We don't want to force texture data to be premultipled if the user
explicitly specifies a non premultiplied internal_format such as
COGL_PIXEL_FORMAT_RGBA_8888. So now Cogl will only automatically
premultiply data when COGL_PIXEL_FORMAT_ANY is given for the
internal_format, or a premultiplied internal format such as
COGL_PIXEL_FORMAT_RGBA_8888_PRE is requested but non-premultiplied source
data is given.
This approach is consistent with OpenVG image formats which have already
influenced Cogl's pixel format semantics.
Many operations, like mixing two textures together or alpha-blending
onto a destination with alpha, are done most logically if texture data
is in premultiplied form. We also have many sources of premultiplied
texture data, like X pixmaps, FBOs, cairo surfaces. Rather than trying
to work with two different types of texture data, simplify things by
always premultiplying texture data before uploading to GL.
Because the default blend function is changed to accommodate this,
uses of pure-color CoglMaterial need to be adapted to add
premultiplication.
gl/cogl-texture.c gles/cogl-texture.c: Always premultiply
non-premultiplied texture data before uploading to GL.
cogl-material.c cogl-material.h: Switch the default blend functions
to ONE, ONE_MINUS_SRC_ALPHA so they work correctly with premultiplied
data.
cogl.c: Make cogl_set_source_color() premultiply the color.
cogl.h.in color-material.h: Add some documentation about
premultiplication and its interaction with color values.
cogl-pango-render.c clutter-texture.c tests/interactive/test-cogl-offscreen.c:
Use premultiplied colors.
http://bugzilla.openedhand.com/show_bug.cgi?id=1406
Signed-off-by: Robert Bragg <robert@linux.intel.com>
Otherwise if there is an error before the slices are created it will
try to free the first_pixels array and crash.
It now also checks whether first_pixels has been created before using
it to update the mipmaps. This should only happen for
cogl_texture_new_from_foreign and doesn't matter if the FBO extension
is available. It would be better in this case to fetch the first pixel
using glGetTexImage as Owen mentioned in the last commit.
tex->first_pixels was never set for foreign textures, leading
to a crash when the texture object is freed.
As a quick fix, simply set to NULL. A more complete fix would
require remembering if we had ever seen the first pixel uploaded,
and if not, doing a glReadPixel to get it before triggering the
mipmap update.
http://bugzilla.openedhand.com/show_bug.cgi?id=1645
Signed-off-by: Neil Roberts <neil@linux.intel.com>
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>
COGL has a debug message system like Clutter's own. In parallel,
it also uses a coupld of #defines. Spread around there are also
calls to printf() instead to the more correct g_log* wrappers.
This commit tries to unify and clean up the macros and the
debug message handling inside COGL to be more consistent.
COGLenum, COGLint and COGLuint which were simply typedefs for GL{enum,int,uint}
have been removed from the API and replaced with specialised enum typedefs, int
and unsigned int. These were causing problems for generating bindings and also
considered poor style.
The cogl texture filter defines CGL_NEAREST and CGL_LINEAR etc are now replaced
by a namespaced typedef 'CoglTextureFilter' so they should be replaced with
COGL_TEXTURE_FILTER_NEAREST and COGL_TEXTURE_FILTER_LINEAR etc.
The shader type defines CGL_VERTEX_SHADER and CGL_FRAGMENT_SHADER are handled by
a CoglShaderType typedef and should be replaced with COGL_SHADER_TYPE_VERTEX and
COGL_SHADER_TYPE_FRAGMENT.
cogl_shader_get_parameteriv has been replaced by cogl_shader_get_type and
cogl_shader_is_compiled. More getters can be added later if desired.
There were several functions I believe no one is currently using that were
only implemented in the GL backend (cogl_offscreen_blit_region and
cogl_offscreen_blit) that have simply been removed so we have a chance to
think about design later with a real use case.
There was one nonsense function (cogl_offscreen_new_multisample) that
sounded exciting but in all cases it just returned COGL_INVALID_HANDLE
(though at least for GL it checked for multisampling support first!?)
it has also been removed.
The MASK draw buffer type has been removed. If we want to expose color
masking later then I think it at least would be nicer to have the mask be a
property that can be set on any draw buffer.
The cogl_draw_buffer and cogl_{push,pop}_draw_buffer function prototypes
have been moved up into cogl.h since they are for managing global Cogl state
and not for modifying or creating the actual offscreen buffers.
This also documents the API so for example desiphering the semantics of
cogl_offscreen_new_to_texture() should be a bit easier now.
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.
None of this code directly related to implementing CoglTextures, and the
code was needlessly duplicated between the GL and GLES backends. This moves
the cogl_rectangle* and cogl_polygon* code into common/cogl-primitives.c
makes which makes lot of sense since the two copies keep needlessly
diverging introducing or fixing bugs in one but not the other. For instance
I came accross one such bug regarding the enabling of texture units when
unifying the code.
The gtk-doc had a copy and paste error, saying the float array should be 8
elements per rectangle instead of 4. There was also no newline in the gles
code before the new function.
It's often nice to be able to draw a batch of vertices, even if these
have no texture coordinates. This add a cogl_rectangles, similar to
cogl_rectangles_with_texture_coords, only without.
There are various constraints for when we can support multi-texturing and
when they can't be met we try and print a clear warning explaining why the
operation isn't supported, but we shouldn't endlessly repeat the warning for
every primitive of every frame. This patch fixes that.
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.
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.
When the quad log contains multiple textures (such as when a sliced
texture is drawn) it dispatches the log with multiple calls to
flush_quad_batch and walks a pointer along the list of vertices.
However this pointer was being incremented by only one vertex so the
next quad would be drawn with three of the vertices from the last
quad.
The quad drawing code keeps track of the number of texture units that
have the tex coord array enabled so that in the next call it can
disabled any that are no longer enabled. However it was using 'i+1' as
the count but 'i' is already set to 'n_layers' from the previous for
loop.
Therefore it was disabling an extra texture unit. This doesn't
normally matter but it was causing GLES 2 to pointlessly realize an
extra unit.
This tries to make a number of files more comparable with the intention of
moving some code into cogl/common/
Files normalized:
cogl.c
cogl-context.c
cogl-context.h
cogl-texture.c
When drawing a texture with waste in _cogl_multitexture_unsliced_quad
it scales the texture coordinates so that the waste is not
included. However the formula was the wrong way around so it was
calculating as if the texture coordinates are ordered x1,x2,y1,y2 but
it is actually x1,y1,x2,y2.
When the texture is sliced it drops back to a fallback function and
passes it the texture coordinates from the rectangle. However if no
tex coords are given it would crash. Now it passes the default
0.0->1.0 tex coords instead.
If no texture coordinates are given then texture_unsliced_quad tries
to generate its own coordinates. However it also tries to read the
texture coordinates to check if they are in [0.0,1.0] range so it will
crash before it reaches that.
This updates cogl/gles in line with the integration of CoglMaterial throughout
Cogl that has been done for cogl/gl.
Note: This is still buggy, but at least it builds again and test-actors works.
Some GLES2 specific changes were made, but these haven't been tested yet.
This changes all GLES code to use the OpenGL function names instead of
the cogl_wrap_* names. For GLES2 we now define the OpenGL name to point
to the wrapper, as opposed to defining the wrapper to point to the
OpenGL name for GLES1.
I've also done a quick pass through gl/cogl.c and gles/cogl.c to make
them more easily comparable. (most of the code is now identical)
The script converted calls to COGL_FIXED_MUL(x,y) to (x*y). However
this fails for cases like this:
COGL_FIXED_MUL(a + b, c)
which become
(a + b * c)
The meaning of this is of course different because multiplication has
a higher precedence than addition.
This was causing breakages in cogl_texture_quad_sw when the vertex
coordinates are not in increasing order. This was the case in
test-backface-culling when NPOTs are not available.
Boolean arguments for functions are pretty evil and usually
lead to combinatorial explosion of parameters in case multiple
settings are added.
In the case of the COGL texture constructors we have a boolean
argument for enabling the auto-mipmapping; it is conceivable that
we might want to add more settings for a COGL texture without
breaking API or ABI compatibility, so the boolean argument should
become a bitmask.
The internals have not been changed: instead of checking for
a non-zero value, we check for a bitmask being set.
To deal with all the corner cases that couldn't be scripted a number of patches
were written for the remaining 10% of the effort.
Note: again no API changes were made in Clutter, only in Cogl.
This is the result of running a number of sed and perl scripts over the code to
do 90% of the work in converting from 16.16 fixed to single precision floating
point.
Note: A pristine cogl-fixed.c has been maintained as a standalone utility API
so that applications may still take advantage of fixed point if they
desire for certain optimisations where lower precision may be acceptable.
Note: no API changes were made in Clutter, only in Cogl.
Overview of changes:
- Within clutter/* all usage of the COGL_FIXED_ macros have been changed to use
the CLUTTER_FIXED_ macros.
- Within cogl/* all usage of the COGL_FIXED_ macros have been completly stripped
and expanded into code that works with single precision floats instead.
- Uses of cogl_fixed_* have been replaced with single precision math.h
alternatives.
- Uses of COGL_ANGLE_* and cogl_angle_* have been replaced so we use a float for
angles and math.h replacements.
The changes from the GL version of cogl-texture.c have been mirrored
in the GLES version. This adds the cogl_texture_new_from_bitmap
function and fixes the build errors.
The GLES 2 wrapper needs to set up some state before each
draw. Previously this was acheived by wrapping glDrawArrays. Since the
multiple-texture-rectangle branch merge, glDrawElements is used
instead so we also need a wrapper for that.
It was also directly calling glBindTexture. GLES 2 uses a wrapper for
this function so that it can cope with GL_ALPHA format textures. The
format of the current texture needs to be stored as well as the target
and object number for this to work.
test-cogl-material now runs on GLES 1 using the PVR GLES1 SDK (though since
only 2 texture units are supported the third rotating light map doesn't show)
Note: It currently doesn't build for GLES 2.0
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.
There's no point in clearing the index array because it is always the
same sequence of indices regardless of the vertices. Instead it is
just added to when there are more vertices than ever before.
* 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.
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.
* clutter/cogl/cogl-color.h:
* clutter/cogl/cogl-path.h:
* clutter/cogl/cogl-types.h:
* clutter/cogl/common/cogl-color.c: Deprecated cogl_color()
in favour of cogl_set_source_color() and friends; store the
CoglColor components as unsigned bytes instead of fixed point
normalized values; add functions for allocating, copying and
freeing CoglColor, for use of language bindings.
* clutter/cogl/cogl.h.in:
* clutter/cogl/cogl-deprecated.h: Added cogl-deprecated.h,
an header file containing the deprecation symbols similar
to clutter-deprecated.h.
* clutter/cogl/gl/Makefile.am:
* clutter/cogl/gl/cogl-texture.c:
* clutter/cogl/gl/cogl.c:
* clutter/cogl/gles/Makefile.am:
* clutter/cogl/gles/cogl-texture.c:
* clutter/cogl/gles/cogl.c: Update the GL and GLES implementations
of COGL after the CoglColor changes.
* clutter/clutter-actor.c:
* clutter/clutter-clone-texture.c:
* clutter/clutter-entry.c:
* clutter/clutter-label.c:
* clutter/clutter-rectangle.c:
* clutter/clutter-texture.c: Do not use CoglColor whenever it
is possible, and use cogl_set_source_color4ub() instead.
* clutter/pango/cogl-pango-render.c: Ditto as above.
* doc/reference/clutter/subclassing-ClutterActor.xml:
* doc/reference/cogl/cogl-sections.txt: Update the documentation.
* tests/interactive/test-cogl-offscreen.c:
* tests/interactive/test-cogl-primitives.c:
* tests/interactive/test-cogl-tex-convert.c:
* tests/interactive/test-cogl-tex-foreign.c:
* tests/interactive/test-cogl-tex-getset.c:
* tests/interactive/test-cogl-tex-polygon.c:
* tests/interactive/test-cogl-tex-tile.c:
* tests/interactive/test-paint-wrapper.c: Drop the usage of
CoglColor whenever it is possible.
coordinates
* clutter/cogl/gl/cogl-texture.c: Instead of sorting the vertex
and texture coordinates passed to cogl_texture_rectangle, just
swap both sets whenever the texture coordinates are backward.
Bug 1219 - Clean up cogl.h
* clutter/cogl/cogl.h.in:
* clutter/cogl/cogl-offscreen.h:
* clutter/cogl/cogl-path.h:
* clutter/cogl/cogl-shader.h:
* clutter/cogl/cogl-texture.h:
* clutter/cogl/cogl-types.h: Split up the massive cogl.h file
into sub-header for each section of the API.
* clutter/cogl/gl/*:
* clutter/cogl/gles/*: Update the GL and GLES implementations
of COGL to cope with the new header structure.
* doc/reference/cogl/Makefile.am: Fix symbol retrieval.
Bug 1210 - Add CoglColor API
* clutter/cogl/cogl-color.h:
* clutter/cogl/cogl.h.in:
* clutter/cogl/common/Makefile.am:
* clutter/cogl/common/cogl-color.c:
* clutter/cogl/gl/Makefile.am:
* clutter/cogl/gl/cogl.c:
* clutter/cogl/gles/Makefile.am:
* clutter/cogl/gles/cogl-texture.c:
* clutter/cogl/gles/cogl.c: Add a new color-type, to be used by
COGL. CoglColor is optimized to allow the minimum amount of
conversions possible for both GL and GLES implementations.
* clutter/clutter-actor.c:
* clutter/clutter-clone-texture.c:
* clutter/clutter-entry.c:
* clutter/clutter-main.c:
* clutter/clutter-rectangle.c:
* clutter/clutter-stage.c:
* clutter/clutter-texture.c: Use CoglColor when needed.
* clutter/pango/pangoclutter-render.c: Use CoglColor when needed.
* doc/reference/cogl/cogl-docs.sgml:
* doc/reference/cogl/cogl-sections.txt: Update the documentation.
* tests/test-cogl-offscreen.c:
* tests/test-cogl-primitives.c:
* tests/test-cogl-tex-convert.c:
* tests/test-cogl-tex-foreign.c:
* tests/test-cogl-tex-getset.c:
* tests/test-cogl-tex-polygon.c:
* tests/test-cogl-tex-tile.c:
* tests/test-paint-wrapper.c: Update the tests.
* README: Update release notes.
Bug 1209 - Move fixed point API in COGL
* clutter/cogl/cogl-fixed.h:
* clutter/cogl/cogl.h.in:
* clutter/cogl/common/Makefile.am:
* clutter/cogl/common/cogl-fixed.c: Add fixed point API, modelled
after the ClutterFixed. The CoglFixed API supercedes the ClutterFixed
one and avoids the dependency of COGL on Clutter's own API.
* clutter/cogl/common/cogl-clip-stack.c:
* clutter/cogl/common/cogl-primitives.c:
* clutter/cogl/common/cogl-primitives.h: Update internal usage of
ClutterFixed to CoglFixed.
* clutter/cogl/gl/Makefile.am:
* clutter/cogl/gl/cogl-primitives.c:
* clutter/cogl/gl/cogl-texture.c:
* clutter/cogl/gl/cogl.c: Ditto, in the GL implementation of the
COGL API.
* clutter/cogl/gles/Makefile.am:
* clutter/cogl/gles/cogl-fbo.c:
* clutter/cogl/gles/cogl-gles2-wrapper.c:
* clutter/cogl/gles/cogl-primitives.c:
* clutter/cogl/gles/cogl-texture.c:
* clutter/cogl/gles/cogl.c: Ditto, in the GLES implementation of
the COGL API.
* clutter/pango/pangoclutter-glyph-cache.c:
* clutter/pango/pangoclutter-glyph-cache.h: Ditto, in the Pango
renderer glyphs cache.
* clutter/clutter-fixed.c:
* clutter/clutter-fixed.h: ClutterFixed and related API becomes
a simple transition API for bindings and public Clutter API.
* clutter/clutter-actor.c:
* clutter/clutter-alpha.c:
* clutter/clutter-backend.c:
* clutter/clutter-behaviour-depth.c:
* clutter/clutter-behaviour-ellipse.c:
* clutter/clutter-behaviour-path.c:
* clutter/clutter-behaviour-rotate.c:
* clutter/clutter-behaviour-scale.c:
* clutter/clutter-clone-texture.c:
* clutter/clutter-color.c:
* clutter/clutter-entry.c:
* clutter/clutter-stage.c:
* clutter/clutter-texture.c:
* clutter/clutter-timeline.c:
* clutter/clutter-units.h: Move from the internal usage of
ClutterFixed to CoglFixed.
* doc/reference/clutter/clutter-sections.txt:
* doc/reference/cogl/cogl-docs.sgml:
* doc/reference/cogl/cogl-sections.txt: Update the documentation.
* tests/test-cogl-tex-tile.c:
* tests/test-project.c: Fix tests after the API change
* README: Add release notes.
* clutter/cogl/gl/cogl-texture.c (cogl_texture_polygon)
(_cogl_texture_quad_sw, _cogl_texture_quad_hw):
* clutter/cogl/gles/cogl-texture.c (cogl_texture_polygon)
(_cogl_texture_quad_sw, _cogl_texture_quad_hw): Enable backface
culling in GL if it is requested.
* clutter/cogl/gles/cogl-texture.c (_cogl_texture_quad_sw)
(_cogl_texture_quad_hw):
* clutter/cogl/gl/cogl-texture.c (_cogl_texture_quad_sw)
(_cogl_texture_quad_hw): Reorder the
vertices so that they are counter-clockwise.
* clutter/cogl/gles/cogl-context.h (CoglContext):
* clutter/cogl/gl/cogl-context.h (CoglContext): Added a flag to
store whether backface culling is currently enabled.
* clutter/cogl/gles/cogl.c (cogl_enable_backface_culling):
* clutter/cogl/gl/cogl.c (cogl_enable_backface_culling): New
function
* doc/reference/cogl/cogl-sections.txt: Add
cogl_enable_backface_culling
