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+// Copyright (C) 2020 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
+
+/*!
+    \page gui-changes-qt6.html
+    \title Changes to Qt GUI
+    \ingroup changes-qt-5-to-6
+    \brief Kernel, Text, Painting, and Utility classes are modified.
+
+    Qt 6 is a result of the conscious effort to make the framework more
+    efficient and easy to use.
+
+    We try to maintain binary and source compatibility for all the public
+    APIs in each release. But some changes were inevitable in an effort to
+    make Qt a better framework.
+
+    In this topic we summarize those changes in Qt GUI, and provide
+    guidance to handle them.
+
+    \section1 Kernel classes
+
+    \section2 The QBitmap class
+
+    Implicit construction of a QBitmap from a QPixmap is no longer supported.
+    The constructor and assignment operator have been made explicit and marked as
+    deprecated. Use the new static factory function \l{QBitmap::}{fromPixmap} instead.
+
+    \section2 The QCursor class
+
+    Implicit construction of a QCursor from a QPixmap is no longer supported, the
+    constructor has been made explicit.
+
+    \section2 The QKeyCombination class
+
+    QKeyCombination is a new class for storing a combination of a key with an
+    optional modifier. It should be used as a replacement for combining values from
+    the Qt::Key enum with a modifier in a type-safe way.
+
+    We recommend migrating code that currently uses operator+() to combine a key and
+    modifiers, as future C++ standards are likely to declare arithmetic operations
+    between unrelated enumeration types as illegal. Use operator|(), and change
+    APIs that expect an \c int to expect a QKeyCombination instead.
+
+    Existing APIs that expect an \c int for a key combination can be called using
+    QKeyCombination::toCombined().
+
+    \section1 Text classes
+
+    \section2 The QFontDatabase class
+
+    The QFontDatabase class has now only static member functions. The constructor
+    has been deprecated. Instead of e.g.
+
+    \code
+    const QStringList fontFamilies = QFontDatabase().families();
+    \endcode
+
+    use
+
+    \code
+    const QStringList fontFamilies = QFontDatabase::families();
+    \endcode
+
+    \section2 The QFont class
+
+    The numerical values of the QFont::Weight enumerator have been changed to
+    be in line with OpenType weight values. QFont::setWeight() expects an enum value
+    instead of an \c int, and code that calls the setter with an integer will fail to
+    compile. To continue to use old integer values, use QFont::setLegacyWeight().
+
+    \section1 Painting classes
+
+    See the porting guide for \l{Changes to Qt Print Support}{Qt Print Support} for
+    information about \l{QPagedPaintDevice} and other printing related classes.
+
+    \section1 Utility classes
+
+    \section2 QIntValidator and QDoubleValidator
+
+    The \l{QIntValidator::}{setRange()} method is no longer marked as virtual.
+
+    \section1 OpenGL classes
+
+    With the introduction of Qt RHI as the rendering foundation in Qt,
+    most classes prefixed by \c QOpenGL have been moved into the \l{Qt OpenGL}
+    module.
+
+    More details can be found in \l{Changes to Qt OpenGL}{the Qt OpenGL porting guide}.
+
+    One notable exception is the class \l QOpenGLContext, which still resides in
+    Qt GUI.
+
+    In addition, the class \l QOpenGLWidget has been moved to a new module, named
+    Qt OpenGL Widgets.
+
+    \section2 The QOpenGLContext class
+
+    The QOpenGLContext::versionFunctions() function is replaced by
+    QOpenGLVersionFunctionsFactory::get(). QOpenGLVersionFunctionsFactory is a public
+    class now, part of the \l{Qt OpenGL} module.
+
+    \section2 ANGLE
+
+    On Windows, ANGLE, a third-party OpenGL ES to Direct 3D translator, is no
+    longer included in Qt. This means Qt::AA_UseOpenGLES and the environment
+    variable \c{QT_OPENGL=angle} no longer have any effect.
+    In \l{Dynamically Loading OpenGL}{dynamic OpenGL builds} there is no automatic fallback to ANGLE in
+    case OpenGL proper fails to initialize. For QWindow or QWidget based
+    applications using OpenGL directly, for example via QOpenGLWidget, this means
+    that OpenGL proper is the only option at run time. However, the alternative of
+    using a pure software OpenGL implementation, such as Mesa llvmpipe that is
+    shipped with the pre-built Qt packages, is still available. For Qt Quick and Qt
+    Quick 3D applications, Qt 6 introduces support for Direct 3D 11, Vulkan, and
+    Metal, in addition to OpenGL. On Windows the default choice is Direct 3D,
+    therefore the removal of ANGLE is alleviated by having support for graphics
+    APIs other than OpenGL as well.
+
+    \section2 Native clipboard integration
+
+    Qt 5 provided interfaces for integrating platform specific or custom
+    clipboard formats into Qt through \c QMacPasteboardMime in \c QtMacExtras,
+    and \c QWindowsMime from the Windows QPA API. Since Qt 6.6, the
+    equivalent functionality is provided by the classes QUtiMimeConverter for
+    \macos, and the QWindowsMimeConverter for Windows.
+
+    Porting from QWindowsMime to QWindowsMimeConverter requires practically no
+    changes, as the virtual interface is identical. However, in Qt 6 it is no
+    longer needed to register a QWindowsMimeConverter implementation;
+    instantiating the type implicitly registers the converter.
+
+    Porting a QMacPasteboardMime to QUtiMimeConverter requires renaming some of
+    the virtual functions. Note that the \c{QMacPasteboardMime} API used the
+    outdated term \c{flavor} for the native clipboard format on \macos, whereas
+    the platform now uses \c{Uniform Type Identifiers}, i.e. \c{UTI}s, which Qt
+    has adapted for function and parameter names.
+
+    The \c{mimeFor} and \c{flavorFor} functions are replaced by the
+    \l{QUtiMimeConverter::}{mimeForUti} and \l{QUtiMimeConverter::}{utiForMime}
+    implementations, respectively. Those should return the name of the mime
+    type or \c{UTI} that the converter can convert the input format to, so a
+    port usually just involves renaming existing overrides. The
+    \c{convertToMime}, \c{convertFromMime}, and \c{count} functions in
+    QUtiMimeConverter are identical to their QMacPasteboardMime versions.
+
+    The \c{canConvert}, \c{converterName} functions are no longer needed, they
+    are implied by implementation of the above functions, so overrides of those
+    functions can be removed.
+
+    As with the the QWindowsMimeConverter, registration is done by instantiating
+    the type.
+*/