GL_ARB_sampler_objects provides a GL object which overrides the
sampler state part of a texture object with different values. The
sampler state that Cogl currently exposes is the wrap modes and
filters. Cogl exposes the state as part of the pipeline layer state
but without this extension GL only exposes it as part of the texture
object state. This means that it won't work to use a single texture
multiple times in one primitive with different sampler states. It also
makes switching between different sampler states with a single texture
not terribly efficient because it has to change the texture object
state every time.
This patch adds a cache for sampler states in a shared hash table
attached to the CoglContext. The entire set of parameters for the
sampler state is used as the key for the hash table. When a unique
state is encountered the sampler cache will create a new entry,
otherwise it will return a const pointer to an existing entry. That
means we can have a single pointer to represent any combination of
sampler state.
Pipeline layers now just store this single pointer rather than storing
all of the sampler state. The two separate state flags for wrap modes
and filters have now been combined into one. It should be faster to
compare the sampler state now because instead of comparing each value
it can just compare the pointers to the cached sampler entries. The
hash table of cached sampler states should only need to perform its
more expensive hash on the state when a property is changed on a
pipeline, not every time it is flushed.
When the sampler objects extension is available each cached sampler
state will also get a sampler object to represent it. The common code
to flush the GL state will now simply bind this object to a unit
instead of flushing the state though the CoglTexture when possible.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
This extension lets you upload texture data from a subregion of a
buffer by passing GL_UNPACK_ROW_LENGTH, GL_UNPACK_SKIP_PIXELS and
GL_UNPACK_SKIP_ROWS to glPixelStore. When this extension is available
the GLES texture driver will now avoid making a copy of the bitmap
when a subregion is used.
Note that Mesa doesn't currently advertise this extension but I've
made a patch to propose it:
http://lists.freedesktop.org/archives/mesa-dev/2012-March/020191.html
This extension allows an application to upload data in BGRA format. We
can use this to avoid a conversion in Cogl whenever it is given BGRA
data. This is quite useful when uploading data generated by Cairo
because at least on little-endian architectures that ends up as BGRA.
The patch just makes the pixel_format_to_gl implementation return
GL_BGRA_EXT for the data format and internal format whenever
COGL_PIXEL_FORMAT_BGRA_8888{,_PRE} is used.
A small caveat with this patch is that once a texture is created as
GL_BGRA, when later using glTexSubImage2D to update the texture it
must always be given data as GL_BGRA. Currently this just works out
because we store the internal format of a texture as a CoglPixelFormat
and we already swizzle the data if it does not match exactly on GLES.
However if we later switch to using a different enum for internal
formats then we might lose the ability to store the component ordering
so we'll have to think of another way to do this.
This is only used internally when debugging is enabled to give a
human-readable name to a GL error so we shouldn't be exporting it
outside of the library. This just adds an underscore to the symbol
name. This shouldn't end up removing any public symbols from the 1.9.8
release because by default a non-git build disables debug so it wasn't
exported anyway.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
This adds api for explicitly choosing what underlying driver cogl should
use internally for rendering as well as api for querying back what
driver is actually in use.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
If the GL_OES_packed_depth_stencil extension is available then we can
try creating a combined depth-stencil buffer with the
GL_DEPTH24_STENCIL8 format. This adds a private flag for the feature.
https://bugzilla.gnome.org/show_bug.cgi?id=666184
Reviewed-by: Robert Bragg <robert@linux.intel.com>
The GL_DEPTH_STENCIL format for renderbuffers is defined in a separate
extension from GL_EXT_framebuffer_object so we probably shouldn't
being trying to use it unless that extension is advertised. This just
replaces the check for whether the driver is GL for a check for a
private feature flag before trying GL_DEPTH_STENCIL. The private
feature flag is set if the extension is available on GL.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
The cogl.h header is meant to be the public header for including the 1.x
api used by Clutter so we should stop using that as a convenient way to
include all likely prototypes and typedefs. Actually we already do a
good job of listing the specific headers we depend on in each of the .c
files we have so mostly this patch just strip out the redundant
includes for cogl.h with a few fixups where that broke the build.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This moves _cogl_get_format_bpp from cogl-bitmap.c to cogl.c and renames
it to _cogl_pixel_format_get_bytes_per_pixel. This makes it clearer that
it doesn't return bits per pixel and makes the naming consistent with
other cogl api. The prototype has been moved to cogl-private.h since it
seems we should be aiming to get rid of cogl-internal.h at some point.
The patch also adds a simple gtk-doc comment since we might want to make
this api public.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
The code for manipulating CoglBoxedValues is now separated from
cogl-program.c into its own file. That way when we add support for
setting uniform values on a CoglPipeline the code for storing the
values can be shared.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
Cogl provides a consistent public interface regardless of whether the
underlying GL driver supports VBOs so it doesn't make much sense to have
this feature as part of the public api. We can't break the api by
removing the enum but at least we no longer ever set the feature flag.
We now have a replacement private feature flag COGL_PRIVATE_FEATURE_VBOS
which cogl now checks for internally.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
Cogl provides a consistent public interface regardless of whether the
underlying GL driver supports PBOs so it doesn't make much sense to have
this feature as part of the public api. We can't break the api by
removing the enum but at least we no longer ever set the feature flag.
We now have a replacement private feature flag COGL_PRIVATE_FEATURE_PBOS
which cogl now checks for internally.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
Cogl doesn't currently expose public api for clip planes so it
doesn't make much sense to have this feature as part of the public api.
We can't break the api by removing the enum but at least we no longer
ever set the feature flag.
We now have a replacement private feature flag
COGL_PRIVATE_FEATURE_FOUR_CLIP_PLANES which cogl now checks for
internally.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
Cogl doesn't expose public api for blitting between framebuffers so it
doesn't make much sense to have this feature as part of the public api
currently. We can't break the api by removing the enum but at least we
no longer ever set the feature flag.
We now have a replacement private feature flag
COGL_PRIVATE_FEATURE_OFFSCREEN_BLIT which cogl now checks for
internally.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
Although we have to leave the COGL_FEATURE_STENCIL_BUFFER enum as part
of the public api we no longer ever set this feature flag.
Cogl doesn't currently expose the concept of a stencil buffer in the
public api (we only indirectly expose it via the clip stack api) so it
doesn't make much sense to have a stencil buffer feature flag.
We now have a COGL_PRIVATE_FEATURE_STENCIL_BUFFER flag instead which
we can check when we need to use the buffer for clipping.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This splits out the core CoglPipelineLayer support code from
cogl-pipeline.c into cogl-pipeline-layer.c; it splits out the debugging
code for dumping a pipeline to a .dot file into cogl-pipeline-debug.c
and it splits the CoglPipelineNode support which is shared between
CoglPipeline and CoglPipelineLayer into cogl-node.c.
Note: cogl-pipeline-layer.c only contains the layer code directly
relating to CoglPipelineLayer objects; it does not contain any
_cogl_pipeline API relating to how CoglPipeline tracks and manipulates
layers.
This adds an internal function to set the backface culling state on a
pipeline. This includes properties to set the culling mode (front,
back or both) and also to set which face is considered the front
(COGL_WINDING_CLOCKWISE or COGL_WINDING_COUNTER_CLOCKWISE). The actual
front face flushed to GL depends on whether we are rendering to an
offscreen buffer or not. This means that when changing between on- and
off- screen framebuffers it now checks whether the last flushed
pipeline has backface culling enabled and forces a reflush of the cull
face state if so.
The backface culling is now set on a pipeline as part of the legacy
state. This is important because some code in Cogl assumes it can
flush a temporary pipeline to revert to a known state, but previously
this wouldn't disable backface culling so things such as flushing the
clip stack could get confused.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
cogl_read_pixels returns image data in a top-down memory order, but
because OpenGL normally returns pixel data in a bottom-up order we
have to flip the data before returning it to the user. If the OpenGL
driver supports the GL_MESA_pack_invert extension though we can ask the
driver to return the data in a top-down order in the first place.
Signed-off-by: Neil Roberts <neil@linux.intel.com>
The GL or GLES library is now dynamically loaded by the CoglRenderer
so that it can choose between GL, GLES1 and GLES2 at runtime. The
library is loaded by the renderer because it needs to be done before
calling eglInitialize. There is a new environment variable called
COGL_DRIVER to choose between gl, gles1 or gles2.
The #ifdefs for HAVE_COGL_GL, HAVE_COGL_GLES and HAVE_COGL_GLES2 have
been changed so that they don't assume the ifdefs are mutually
exclusive. They haven't been removed entirely so that it's possible to
compile the GLES backends without the the enums from the GL headers.
When using GLX the winsys additionally dynamically loads libGL because
that also contains the GLX API. It can't be linked in directly because
that would probably conflict with the GLES API if the EGL is
selected. When compiling with EGL support the library links directly
to libEGL because it doesn't contain any GL API so it shouldn't have
any conflicts.
When building for WGL or OSX Cogl still directly links against the GL
API so there is a #define in config.h so that Cogl won't try to dlopen
the library.
Cogl-pango previously had a #ifdef to detect when the GL backend is
used so that it can sneakily pass GL_QUADS to
cogl_vertex_buffer_draw. This is now changed so that it queries the
CoglContext for the backend. However to get this to work Cogl now
needs to export the _cogl_context_get_default symbol and cogl-pango
needs some extra -I flags to so that it can include
cogl-context-private.h
cogl-ext-functions.h now contains definitions for all of the core GL
and GLES functions that we would normally link to directly. All of the
code has changed to access them through the cogl context pointer. The
GE macro now takes an extra parameter to specify the context because
the macro itself needs to make GL calls but various points in the Cogl
source use different names for the context variable.
This removes the unused COGL_PRIVATE_FEATURE_EGL flags since
check_egl_extensions doesn't refer to these flags it uses the
COGL_EGL_WINSYS_FEATURE flags.
Signed-off-by: Neil Roberts <neil@linux.intel.com>
This adds internal API to be able to wrap a wayland buffer as a
CoglTexture2D. There is a --enable-wayland-egl-server option to decide
if Cogl should support this feature and potentially any EGL based winsys
could support this through the EGL_KHR_image_base and
EGL_WL_bind_display extensions.
By using the EGL_KHR_image_base/pixmap extensions this adds support for
wrapping X11 pixmaps as CoglTexture2D textures. Clutter will
automatically take advantage of this if using the
ClutterX11TexturePixmap actor.
This adds an internal texture_2d constructor that can wrap an EGLImage
as a CoglTexture2D. The plan is to utilize this for texture-from-pixmap
support with EGL as well as creating textures from wayland buffers.
This migrates all the GLX window system code down from the Clutter
backend code into a Cogl winsys. Moving OpenGL window system binding
code down from Clutter into Cogl is the biggest blocker to having Cogl
become a standalone 3D graphics library, so this is an important step in
that direction.
There is no corresponding implementation of _cogl_features_init any more
so it was simply an oversight that the prototype wasn't removed when the
implementation was removed.
When the GLES2 wrapper is removed we can't use the fixed function API
such as glColorPointer to set the builtin attributes. Instead the GLSL
progend now maintains a cache of attribute locations that are queried
with glGetAttribLocation. The code that previously maintained a cache
of the enabled texture coord arrays has been modified to also cache
the enabled vertex attributes under GLES2. The vertex attribute API is
now the only place that is using this cache so it has been moved into
cogl-vertex-attribute.c
This merges the two implementations of CoglProgram for the GLES2 and
GL backends into one. The implementation is more like the GLES2
version which would track the uniform values and delay sending them to
GL. CoglProgram is now effectively just a GList of CoglShaders along
with an array of stored uniform values. CoglProgram never actually
creates a GL program, instead this is left up to the GLSL material
backend. This is necessary on GLES2 where we may need to relink the
user's program with different generated shaders depending on the other
emulated fixed function state. It will also be necessary in the future
GLSL backends for regular OpenGL. The GLSL and ARBfp material backends
are now the ones that create and link the GL program from the list of
shaders. The linked program is attached to the private material state
so that it can be reused if the CoglProgram is used again with the
same material. This does mean the program will get relinked if the
shader is used with multiple materials. This will be particularly bad
if the legacy cogl_program_use function is used because that
effectively always makes one-shot materials. This problem will
hopefully be alleviated if we make a hash table with a cache of
generated programs. The cogl program would then need to become part of
the hash lookup.
Each CoglProgram now has an age counter which is incremented every
time a shader is added. This is used by the material backends to
detect when we need to create a new GL program for the user program.
The internal _cogl_use_program function now takes a GL program handle
rather than a CoglProgram. It no longer needs any special differences
for GLES2. The GLES2 wrapper function now also uses this function to
bind its generated shaders.
The ARBfp shaders no longer store a copy of the program source but
instead just directly create a program object when cogl_shader_source
is called. This avoids having to reupload the source if the same
shader is used in multiple materials.
There are currently a few gross hacks to get the GLES2 backend to work
with this. The problem is that the GLSL material backend is now
generating a complete GL program but the GLES2 wrapper still needs to
add its fixed function emulation shaders if the program doesn't
provide either a vertex or fragment shader. There is a new function in
the GLES2 wrapper called _cogl_gles2_use_program which replaces the
previous cogl_program_use implementation. It extracts the GL shaders
from the GL program object and creates a new GL program containing all
of the shaders plus its fixed function emulation. This new program is
returned to the GLSL material backend so that it can still flush the
custom uniforms using it. The user_program is attached to the GLES2
settings struct as before but its stored using a GL program handle
rather than a CoglProgram pointer. This hack will go away once the
GLSL material backend replaces the GLES2 wrapper by generating the
code itself.
Under Mesa this currently generates some GL errors when glClear is
called in test-cogl-shader-glsl. I think this is due to a bug in Mesa
however. When the user program on the material is changed the GLSL
backend gets notified and deletes the GL program that it linked from
the user shaders. The program will still be bound in GL
however. Leaving a deleted shader bound exposes a bug in Mesa's
glClear implementation. More details are here:
https://bugs.freedesktop.org/show_bug.cgi?id=31194
The Clutter X11 backend now passes all events through
_cogl_xlib_handle_event. This function can now internally be hooked
with _cogl_xlib_add_filter. These are added to a list of callbacks
which are all called in turn by _cogl_xlib_handle_event. This is
intended to be used internally in Cogl by any parts that need to see
Xlib events.
Cogl now also has an internally exposed function to set a pointer to
the Xlib display. This is stored in a global variable. The Clutter X11
backend sets this.
_cogl_xlib_handle_event and _cogl_xlib_set_display can be removed once
Cogl gains a proper window system abstraction.
This is a complete overhaul of the data structures used to manage
CoglMaterial state.
We have these requirements that were aiming to meet:
(Note: the references to "renderlists" correspond to the effort to
support scenegraph level shuffling of Clutter actor primitives so we can
minimize GPU state changes)
Sparse State:
We wanted a design that allows sparse descriptions of state so it scales
well as we make CoglMaterial responsible for more and more state. It
needs to scale well in terms of memory usage and the cost of operations
we need to apply to materials such as comparing, copying and flushing
their state. I.e. we would rather have these things scale by the number
of real changes a material represents not by how much overall state
CoglMaterial becomes responsible for.
Cheap Copies:
As we add support for renderlists in Clutter we will need to be able to
get an immutable handle for a given material's current state so that we
can retain a record of a primitive with its associated material without
worrying that changes to the original material will invalidate that
record.
No more flush override options:
We want to get rid of the flush overrides mechanism we currently use to
deal with texture fallbacks, wrap mode changes and to handle the use of
highlevel CoglTextures that need to be resolved into lowlevel textures
before flushing the material state.
The flush options structure has been expanding in size and the structure
is logged with every journal entry so it is not an approach that scales
well at all. It also makes flushing material state that much more
complex.
Weak Materials:
Again for renderlists we need a way to create materials derived from
other materials but without the strict requirement that modifications to
the original material wont affect the derived ("weak") material. The
only requirement is that its possible to later check if the original
material has been changed.
A summary of the new design:
A CoglMaterial now basically represents a diff against its parent.
Each material has a single parent and a mask of state that it changes.
Each group of state (such as the blending state) has an "authority"
which is found by walking up from a given material through its ancestors
checking the difference mask until a match for that group is found.
There is only one root node to the graph of all materials, which is the
default material first created when Cogl is being initialized.
All the groups of state are divided into two types, such that
infrequently changed state belongs in a separate "BigState" structure
that is only allocated and attached to a material when necessary.
CoglMaterialLayers are another sparse structure. Like CoglMaterials they
represent a diff against their parent and all the layers are part of
another graph with the "default_layer_0" layer being the root node that
Cogl creates during initialization.
Copying a material is now basically just a case of slice allocating a
CoglMaterial, setting the parent to be the source being copied and
zeroing the mask of changes.
Flush overrides should now be handled by simply relying on the cheapness
of copying a material and making changes to it. (This will be done in a
follow on commit)
Weak material support will be added in a follow on commit.
The transform_point function takes a modelview matrix, projection
matrix and a viewport and performs all three transformations on a
point to give a Cogl window coordinate. This is useful in a number of
places in Cogl so this patch moves it to cogl.c and adds it to
cogl-internal.h
As part of an effort to improve the architecture of CoglMaterial
internally this overhauls how we flush layer state to OpenGL by adding a
formal backend abstraction for fragment processing and further
formalizing the CoglTextureUnit abstraction.
There are three backends: "glsl", "arbfp" and "fixed". The fixed backend
uses the OpenGL fixed function APIs to setup the fragment processing,
the arbfp backend uses code generation to handle fragment processing
using an ARBfp program, and the GLSL backend is currently only there as
a formality to handle user programs associated with a material. (i.e.
the glsl backend doesn't yet support code generation)
The GLSL backend has highest precedence, then arbfp and finally the
fixed. If a backend can't support some particular CoglMaterial feature
then it will fallback to the next backend.
This adds three new COGL_DEBUG options:
* "disable-texturing" as expected should disable all texturing
* "disable-arbfp" always make the arbfp backend fallback
* "disable-glsl" always make the glsl backend fallback
* "show-source" show code generated by the arbfp/glsl backends
The Cogl context has now a feature_flags_private enum that will allow us
to query and use OpenGL features without exposing them in the public
API.
The ARB_fragment_program extension is the first user of those flags.
Looking for this extension only happens in the gl driver as the gles
drivers will not expose them.
One can use _cogl_features_available_private() to check for the
availability of such private features.
While at it, reindent cogl-internal.h as described in CODING_STYLE.
When _cogl_disable_other_texcoord_arrays is called it disables the
neccessary texcoord arrays and then removes the bits for the disabled
arrays in ctx->texcoord_arrays_enabled. However none of the places
that call the function then set any bits in ctx->texcoord_arrays_enabled
so the arrays would never get marked and they would never get disabled
again.
This patch just changes it so that _cogl_disable_other_texcoord_arrays
also sets the corresponding bits in ctx->texcoord_arrays_enabled.
Instead of directly using a guint32 to store a bitmask for each used
texcoord array, it now stores them in a CoglBitmask. This removes the
limitation of 32 layers (although there are still other places in Cogl
that imply this restriction). To disable texcoord arrays code should
call _cogl_disable_other_texcoord_arrays which takes a bitmask of
texcoord arrays that should not be disabled. There are two extra
bitmasks stored in the CoglContext which are used temporarily for this
function to avoid allocating a new bitmask each time.
http://bugzilla.openedhand.com/show_bug.cgi?id=2132
It should be quite acceptable to use a texture without defining any
texture coords. For example a shader may be in use that is doing
texture lookups without referencing the texture coordinates. Also it
should be possible to replace the vertex colors using a texture layer
without a texture but with a constant layer color.
enable_state_for_drawing_buffer no longer sets any disabled layers in
the overrides. Instead of counting the number of units with texture
coordinates it now keeps them in a mask. This means there can now be
gaps in the list of enabled texture coordinate arrays. To cope with
this, the Cogl context now also stores a mask to track the enabled
arrays. Instead of code manually iterating each enabled array to
disable them, there is now an internal function called
_cogl_disable_texcoord_arrays which disables a given mask.
I think this could also fix potential bugs when a vertex buffer has
gaps in the texture coordinate attributes that it provides. For
example if the vertex buffer only had texture coordinates for layer 2
then the disabling code would not disable the coordinates for layers 0
and 1 even though they are not used. This could cause a crash if the
previous data for those arrays is no longer valid.
http://bugzilla.openedhand.com/show_bug.cgi?id=2132
This stubs out an xlib event handling mechanism for Cogl. The intention
is for Clutter to use this to forward all x11 events to Cogl. As we move
winsys functionality down into Cogl, Cogl will become responsible for
handling a number of X events: ConfigureNotify events for onscreen
framebuffers, swap events and Damage events for cogl_x11_texture_pixmap.
This adds three new API calls:
CoglHandle cogl_path_get()
void cogl_path_set(CoglHandle path)
CoglHandle cogl_path_copy(CoglHandle path)
All of the fields relating to the path have been moved from the Cogl
context to a new CoglPath handle type. The cogl context now just
contains a CoglPath handle. All of the existing path commands
manipulate the data in the current path handle. cogl_path_new now just
creates a new path handle and unrefs the old one.
The path handle can be stored for later with cogl_path_get. The path
can then be copied with cogl_path_copy. Internally it implements
copy-on-write semantics with an extra optimisation that it will only
copy the data if the new path is modified, but not if the original
path is modified. It can do this because the only way to modify a path
is by appending to it so the copied path is able to store its own path
length and only render the nodes up to that length. For this to work
the copied path also needs to keep its own copies of the path extents
because the parent path may change these by adding nodes.
The clip stack now uses the cogl_path_copy mechanism to store paths in
the stack instead of directly copying the data. This should save some
memory and processing time.
Every now and then someone sees the cogl_enable API and gets confused,
thinking its public API so this renames the symbol to be clear that it's
is an internal only API.
Since using addresses that might change is something that finally
the FSF acknowledge as a plausible scenario (after changing address
twice), the license blurb in the source files should use the URI
for getting the license in case the library did not come with it.
Not that URIs cannot possibly change, but at least it's easier to
set up a redirection at the same place.
As a side note: this commit closes the oldes bug in Clutter's bug
report tool.
http://bugzilla.openedhand.com/show_bug.cgi?id=521
The function prototypes for the primitives API were spread between
cogl-path.h and cogl-texture.h and should have been in a
cogl-primitives.h.
As well as shuffling the prototypes around into more sensible places
this commit splits the cogl-path API out from cogl-primitives.c into
a cogl-path.c
We've had complaints that our Cogl code/headers are a bit "special" so
this is a first pass at tidying things up by giving them some
consistency. These changes are all consistent with how new code in Cogl
is being written, but the style isn't consistently applied across all
code yet.
There are two parts to this patch; but since each one required a large
amount of effort to maintain tidy indenting it made sense to combine the
changes to reduce the time spent re indenting the same lines.
The first change is to use a consistent style for declaring function
prototypes in headers. Cogl headers now consistently use this style for
prototypes:
return_type
cogl_function_name (CoglType arg0,
CoglType arg1);
Not everyone likes this style, but it seems that most of the currently
active Cogl developers agree on it.
The second change is to constrain the use of redundant glib data types
in Cogl. Uses of gint, guint, gfloat, glong, gulong and gchar have all
been replaced with int, unsigned int, float, long, unsigned long and char
respectively. When talking about pixel data; use of guchar has been
replaced with guint8, otherwise unsigned char can be used.
The glib types that we continue to use for portability are gboolean,
gint{8,16,32,64}, guint{8,16,32,64} and gsize.
The general intention is that Cogl should look palatable to the widest
range of C programmers including those outside the Gnome community so
- especially for the public API - we want to minimize the number of
foreign looking typedefs.
OpenGL is an implementation detail for Cogl so it's not appropriate to
expose OpenGL extensions through the Cogl API.
Note: Clutter is currently still using this API, because it is still
doing raw GL calls in ClutterGLXTexturePixmap, so this introduces a
couple of (legitimate) build warnings while compiling Clutter.
Some GL functions have a return value that the GE() macro is not able to
handle. Let's define a new Ge_RET() macro which will be able to handle
functions such as glMapBuffer().
While at it, removed the unused variadic dots to the GE() macro.
We were checking the number of texture units against the GL enum that is
used in glGetInteger() to query that number. Let's abstract this in a
little function.
Took the opportunity to dig a bit on the usage of GL limits for the
number of texture (image) units and document our use of them. We'll need
something finer grained if we want to fully exploit texture image units
with a programmable pipeline.
Because Cogl defines the origin for texture as top left and offscreen draw
buffers can be used to render to textures, we (internally) force all
offscreen rendering to be upside down. (because OpenGL defines the origin
to be bottom left)
By forcing the users scene to be rendered upside down though we also reverse
the winding order of all the drawn triangles which may interfere with the
users use of backface culling. This patch ensures that we reverse the
winding order for a front face (if culling is in use) while rendering
offscreen so we don't conflict with the users back face culling.
The indirection through this API isn't necessary since we no longer
arbitrate between the OpenGL matrix API and Cogl's client side API. Also it
doesn't help to maintain an OpenGL style matrix mode API for internal use
since it's awkward to keep restoring the MODELVIEW mode and easy enough to
directly work with the matrix stacks of interest.
This replaces use of the _cogl_current_matrix API with direct use of the
_cogl_matrix_stack API. All the unused cogl_current_matrix API is removed
and the matrix utility code left in cogl-current-matrix.c was moved to
cogl.c.
