Add Selection Mode

The selection mode action is a checkable toggle action named
"Select Files and Folders" which has "Space" as the default
shortcut.

In selection mode a bottom bar with contextual actions is shown.
These should mostly mirror the actions which are available through
the right-click context menu aka DolphinContextMenu.

Resizing of the window might make a overflow button appear in the
bottom selection mode bar.

This commit makes press and hold in the view activate selection
mode. This behaviour is not triggered if the press and hold is
used to either start a rubberband selection or a drag operation
within a short time. The length of the short timeframe is defined
by a QStyleHint. This is currently not implemented in touch
because I can't test it.

Mix the selection mode bars' background colors using a nice
combination of colors from the current color scheme

BUG: 427202

1 files changed, 131 insertions, 0 deletions

diff --git a/src/selectionmode/selectionmodetopbar.cpp b/src/selectionmode/selectionmodetopbar.cpp
new file mode 100644
index 000000000..89a4aa03a
--- /dev/null
+++ b/src/selectionmode/selectionmodetopbar.cpp
@@ -0,0 +1,131 @@
+/*
+    This file is part of the KDE project
+    SPDX-FileCopyrightText: 2022 Felix Ernst <[email protected]>
+
+    SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only OR LicenseRef-KDE-Accepted-LGPL
+*/
+
+#include "selectionmodetopbar.h"
+
+#include "backgroundcolorhelper.h"
+
+#include <KColorScheme>
+#include <KLocalizedString>
+#include <KToolTipHelper>
+
+#include <QHBoxLayout>
+#include <QLabel>
+#include <QPalette>
+#include <QPropertyAnimation>
+#include <QPushButton>
+#include <QScrollArea>
+#include <QStyle>
+#include <QtGlobal>
+
+#include <type_traits>
+#include <iostream>
+
+SelectionModeTopBar::SelectionModeTopBar(QWidget *parent) :
+    QWidget{parent}
+{
+    // Showing of this widget is normally animated. We hide it for now and make it small.
+    hide();
+    setMaximumHeight(0);
+
+    setToolTip(KToolTipHelper::whatsThisHintOnly());
+    setWhatsThis(xi18nc("@info:whatsthis", "<title>Selection Mode</title><para>Select files or folders to manage or manipulate them."
+        "<list><item>Press on a file or folder to select it.</item><item>Press on an already selected file or folder to deselect it.</item>"
+        "<item>Pressing an empty area does <emphasis>not</emphasis> clear the selection.</item>"
+        "<item>Selection rectangles (created by dragging from an empty area) invert the selection status of items within.</item></list></para>"
+        "<para>The available action buttons at the bottom change depending on the current selection.</para>"));
+
+    auto fillParentLayout = new QGridLayout(this);
+    fillParentLayout->setContentsMargins(0, 0, 0, 0);
+
+    // Put the contents into a QScrollArea. This prevents increasing the view width
+    // in case that not enough width for the contents is available. (this trick is also used in selectionmodebottombar.cpp.)
+    auto scrollArea = new QScrollArea(this);
+    fillParentLayout->addWidget(scrollArea);
+    scrollArea->setFrameShape(QFrame::NoFrame);
+    scrollArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+    scrollArea->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+    scrollArea->setWidgetResizable(true);
+
+    auto contentsContainer = new QWidget(scrollArea);
+    scrollArea->setWidget(contentsContainer);
+
+    BackgroundColorHelper::instance()->controlBackgroundColor(this);
+
+    setMinimumWidth(0);
+
+    m_fullLabelString = i18nc("@info label above the view explaining the state",
+                                     "Selection Mode: Click on files or folders to select or deselect them.");
+    m_shortLabelString = i18nc("@info label above the view explaining the state",
+                                     "Selection Mode");
+    m_label = new QLabel(contentsContainer);
+    m_label->setMinimumWidth(0);
+    BackgroundColorHelper::instance()->controlBackgroundColor(m_label);
+
+    m_closeButton = new QPushButton(QIcon::fromTheme(QStringLiteral("window-close-symbolic")), "", contentsContainer);
+    m_closeButton->setToolTip(i18nc("@action:button", "Exit Selection Mode"));
+    m_closeButton->setAccessibleName(m_closeButton->toolTip());
+    m_closeButton->setFlat(true);
+    connect(m_closeButton, &QAbstractButton::pressed,
+            this, &SelectionModeTopBar::leaveSelectionModeRequested);
+
+    QHBoxLayout *layout = new QHBoxLayout(contentsContainer);
+    auto contentsMargins = layout->contentsMargins();
+    m_preferredHeight = contentsMargins.top() + m_label->sizeHint().height() + contentsMargins.bottom();
+    scrollArea->setMaximumHeight(m_preferredHeight);
+    m_closeButton->setFixedHeight(m_preferredHeight);
+    layout->setContentsMargins(0, 0, 0, 0);
+
+    layout->addStretch();
+    layout->addWidget(m_label);
+    layout->addStretch();
+    layout->addWidget(m_closeButton);
+}
+
+void SelectionModeTopBar::setVisible(bool visible, Animated animated)
+{
+    Q_ASSERT_X(animated == WithAnimation, "SelectionModeTopBar::setVisible", "This wasn't implemented.");
+
+    if (!m_heightAnimation) {
+        m_heightAnimation = new QPropertyAnimation(this, "maximumHeight");
+    }
+    disconnect(m_heightAnimation, &QAbstractAnimation::finished,
+               this, &QWidget::hide);
+    m_heightAnimation->setDuration(2 *
+            style()->styleHint(QStyle::SH_Widget_Animation_Duration, nullptr, this) *
+            GlobalConfig::animationDurationFactor());
+
+    if (visible) {
+        show();
+        m_heightAnimation->setStartValue(0);
+        m_heightAnimation->setEndValue(m_preferredHeight);
+        m_heightAnimation->setEasingCurve(QEasingCurve::OutCubic);
+    } else {
+        m_heightAnimation->setStartValue(height());
+        m_heightAnimation->setEndValue(0);
+        m_heightAnimation->setEasingCurve(QEasingCurve::OutCubic);
+        connect(m_heightAnimation, &QAbstractAnimation::finished,
+                this, &QWidget::hide);
+    }
+
+    m_heightAnimation->start();
+}
+
+void SelectionModeTopBar::resizeEvent(QResizeEvent */* resizeEvent */)
+{
+    updateLabelString();
+}
+
+void SelectionModeTopBar::updateLabelString()
+{
+    QFontMetrics fontMetrics = m_label->fontMetrics();
+    if (fontMetrics.horizontalAdvance(m_fullLabelString) + m_closeButton->sizeHint().width() + style()->pixelMetric(QStyle::PM_LayoutLeftMargin) * 2 + style()->pixelMetric(QStyle::PM_LayoutRightMargin) * 2 < width()) {
+        m_label->setText(m_fullLabelString);
+    } else {
+        m_label->setText(m_shortLabelString);
+    }
+}