Explicitly indicate support for window rules

This way it's more difficult to overlook the case where a new client
type unexpectedly advertises that it supports window rules.

abstract_client.cpp

@@ -2747,7 +2747,7 @@ bool AbstractClient::isInternal() const
 
 bool AbstractClient::supportsWindowRules() const
 {
-    return true;
+    return false;
 }
 
 QMargins AbstractClient::frameMargins() const

abstract_client.h

@@ -852,7 +852,7 @@ public:
     /**
      * Returns whether window rules can be applied to this client.
      *
-     * Default implementation returns @c true.
+     * Default implementation returns @c false.
      */
     virtual bool supportsWindowRules() const;
 

inputpanelv1client.h

@@ -38,7 +38,6 @@ public:
     bool isMovable() const override { return false; }
     bool isMovableAcrossScreens() const override { return false; }
     bool acceptsFocus() const override { return false; }
-    bool supportsWindowRules() const override { return false; }
     void closeWindow() override {}
     bool takeFocus() override { return false; }
     bool wantsInput() const override { return false; }

internal_client.cpp

@@ -321,11 +321,6 @@ void InternalClient::setFrameGeometry(const QRect &rect, ForceGeometry_t force)
     }
 }
 
-bool InternalClient::supportsWindowRules() const
-{
-    return false;
-}
-
 AbstractClient *InternalClient::findModal(bool allow_itself)
 {
     Q_UNUSED(allow_itself)

internal_client.h

@@ -59,7 +59,6 @@ public:
     void hideClient(bool hide) override;
     void resizeWithChecks(const QSize &size, ForceGeometry_t force = NormalGeometrySet) override;
     void setFrameGeometry(const QRect &rect, ForceGeometry_t force = NormalGeometrySet) override;
-    bool supportsWindowRules() const override;
     AbstractClient *findModal(bool allow_itself = false) override;
     void setOnAllActivities(bool set) override;
     bool takeFocus() override;

x11client.cpp

@@ -4991,6 +4991,11 @@ void X11Client::applyWindowRules()
     setBlockingCompositing(info->isBlockingCompositing());
 }
 
+bool X11Client::supportsWindowRules() const
+{
+    return true;
+}
+
 void X11Client::damageNotifyEvent()
 {
     if (m_syncRequest.isPending && isResize()) {

x11client.h

@@ -103,6 +103,7 @@ public:
     Group* group() override;
     void checkGroup(Group* gr = nullptr, bool force = false);
     void changeClientLeaderGroup(Group* gr);
+    bool supportsWindowRules() const override;
     void updateWindowRules(Rules::Types selection) override;
     void applyWindowRules() override;
     void updateFullscreenMonitors(NETFullscreenMonitors topology);

xdgshellclient.cpp

@@ -2012,11 +2012,6 @@ void XdgPopupClient::closeWindow()
 {
 }
 
-bool XdgPopupClient::supportsWindowRules() const
-{
-    return false;
-}
-
 bool XdgPopupClient::wantsInput() const
 {
     return false;

xdgshellclient.h

@@ -248,7 +248,6 @@ public:
     void closeWindow() override;
     bool wantsInput() const override;
     bool takeFocus() override;
-    bool supportsWindowRules() const override;
     void installPlasmaShellSurface(KWaylandServer::PlasmaShellSurfaceInterface *shellSurface) override;
 
 protected: