Introduce a method shouldUseWaylandForCompositing() in KWin::Application

Returns true if the OperationMode requires KWin to composite to a
Wayland surface. This replaces the checks for the WaylandBackend or env
variable used so far in the construction of the Scene.

compositingprefs.cpp

@@ -20,6 +20,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #include "compositingprefs.h"
 
+#include "main.h"
 #include "xcbutils.h"
 #include "kwinglplatform.h"
 
@@ -62,6 +63,11 @@ bool CompositingPrefs::compositingPossible()
         gl_workaround_group.readEntry(unsafeKey, false))
         return false;
 
+    if (kwinApp()->shouldUseWaylandForCompositing()) {
+        // don't do X specific checks if we are not going to use X for compositing
+        return true;
+    }
+
     if (!Xcb::Extensions::self()->isCompositeAvailable()) {
         qDebug() << "No composite extension available";
         return false;

main.cpp

@@ -213,6 +213,11 @@ void Application::setOperationMode(OperationMode mode)
     m_operationMode = mode;
 }
 
+bool Application::shouldUseWaylandForCompositing() const
+{
+    return m_operationMode == OperationModeWaylandAndX11;
+}
+
 void Application::start()
 {
     setQuitOnLastWindowClosed(false);

main.h

@@ -86,6 +86,7 @@ public:
     */
     OperationMode operationMode() const;
     void setOperationMode(OperationMode mode);
+    bool shouldUseWaylandForCompositing() const;
 
     static void setCrashCount(int count);
     static bool wasCrash();

scene_opengl.cpp

@@ -43,6 +43,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "deleted.h"
 #include "effects.h"
 #include "lanczosfilter.h"
+#include "main.h"
 #include "overlaywindow.h"
 #include "paintredirector.h"
 #include "screens.h"
@@ -198,8 +199,8 @@ SceneOpenGL *SceneOpenGL::createScene()
     OpenGLPlatformInterface platformInterface = NoOpenGLPlatformInterface;
     // should we use glx?
 #ifndef KWIN_HAVE_OPENGLES
-    // on OpenGL we default to glx
-    platformInterface = GlxPlatformInterface;
+    // on OpenGL we default to glx on X11 and to egl on Wayland
+    platformInterface = kwinApp()->shouldUseWaylandForCompositing() ? EglPlatformInterface : GlxPlatformInterface;
 #endif
 
     const QByteArray envOpenGLInterface(qgetenv("KWIN_OPENGL_INTERFACE"));
@@ -209,8 +210,7 @@ SceneOpenGL *SceneOpenGL::createScene()
     platformInterface = EglPlatformInterface;
 #else
     // check environment variable
-    if (qstrcmp(envOpenGLInterface, "egl") == 0 ||
-            qstrcmp(envOpenGLInterface, "egl_wayland") == 0) {
+    if (qstrcmp(envOpenGLInterface, "egl") == 0) {
         qDebug() << "Forcing EGL native interface through environment variable";
         platformInterface = EglPlatformInterface;
     }
@@ -226,7 +226,7 @@ SceneOpenGL *SceneOpenGL::createScene()
     case EglPlatformInterface:
 #ifdef KWIN_HAVE_EGL
 #ifdef WAYLAND_FOUND
-        if (qstrcmp(envOpenGLInterface, "egl_wayland") == 0) {
+        if (kwinApp()->shouldUseWaylandForCompositing()) {
             backend = new EglWaylandBackend();
         } else {
             backend = new EglOnXBackend();

scene_qpainter.cpp

@@ -23,6 +23,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "composite.h"
 #include "deleted.h"
 #include "effects.h"
+#include "main.h"
 #include "paintredirector.h"
 #include "toplevel.h"
 #ifdef WAYLAND_FOUND
@@ -209,7 +210,7 @@ SceneQPainter *SceneQPainter::createScene()
 {
     QScopedPointer<QPainterBackend> backend;
 #ifdef WAYLAND_FOUND
-    if (Wayland::WaylandBackend::self()) {
+    if (kwinApp()->shouldUseWaylandForCompositing()) {
         backend.reset(new WaylandQPainterBackend);
         if (backend->isFailed()) {
             return NULL;

scene_xrender.cpp

@@ -29,6 +29,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "decorations.h"
 #include "deleted.h"
 #include "effects.h"
+#include "main.h"
 #include "overlaywindow.h"
 #include "paintredirector.h"
 #include "workspace.h"
@@ -367,7 +368,7 @@ SceneXrender* SceneXrender::createScene()
 {
     QScopedPointer<XRenderBackend> backend;
 #ifdef WAYLAND_FOUND
-    if (Wayland::WaylandBackend::self()) {
+    if (kwinApp()->shouldUseWaylandForCompositing()) {
         backend.reset(new WaylandXRenderBackend);
         if (backend->isFailed()) {
             return NULL;