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, 181 insertions, 0 deletions

diff --git a/src/selectionmode/selectionmodebottombar.h b/src/selectionmode/selectionmodebottombar.h
new file mode 100644
index 000000000..61cb90334
--- /dev/null
+++ b/src/selectionmode/selectionmodebottombar.h
@@ -0,0 +1,181 @@
+/*
+    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
+*/
+
+#ifndef SELECTIONMODEBOTTOMBAR_H
+#define SELECTIONMODEBOTTOMBAR_H
+
+#include "actionwithwidget.h"
+#include "global.h"
+
+#include <QAction>
+#include <QPointer>
+#include <QPropertyAnimation>
+#include <QWidget>
+
+#include <memory>
+
+class DolphinContextMenu;
+class KActionCollection;
+class KFileItemActions;
+class KFileItemList;
+class QAbstractButton;
+class QAction;
+class QFontMetrics;
+class QHBoxLayout;
+class QLabel;
+class QPushButton;
+class QResizeEvent;
+class QToolButton;
+class QUrl;
+
+/**
+ * A bar mainly used in selection mode that serves various purposes depending on what the user is currently trying to do.
+ *
+ * The Contents enum below gives a rough idea about the different states this bar might have.
+ * The bar is notified of various changes that make changing or updating the content worthwhile.
+ */
+class SelectionModeBottomBar : public QWidget
+{
+    Q_OBJECT
+
+public:
+    /** The different contents this bar can have. */
+    enum Contents{
+        CopyContents,
+        CopyLocationContents,
+        CopyToOtherViewContents,
+        CutContents,
+        DeleteContents,
+        DuplicateContents,
+        GeneralContents,
+        MoveToOtherViewContents,
+        MoveToTrashContents,
+        PasteContents,
+        RenameContents
+    };
+
+    /**
+     * Default constructor
+     */
+    explicit SelectionModeBottomBar(KActionCollection *actionCollection, QWidget *parent);
+
+    /**
+     * Plays a show or hide animation while changing visibility.
+     * Therefore, if this method is used to hide this widget, the actual hiding will be postponed until the animation finished.
+     * @see QWidget::setVisible()
+     */
+    void setVisible(bool visible, Animated animated);
+    using QWidget::setVisible; // Makes sure that the setVisible() declaration above doesn't hide the one from QWidget.
+
+    void resetContents(Contents contents);
+    inline Contents contents() const
+    {
+        return m_contents;
+    };
+
+    QSize sizeHint() const override;
+
+public Q_SLOTS:
+    void slotSelectionChanged(const KFileItemList &selection, const QUrl &baseUrl);
+
+    /** Used to notify the m_selectionModeBottomBar that there is no other ViewContainer in the tab. */
+    void slotSplitTabDisabled();
+
+Q_SIGNALS:
+    /**
+     * Forwards the errors from the KFileItemAction::error() used for contextual actions.
+     */
+    void error(const QString &errorMessage);
+
+    void leaveSelectionModeRequested();
+
+protected:
+    /** Is installed on an internal widget to make sure that the height of the bar is adjusted to its contents. */
+    bool eventFilter(QObject *watched, QEvent *event) override;
+    void resizeEvent(QResizeEvent *resizeEvent) override;
+
+private:
+    void addCopyContents();
+    void addCopyLocationContents();
+    void addCopyToOtherViewContents();
+    void addCutContents();
+    void addDeleteContents();
+    void addDuplicateContents();
+    /**
+     * Adds the actions of m_generalBarActions as buttons to the bar. An overflow menu button is
+     * created to make sure any amount of actions can be accessed.
+     */
+    void addGeneralContents();
+    void addMoveToOtherViewContents();
+    void addMoveToTrashContents();
+    void addPasteContents();
+    void addRenameContents();
+
+    /**
+     * Deletes all visible widgets and layouts from the bar.
+     */
+    void emptyBarContents();
+
+    /**
+     * @returns A vector containing contextual actions for the given \a selection in the \a baseUrl.
+     * Cut, Copy, Rename and MoveToTrash are always added. Any further contextual actions depend on
+     * \a selection and \a baseUrl. \a selection and \a baseUrl can be empty/default constructed if
+     * no item- or view-specific actions should be added aside from Cut, Copy, Rename, MoveToTrash.
+     * @param selectedItems The selected items for which contextual actions should be displayed.
+     * @param baseUrl       Base URL of the viewport the contextual actions apply to.
+     */
+    std::vector<QAction *> contextActionsFor(const KFileItemList &selectedItems, const QUrl &baseUrl);
+
+    /**
+     * @returns the amount of pixels that can be spared to add more widgets. A negative value might
+     * be returned which signifies that some widgets should be hidden or removed from this bar to
+     * make sure that this SelectionModeBottomBar won't stretch the width of its parent.
+     */
+    int unusedSpace() const;
+
+    /**
+     * The label isn't that important. This method hides it if there isn't enough room on the bar or
+     * shows it if there is.
+     */
+    void updateExplanatoryLabelVisibility();
+
+    /**
+     * Changes the text and enabled state of the main action button
+     * based on the amount of currently selected items and the state of the current m_mainAction.
+     * The current main action depends on the current barContents.
+     * @param selection the currently selected fileItems.
+     */
+    void updateMainActionButton(const KFileItemList &selection);
+
+private:
+    /// All the actions that should be available from this bar when in general mode.
+    std::vector<ActionWithWidget> m_generalBarActions;
+    /// The context menu used to retrieve all the actions that are relevant for the current selection.
+    std::unique_ptr<DolphinContextMenu> m_internalContextMenu;
+    /// An object that is necessary to keep around for m_internalContextMenu.
+    KFileItemActions *m_fileItemActions = nullptr;
+
+    /// @see updateMainActionButtonText
+    ActionWithWidget m_mainAction = ActionWithWidget(nullptr);
+    /// The button containing all the actions that don't currently fit into the bar.
+    QPointer<QToolButton> m_overflowButton;
+    /// The actionCollection from which the actions for this bar are retrieved.
+    KActionCollection *m_actionCollection;
+    /// Describes the current contents of the bar.
+    Contents m_contents;
+    /** The layout all the buttons and labels are added to.
+     * Do not confuse this with layout() because we do have a QScrollView in between this widget and m_layout. */
+    QHBoxLayout *m_layout;
+
+    /// @see SelectionModeBottomBar::setVisible()
+    QPointer<QPropertyAnimation> m_heightAnimation;
+
+    /// The info label used for some of the BarContents. Is hidden for narrow widths.
+    QPointer<QLabel> m_explanatoryLabel;
+};
+
+#endif // SELECTIONMODEBOTTOMBAR_H