tests/cogl: Add test checking rgb10 fbo precision

There are two tests; one checks that clearing with a color that cannot
be represented using 8 bits per channel doesn't loose precision when
painted, then read back using glReadPixels(). Would the texture backing
store have 8 bits per channel instead of 10, we'd get a different value
back.

The other test checks that painting from one fbo to another also doesn't
loose that precision.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2461>

2 files changed, 238 insertions, 0 deletions

diff --git a/src/tests/cogl/conform/meson.build b/src/tests/cogl/conform/meson.build
index e076733a5..39ada1c67 100644
--- a/src/tests/cogl/conform/meson.build
+++ b/src/tests/cogl/conform/meson.build
@@ -15,6 +15,7 @@ cogl_tests = [
   [ 'test-sub-texture', [] ],
   [ 'test-custom-attributes', [] ],
   [ 'test-offscreen', [] ],
+  [ 'test-offscreen-texture-formats', [] ],
   [ 'test-journal', [] ],
   [ 'test-primitive', [] ],
   [ 'test-sparse-pipeline', [] ],
diff --git a/src/tests/cogl/conform/test-offscreen-texture-formats.c b/src/tests/cogl/conform/test-offscreen-texture-formats.c
new file mode 100644
index 000000000..7b6e61ec7
--- /dev/null
+++ b/src/tests/cogl/conform/test-offscreen-texture-formats.c
@@ -0,0 +1,237 @@
+/*
+ * Copyright (C) 2022 Intel Corporation.
+ * Copyright (C) 2022 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <cogl/cogl.h>
+
+#include "tests/cogl-test-utils.h"
+
+static int
+get_bits (uint32_t in,
+          int      end,
+          int      begin)
+{
+  int mask = (1 << (end - begin + 1)) - 1;
+
+  return (in >> begin) & mask;
+}
+
+static int
+rgb10_to_rgb8 (int rgb10)
+{
+  float r;
+
+  r = rgb10 / (float) (1 << 10);
+  return (int) (r * (float) (1 << 8));
+}
+
+static int
+rgb8_to_rgb10 (int rgb8)
+{
+  float r;
+
+  r = rgb8 / (float) (1 << 8);
+  return (int) (r * (float) (1 << 10));
+}
+
+static void
+test_offscreen_texture_formats_store_rgb10 (void)
+{
+  const int rgb10_red = 514;
+  const int rgb10_green = 258;
+  const int rgb10_blue = 18;
+  float red;
+  float green;
+  float blue;
+  GError *error = NULL;
+  CoglPixelFormat formats[] = {
+    COGL_PIXEL_FORMAT_ABGR_2101010,
+    COGL_PIXEL_FORMAT_ARGB_2101010,
+    COGL_PIXEL_FORMAT_XRGB_2101010,
+    COGL_PIXEL_FORMAT_RGBA_1010102,
+    COGL_PIXEL_FORMAT_BGRA_1010102,
+    COGL_PIXEL_FORMAT_XBGR_2101010,
+  };
+  int i;
+
+  /* The extra fraction is there to avoid rounding inconsistencies in OpenGL
+   * implementations. */
+  red = (rgb10_red / (float) (1 << 10)) + 0.00001;
+  green = (rgb10_green / (float) (1 << 10)) + 0.00001;
+  blue = (rgb10_blue / (float) (1 << 10)) + 0.00001;
+
+  /* Make sure that that the color value can't be represented using rgb8. */
+  g_assert_cmpint (rgb8_to_rgb10 (rgb10_to_rgb8 (rgb10_red)), !=, rgb10_red);
+  g_assert_cmpint (rgb8_to_rgb10 (rgb10_to_rgb8 (rgb10_green)), !=, rgb10_green);
+  g_assert_cmpint (rgb8_to_rgb10 (rgb10_to_rgb8 (rgb10_blue)), !=, rgb10_blue);
+
+  for (i = 0; i < G_N_ELEMENTS (formats); i++)
+    {
+      CoglTexture2D *tex;
+      CoglOffscreen *offscreen;
+      uint32_t rgb8_readback[4];
+      uint8_t *rgb8_buf;
+      int j;
+
+      /* Allocate 2x2 to ensure we avoid any fast paths. */
+      tex = cogl_texture_2d_new_with_format (test_ctx, 2, 2, formats[i]);
+
+      offscreen = cogl_offscreen_new_with_texture (COGL_TEXTURE (tex));
+      cogl_framebuffer_allocate (COGL_FRAMEBUFFER (offscreen), &error);
+      g_assert_no_error (error);
+
+      cogl_framebuffer_clear4f (COGL_FRAMEBUFFER (offscreen),
+                                COGL_BUFFER_BIT_COLOR,
+                                red, green, blue, 1.0);
+
+      for (j = 0; j < G_N_ELEMENTS (formats); j++)
+        {
+          uint32_t rgb10_readback[4];
+          int channels[3];
+          int alpha;
+
+          cogl_framebuffer_read_pixels (COGL_FRAMEBUFFER (offscreen), 0, 0, 2, 2,
+                                        formats[j],
+                                        (uint8_t *) &rgb10_readback);
+
+          switch (formats[j])
+            {
+            case COGL_PIXEL_FORMAT_RGBA_1010102:
+            case COGL_PIXEL_FORMAT_BGRA_1010102:
+              channels[0] = get_bits (rgb10_readback[0], 31, 22);
+              channels[1] = get_bits (rgb10_readback[0], 21, 12);
+              channels[2] = get_bits (rgb10_readback[0], 11, 2);
+              alpha = get_bits (rgb10_readback[0], 1, 0);
+              break;
+            case COGL_PIXEL_FORMAT_XRGB_2101010:
+            case COGL_PIXEL_FORMAT_ARGB_2101010:
+            case COGL_PIXEL_FORMAT_XBGR_2101010:
+            case COGL_PIXEL_FORMAT_ABGR_2101010:
+              alpha = get_bits (rgb10_readback[0], 31, 30);
+              channels[0] = get_bits (rgb10_readback[0], 29, 20);
+              channels[1] = get_bits (rgb10_readback[0], 19, 10);
+              channels[2] = get_bits (rgb10_readback[0], 9, 0);
+              break;
+            default:
+              g_assert_not_reached ();
+            }
+
+          g_assert_cmpint (alpha, ==, 0x3);
+
+          switch (formats[j])
+            {
+            case COGL_PIXEL_FORMAT_RGBA_1010102:
+            case COGL_PIXEL_FORMAT_XRGB_2101010:
+            case COGL_PIXEL_FORMAT_ARGB_2101010:
+              g_assert_cmpint (channels[0], ==, rgb10_red);
+              g_assert_cmpint (channels[1], ==, rgb10_green);
+              g_assert_cmpint (channels[2], ==, rgb10_blue);
+              break;
+            case COGL_PIXEL_FORMAT_BGRA_1010102:
+            case COGL_PIXEL_FORMAT_XBGR_2101010:
+            case COGL_PIXEL_FORMAT_ABGR_2101010:
+              g_assert_cmpint (channels[0], ==, rgb10_blue);
+              g_assert_cmpint (channels[1], ==, rgb10_green);
+              g_assert_cmpint (channels[2], ==, rgb10_red);
+              break;
+            default:
+              g_assert_not_reached ();
+            }
+        }
+
+      cogl_framebuffer_read_pixels (COGL_FRAMEBUFFER (offscreen), 0, 0, 2, 2,
+                                    COGL_PIXEL_FORMAT_RGBA_8888,
+                                    (uint8_t *) &rgb8_readback);
+      rgb8_buf = (uint8_t *) &rgb8_readback[0];
+
+      g_assert_cmpint (rgb8_buf[0], ==, rgb10_to_rgb8 (rgb10_red));
+      g_assert_cmpint (rgb8_buf[1], ==, rgb10_to_rgb8 (rgb10_green));
+      g_assert_cmpint (rgb8_buf[2], ==, rgb10_to_rgb8 (rgb10_blue));
+      g_assert_cmpint (rgb8_buf[3], ==, 0xff);
+
+      g_object_unref (offscreen);
+      cogl_object_unref (tex);
+    }
+}
+
+static void
+test_offscreen_texture_formats_paint_rgb10 (void)
+{
+  const int rgb10_red = 514;
+  const int rgb10_green = 258;
+  const int rgb10_blue = 18;
+  float red;
+  float green;
+  float blue;
+  CoglTexture2D *tex_src;
+  CoglOffscreen *offscreen_src;
+  CoglTexture2D *tex_dst;
+  CoglOffscreen *offscreen_dst;
+  CoglPipeline *pipeline;
+  uint32_t rgb10_readback[4];
+  GError *error = NULL;
+
+  /* The extra fraction is there to avoid rounding inconsistencies in OpenGL
+   * implementations. */
+  red = (rgb10_red / (float) (1 << 10)) + 0.00001;
+  green = (rgb10_green / (float) (1 << 10)) + 0.00001;
+  blue = (rgb10_blue / (float) (1 << 10)) + 0.00001;
+
+  /* Make sure that that the color value can't be represented using rgb8. */
+  g_assert_cmpint (rgb8_to_rgb10 (rgb10_to_rgb8 (rgb10_red)), !=, rgb10_red);
+  g_assert_cmpint (rgb8_to_rgb10 (rgb10_to_rgb8 (rgb10_green)), !=, rgb10_green);
+  g_assert_cmpint (rgb8_to_rgb10 (rgb10_to_rgb8 (rgb10_blue)), !=, rgb10_blue);
+
+  tex_src = cogl_texture_2d_new_with_format (test_ctx, 2, 2,
+                                             COGL_PIXEL_FORMAT_RGBA_1010102);
+  offscreen_src = cogl_offscreen_new_with_texture (COGL_TEXTURE (tex_src));
+  cogl_framebuffer_allocate (COGL_FRAMEBUFFER (offscreen_src), &error);
+  g_assert_no_error (error);
+
+  tex_dst = cogl_texture_2d_new_with_format (test_ctx, 2, 2,
+                                             COGL_PIXEL_FORMAT_ABGR_2101010);
+  offscreen_dst = cogl_offscreen_new_with_texture (COGL_TEXTURE (tex_dst));
+  cogl_framebuffer_allocate (COGL_FRAMEBUFFER (offscreen_dst), &error);
+  g_assert_no_error (error);
+
+  cogl_framebuffer_clear4f (COGL_FRAMEBUFFER (offscreen_src),
+                            COGL_BUFFER_BIT_COLOR,
+                            red, green, blue, 1.0);
+
+  pipeline = cogl_pipeline_new (test_ctx);
+  cogl_pipeline_set_layer_texture (pipeline, 0, tex_src);
+  cogl_framebuffer_draw_rectangle (COGL_FRAMEBUFFER (offscreen_dst),
+                                   pipeline,
+                                   -1.0, -1.0, 1.0, 1.0);
+  cogl_object_unref (pipeline);
+
+  cogl_framebuffer_read_pixels (COGL_FRAMEBUFFER (offscreen_dst), 0, 0, 2, 2,
+                                COGL_PIXEL_FORMAT_ABGR_2101010,
+                                (uint8_t *) &rgb10_readback);
+  g_assert_cmpint (get_bits (rgb10_readback[0], 31, 30), ==, 0x3);
+  g_assert_cmpint (get_bits (rgb10_readback[0], 29, 20), ==, rgb10_blue);
+  g_assert_cmpint (get_bits (rgb10_readback[0], 19, 10), ==, rgb10_green);
+  g_assert_cmpint (get_bits (rgb10_readback[0], 9, 0), ==, rgb10_red);
+}
+
+COGL_TEST_SUITE (
+  g_test_add_func ("/offscreen/texture-formats/store-rgb10",
+                   test_offscreen_texture_formats_store_rgb10);
+  g_test_add_func ("/offscreen/texture-formats/paint-rgb10",
+                   test_offscreen_texture_formats_paint_rgb10);
+)