This avoids some calls to glGetFloatv, which have at least proven to be very
in-efficient in mesa at this point in time, since it always updates all derived
state even when it may not relate to the state being requested.
Although we wouldn't recommend developers try and interleve OpenGL drawing
with Cogl drawing - we would prefer patches that improve Cogl to avoid this
if possible - we are providing a simple mechanism that will at least give
developers a fighting chance if they find it necissary.
Note: we aren't helping developers change OpenGL state to modify the
behaviour of Cogl drawing functions - it's unlikley that can ever be
reliably supported - but if they are trying to do something like:
- setup some OpenGL state.
- draw using OpenGL (e.g. glDrawArrays() )
- reset modified OpenGL state.
- continue using Cogl to draw
They should surround their blocks of raw OpenGL with cogl_begin_gl() and
cogl_end_gl():
cogl_begin_gl ();
- setup some OpenGL state.
- draw using OpenGL (e.g. glDrawArrays() )
- reset modified OpenGL state.
cogl_end_gl ();
- continue using Cogl to draw
Again; we aren't supporting code like this:
- setup some OpenGL state.
- use Cogl to draw
- reset modified OpenGL state.
When the internals of Cogl evolves, this is very liable to break.
cogl_begin_gl() will flush all internally batched Cogl primitives, and emit
all internal Cogl state to OpenGL as if it were going to draw something
itself.
The result is that the OpenGL modelview matrix will be setup; the state
corresponding to the current source material will be setup and other world
state such as backface culling, depth and fogging enabledness will be also
be sent to OpenGL.
Note: no special material state is flushed, so if developers want Cogl to setup
a simplified material state it is the their responsibility to set a simple
source material before calling cogl_begin_gl. E.g. by calling
cogl_set_source_color4ub().
Note: It is the developers responsibility to restore any OpenGL state that they
modify to how it was after calling cogl_begin_gl() if they don't do this then
the result of further Cogl calls is undefined.
Previously the journal was always flushed at the end of
_cogl_rectangles_with_multitexture_coords, (i.e. the end of any
cogl_rectangle* calls) but now we have broadened the potential for batching
geometry. In ideal circumstances we will only flush once per scene.
In summary the journal works like this:
When you use any of the cogl_rectangle* APIs then nothing is emitted to the
GPU at this point, we just log one or more quads into the journal. A
journal entry consists of the quad coordinates, an associated material
reference, and a modelview matrix. Ideally the journal only gets flushed
once at the end of a scene, but in fact there are things to consider that
may cause unwanted flushing, including:
- modifying materials mid-scene
This is because each quad in the journal has an associated material
reference (i.e. not copy), so if you try and modify a material that is
already referenced in the journal we force a flush first)
NOTE: For now this means you should avoid using cogl_set_source_color()
since that currently uses a single shared material. Later we
should change it to use a pool of materials that is recycled
when the journal is flushed.
- modifying any state that isn't currently logged, such as depth, fog and
backface culling enables.
The first thing that happens when flushing, is to upload all the vertex data
associated with the journal into a single VBO.
We then go through a process of splitting up the journal into batches that
have compatible state so they can be emitted to the GPU together. This is
currently broken up into 3 levels so we can stagger the state changes:
1) we break the journal up according to changes in the number of material layers
associated with logged quads. The number of layers in a material determines
the stride of the associated vertices, so we have to update our vertex
array offsets at this level. (i.e. calling gl{Vertex,Color},Pointer etc)
2) we further split batches up according to material compatability. (e.g.
materials with different textures) We flush material state at this level.
3) Finally we split batches up according to modelview changes. At this level
we update the modelview matrix and actually emit the actual draw command.
This commit is largely about putting the initial design in-place; this will be
followed by other changes that take advantage of the extended batching.
Previously this was RGBA_8888. It souldn't really make a difference but for
consistency we expect almost all textures in use to have an internaly
premultiplied pixel format.
Instead of using GL_TRIANGLES and uploading the indices every time, it
now uses GL_QUADS instead on OpenGL. Under GLES it still uses indices
but it uses the new cogl_vertex_buffer_indices_get_for_quads function
to avoid uploading the vertices every time.
This requires the _cogl_vertex_buffer_indices_pointer_from_handle
function to be exposed privately to the rest of Cogl.
The static_indices array has been removed from the Cogl context.
This function can be used as an efficient way of drawing groups of
quads without using GL_QUADS. It generates a VBO containing the
indices needed to render using pairs of GL_TRIANGLES. The VBO is
globally cached so that it only needs to be uploaded whenever more
indices are requested than ever before.
cogl_create_context is dealt with internally when _cogl_get_default context
is called, and cogl_destroy_context is currently never called.
It might be nicer later to get an object back when creating a context so
Cogl can support multiple contexts, so these functions are being removed
from the API until we get a chance to address context management properly.
For now cogl_destroy_context is still exported as _cogl_destroy_context so
Clutter could at least install a library deinit handler to call it.
There were a number of functions intended to support creating of new
primitives using materials, but at this point they aren't used outside of
Cogl so until someone has a usecase and we can get feedback on this
API, it's being removed before we release Clutter 1.0.
Setting up layer combine functions and blend modes is very awkward to do
programatically. This adds a parser for string based descriptions which are
more consise and readable.
E.g. a material layer combine function could now be given as:
"RGBA = ADD (TEXTURE[A], PREVIOUS[RGB])"
or
"RGB = REPLACE (PREVIOUS)"
"A = MODULATE (PREVIOUS, TEXTURE)"
The simple syntax and grammar are only designed to expose standard fixed
function hardware, more advanced combining must be done with shaders.
This includes standalone documentation of blend strings covering the aspects
that are common to blending and texture combining, and adds documentation
with examples specific to the new cogl_material_set_blend() and
cogl_material_layer_set_combine() functions.
Note: The hope is to remove the now redundant bits of the material API
before 1.0
The CoglTexture constructors expose the "max-waste" argument for
controlling the maximum amount of wasted areas for slicing or,
if set to -1, disables slicing.
Slicing is really relevant only for large images that are never
repeated, so it's a useful feature only in controlled use cases.
Specifying the amount of wasted area is, on the other hand, just
a way to mess up this feature; 99% the times, you either pull this
number out of thin air, hoping it's right, or you try to do the
right thing and you choose the wrong number anyway.
Instead, we can use the CoglTextureFlags to control whether the
texture should not be sliced (useful for Clutter-GST and for the
texture-from-pixmap actors) and provide a reasonable value for
enabling the slicing ourself. At some point, we might even
provide a way to change the default at compile time or at run time,
for particular platforms.
Since max_waste is gone, the :tile-waste property of ClutterTexture
becomes read-only, and it proxies the cogl_texture_get_max_waste()
function.
Inside Clutter, the only cases where the max_waste argument was
not set to -1 are in the Pango glyph cache (which is a POT texture
anyway) and inside the test cases where we want to force slicing;
for the latter we can create larger textures that will be bigger than
the threshold we set.
Signed-off-by: Emmanuele Bassi <ebassi@linux.intel.com>
Signed-off-by: Robert Bragg <robert@linux.intel.com>
Signed-off-by: Neil Roberts <neil@linux.intel.com>
These are necessary if nesting redirections to an fbo,
otherwise there's no way to know how to restore
previous state.
glPushAttrib(GL_COLOR_BUFFER_BIT) would save draw buffer
state, but also saves a lot of other stuff, and
cogl_draw_buffer() relies on knowing about all draw
buffer state changes. So we have to implement a
draw buffer stack ourselves.
Signed-off-by: Robert Bragg <robert@linux.intel.com>
Adds missing notices, and ensures all the notices are consistent. The Cogl
blurb also now reads:
* Cogl
*
* An object oriented GL/GLES Abstraction/Utility Layer
The cogl_is_* functions were showing up quite high on profiles due to
iterating through arrays of cogl handles.
This does away with all the handle arrays and implements a simple struct
inheritance scheme. All cogl objects now add a CoglHandleObject _parent;
member to their main structures. The base object includes 2 members a.t.m; a
ref_count, and a klass pointer. The klass in turn gives you a type and
virtual function for freeing objects of that type.
Each handle type has a _cogl_##handle_type##_get_type () function
automatically defined which returns a GQuark of the handle type, so now
implementing the cogl_is_* funcs is just a case of comparing with
obj->klass->type.
Another outcome of the re-work is that cogl_handle_{ref,unref} are also much
more efficient, and no longer need extending for each handle type added to
cogl. The cogl_##handle_type##_{ref,unref} functions are now deprecated and
are no longer used internally to Clutter or Cogl. Potentially we can remove
them completely before 1.0.
This is useful because sometimes we need to get the current matrix, which
is too expensive when indirect rendering.
In addition, this virtualization makes it easier to clean up the API in
the future.
The private CoglContext is created using g_malloc() and not
zeroed; this means we have to initialize the values we are
going to check, to avoid hitting garbage.
Thanks to Tommi Komulainen.
Bug #1460 - Handling of flags in cogl_material_set_color
Cogl automatically enables/disables blending based on whether the source color
has an alhpa < 1.0, or if any textures with an alpha component are in use, but
it wasn't doing it quite right.
At the same time I removed some of the dirty flags which on second thought
are nothing more than micro-optimsations that only helped clutter the code.
thanks to Owen Taylor for reporting the bug
All GL functions that are defined in a version later than 1.1 need to
be called through cogl_get_proc_address because the Windows GL DLL
does not export them to directly link against.
The GL blend function and alpha function are now controlled by the material
code, and even internally Cogl should now be using the material API when
it needs control of these.
This glues CoglMaterial in as the fundamental way that Cogl describes how to
fill in geometry.
It adds cogl_set_source (), which is used to set the material which will be
used by all subsequent drawing functions
It adds cogl_set_source_texture as a convenience for setting up a default
material with a single texture layer, and cogl_set_source_color is now also
a convenience for setting up a material with a solid fill.
"drawing functions" include, cogl_rectangle, cogl_texture_rectangle,
cogl_texture_multiple_rectangles, cogl_texture_polygon (though the
cogl_texture_* funcs have been renamed; see below for details),
cogl_path_fill/stroke and cogl_vertex_buffer_draw*.
cogl_texture_rectangle, cogl_texture_multiple_rectangles and
cogl_texture_polygon no longer take a texture handle; instead the current
source material is referenced. The functions have also been renamed to:
cogl_rectangle_with_texture_coords, cogl_rectangles_with_texture_coords
and cogl_polygon respectivly.
Most code that previously did:
cogl_texture_rectangle (tex_handle, x, y,...);
needs to be changed to now do:
cogl_set_source_texture (tex_handle);
cogl_rectangle_with_texture_coords (x, y,....);
In the less likely case where you were blending your source texture with a color
like:
cogl_set_source_color4ub (r,g,b,a); /* where r,g,b,a isn't just white */
cogl_texture_rectangle (tex_handle, x, y,...);
you will need your own material to do that:
mat = cogl_material_new ();
cogl_material_set_color4ub (r,g,b,a);
cogl_material_set_layer (mat, 0, tex_handle));
cogl_set_source_material (mat);
Code that uses the texture coordinates, 0, 0, 1, 1 don't need to use
cog_rectangle_with_texure_coords since these are the coordinates that
cogl_rectangle will use.
For cogl_texture_polygon; as well as dropping the texture handle, the
n_vertices and vertices arguments were transposed for consistency. So
code previously written as:
cogl_texture_polygon (tex_handle, 3, verts, TRUE);
need to be written as:
cogl_set_source_texture (tex_handle);
cogl_polygon (verts, 3, TRUE);
All of the unit tests have been updated to now use the material API and
test-cogl-material has been renamed to test-cogl-multitexture since any
textured quad is now technically a test of CoglMaterial but this test
specifically creates a material with multiple texture layers.
Note: The GLES backend has not been updated yet; that will be done in a
following commit.
This better reflects the fact that the api manages sets of vertex attributes,
and the attributes really have no implied form. It is only when you use the
attributes to draw that they become mesh like; when you specify how they should
be interpreted, e.g. as triangle lists or fans etc. This rename frees up the
term "mesh", which can later be applied to a concept slightly more fitting.
E.g. at some point it would be nice to have a higher level abstraction that
sits on top of cogl vertex buffers that adds the concept of faces. (Somthing
like Blender's mesh objects.) There have also been some discussions over
particle engines, and these can be defined in terms of emitter faces; so some
other kind of mesh abstraction might be usefull here.
Bug 1289 - Draw multiple glyphs at once
The multiple-texture-rectangle branch adds a new Cogl texture function
called cogl_texture_multiple_rectangles which is used to draw multiple
rectangles out of a texture using a single GL call. This is
significantly faster than drawing the rectangles with individual calls
on some platforms. The Pango renderer now uses this to speed up
rendering.
The conflicts are just due to the whitespace fixes in cb569a5.
Conflicts:
clutter/cogl/gl/cogl-context.c
clutter/cogl/gl/cogl-context.h
clutter/cogl/gl/cogl-texture.c
This flattens the three functions: cogl_material_flush_gl_material_state,
.._flush_gl_alpha_func and .._flush_gl_blend_func into one:
cogl_flush_material_gl_state which doesn't takes a material handle. (the handle
is instead taken from the context.)
This has allows us to avoid re-submitting some state to OpenGL when the
material has not been replaced.
Note: Avoiding redundant state changes for material layers isn't dealt with
in this patch.
Removed trailing white space from the following files:
- clutter-clone-texture.c
- clutter-texture.c
- clutter-texture.h
- cogl/cogl-texture.h
- cogl/gl/cogl-context.c
- cogl/gl/cogl-texture.c
- cogl/gl/cogl-context.h
My previous work to provide muti-texturing support has been extended into
a CoglMaterial abstraction that adds control over the texture combine
functions (controlling how multiple texture layers are blended together),
the gl blend function (used for blending the final primitive with the
framebuffer), the alpha function (used to discard fragments based on
their alpha channel), describing attributes such as a diffuse, ambient and
specular color (for use with the standard OpenGL lighting model), and
per layer rotations. (utilizing the new CoglMatrix utility API)
For now the only way this abstraction is exposed is via a new
cogl_material_rectangle function, that is similar to cogl_texture_rectangle
but doesn't take a texture handle (the source material is pulled from
the context), and the array of texture coordinates is extended to be able
to supply coordinates for each layer.
Note: this function doesn't support sliced textures; supporting sliced
textures is a non trivial problem, considering the ability to rotate layers.
Note: cogl_material_rectangle, has quite a few workarounds, for a number of
other limitations within Cogl a.t.m.
Note: The GLES1/2 multi-texturing support has yet to be updated to use
the material abstraction.
Multitexturing allows blending multiple layers of texture data when texturing
some geometry. A common use is for pre-baked light maps which can give nice
lighting effects relativly cheaply. Another is for dot-3 bump mapping, and
another is applying alpha channel masks.
The dot-3 bump mapping would be really nice one day, but currently cogl doesn't
support lighting so that's not dealt with in this patch.
notable limitations:
- It can only texture rectangles a.t.m - and like cogl_texture_rectangle there
is no support for rotated texturing.
- Sliced textures are not supported. I think I've figured out how to handle
layers with different slice sizes at least for rectangular geometry, but I'm
not sure how complex it becomes once rotations are possible and texturing
arbitrary cogl_polygons.
- Except for this new API, cogl still doesn't know about more than one texture
unit, and so has no way of caching any enables related to other units. So that
things don't break it's currently necessary to disable anything to do with
additional units as soon as we are done with them which isn't ideal.
- No clutter API yet.
* clutter/cogl/cogl-path.h:
* clutter/cogl/common/cogl-primitives.c:
* clutter/cogl/common/cogl-primitives.h:
* clutter/cogl/gl/cogl-primitives.c:
* clutter/cogl/gles/cogl-primitives.c: Changed the semantics of
cogl_path_move_to. Previously this always started a new path but
now it instead starts a new disjoint sub path. The path isn't
cleared until you call either cogl_path_stroke, cogl_path_fill or
cogl_path_new. There are also cogl_path_stroke_preserve and
cogl_path_fill_preserve functions.
* clutter/cogl/gl/cogl-context.c:
* clutter/cogl/gl/cogl-context.h:
* clutter/cogl/gles/cogl-context.c:
* clutter/cogl/gles/cogl-context.h: Convert the path nodes array
to a GArray.
* clutter/cogl/gl/cogl-texture.c:
* clutter/cogl/gles/cogl-texture.c: Call cogl_clip_ensure
* clutter/cogl/common/cogl-clip-stack.c:
* clutter/cogl/common/cogl-clip-stack.h: Simplified the clip
stack code quite a bit to make it more maintainable. Previously
whenever you added a new clip it would go through a separate route
to immediately intersect with the current clip and when you
removed it again it would immediately rebuild the entire clip. Now
when you add or remove a clip it doesn't do anything immediately
but just sets a dirty flag instead.
* clutter/cogl/gl/cogl.c:
* clutter/cogl/gles/cogl.c: Taken away the code to intersect
stencil clips when there is exactly one stencil bit. It won't work
with path clips and I don't know of any platform that doesn't have
eight or zero stencil bits. It needs at least three bits to
intersect a path with an existing clip. cogl_features_init now
just decides you don't have a stencil buffer at all if you have
less than three bits.
* clutter/cogl/cogl.h.in: New functions and documentation.
* tests/interactive/test-clip.c: Replaced with a different test
that lets you add and remove clips. The three different mouse
buttons add clips in different shapes. This makes it easier to
test multiple levels of clipping.
* tests/interactive/test-cogl-primitives.c: Use
cogl_path_stroke_preserve when using the same path again.
* doc/reference/cogl/cogl-sections.txt: Document the new
functions.
`_glDrawRangeElements@24'
Resolve glDrawRangeElements with cogl_get_proc_address instead of
calling it directly because functions defined in GL > 1.1 are not
directly exported under Windows.
* clutter/cogl/common/cogl-mesh.c: Use the function pointer from
the context
* clutter/cogl/gl/cogl-context.c (cogl_create_context): Initialise
function pointer.
* clutter/cogl/gl/cogl-context.h (CoglContext): Add a function
pointer
* clutter/cogl/gl/cogl-defines.h.in: Add a typedef for the
function pointer.
* clutter/cogl/gl/cogl.c (_cogl_features_init): Resolve
glDrawRangeElements
differences and improve maintainability.
* clutter/cogl/gl/cogl-context.h:
Adds a CoglTextureGLVertex typedef + texture_vertices and
texture_vertices_size members to CoglContext for using vertex arrays
like GLES does
* clutter/cogl/gl/cogl-context.c:
Initializes texture_vertices + texture_vertices_size members
* clutter/cogl/gl/cogl-internal.h:
Adds COGL_ENABLE_COLOR_ARRAY
* clutter/cogl/gl/cogl.c:
Add COGL_ENABLE_COLOR_ARRAY support to cogl_enable
* clutter/cogl/gles/cogl-context.h:
Change the CoglTextureGLVertex to use GLfloat for the position
and texture coord attributes and GLubyte for the color.
* clutter/cogl/gles/cogl-texture-private.h:
Adds a wrap_mode member like GL has.
* clutter/cogl/gl/cogl-texture.c
* clutter/cogl/gles/cogl-texture.c:
Improves the comparability of the files, such that the remaining
differences, better reflect the fundamental differences needed
between GL and GLES. Notably GL no longer uses glBegin/glEnd for
submitting vertices, it uses vertex arrays like GLES and this gives
a small but measurable fps improvement for test-text.
Bug 1049 - Clutter doesn't support most GLSL uniforms (patch
by Chris Lord and Neil Roberts)
* README: Update release notes.
* clutter/Makefile.am:
* clutter/clutter-shader-types.[ch]: Add GValue types for
shader values.
* clutter/clutter-actor.[ch]: Update the shader API to use
the newly added GValue support for GLSL shader uniform
setters.
* clutter/clutter-shader.[ch]: Add float and integer convenience
API for single value GLSL uniform setters.
* clutter/cogl/cogl-shader.h: Add new uniform setters.
* clutter/cogl/gl/cogl-context.c:
* clutter/cogl/gl/cogl-context.h:
* clutter/cogl/gl/cogl-defines.h.in:
* clutter/cogl/gl/cogl-program.c:
* clutter/cogl/gl/cogl.c: Update the GL implementation of COGL
to handle the GLSL uniform setters.
* clutter/cogl/gles/cogl-gles2-wrapper.c:
* clutter/cogl/gles/cogl-gles2-wrapper.h:
* clutter/cogl/gles/cogl-internal.h:
* clutter/cogl/gles/cogl-program.c: Update the GLES 2.0 implementation
of COGL to handle the GLSL uniform setters.
* doc/reference/clutter/clutter-sections.txt:
* doc/reference/cogl/cogl-sections.txt: Update the documentation.
* tests/interactive/test-fbo.c:
* tests/interactive/test-shader.c: Update the shader tests.
* clutter/cogl/cogl-mesh.h
* clutter/cogl/cogl-types.h
* clutter/cogl/cogl.h.in
* clutter/cogl/common/Makefile.am
* clutter/cogl/common/cogl-mesh-private.h
* clutter/cogl/common/cogl-mesh.c
* clutter/cogl/gl/cogl-context.c
* clutter/cogl/gl/cogl-context.h
* clutter/cogl/gl/cogl-defines.h.in
* clutter/cogl/gl/cogl.c
* clutter/cogl/gles/cogl-context.c
* clutter/cogl/gles/cogl-context.h
* doc/reference/cogl/cogl-docs.sgml
* doc/reference/cogl/cogl-sections.txt:
The Mesh API provides a means for submitting an extensible number of
per vertex attributes to OpenGL in a way that doesn't require format
conversions and so that the data can be mapped into the GPU (in vertex
buffer objects) for - hopefully - fast re-use.
There are a number of things we can potentially use this API for, but
right now this just provides a foundation to build on. Please read
the extensive list of TODO items in cogl-mesh.c for examples.
Please refer to the cogl-mesh section in the reference manual for
documentation of the API.
* tests/conform/Makefile.am
* tests/conform/test-conform-main.c
* tests/conform/test-mesh-contiguous.c
* tests/conform/test-mesh-interleved.c
* tests/conform/test-mesh-mutability.c:
Privides basic coverage testing for the mesh API.
cogl_blend_func caches blending setup much like cogl_enable
does with the enable flags. This separates blending factors
setup from the enable/disable operation in preparation of
the texture image retrieval fix for alpha channel on GLES.
(cogl_enable:) Does not modify blending factors anymore.
* clutter/cogl/gl(es)/cogl-context.h: CoglContext holds two
new variables to cache blending src and dst factors.
* clutter/cogl/gl(es)/cogl-context.c:
(cogl_create_context:) Initialize blending factors.
* clutter/cogl/gles/cogl-texture.c:
(cogl_texture_download_from_gl:) Set blending factors to
CGL_ONE, CGL_ZERO which fixes the slighlty improper behavior
where source colour was actually multiplied with its alpha
value in the result (not noticable on current tests).
wrapped in reference-counted CoglHandles instead.
* clutter/cogl/gl/cogl-shader.c:
* clutter/cogl/gl/cogl-shader.h:
* clutter/cogl/gl/cogl-program.c:
* clutter/cogl/gl/cogl-program.h:
New files to hold the shader and program functions.
* clutter/cogl/gl/cogl.c: Removed shader and program functions.
* clutter/cogl/common/cogl-handle.h: New header to define
COGL_HANDLE_DEFINE which helps build functions to create
reference-counted handles. This reduces the amount of duplicated
code.
* clutter/cogl/gl/cogl-texture.c:
* clutter/cogl/gles/cogl-texture.c:
* clutter/cogl/gl/cogl-fbo.c: Converted to use COGL_HANDLE_DEFINE
from cogl-handle.h to avoid duplicating some of the common code.
* clutter/cogl/gles/cogl-defines.h.in:
* clutter/cogl/gl/cogl-defines.h.in: Removed COGLhandle
* clutter/cogl/gl/cogl-context.h: Added handle arrays for programs
and shaders.
* clutter/cogl/gl/cogl-context.c (cogl_create_context): Added
initialisers for shader_handles and program_handles.
(cogl_destroy_context): Added calls to g_array_free for all handle
arrays.
* clutter/cogl/gl/Makefile.am (libclutter_cogl_la_SOURCES): Added
cogl-{program,shader}.{c,h}
* clutter/cogl/common/Makefile.am
(libclutter_cogl_common_la_SOURCES): Added cogl-handle.h
* clutter/cogl/gles/cogl.c:
* clutter/cogl/cogl.h.in: Programs and shaders are now wrapped in
CoglHandles instead of COGLhandles. cogl_program_destroy and
cogl_shader_destroy is now replaced with cogl_program_unref and
cogl_shader_unref. cogl_program_ref and cogl_shader_ref are also
added.
* clutter/clutter-shader.c: Converted to use CoglHandles for the
programs and shaders instead of COGLhandles.
* cogl/cogl-sections.txt: Added cogl_shader_ref,
cogl_shader_unref, cogl_is_shader, cogl_program_ref,
cogl_program_unref, cogl_is_program and cogl_is_offscreen.
