[mutter] cogl: Replace ANGLE with GLES3 and NV framebuffer_blit

[Jonas Ådahl <jadahl src gnome org>]

commit 3e68c9e8faa78298039fa3583898f18550740812
Author: Pekka Paalanen <pekka paalanen collabora com>
Date:   Mon May 6 13:40:31 2019 +0300

    cogl: Replace ANGLE with GLES3 and NV framebuffer_blit
    
    ANGLE extensions are only provided by Google's Almost Native Graphics Layer
    Engine (ANGLE) implementation. Therefore they do not seem too useful for
    Mutter.
    
    The reason to drop GL_ANGLE_framebuffer_blit support is that it has more
    limitations compared to the glBlitFramebuffer in GL_EXT_framebuffer_blit,
    GL_NV_framebuffer_bit, OpenGL 3.0 and OpenGL ES 3.0. Most importantly, the
    ANGLE version cannot flip the image while copying, which limits
    _cogl_blit_framebuffer to only off-screen <-> off-screen copies. Follow-up work
    will need off-screen <-> on-screen copies.
    
    Instead of adding yet more capability flags to Cogl, dropping ANGLE support
    seems appropriate.
    
    The NV extension is added to the list of glBlitFramebuffer providers because it
    provides the same support as ANGLE and more.
    
    Likewise OpenGL ES 3.0 is added to the list of glBlitFramebuffer providers
    because e.g. Mesa GLES implementation usually provides it and that makes it
    widely available, again surpassing the ANGLE supported features.
    
    Follow-up patches will lift some of the Cogl assumptions of what
    glBlitFramebuffer cannot do.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/615

 cogl/cogl/cogl-framebuffer-private.h         | 3 +--
 cogl/cogl/gl-prototypes/cogl-all-functions.h | 5 +++--
 2 files changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/cogl/cogl/cogl-framebuffer-private.h b/cogl/cogl/cogl-framebuffer-private.h
index 59896ddf3..4e87a46b2 100644
--- a/cogl/cogl/cogl-framebuffer-private.h
+++ b/cogl/cogl/cogl-framebuffer-private.h
@@ -384,8 +384,7 @@ _cogl_push_framebuffers (CoglFramebuffer *draw_buffer,
  * Note that this function differs a lot from the glBlitFramebuffer
  * function provided by the GL_EXT_framebuffer_blit extension. Notably
  * it doesn't support having different sizes for the source and
- * destination rectangle. This isn't supported by the corresponding
- * GL_ANGLE_framebuffer_blit extension on GLES2.0 and it doesn't seem
+ * destination rectangle. This doesn't seem
  * like a particularly useful feature. If the application wanted to
  * scale the results it may make more sense to draw a primitive
  * instead.
diff --git a/cogl/cogl/gl-prototypes/cogl-all-functions.h b/cogl/cogl/gl-prototypes/cogl-all-functions.h
index 8c92bdb05..ca32a3a12 100644
--- a/cogl/cogl/gl-prototypes/cogl-all-functions.h
+++ b/cogl/cogl/gl-prototypes/cogl-all-functions.h
@@ -4,6 +4,7 @@
  * A Low Level GPU Graphics and Utilities API
  *
  * Copyright (C) 2009, 2011 Intel Corporation.
+ * Copyright (C) 2019 DisplayLink (UK) Ltd.
  *
  * Permission is hereby granted, free of charge, to any person
  * obtaining a copy of this software and associated documentation
@@ -111,8 +112,8 @@ COGL_EXT_END ()
 
 
 COGL_EXT_BEGIN (offscreen_blit, 3, 0,
-                0, /* not in either GLES */
-                "EXT\0ANGLE\0",
+                COGL_EXT_IN_GLES3,
+                "EXT\0NV\0",
                 "framebuffer_blit\0")
 COGL_EXT_FUNCTION (void, glBlitFramebuffer,
                    (GLint                 srcX0,