crtc: Make implementations inherit MetaCrtc

Just as with MetaOutput, instead of the home baked "inheritance" system,
using a gpointer and a GDestroyNotify function to keep the what
effectively is sub type details, make MetaCrtc an abstract derivable
type, and make the implementations inherit it.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1287

src/tests/headless-start-test.c

@@ -138,7 +138,7 @@ meta_test_headless_monitor_connect (void)
   test_setup->modes = g_list_append (NULL, crtc_mode);
 
   gpu = META_GPU (meta_backend_get_gpus (meta_get_backend ())->data);
-  crtc = g_object_new (META_TYPE_CRTC,
+  crtc = g_object_new (META_TYPE_CRTC_TEST,
                        "id", 1,
                        "gpu", gpu,
                        NULL);

src/tests/meta-monitor-manager-test.c

@@ -28,6 +28,7 @@
 #include "backends/meta-output.h"
 #include "tests/meta-backend-test.h"
 
+G_DEFINE_TYPE (MetaCrtcTest, meta_crtc_test, META_TYPE_CRTC)
 G_DEFINE_TYPE (MetaOutputTest, meta_output_test, META_TYPE_OUTPUT)
 
 struct _MetaMonitorManagerTest
@@ -436,3 +437,13 @@ static void
 meta_output_test_class_init (MetaOutputTestClass *klass)
 {
 }
+
+static void
+meta_crtc_test_init (MetaCrtcTest *crtc_test)
+{
+}
+
+static void
+meta_crtc_test_class_init (MetaCrtcTestClass *klass)
+{
+}

src/tests/meta-monitor-manager-test.h

@@ -20,6 +20,7 @@
 #ifndef META_MONITOR_MANAGER_TEST_H
 #define META_MONITOR_MANAGER_TEST_H
 
+#include "backends/meta-crtc.h"
 #include "backends/meta-monitor-manager-private.h"
 #include "backends/meta-output.h"
 
@@ -30,6 +31,11 @@ typedef struct _MetaMonitorTestSetup
   GList *crtcs;
 } MetaMonitorTestSetup;
 
+struct _MetaCrtcTest
+{
+  MetaCrtc parent;
+};
+
 struct _MetaOutputTest
 {
   MetaOutput parent;
@@ -39,6 +45,11 @@ struct _MetaOutputTest
 
 typedef MetaMonitorTestSetup * (* CreateTestSetupFunc) (void);
 
+#define META_TYPE_CRTC_TEST (meta_crtc_test_get_type ())
+G_DECLARE_FINAL_TYPE (MetaCrtcTest, meta_crtc_test,
+                      META, CRTC_TEST,
+                      MetaCrtc)
+
 #define META_TYPE_OUTPUT_TEST (meta_output_test_get_type ())
 G_DECLARE_FINAL_TYPE (MetaOutputTest, meta_output_test,
                       META, OUTPUT_TEST,

src/tests/monitor-test-utils.c

@@ -560,7 +560,7 @@ create_monitor_test_setup (MonitorTestCaseSetup *setup,
     {
       MetaCrtc *crtc;
 
-      crtc = g_object_new (META_TYPE_CRTC,
+      crtc = g_object_new (META_TYPE_CRTC_TEST,
                            "id", i + 1,
                            "gpu", test_get_gpu (),
                            NULL);