Add support for RG textures

This adds COGL_PIXEL_FORMAT_RG_88 and COGL_TEXTURE_COMPONENTS_RG in
order to support two-component textures. The RG components for a
texture is only supported if COGL_FEATURE_ID_TEXTURE_RG is advertised.
This is only available on GL 3, GL 2 with the GL_ARB_texture_rg
extension or GLES with the GL_EXT_texture_rg extension. The RG pixel
format is always supported for images because Cogl can easily do the
conversion if an application uses this format to upload to a texture
with a different format.

If an application tries to create an RG texture when the feature isn't
supported then it will raise an error when the texture is allocated.

https://bugzilla.gnome.org/show_bug.cgi?id=712830

Reviewed-by: Robert Bragg <robert@linux.intel.com>

(cherry picked from commit 568677ab3bcb62ababad1623be0d6b9b117d0a26)

Conflicts:
	cogl/cogl-bitmap-packing.h
	cogl/cogl-types.h
	cogl/driver/gl/gl/cogl-driver-gl.c
	tests/conform/test-read-texture-formats.c
	tests/conform/test-write-texture-formats.c

1 files changed, 36 insertions, 0 deletions

diff --git a/cogl/cogl-bitmap-packing.h b/cogl/cogl-bitmap-packing.h
index e631c17f..e2bc8a10 100644
--- a/cogl/cogl-bitmap-packing.h
+++ b/cogl/cogl-bitmap-packing.h
@@ -79,6 +79,22 @@ G_PASTE (_cogl_unpack_g_8_, component_size) (const uint8_t *src,
 }
 
 inline static void
+G_PASTE (_cogl_unpack_rg_88_, component_size) (const uint8_t *src,
+                                               component_type *dst,
+                                               int width)
+{
+  while (width-- > 0)
+    {
+      dst[0] = UNPACK_BYTE (src[0]);
+      dst[1] = UNPACK_BYTE (src[1]);
+      dst[2] = 0;
+      dst[3] = UNPACK_BYTE (255);
+      dst += 4;
+      src += 2;
+    }
+}
+
+inline static void
 G_PASTE (_cogl_unpack_rgb_888_, component_size) (const uint8_t *src,
                                                  component_type *dst,
                                                  int width)
@@ -321,6 +337,9 @@ G_PASTE (_cogl_unpack_, component_size) (CoglPixelFormat format,
     case COGL_PIXEL_FORMAT_G_8:
       G_PASTE (_cogl_unpack_g_8_, component_size) (src, dst, width);
       break;
+    case COGL_PIXEL_FORMAT_RG_88:
+      G_PASTE (_cogl_unpack_rg_88_, component_size) (src, dst, width);
+      break;
     case COGL_PIXEL_FORMAT_RGB_888:
       G_PASTE (_cogl_unpack_rgb_888_, component_size) (src, dst, width);
       break;
@@ -425,6 +444,20 @@ G_PASTE (_cogl_pack_g_8_, component_size) (const component_type *src,
 }
 
 inline static void
+G_PASTE (_cogl_pack_rg_88_, component_size) (const component_type *src,
+                                             uint8_t *dst,
+                                             int width)
+{
+  while (width-- > 0)
+    {
+      dst[0] = PACK_BYTE (src[0]);
+      dst[1] = PACK_BYTE (src[1]);
+      src += 4;
+      dst += 2;
+    }
+}
+
+inline static void
 G_PASTE (_cogl_pack_rgb_888_, component_size) (const component_type *src,
                                                uint8_t *dst,
                                                int width)
@@ -665,6 +698,9 @@ G_PASTE (_cogl_pack_, component_size) (CoglPixelFormat format,
     case COGL_PIXEL_FORMAT_G_8:
       G_PASTE (_cogl_pack_g_8_, component_size) (src, dst, width);
       break;
+    case COGL_PIXEL_FORMAT_RG_88:
+      G_PASTE (_cogl_pack_rg_88_, component_size) (src, dst, width);
+      break;
     case COGL_PIXEL_FORMAT_RGB_888:
       G_PASTE (_cogl_pack_rgb_888_, component_size) (src, dst, width);
       break;