Introduce new mechanism to manage palette functionality in QML

Main goals of these changes:
1) Add an ability to work with disabled and inactive palettes from QML
2) Eliminate massive code duplication in qtquickcontrols2 module
3) Provide easily extensible architecture for this piece of
functionality

Architectural part.

Palette
It was decided to not change existing QPalette, but add thin wrappers
around it to provide all required functionality. These wrappers are
highly coupled with QPalette class because of using some enum values
from it.
There are two new classes QQuickPalette and QQuickColorGroup.
QQuickPalette class inherits QQuickColorGroup class and represents
Active/All color group. QQuickPalette also provides an access to three
color groups: Active, Inactive, and Disabled.
In order to access colors the special class QQuickPaletteColorProvider
is used. This is a wrapper around QPalette that provides some
convenience functions.

Interface
The private property "palette" should be exposed.

Implementation
All private parts of classes that implement
QQuickAbstractPaletteProvider have to inherit
QQuickPaletteProviderPrivateBase class. This template class implement
all functionality: create palette, resolve dependencies, connect objects
etc. This is important to mention that related data is lazily
allocatable on demand only. Hence, there is no memory overhead for
regular items.

Change-Id: I911424b730451b1ad47f68fd8007953b66eddb28
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 571 insertions, 0 deletions

diff --git a/src/quick/items/qquickcolorgroup.cpp b/src/quick/items/qquickcolorgroup.cpp
new file mode 100644
index 0000000000..5eedefea83
--- /dev/null
+++ b/src/quick/items/qquickcolorgroup.cpp
@@ -0,0 +1,571 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtQuick module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** 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.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+#include "qquickcolorgroup_p.h"
+
+#include <QScopeGuard>
+
+#include <QtQuick/private/qquickabstractpaletteprovider_p.h>
+#include <QtQuick/private/qquickpalette_p.h>
+#include <QtQuick/private/qquickpalettecolorprovider_p.h>
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \class QQuickColorGroup
+    \brief The QQuickColorGroup class represents a set of colors.
+    \inmodule QtQuick
+    \since 6.0
+
+    Used by QQuickPalette to provide different groups of colors by roles.
+
+    \sa QQuickPalette, QQuickAbstractPaletteProvider, QPalette::ColorRole
+ */
+
+/*!
+    \qmltype ColorGroup
+    \instantiates QQuickColorGroup
+    \inherits QtObject
+    \inqmlmodule QtQuick
+    \ingroup qtquick-visual
+    \brief The set of colors by roles.
+
+    The ColorGroup type is used to define a set of colors with certain roles. Although a ColorGroup
+    has no visual appearance, it defines colors used to customize rendered items.
+
+    Default values of colors are equal to active group colors of default-constructed \c QPalette.
+
+    The following code can be used to create a color group with some colors specified:
+
+    \code
+    ColorGroup {
+        alternateBase: "red"
+        base: "green"
+    }
+    \endcode
+ */
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::alternateBase
+
+    Used as the alternate background color in item views with alternating row colors.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::base
+
+    Used mostly as the background color for text editor controls and item views.
+    It is usually white or another light color.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::brightText
+
+    A text color that is very different from \c windowText, and contrasts
+    well with e.g. \c dark. Typically used for text that needs to be drawn
+    where \c text, \c windowText or \c buttonText would
+    give poor contrast, such as on highlighted buttons.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::button
+
+    The general button background color. This background can be different from
+    \c window as some styles require a different background color for buttons.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::buttonText
+
+    A foreground color used with the \c palette color.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::dark
+
+    A foreground color used with the \c palette color.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::highlight
+
+    A color to indicate a selected item or the current item.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::highlightedText
+
+    A text color that contrasts with \c highlight.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::light
+
+    Lighter than \c button.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::link
+
+    A text color used for hyperlinks.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::linkVisited
+
+    A text color used for already visited hyperlinks.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::mid
+
+    Between \c palette.button and \c dark.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::midlight
+
+    Between \c button and \c light.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::shadow
+
+    A very dark color.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::text
+
+    The foreground color used with \c base. This is usually the same as
+    the \c windowText, in which case it must provide good contrast with
+    \c window and \c base.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::toolTipBase
+
+    Used as the background color for tooltips.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::toolTipText
+
+    Used as the foreground color for tooltips.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::window
+
+    A general background color.
+*/
+
+/*!
+    \qmlproperty color QtQuick::ColorGroup::windowText
+
+    A general foreground color.
+*/
+
+/*!
+    \qmlsignal QtQuick::ColorGroup::changed
+
+    Additional signal indicates that the current state of this color group
+    has been changed. Usually it means that one of the colors is changed.
+
+    \sa QtQuick::Palette::changed
+*/
+
+/*!
+    Construct object in default state.
+ */
+QQuickColorGroup::QQuickColorGroup(QQuickPalette &parent)
+    : QObject(&parent)
+    , m_groupTag(defaultGroupTag())
+    , m_colorProvider(parent.colorProvider().shared_from_this())
+{
+}
+
+QPalette::ColorGroup QQuickColorGroup::currentColorGroup() const
+{
+    return groupTag();
+}
+
+QColor QQuickColorGroup::alternateBase() const
+{
+    return color(QPalette::AlternateBase);
+}
+
+void QQuickColorGroup::setAlternateBase(const QColor &color)
+{
+    setColor(QPalette::AlternateBase, color, &QQuickColorGroup::alternateBaseChanged);
+}
+
+void QQuickColorGroup::resetAlternateBase()
+{
+    resetColor(QPalette::AlternateBase, &QQuickColorGroup::alternateBaseChanged);
+}
+
+QColor QQuickColorGroup::base() const
+{
+    return color(QPalette::Base);
+}
+
+void QQuickColorGroup::setBase(const QColor &color)
+{
+    setColor(QPalette::Base, color, &QQuickColorGroup::baseChanged);
+}
+
+void QQuickColorGroup::resetBase()
+{
+    resetColor(QPalette::Base, &QQuickColorGroup::baseChanged);
+}
+
+QColor QQuickColorGroup::brightText() const
+{
+    return color(QPalette::BrightText);
+}
+
+void QQuickColorGroup::setBrightText(const QColor &color)
+{
+    setColor(QPalette::BrightText, color, &QQuickColorGroup::brightTextChanged);
+}
+
+void QQuickColorGroup::resetBrightText()
+{
+    resetColor(QPalette::BrightText, &QQuickColorGroup::brightTextChanged);
+}
+
+QColor QQuickColorGroup::button() const
+{
+    return color(QPalette::Button);
+}
+
+void QQuickColorGroup::setButton(const QColor &color)
+{
+    setColor(QPalette::Button, color, &QQuickColorGroup::buttonChanged);
+}
+
+void QQuickColorGroup::resetButton()
+{
+    resetColor(QPalette::Button, &QQuickColorGroup::buttonChanged);
+}
+
+QColor QQuickColorGroup::buttonText() const
+{
+    return color(QPalette::ButtonText);
+}
+
+void QQuickColorGroup::setButtonText(const QColor &color)
+{
+    setColor(QPalette::ButtonText, color, &QQuickColorGroup::buttonTextChanged);
+}
+
+void QQuickColorGroup::resetButtonText()
+{
+    resetColor(QPalette::ButtonText, &QQuickColorGroup::buttonTextChanged);
+}
+
+QColor QQuickColorGroup::dark() const
+{
+    return color(QPalette::Dark);
+}
+
+void QQuickColorGroup::setDark(const QColor &color)
+{
+    setColor(QPalette::Dark, color, &QQuickColorGroup::darkChanged);
+}
+
+void QQuickColorGroup::resetDark()
+{
+    resetColor(QPalette::Dark, &QQuickColorGroup::darkChanged);
+}
+
+QColor QQuickColorGroup::highlight() const
+{
+    return color(QPalette::Highlight);
+}
+
+void QQuickColorGroup::setHighlight(const QColor &color)
+{
+    setColor(QPalette::Highlight, color, &QQuickColorGroup::highlightChanged);
+}
+
+void QQuickColorGroup::resetHighlight()
+{
+    resetColor(QPalette::Highlight, &QQuickColorGroup::highlightChanged);
+}
+
+QColor QQuickColorGroup::highlightedText() const
+{
+    return color(QPalette::HighlightedText);
+}
+
+void QQuickColorGroup::setHighlightedText(const QColor &color)
+{
+    setColor(QPalette::HighlightedText, color, &QQuickColorGroup::highlightedTextChanged);
+}
+
+void QQuickColorGroup::resetHighlightedText()
+{
+    resetColor(QPalette::HighlightedText, &QQuickColorGroup::highlightedTextChanged);
+}
+
+QColor QQuickColorGroup::light() const
+{
+    return color(QPalette::Light);
+}
+
+void QQuickColorGroup::setLight(const QColor &color)
+{
+    setColor(QPalette::Light, color, &QQuickColorGroup::lightChanged);
+}
+
+void QQuickColorGroup::resetLight()
+{
+    resetColor(QPalette::Light, &QQuickColorGroup::lightChanged);
+}
+
+QColor QQuickColorGroup::link() const
+{
+    return color(QPalette::Link);
+}
+
+void QQuickColorGroup::setLink(const QColor &color)
+{
+    setColor(QPalette::Link, color, &QQuickColorGroup::linkChanged);
+}
+
+void QQuickColorGroup::resetLink()
+{
+    resetColor(QPalette::Link, &QQuickColorGroup::linkChanged);
+}
+
+QColor QQuickColorGroup::linkVisited() const
+{
+    return color(QPalette::LinkVisited);
+}
+
+void QQuickColorGroup::setLinkVisited(const QColor &color)
+{
+    setColor(QPalette::LinkVisited, color, &QQuickColorGroup::linkVisitedChanged);
+}
+
+void QQuickColorGroup::resetLinkVisited()
+{
+    resetColor(QPalette::LinkVisited, &QQuickColorGroup::linkVisitedChanged);
+}
+
+QColor QQuickColorGroup::mid() const
+{
+    return color(QPalette::Mid);
+}
+
+void QQuickColorGroup::setMid(const QColor &color)
+{
+    setColor(QPalette::Mid, color, &QQuickColorGroup::midChanged);
+}
+
+void QQuickColorGroup::resetMid()
+{
+    resetColor(QPalette::Mid, &QQuickColorGroup::midChanged);
+}
+
+QColor QQuickColorGroup::midlight() const
+{
+    return color(QPalette::Midlight);
+}
+
+void QQuickColorGroup::setMidlight(const QColor &color)
+{
+    setColor(QPalette::Midlight, color, &QQuickColorGroup::midlightChanged);
+}
+
+void QQuickColorGroup::resetMidlight()
+{
+    resetColor(QPalette::Midlight, &QQuickColorGroup::midlightChanged);
+}
+
+QColor QQuickColorGroup::shadow() const
+{
+    return color(QPalette::Shadow);
+}
+
+void QQuickColorGroup::setShadow(const QColor &color)
+{
+    setColor(QPalette::Shadow, color, &QQuickColorGroup::shadowChanged);
+}
+
+void QQuickColorGroup::resetShadow()
+{
+    resetColor(QPalette::Shadow, &QQuickColorGroup::shadowChanged);
+}
+
+QColor QQuickColorGroup::text() const
+{
+    return color(QPalette::Text);
+}
+
+void QQuickColorGroup::setText(const QColor &color)
+{
+    setColor(QPalette::Text, color, &QQuickColorGroup::textChanged);
+}
+
+void QQuickColorGroup::resetText()
+{
+    resetColor(QPalette::Text, &QQuickColorGroup::textChanged);
+}
+
+QColor QQuickColorGroup::toolTipBase() const
+{
+    return color(QPalette::ToolTipBase);
+}
+
+void QQuickColorGroup::setToolTipBase(const QColor &color)
+{
+    setColor(QPalette::ToolTipBase, color, &QQuickColorGroup::toolTipBaseChanged);
+}
+
+void QQuickColorGroup::resetToolTipBase()
+{
+    resetColor(QPalette::ToolTipBase, &QQuickColorGroup::toolTipBaseChanged);
+}
+
+QColor QQuickColorGroup::toolTipText() const
+{
+    return color(QPalette::ToolTipText);
+}
+
+void QQuickColorGroup::setToolTipText(const QColor &color)
+{
+    setColor(QPalette::ToolTipText, color, &QQuickColorGroup::toolTipTextChanged);
+}
+
+void QQuickColorGroup::resetToolTipText()
+{
+    resetColor(QPalette::ToolTipText, &QQuickColorGroup::toolTipTextChanged);
+}
+
+QColor QQuickColorGroup::window() const
+{
+    return color(QPalette::Window);
+}
+
+void QQuickColorGroup::setWindow(const QColor &color)
+{
+    setColor(QPalette::Window, color, &QQuickColorGroup::windowChanged);
+}
+
+void QQuickColorGroup::resetWindow()
+{
+    resetColor(QPalette::Window, &QQuickColorGroup::windowChanged);
+}
+
+QColor QQuickColorGroup::windowText() const
+{
+    return color(QPalette::WindowText);
+}
+
+void QQuickColorGroup::setWindowText(const QColor &color)
+{
+    setColor(QPalette::WindowText, color, &QQuickColorGroup::windowTextChanged);
+}
+
+void QQuickColorGroup::resetWindowText()
+{
+    resetColor(QPalette::WindowText, &QQuickColorGroup::windowTextChanged);
+}
+
+QPalette::ColorGroup QQuickColorGroup::groupTag() const
+{
+    return m_groupTag;
+}
+
+QQuickColorGroup::QQuickColorGroup(QObject *parent)
+    : QObject(parent)
+    , m_groupTag(defaultGroupTag())
+    , m_colorProvider(std::make_shared<QQuickPaletteColorProvider>())
+{
+}
+
+void QQuickColorGroup::setGroupTag(QPalette::ColorGroup tag)
+{
+    if (m_groupTag != tag) {
+        m_groupTag = tag;
+        Q_EMIT changed();
+    }
+}
+
+const QQuickPaletteColorProvider &QQuickColorGroup::colorProvider() const
+{
+    Q_ASSERT(m_colorProvider);
+    return *m_colorProvider;
+}
+
+QQuickPaletteColorProvider &QQuickColorGroup::colorProvider()
+{
+    return const_cast<QQuickPaletteColorProvider &>(
+                const_cast<const QQuickColorGroup*>(this)->colorProvider());
+}
+
+QQuickColorGroup *QQuickColorGroup::createWithParent(QQuickPalette &parent)
+{
+    return new QQuickColorGroup(parent);
+}
+
+QColor QQuickColorGroup::color(QPalette::ColorRole role) const
+{
+    return colorProvider().color(currentColorGroup(), role);
+}
+
+void QQuickColorGroup::setColor(QPalette::ColorRole role, QColor color, Notifier notifier)
+{
+    if (colorProvider().setColor(groupTag(), role, color)) {
+        Q_EMIT (this->*notifier)();
+        Q_EMIT changed();
+    }
+}
+
+void QQuickColorGroup::resetColor(QPalette::ColorRole role, Notifier notifier)
+{
+    if (colorProvider().resetColor(groupTag(), role)) {
+        Q_EMIT (this->*notifier)();
+        Q_EMIT changed();
+    }
+}
+
+QT_END_NAMESPACE