Show reason (extensions not available or kwin support disabled at compile time)

when compositing cannot be used.

svn path=/trunk/KDE/kdebase/workspace/; revision=735788

compositingprefs.cpp

@@ -14,6 +14,7 @@ License. See the file "COPYING" for the exact licensing terms.
 
 #include <kdebug.h>
 #include <kxerrorhandler.h>
+#include <klocale.h>
 
 
 namespace KWin
@@ -53,6 +54,22 @@ bool CompositingPrefs::compositingPossible()
 #endif
     }
 
+QString CompositingPrefs::compositingNotPossibleReason()
+    {
+#if defined( HAVE_XCOMPOSITE ) && defined( HAVE_XDAMAGE )
+    Extensions::init();
+    if( !Extensions::compositeAvailable() || Extensions::damageAvailable())
+        {
+        return i18n("Required X extensions (XComposite and XDamage) are not available.");
+        }
+
+    return QString();
+#else
+    return i18n("Compositing was disabled at compile time.\n"
+            "Probably Xorg development headers were not installed.");
+#endif
+    }
+
 void CompositingPrefs::detect()
     {
     if( !compositingPossible())

compositingprefs.h

@@ -41,6 +41,7 @@ public:
     };
 
     static bool compositingPossible();
+    static QString compositingNotPossibleReason();
     bool enableCompositing() const  { return mEnableCompositing; }
     bool enableVSync() const  { return mEnableVSync; }
     bool enableDirectRendering() const  { return mEnableDirectRendering; }

kcmkwin/kwincompositing/main.cpp

@@ -97,7 +97,10 @@ KWinCompositingConfig::KWinCompositingConfig(QWidget *parent, const QVariantList
         ui.useCompositing->setChecked(false);
         compositingEnabled(false);
 
-        ui.statusLabel->setText(i18n("Compositing is not supported on your system."));
+        QString text = i18n("Compositing is not supported on your system.");
+        text += "<br><br>";
+        text += CompositingPrefs::compositingNotPossibleReason();
+        ui.statusLabel->setText(text);
         ui.statusLabel->show();
     }