tests/cogl: Migrate atlas-migration test

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2555>

src/tests/cogl/conform/meson.build

@@ -1,4 +1,5 @@
 cogl_tests = [
+  'test-atlas-migration',
 ]
 
 cogl_test_conformance_includes = [

src/tests/cogl/conform/test-atlas-migration.c

@@ -0,0 +1,149 @@
+#include <cogl/cogl.h>
+
+#include "tests/cogl-test-utils.h"
+
+#define N_TEXTURES 128
+
+#define OPACITY_FOR_ROW(y) \
+  (0xff - ((y) & 0xf) * 0x10)
+
+#define COLOR_FOR_SIZE(size) \
+  (colors + (size) % 3)
+
+typedef struct
+{
+  uint8_t red, green, blue, alpha;
+} TestColor;
+
+static const TestColor colors[] =
+  { { 0xff, 0x00, 0x00, 0xff },
+    { 0x00, 0xff, 0x00, 0xff },
+    { 0x00, 0x00, 0xff, 0xff } };
+
+static CoglTexture *
+create_texture (int size)
+{
+  CoglTexture *texture;
+  const TestColor *color;
+  uint8_t *data, *p;
+  int x, y;
+
+  /* Create a red, green or blue texture depending on the size */
+  color = COLOR_FOR_SIZE (size);
+
+  p = data = g_malloc (size * size * 4);
+
+  /* Fill the data with the color but fade the opacity out with
+     increasing y coordinates so that we can see the blending it the
+     atlas migration accidentally blends with garbage in the
+     texture */
+  for (y = 0; y < size; y++)
+    {
+      int opacity = OPACITY_FOR_ROW (y);
+
+      for (x = 0; x < size; x++)
+        {
+          /* Store the colors premultiplied */
+          p[0] = color->red * opacity / 255;
+          p[1] = color->green * opacity / 255;
+          p[2] = color->blue * opacity / 255;
+          p[3] = opacity;
+
+          p += 4;
+        }
+    }
+
+  texture = test_utils_texture_new_from_data (test_ctx,
+                                              size, /* width */
+                                              size, /* height */
+                                              TEST_UTILS_TEXTURE_NONE, /* flags */
+                                              /* format */
+                                              COGL_PIXEL_FORMAT_RGBA_8888_PRE,
+                                              /* rowstride */
+                                              size * 4,
+                                              data);
+
+  g_free (data);
+
+  return texture;
+}
+
+static void
+verify_texture (CoglTexture *texture, int size)
+{
+  uint8_t *data, *p;
+  int x, y;
+  const TestColor *color;
+
+  color = COLOR_FOR_SIZE (size);
+
+  p = data = g_malloc (size * size * 4);
+
+  cogl_texture_get_data (texture,
+                         COGL_PIXEL_FORMAT_RGBA_8888_PRE,
+                         size * 4,
+                         data);
+
+  for (y = 0; y < size; y++)
+    {
+      int opacity = OPACITY_FOR_ROW (y);
+
+      for (x = 0; x < size; x++)
+        {
+          TestColor real_color =
+            {
+              color->red * opacity / 255,
+              color->green * opacity / 255,
+              color->blue * opacity / 255
+            };
+
+          test_utils_compare_pixel (p,
+                                    (((guint32) real_color.red) << 24) |
+                                    (((guint32) real_color.green) << 16) |
+                                    (((guint32) real_color.blue) << 8) |
+                                    opacity);
+          g_assert_cmpint (p[3], ==, opacity);
+
+          p += 4;
+        }
+    }
+
+  g_free (data);
+}
+
+static void
+test_atlas_migration (void)
+{
+  CoglTexture *textures[N_TEXTURES];
+  int i, tex_num;
+
+  /* Create and destroy all of the textures a few times to increase
+     the chances that we'll end up reusing the buffers for previously
+     discarded atlases */
+  for (i = 0; i < 5; i++)
+    {
+      for (tex_num = 0; tex_num < N_TEXTURES; tex_num++)
+        textures[tex_num] = create_texture (tex_num + 1);
+      for (tex_num = 0; tex_num < N_TEXTURES; tex_num++)
+        cogl_object_unref (textures[tex_num]);
+    }
+
+  /* Create all the textures again */
+  for (tex_num = 0; tex_num < N_TEXTURES; tex_num++)
+    textures[tex_num] = create_texture (tex_num + 1);
+
+  /* Verify that they all still have the right data */
+  for (tex_num = 0; tex_num < N_TEXTURES; tex_num++)
+    verify_texture (textures[tex_num], tex_num + 1);
+
+  /* Destroy them all */
+  for (tex_num = 0; tex_num < N_TEXTURES; tex_num++)
+    cogl_object_unref (textures[tex_num]);
+
+  if (cogl_test_verbose ())
+    g_print ("OK\n");
+}
+
+COGL_TEST_SUITE (
+  g_test_add_func ("/atlas-migration", test_atlas_migration);
+)