[kstyle] Use QX11Info::isCompositingManagerRunning()

Summary:
Every time Breeze needs to check whether given widget has an alpha
channel, it makes a synchronous X call to figure out whether a
compositing window manager is running on a particular screen. This
is inefficient!

Luckily for us, Qt XCB QPA monitors compositing manager selections
and caches the ownership status of each one. That cached ownership
data can be accessed via QX11Info::isCompositingManagerRunning().

Reviewers: #plasma, hpereiradacosta

Reviewed By: hpereiradacosta

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D26978

kstyle/breezehelper.cpp

@@ -43,7 +43,7 @@ namespace Breeze
     //____________________________________________________________________
     Helper::Helper( KSharedConfig::Ptr config ):
         _config( std::move( config ) )
-    { init(); }
+    {}
 
     //____________________________________________________________________
     KSharedConfig::Ptr Helper::config() const
@@ -1577,13 +1577,7 @@ namespace Breeze
 
         #if BREEZE_HAVE_X11
         if( isX11() )
-        {
-            // direct call to X
-            xcb_get_selection_owner_cookie_t cookie( xcb_get_selection_owner( QX11Info::connection(), _compositingManagerAtom ) );
-            ScopedPointer<xcb_get_selection_owner_reply_t> reply( xcb_get_selection_owner_reply( QX11Info::connection(), cookie, nullptr ) );
-            return reply && reply->owner;
-
-        }
+        { return QX11Info::isCompositingManagerRunning( QX11Info::appScreen() ); }
         #endif
 
         // use KWindowSystem
@@ -1610,39 +1604,4 @@ namespace Breeze
         return pixmap.devicePixelRatio();
     }
 
-    #if BREEZE_HAVE_X11
-
-    //____________________________________________________________________
-    xcb_atom_t Helper::createAtom( const QString& name ) const
-    {
-        if( isX11() )
-        {
-
-            xcb_connection_t* connection( QX11Info::connection() );
-            xcb_intern_atom_cookie_t cookie( xcb_intern_atom( connection, false, name.size(), qPrintable( name ) ) );
-            ScopedPointer<xcb_intern_atom_reply_t> reply( xcb_intern_atom_reply( connection, cookie, nullptr) );
-            return reply ? reply->atom:0;
-
-        } else return 0;
-
-    }
-
-    #endif
-
-    //____________________________________________________________________
-    void Helper::init()
-    {
-        #if BREEZE_HAVE_X11
-
-        if( isX11() )
-        {
-            // create compositing screen
-            const QString atomName( QStringLiteral( "_NET_WM_CM_S%1" ).arg( QX11Info::appScreen() ) );
-            _compositingManagerAtom = createAtom( atomName );
-        }
-
-        #endif
-
-    }
-
 }

kstyle/breezehelper.h

@@ -31,10 +31,6 @@
 #include <QPainterPath>
 #include <QWidget>
 
-#if BREEZE_HAVE_X11
-#include <xcb/xcb.h>
-#endif
-
 namespace Breeze
 {
 
@@ -288,18 +284,6 @@ namespace Breeze
 
         //@}
 
-        //*@name X11 utilities
-        //@{
-
-        #if BREEZE_HAVE_X11
-
-        //* create xcb atom
-        xcb_atom_t createAtom( const QString& ) const;
-
-        #endif
-
-        //@}
-
         //* frame radius
         constexpr qreal frameRadius( const int penWidth = PenWidth::NoPen, const qreal bias = 0 ) const
         { return qMax( Metrics::Frame_FrameRadius - (0.5 * penWidth) + bias, 0.0 ); }
@@ -316,9 +300,6 @@ namespace Breeze
 
         protected:
 
-        //* initialize
-        void init();
-
         //* return rounded path in a given rect, with only selected corners rounded, and for a given radius
         QPainterPath roundedPath( const QRectF&, Corners, qreal ) const;
 
@@ -342,13 +323,6 @@ namespace Breeze
         QColor _inactiveTitleBarTextColor;
         //@}
 
-        #if BREEZE_HAVE_X11
-
-        //* atom used for compositing manager
-        xcb_atom_t _compositingManagerAtom;
-
-        #endif
-
     };
 
 }