tests/monitor-test-utils: Add way to make the GAMMA_LUT zero sized

This will be used to test devices that has no gamma capabilities.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2611>

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

@@ -488,7 +488,9 @@ meta_output_test_class_init (MetaOutputTestClass *klass)
 static size_t
 meta_crtc_test_get_gamma_lut_size (MetaCrtc *crtc)
 {
-  return GAMMA_SIZE;
+  MetaCrtcTest *crtc_test = META_CRTC_TEST (crtc);
+
+  return crtc_test->gamma.size;
 }
 
 static MetaGammaLut *
@@ -497,6 +499,8 @@ meta_crtc_test_get_gamma_lut (MetaCrtc *crtc)
   MetaCrtcTest *crtc_test = META_CRTC_TEST (crtc);
   MetaGammaLut *lut;
 
+  g_assert_cmpint (crtc_test->gamma.size, >, 0);
+
   lut = g_new0 (MetaGammaLut, 1);
   lut->size = crtc_test->gamma.size;
   lut->red = g_memdup2 (crtc_test->gamma.red,
@@ -573,3 +577,12 @@ meta_crtc_test_init (MetaCrtcTest *crtc_test)
       crtc_test->gamma.blue[i] = gamma;
     }
 }
+
+void
+meta_crtc_test_disable_gamma_lut (MetaCrtcTest *crtc_test)
+{
+  crtc_test->gamma.size = 0;
+  g_clear_pointer (&crtc_test->gamma.red, g_free);
+  g_clear_pointer (&crtc_test->gamma.green, g_free);
+  g_clear_pointer (&crtc_test->gamma.blue, g_free);
+}

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

@@ -87,4 +87,7 @@ void meta_monitor_manager_test_set_handles_transforms (MetaMonitorManagerTest *m
 META_EXPORT
 int meta_monitor_manager_test_get_tiled_monitor_count (MetaMonitorManagerTest *manager_test);
 
+META_EXPORT
+void meta_crtc_test_disable_gamma_lut (MetaCrtcTest *crtc_test);
+
 #endif /* META_MONITOR_MANAGER_TEST_H */

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

@@ -666,6 +666,8 @@ meta_create_monitor_test_setup (MetaBackend          *backend,
                            "id", (uint64_t) i + 1,
                            "gpu", meta_test_get_gpu (backend),
                            NULL);
+      if (setup->crtcs[i].disable_gamma_lut)
+        meta_crtc_test_disable_gamma_lut (META_CRTC_TEST (crtc));
 
       test_setup->crtcs = g_list_append (test_setup->crtcs, crtc);
     }

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

@@ -119,6 +119,7 @@ typedef struct _MonitorTestCaseOutput
 typedef struct _MonitorTestCaseCrtc
 {
   int current_mode;
+  gboolean disable_gamma_lut;
 } MonitorTestCaseCrtc;
 
 typedef struct _MonitorTestCaseSetup