Make Compositor::finish more generic

Summary:
KWin is not only an X11 compositing window manager, but also a Wayland
compositor. The Compositor class is used in both cases so in general it
would be nice to keep it as much as possible generic.

Reviewers: #kwin, davidedmundson

Reviewed By: #kwin, davidedmundson

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D19879

composite.cpp

@@ -423,17 +423,6 @@ void Compositor::finish()
     m_scene = NULL;
     compositeTimer.stop();
     repaints_region = QRegion();
-    if (Workspace::self()) {
-        for (ClientList::ConstIterator it = Workspace::self()->clientList().constBegin();
-                it != Workspace::self()->clientList().constEnd();
-                ++it) {
-            // forward all opacity values to the frame in case there'll be other CM running
-            if ((*it)->opacity() != 1.0) {
-                NETWinInfo i(connection(), (*it)->frameId(), rootWindow(), 0, 0);
-                i.setOpacity(static_cast< unsigned long >((*it)->opacity() * 0xffffffff));
-            }
-        }
-    }
     m_finishing = false;
     emit compositingToggled(false);
 }

manage.cpp

@@ -28,6 +28,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #ifdef KWIN_BUILD_ACTIVITIES
 #include "activities.h"
 #endif
+#include "composite.h"
 #include "cursor.h"
 #include "rules.h"
 #include "group.h"
@@ -652,6 +653,20 @@ bool Client::manage(xcb_window_t w, bool isMapped)
     setBlockingCompositing(info->isBlockingCompositing());
     readShowOnScreenEdge(showOnScreenEdgeCookie);
 
+    // Forward all opacity values to the frame in case there'll be other CM running.
+    connect(Compositor::self(), &Compositor::compositingToggled, this,
+        [this](bool active) {
+            if (active) {
+                return;
+            }
+            if (opacity() == 1.0) {
+                return;
+            }
+            NETWinInfo info(connection(), frameId(), rootWindow(), 0, 0);
+            info.setOpacity(static_cast<unsigned long>(opacity() * 0xffffffff));
+        }
+    );
+
     // TODO: there's a small problem here - isManaged() depends on the mapping state,
     // but this client is not yet in Workspace's client list at this point, will
     // be only done in addClient()