[libkwineffects] Add keepBelow property to EffectWindow

Summary:
EffectWindow has keepAbove property, but not keepBelow.

This change adds keepBelow property as a counterpart to keepAbove.

Test Plan: Manually.

Reviewers: #kwin, mart

Reviewed By: #kwin, mart

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D13650

libkwineffects/kwineffects.cpp

@@ -861,6 +861,7 @@ WINDOW_HELPER_DEFAULT(bool, isMovable, "moveable", false)
 WINDOW_HELPER_DEFAULT(bool, isMovableAcrossScreens, "moveableAcrossScreens", false)
 WINDOW_HELPER_DEFAULT(QString, caption, "caption", QString())
 WINDOW_HELPER_DEFAULT(bool, keepAbove, "keepAbove", true)
+WINDOW_HELPER_DEFAULT(bool, keepBelow, "keepBelow", false)
 WINDOW_HELPER_DEFAULT(bool, isModal, "modal", false)
 WINDOW_HELPER_DEFAULT(QSize, basicUnit, "basicUnit", QSize(1, 1))
 WINDOW_HELPER_DEFAULT(bool, isUserMove, "move", false)

libkwineffects/kwineffects.h

@@ -1836,6 +1836,10 @@ class KWINEFFECTS_EXPORT EffectWindow : public QObject
      * Whether the window is set to be kept above other windows.
      **/
     Q_PROPERTY(bool keepAbove READ keepAbove)
+    /**
+     * Whether the window is set to be kept below other windows.
+     **/
+    Q_PROPERTY(bool keepBelow READ keepBelow)
     /**
      * Whether the window is minimized.
      **/
@@ -2140,6 +2144,10 @@ public:
      * Returns whether or not the window is kept above all other windows.
      */
     bool keepAbove() const;
+    /**
+     * Returns whether the window is kept below all other windows.
+     */
+    bool keepBelow() const;
 
     bool isModal() const;
     Q_SCRIPTABLE virtual KWin::EffectWindow* findModal() = 0;