Unicode:"),
+    QT_TRANSLATE_NOOP("EncodingDialog", "UTF-8:"),
+    QT_TRANSLATE_NOOP("EncodingDialog", "UTF-16:"),
+    QT_TRANSLATE_NOOP("EncodingDialog", "UTF-32:"),
+    QT_TRANSLATE_NOOP("EncodingDialog", "Latin1:")
+};
+
+static const char *encodingToolTips[]
+{
+    QT_TRANSLATE_NOOP("EncodingDialog", "Unicode points for use with any encoding (C++, Python)"),
+    QT_TRANSLATE_NOOP("EncodingDialog", "QString::fromUtf8()"),
+    QT_TRANSLATE_NOOP("EncodingDialog", "QStringViewLiteral(), wchar_t on Windows"),
+    QT_TRANSLATE_NOOP("EncodingDialog", "wchar_t on Unix (Ucs4)"),
+    QT_TRANSLATE_NOOP("EncodingDialog", "QLatin1String")
+};
+
+// A read-only line edit with a tool button to copy the contents
+class DisplayLineEdit : public QLineEdit
+{
+    Q_OBJECT
+public:
+    explicit DisplayLineEdit(const QIcon &icon, QWidget *parent = nullptr);
+
+public slots:
+    void copyAll();
+};
+
+DisplayLineEdit::DisplayLineEdit(const QIcon &icon, QWidget *parent) :
+    QLineEdit(parent)
+{
+    setReadOnly(true);
+#if QT_CONFIG(clipboard) && QT_CONFIG(action)
+    auto copyAction = addAction(icon, QLineEdit::TrailingPosition);
+    connect(copyAction, &QAction::triggered, this, &DisplayLineEdit::copyAll);
+#endif
+}
+
+void DisplayLineEdit::copyAll()
+{
+#if QT_CONFIG(clipboard)
+    QGuiApplication::clipboard()->setText(text());
+#endif
+}
+
+static void addFormLayoutRow(QFormLayout *formLayout, const QString &text,
+                             QWidget *w, const QString &toolTip)
+{
+    auto label = new QLabel(text);
+    label->setToolTip(toolTip);
+    w->setToolTip(toolTip);
+    label->setBuddy(w);
+    formLayout->addRow(label, w);
+}
+
+EncodingDialog::EncodingDialog(QWidget *parent) :
+    QDialog(parent)
+{
+    setWindowFlags(windowFlags() & ~Qt::WindowContextHelpButtonHint);
+    setWindowTitle(tr("Encodings"));
+
+    auto formLayout = new QFormLayout;
+    auto sourceLineEdit = new QLineEdit(this);
+    sourceLineEdit->setClearButtonEnabled(true);
+    connect(sourceLineEdit, &QLineEdit::textChanged, this, &EncodingDialog::textChanged);
+
+    addFormLayoutRow(formLayout, tr("&Source:"), sourceLineEdit, tr("Enter text"));
+
+    const auto copyIcon = QIcon::fromTheme(QLatin1String("edit-copy"),
+                                           QIcon(QLatin1String(":/images/editcopy")));
+    for (int i = 0; i < EncodingCount; ++i) {
+        m_lineEdits[i] = new DisplayLineEdit(copyIcon, this);
+        addFormLayoutRow(formLayout, tr(encodingLabels[i]),
+                         m_lineEdits[i], tr(encodingToolTips[i]));
+    }
+
+    auto mainLayout = new QVBoxLayout(this);
+    mainLayout->addLayout(formLayout);
+    auto buttonBox = new QDialogButtonBox(QDialogButtonBox::Close);
+    connect(buttonBox, &QDialogButtonBox::rejected, this, &QDialog::reject);
+    mainLayout->addWidget(buttonBox);
+}
+
+void EncodingDialog::textChanged(const QString &t)
+{
+    if (t.isEmpty()) {
+        for (auto lineEdit : m_lineEdits)
+            lineEdit->clear();
+    } else {
+         for (int i = 0; i < EncodingCount; ++i)
+             m_lineEdits[i]->setText(encodedString(t, static_cast<Encoding>(i)));
+    }
+}
+
+#include "encodingdialog.moc"

examples/widgets/tools/codecs/encodingdialog.h

@@ -0,0 +1,73 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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 https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef ENCODINGDIALOG_H
+#define ENCODINGDIALOG_H
+
+#include <QDialog>
+
+QT_FORWARD_DECLARE_CLASS(QLineEdit)
+
+class EncodingDialog : public QDialog
+{
+    Q_OBJECT
+public:
+    explicit EncodingDialog(QWidget *parent = nullptr);
+
+    enum Encoding { Unicode, Utf8, Utf16, Utf32, Latin1, EncodingCount };
+
+private slots:
+    void textChanged(const QString &t);
+
+private:
+    QLineEdit *m_lineEdits[EncodingCount];
+};
+
+#endif // ENCODINGDIALOG_H

examples/widgets/tools/codecs/mainwindow.cpp

@@ -51,6 +51,7 @@
 #include <QtWidgets>
 
 #include "mainwindow.h"
+#include "encodingdialog.h"
 #include "previewform.h"
 
 MainWindow::MainWindow()
@@ -188,9 +189,27 @@ void MainWindow::createMenus()
     QAction *exitAct = fileMenu->addAction(tr("E&xit"), this, &QWidget::close);
     exitAct->setShortcuts(QKeySequence::Quit);
 
+    auto toolMenu =  menuBar()->addMenu(tr("&Tools"));
+    auto encodingAction = toolMenu->addAction(tr("Encodings"), this, &MainWindow::encodingDialog);
+    encodingAction->setShortcut(Qt::CTRL + Qt::Key_E);
+    encodingAction->setToolTip(tr("Shows a dialog allowing to convert to common encoding in programming languages."));
+
+
     menuBar()->addSeparator();
 
     QMenu *helpMenu = menuBar()->addMenu(tr("&Help"));
     helpMenu->addAction(tr("&About"), this, &MainWindow::about);
     helpMenu->addAction(tr("About &Qt"), qApp, &QApplication::aboutQt);
 }
+
+void MainWindow::encodingDialog()
+{
+    if (!m_encodingDialog) {
+        m_encodingDialog = new EncodingDialog(this);
+        const QRect screenGeometry = QApplication::desktop()->screenGeometry(this);
+        m_encodingDialog->setMinimumWidth(screenGeometry.width() / 4);
+    }
+    m_encodingDialog->show();
+    m_encodingDialog->raise();
+
+}

examples/widgets/tools/codecs/mainwindow.h

@@ -59,6 +59,8 @@ class QAction;
 class QTextCodec;
 class QPlainTextEdit;
 QT_END_NAMESPACE
+
+class EncodingDialog;
 class PreviewForm;
 
 class MainWindow : public QMainWindow
@@ -73,6 +75,7 @@ private slots:
     void save();
     void about();
     void aboutToShowSaveAsMenu();
+    void encodingDialog();
 
 private:
     void findCodecs();
@@ -82,6 +85,7 @@ private:
     QPlainTextEdit *textEdit;
     PreviewForm *previewForm;
     QList<QTextCodec *> codecs;
+    EncodingDialog *m_encodingDialog = nullptr;
 };
 
 #endif