Export supported openGLPlatformInterfaces to the DBus interface

Allows the KCM to know which platforms are supported (e.g. glx and egl or
just egl).

composite.cpp

@@ -862,6 +862,22 @@ QString Compositor::compositingType() const
     }
 }
 
+QStringList Compositor::supportedOpenGLPlatformInterfaces() const
+{
+    QStringList interfaces;
+    bool supportsGlx = (kwinApp()->operationMode() == Application::OperationModeX11);
+#ifdef KWIN_HAVE_OPENGLES
+    supportsGlx = false;
+#endif
+    if (supportsGlx) {
+        interfaces << QStringLiteral("glx");
+    }
+#ifdef KWIN_HAVE_EGL
+    interfaces << QStringLiteral("egl");
+#endif
+    return interfaces;
+}
+
 /*****************************************************
  * Workspace
  ****************************************************/

composite.h

@@ -79,6 +79,16 @@ class Compositor : public QObject {
      * @li @c gles OpenGL ES 2
      **/
     Q_PROPERTY(QString compositingType READ compositingType)
+    /**
+     * @brief All currently supported OpenGLPlatformInterfaces.
+     *
+     * Possible values:
+     * @li glx
+     * @li egl
+     *
+     * Values depend on operation mode and compile time options.
+     **/
+    Q_PROPERTY(QStringList supportedOpenGLPlatformInterfaces READ supportedOpenGLPlatformInterfaces)
 public:
     enum SuspendReason { NoReasonSuspend = 0, UserSuspend = 1<<0, BlockRuleSuspend = 1<<1, ScriptSuspend = 1<<2, AllReasonSuspend = 0xff };
     Q_DECLARE_FLAGS(SuspendReasons, SuspendReason)
@@ -158,6 +168,7 @@ public:
     QString compositingNotPossibleReason() const;
     bool isOpenGLBroken() const;
     QString compositingType() const;
+    QStringList supportedOpenGLPlatformInterfaces() const;
 
 public Q_SLOTS:
     void addRepaintFull();

org.kde.kwin.Compositing.xml

@@ -6,6 +6,7 @@
     <property name="compositingNotPossibleReason" type="s" access="read"/>
     <property name="openGLIsBroken" type="b" access="read"/>
     <property name="compositingType" type="s" access="read"/>
+    <property name="supportedOpenGLPlatformInterfaces" type="as" access="read"/>
     <signal name="compositingToggled">
       <arg name="active" type="b" direction="out"/>
     </signal>