MythDisplay: Add MythDisplayMutter subclass (for Wayland)

- N.B. this is disabled until testing is complete
- MythDisplayMutter uses the org.gnome.Mutter.DisplayConfig DBUS
interface to query and change the screen settings
- it provides display resolution and rate switching when running Wayland
- as far as I can see, this is the only way to handle this with pure
(i.e. no X11) Wayland compositors. Under the hood Wayland will be using
DRM for modeswitching etc - and we will never have the correct
permissions to access this directly.

mythtv/libs/libmythui/libmythui.pro

@@ -133,6 +133,8 @@ using_qtdbus {
     DEFINES += USING_DBUS
     HEADERS += screensaver-dbus.h
     SOURCES += screensaver-dbus.cpp
+    HEADERS += platforms/mythdisplaymutter.h
+    SOURCES += platforms/mythdisplaymutter.cpp
 }
 
 macx {

mythtv/libs/libmythui/mythdisplay.cpp

@@ -14,23 +14,26 @@
 #include "mythegl.h"
 #include "mythmainwindow.h"
 
+#ifdef USING_DBUS
+#include "platforms/mythdisplaymutter.h"
+#endif
 #ifdef Q_OS_ANDROID
-#include "mythdisplayandroid.h"
+#include "platforms/mythdisplayandroid.h"
 #endif
 #if defined(Q_OS_MAC)
-#include "mythdisplayosx.h"
+#include "platforms/mythdisplayosx.h"
 #endif
 #ifdef USING_X11
-#include "mythdisplayx11.h"
+#include "platforms/mythdisplayx11.h"
 #endif
 #ifdef USING_DRM
-#include "mythdisplaydrm.h"
+#include "platforms/mythdisplaydrm.h"
 #endif
 #if defined(Q_OS_WIN)
-#include "mythdisplaywindows.h"
+#include "platforms/mythdisplaywindows.h"
 #endif
 #ifdef USING_MMAL
-#include "mythdisplayrpi.h"
+#include "platforms/mythdisplayrpi.h"
 #endif
 
 #define LOC QString("Display: ")
@@ -86,6 +89,12 @@ MythDisplay* MythDisplay::AcquireRelease(bool Acquire)
             if (MythDisplayX11::IsAvailable())
                 s_display = new MythDisplayX11();
 #endif
+#ifdef USING_DBUS
+            /* disabled until testing can be completed (add docs on subclass choice when done)
+            if (!s_display)
+                s_display = MythDisplayMutter::Create();
+            */
+#endif
 #ifdef USING_MMAL
             if (!s_display)
                 s_display = new MythDisplayRPI();