backend/test: Add support for gamma getting/setting

The set gamma is just stored in the object, nothing else. It's
initialized to a linear gamma ramp from 0 to UINT16_MAX for each color
channel.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2165>

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

@@ -483,12 +483,93 @@ meta_output_test_class_init (MetaOutputTestClass *klass)
 {
 }
 
-static void
+#define GAMMA_SIZE 256
-meta_crtc_test_init (MetaCrtcTest *crtc_test)
+
+static size_t
+meta_crtc_test_get_gamma_lut_size (MetaCrtc *crtc)
 {
+  return GAMMA_SIZE;
+}
+
+static MetaGammaLut *
+meta_crtc_test_get_gamma_lut (MetaCrtc *crtc)
+{
+  MetaCrtcTest *crtc_test = META_CRTC_TEST (crtc);
+  MetaGammaLut *lut;
+
+  lut = g_new0 (MetaGammaLut, 1);
+  lut->size = crtc_test->gamma.size;
+  lut->red = g_memdup2 (crtc_test->gamma.red,
+                        lut->size * sizeof (uint16_t));
+  lut->green = g_memdup2 (crtc_test->gamma.green,
+                          lut->size * sizeof (uint16_t));
+  lut->blue = g_memdup2 (crtc_test->gamma.blue,
+                         lut->size * sizeof (uint16_t));
+  return lut;
+}
+
+static void
+meta_crtc_test_set_gamma_lut (MetaCrtc           *crtc,
+                              const MetaGammaLut *lut)
+{
+  MetaCrtcTest *crtc_test = META_CRTC_TEST (crtc);
+
+  g_assert_cmpint (crtc_test->gamma.size, ==, lut->size);
+
+  g_free (crtc_test->gamma.red);
+  g_free (crtc_test->gamma.green);
+  g_free (crtc_test->gamma.blue);
+
+  crtc_test->gamma.red = g_memdup2 (lut->red,
+                                    sizeof (uint16_t) * lut->size);
+  crtc_test->gamma.green = g_memdup2 (lut->green,
+                                      sizeof (uint16_t) * lut->size);
+  crtc_test->gamma.blue = g_memdup2 (lut->blue,
+                                     sizeof (uint16_t) * lut->size);
+}
+
+static void
+meta_crtc_test_finalize (GObject *object)
+{
+  MetaCrtcTest *crtc_test = META_CRTC_TEST (object);
+
+  g_free (crtc_test->gamma.red);
+  g_free (crtc_test->gamma.green);
+  g_free (crtc_test->gamma.blue);
+
+  G_OBJECT_CLASS (meta_crtc_test_parent_class)->finalize (object);
 }
 
 static void
 meta_crtc_test_class_init (MetaCrtcTestClass *klass)
 {
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+  MetaCrtcClass *crtc_class = META_CRTC_CLASS (klass);
+
+  object_class->finalize = meta_crtc_test_finalize;
+
+  crtc_class->get_gamma_lut_size = meta_crtc_test_get_gamma_lut_size;
+  crtc_class->get_gamma_lut = meta_crtc_test_get_gamma_lut;
+  crtc_class->set_gamma_lut = meta_crtc_test_set_gamma_lut;
+}
+
+static void
+meta_crtc_test_init (MetaCrtcTest *crtc_test)
+{
+  int i;
+
+  crtc_test->gamma.size = GAMMA_SIZE;
+  crtc_test->gamma.red = g_new0 (uint16_t, GAMMA_SIZE);
+  crtc_test->gamma.green = g_new0 (uint16_t, GAMMA_SIZE);
+  crtc_test->gamma.blue = g_new0 (uint16_t, GAMMA_SIZE);
+
+  for (i = 0; i < GAMMA_SIZE; i++)
+    {
+      uint16_t gamma;
+
+      gamma = ((float) i / GAMMA_SIZE) * UINT16_MAX;
+      crtc_test->gamma.red[i] = gamma;
+      crtc_test->gamma.green[i] = gamma;
+      crtc_test->gamma.blue[i] = gamma;
+    }
 }

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

@@ -35,6 +35,13 @@ typedef struct _MetaMonitorTestSetup
 struct _MetaCrtcTest
 {
   MetaCrtc parent;
+
+  struct {
+    size_t size;
+    uint16_t *red;
+    uint16_t *green;
+    uint16_t *blue;
+  } gamma;
 };
 
 struct _MetaOutputTest