[tabbox] Expose noModifierGrab to QtQuick

Summary:
There is a special mode in TabBox which is the noModifierGrab mode. This
is Alt+Tab active without a modifier being hold. This mode is entered
when being activated through screen edges (either pointer or touch). So
far this was not exposed to QtQuick and thus one could not end the mode
using pointer or touch. It is possible to select another window, but not
to activate it. That required the press of a keyboard key.

This setup is rather unfortunate. By exposing the mode to QtQuick we can
react from QtQuick side to it and invoke already exposed functionality to
select and item and directly activate it - existing left-over from the
Plasma Active window switcher.

Test Plan:
Tested on X11 and Wayland with an adjusted lnf package. It kind
of works, but there are additional issues on both X11 and Wayland.

Reviewers: #kwin, #plasma

Subscribers: plasma-devel, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D5414

autotests/tabbox/mock_tabboxhandler.h

@@ -98,6 +98,10 @@ public:
         Q_UNUSED(controller)
     }
 
+    bool noModifierGrab() const override {
+        return false;
+    }
+
     // mock methods
     QWeakPointer<TabBox::TabBoxClient> createMockWindow(const QString &caption, WId id);
     void closeWindow(TabBox::TabBoxClient *client);

tabbox/switcheritem.cpp

@@ -102,5 +102,14 @@ void SwitcherItem::setAllDesktops(bool all)
     emit allDesktopsChanged();
 }
 
+void SwitcherItem::setNoModifierGrab(bool set)
+{
+    if (m_noModifierGrab == set) {
+        return;
+    }
+    m_noModifierGrab = set;
+    emit noModifierGrabChanged();
+}
+
 }
 }

tabbox/switcheritem.h

@@ -38,6 +38,7 @@ class SwitcherItem : public QObject
     Q_PROPERTY(bool visible READ isVisible NOTIFY visibleChanged)
     Q_PROPERTY(bool allDesktops READ isAllDesktops NOTIFY allDesktopsChanged)
     Q_PROPERTY(int currentIndex READ currentIndex WRITE setCurrentIndex NOTIFY currentIndexChanged)
+    Q_PROPERTY(bool noModifierGrab READ noModifierGrab NOTIFY noModifierGrabChanged)
 
     /**
      * The main QML item that will be displayed in the Dialog
@@ -57,11 +58,15 @@ public:
     void setCurrentIndex(int index);
     QObject *item() const;
     void setItem(QObject *item);
+    bool noModifierGrab() const {
+        return m_noModifierGrab;
+    }
 
     // for usage from outside
     void setModel(QAbstractItemModel *model);
     void setAllDesktops(bool all);
     void setVisible(bool visible);
+    void setNoModifierGrab(bool set);
 
 Q_SIGNALS:
     void visibleChanged();
@@ -70,6 +75,7 @@ Q_SIGNALS:
     void allDesktopsChanged();
     void screenGeometryChanged();
     void itemChanged();
+    void noModifierGrabChanged();
 
 private:
     QAbstractItemModel *m_model;
@@ -78,6 +84,7 @@ private:
     bool m_allDesktops;
     int m_currentIndex;
     QMetaObject::Connection m_selectedIndexConnection;
+    bool m_noModifierGrab = false;
 };
 
 inline QAbstractItemModel *SwitcherItem::model() const

tabbox/tabbox.cpp

@@ -359,6 +359,11 @@ void TabBoxHandlerImpl::highlightWindows(TabBoxClient *window, QWindow *controll
     static_cast<EffectsHandlerImpl*>(effects)->highlightWindows(windows);
 }
 
+bool TabBoxHandlerImpl::noModifierGrab() const
+{
+    return m_tabBox->noModifierGrab();
+}
+
 /*********************************************************
 * TabBoxClientImpl
 *********************************************************/

tabbox/tabbox.h

@@ -75,6 +75,7 @@ public:
     virtual QWeakPointer< TabBoxClient > desktopClient() const;
     virtual void activateAndClose();
     void highlightWindows(TabBoxClient *window = nullptr, QWindow *controller = nullptr) override;
+    bool noModifierGrab() const override;
 
 private:
     bool checkDesktop(TabBoxClient* client, int desktop) const;
@@ -187,6 +188,10 @@ public:
         return m_forcedGlobalMouseGrab;
     }
 
+    bool noModifierGrab() const {
+        return m_noModifierGrab;
+    }
+
     static TabBox *self();
     static TabBox *create(QObject *parent);
 

tabbox/tabboxhandler.cpp

@@ -337,6 +337,7 @@ void TabBoxHandlerPrivate::show()
         }
         item->setAllDesktops(config.clientDesktopMode() == TabBoxConfig::AllDesktopsClients);
         item->setCurrentIndex(indexRow);
+        item->setNoModifierGrab(q->noModifierGrab());
         // everything is prepared, so let's make the whole thing visible
         item->setVisible(true);
     }

tabbox/tabboxhandler.h

@@ -336,6 +336,12 @@ public:
 
     bool eventFilter(QObject *watcher, QEvent *event) override;
 
+    /**
+     * @returns whether the TabBox operates in a no modifier grab mode.
+     * In this mode a click on an item should directly accept and close the tabbox.
+     **/
+    virtual bool noModifierGrab() const = 0;
+
 Q_SIGNALS:
     /**
     * This signal is fired when the TabBoxConfig changes