x11: Drop support for "let windows cover panel" mode in _KDE_NET_WM_SCREEN_EDGE_SHOW

This seems really hacky and plasmashell dropped "let windows cover panel" mode.

src/window.cpp

@@ -636,12 +636,6 @@ bool Window::belongsToDesktop() const
 
 Layer Window::layerForDock() const
 {
-    // slight hack for the 'allow window to cover panel' Kicker setting
-    // don't move keepbelow docks below normal window, but only to the same
-    // layer, so that both may be raised to cover the other
-    if (keepBelow()) {
-        return NormalLayer;
-    }
     if (keepAbove()) { // slight hack for the autohiding panels
         return AboveLayer;
     }

src/x11window.cpp

@@ -2898,11 +2898,6 @@ Xcb::Property X11Window::fetchShowOnScreenEdge() const
 
 void X11Window::readShowOnScreenEdge(Xcb::Property &property)
 {
-    // value comes in two parts, edge in the lower byte
-    // then the type in the upper byte
-    //  0 = autohide
-    //  1 = raise in front on activate
-
     const uint32_t value = property.value<uint32_t>(ElectricNone);
     ElectricBorder border = ElectricNone;
     switch (value & 0xFF) {
@@ -2920,28 +2915,15 @@ void X11Window::readShowOnScreenEdge(Xcb::Property &property)
         break;
     }
     if (border != ElectricNone) {
-        disconnect(m_edgeRemoveConnection);
         disconnect(m_edgeGeometryTrackingConnection);
-        bool successfullyHidden = false;
 
-        if (((value >> 8) & 0xFF) == 1) {
-            setKeepBelow(true);
-            successfullyHidden = keepBelow(); // request could have failed due to user kwin rules
-
-            m_edgeRemoveConnection = connect(this, &Window::keepBelowChanged, this, [this]() {
-                if (!keepBelow()) {
-                    workspace()->screenEdges()->reserve(this, ElectricNone);
-                }
-            });
-        } else {
         hideClient();
-            successfullyHidden = isHiddenInternal();
+        const bool successfullyHidden = isHiddenInternal();
 
         m_edgeGeometryTrackingConnection = connect(this, &X11Window::frameGeometryChanged, this, [this, border]() {
             hideClient();
             workspace()->screenEdges()->reserve(this, border);
         });
-        }
 
         if (successfullyHidden) {
             workspace()->screenEdges()->reserve(this, border);
@@ -2970,10 +2952,7 @@ void X11Window::updateShowOnScreenEdge()
 
 void X11Window::showOnScreenEdge()
 {
-    disconnect(m_edgeRemoveConnection);
-
     showClient();
-    setKeepBelow(false);
     xcb_delete_property(kwinApp()->x11Connection(), window(), atoms->kde_screen_edge_show);
 }
 

src/x11window.h

@@ -523,7 +523,6 @@ private:
     QTimer *m_focusOutTimer;
     QTimer m_releaseTimer;
 
-    QMetaObject::Connection m_edgeRemoveConnection;
     QMetaObject::Connection m_edgeGeometryTrackingConnection;
 
     QMarginsF m_clientFrameExtents;