This splits out most of the OpenGL specific code from cogl-framebuffer.c
into cogl-framebuffer-gl.c and extends the CoglDriverVtable interface
for cogl-framebuffer.c to use.
There are hopes to support several different backends for Cogl
eventually to hopefully get us closer to the metal so this makes some
progress in organizing which parts of Cogl are OpenGL specific so these
parts can potentially be switched out later.
The only remaining use of OpenGL still in cogl-framebuffer.c is to
handle cogl_framebuffer_read_pixels.
This commit introduces some new framebuffer api to be able to
enable texture based depth buffers for a framebuffer (currently
only supported for offscreen framebuffers) and once allocated
to be able to retrieve the depth buffer as a texture for further
usage, say, to implement shadow mapping.
The API works as follow:
* Before the framebuffer is allocated, you can request that a depth
texture is created with
cogl_framebuffer_set_depth_texture_enabled()
* cogl_framebuffer_get_depth_texture() can then be used to grab a
CoglTexture once the framebuffer has been allocated.
When the GL_EXT_unpack_subimage extension is not available and a
subregion of a texture is uploaded then it should first copy the
subregion to a newly allocated bitmap. However it was then later still
trying to prepare the upload using the original src_x and src_y values
which would cause an assertion failure. This patch fixes it to just
reset those to zero if the subregion is first copied.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 6f9a62db6f846f1d76e3ca16d9d8cdadf82a7009)
This adds two new configuration environment variables:
COGL_DISABLE_GL_EXTENSIONS and
COGL_OVERRIDE_GL_VERSION
The variables can also be set in the cogl.conf file using the same
names.
The first one is a list of GL extension names separated by commas.
When set Cogl will assume any extension listed here is not available
by removing it from the string returned from
glGetString(GL_EXTENSIONS). If the string is set in both the config
file and the environment variable then the union of the two lists will
be used.
The second overrides the value returned from glGetString(GL_VERSION).
If the string is set in both places the version from the environment
variable will take priority.
These are sometimes useful for debugging Cogl to test the various
combinations of extensions. It could also be useful to work around
driver bugs where an extension is badly supported and it would be
better not to use it.
The variables in cogl-config that just set a global char * variable
have been put together in an array instead of having a separate blob
of code for each one in order to make it simpler to add new variables.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit ec69c2dc576c78664e0b73879365cb7414ecf441)
According to the EGL spec, eglGetProcAddress should only be used to
retrieve extension functions. It also says that returning non-NULL
does not mean the extension is available so you could interpret this
as saying that the function is allowed to return garbage for core
functions. This seems to happen at least for the Android
implementation of EGL.
To workaround this the winsys's are now passed down a flag to say
whether the function is from the core API. This information is already
in the gl-prototypes headers as the minimum core GL version and as a
pair of flags to specify whether it is available in core GLES1 and
GLES2. If the function is in core the EGL winsys will now avoid using
eglGetProcAddress and always fallback to querying the library directly
with the GModule API.
The GLX winsys is left alone because glXGetProcAddress apparently
supports querying core API and extension functions.
The WGL winsys could ideally be changed because wglGetProcAddress
should also only be used for extension functions but the situation is
slightly different because WGL considers anything from GL > 1.1 to be
an extension so it would need a bit more information to determine
whether to query the function directly from the library.
The SDL winsys is also left alone because it's not as easy to portably
determine which GL library SDL has chosen to load in order to resolve
the symbols directly.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 72089730ad06ccdd38a344279a893965ae68cec1)
Since we aren't able to break API on the 1.12 branch
cogl_get_proc_address is still supported but isn't easily able to
determine whether the given name corresponds to a core symbol or
not. For now we just assume the symbol being queried isn't part
of the core GL api and update the documentation accordingly.
Until now, we hardcoded the internal format to GL_RGBA and used the
internal format returned by pixel_format_to_gl() as the format for
checking the texture size and format we're asked to create.
Let's use the proper internal format/format from now on.
This is needed as a later patch introduces DEPTH and DEPTH_STENCIL
textures.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit ec45f60ee2545f88302da314bcdbe1439c4ba9c9)
This detects when we are running on any of Mesa's software rasterizer
backends and disables use of glBlitFramebuffer and glXCopySubBuffer.
Both of these currently result in full-screen copies so there's little
point in using these to optimize how much of the screen we present.
To help ensure we re-evaluate this workaround periodically we have added
a comment marker of "ONGOING BUG" above the workaround and added a note
to our RELEASING document that says we should grep for this marker and
write a NEWS section about ongoing bug workarounds.
https://bugzilla.gnome.org/show_bug.cgi?id=674208
Reviewed-by: Neil Roberts <neil@linux.intel.com>
(cherry picked from commit 11f2f6ebb42398978ec8dd92b3c332ae8140a728)
The coding style has for a long time said to avoid using redundant glib
data types such as gint or gchar etc because we feel that they make the
code look unnecessarily foreign to developers coming from outside of the
Gnome developer community.
Note: When we tried to find the historical rationale for the types we
just found that they were apparently only added for consistent syntax
highlighting which didn't seem that compelling.
Up until now we have been continuing to use some of the platform
specific type such as gint{8,16,32,64} and gsize but this patch switches
us over to using the standard c99 equivalents instead so we can further
ensure that our code looks familiar to the widest range of C developers
who might potentially contribute to Cogl.
So instead of using the gint{8,16,32,64} and guint{8,16,32,64} types this
switches all Cogl code to instead use the int{8,16,32,64}_t and
uint{8,16,32,64}_t c99 types instead.
Instead of gsize we now use size_t
For now we are not going to use the c99 _Bool type and instead we have
introduced a new CoglBool type to use instead of gboolean.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
(cherry picked from commit 5967dad2400d32ca6319cef6cb572e81bf2c15f0)
Removing CoglHandle has been an on going goal for quite a long time now
and finally this patch removes the last remaining uses of the CoglHandle
type and the cogl_handle_ apis.
Since the big remaining users of CoglHandle were the cogl_program_ and
cogl_shader_ apis which have replaced with the CoglSnippets api this
patch removes both of these apis.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
(cherry picked from commit 6ed3aaf4be21d605a1ed3176b3ea825933f85cf0)
Since the original patch was done after removing deprecated API
this back ported patch doesn't affect deprecated API and so
actually this cherry-pick doesn't remove all remaining use of
CoglHandle as it did for the master branch of Cogl.
The Intel driver currently has an optimisation when calling
glReadPixels into a PBO so that it will use a blit instead of the Mesa
fallback path. However this only works if the GL_PACK_ALIGNMENT is
exactly 1, even if this would be equivalent to a higher alignment
value because the bpp*width is already aligned. To make it more likely
to hit this fast path, we now detect this situation and explicitly use
an alignment of 1. To make this work the texture driver needs to be
passed down the bpp*width as well as the rowstride when configuring
the alignment.
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.
Cogl already had a vtable for the texture driver. This ended up being
used for some things that are not strictly related to texturing such
as converting between pixel formats and GL enums. Some other functions
that are driver dependent such as updating the features were not
indirected through a vtable but instead switched directly by looking
at the ctx->driver enum value. This patch normalises to the two uses
by adding a separate vtable for driver functions not related to
texturing and moves the pixel format conversion functions to it from
the texture driver vtable. It also adds a context parameter to all of
the functions in the new driver vtable so that they won't have to rely
on the global context.
This creates a CoglBitmap which points into an existing buffer in
system memory. That way it can be used to create a texture or to read
pixel data into. The function replaces the existing internal function
_cogl_bitmap_new_from_data but removes the destroy notify call back.
If the application wants notification of destruction it can just use
the cogl_object_set_user_data function as normal. Internally there is
now a convenience function to create a bitmap for system memory and
automatically free the buffer using that mechanism.
The name of the function is inspired by
cairo_image_surface_create_for_data which has similar semantics.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
This option to GCC makes it give a warning whenever a global function
is defined without a declaration. This should catch cases were we've
defined a function but forgot to put it in a header. In that case it
is either only used within one file so we should make it static or we
should declare it in a header.
The following changes where made to fix problems:
• Some functions were made static
• cogl-path.h (the one containing the 1.0 API) was split into two
files, one defining the functions and one defining the enums so that
cogl-path.c can include the enum and function declarations from the
2.0 API as well as the function declarations from the 1.0 API.
• cogl2-clip-state has been removed. This only had one experimental
function called cogl_clip_push_from_path but as this is unstable we
might as well remove it favour of the equivalent cogl_framebuffer_*
API.
• The GLX, SDL and WGL winsys's now have a private header to define
their get_vtable function instead of directly declaring in the C
file where it is called.
• All places that were calling COGL_OBJECT_DEFINE need to have the
cogl_is_whatever function declared so these have been added either
as a public function or in a private header.
• Some files that were not including the header containing their
function declarations have been fixed to do so.
• Any unused error quark functions have been removed. If we later want
them we should add them back one by one and add a declaration for
them in a header.
• _cogl_is_framebuffer has been renamed to cogl_is_framebuffer and
made a public function with a declaration in cogl-framebuffer.h
• Similarly for CoglOnscreen.
• cogl_vdraw_indexed_attributes is called
cogl_framebuffer_vdraw_indexed_attributes in the header. The
definition has been changed to match the header.
• cogl_index_buffer_allocate has been removed. This had no declaration
and I'm not sure what it's supposed to do.
• CoglJournal has been changed to use the internal CoglObject macro so
that it won't define an exported cogl_is_journal symbol.
• The _cogl_blah_pointer_from_handle functions have been removed.
CoglHandle isn't used much anymore anyway and in the few places
where it is used I think it's safe to just use the implicit cast
from void* to the right type.
• The test-utils.h header for the conformance tests explicitly
disables the -Wmissing-declaration option using a pragma because all
of the tests declare their main function without a header. Any
mistakes relating to missing declarations aren't really important
for the tests.
• cogl_quaternion_init_from_quaternion and init_from_matrix have been
given declarations in cogl-quaternion.h
Reviewed-by: Robert Bragg <robert@linux.intel.com>
The assert could use a 'default:' label but that would stop GCC from
giving a warning when a new enum value is added.
https://bugzilla.gnome.org/show_bug.cgi?id=671016
Reviewed-by: Robert Bragg <robert@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 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>
The _cogl_texture_driver_pixel_format_to_gl functions for OpenGL and
OpenGLES convert CoglPixelFormats into corresponding gl enums that can
be used to upload texture data. Previously we were only handling a few
specific formats but this patch updates the functions to handle all the
formats we know about. The functions now also switch() on the format so
that we will get build time warnings if we forget to handle new formats
in these functions.
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>
This adds COGL_PIPELINE_WRAP_MODE_MIRRORED_REPEAT enum so that mirrored
texture repeating can be used. This also adds support for emulating the
MIRRORED_REPEAT mode via the cogl-spans API so it can also be used with
meta textures such as sliced and atlas textures.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
Currently features are represented as bits in a 32bit mask so we
obviously can't have more than 32 features with that approach. The new
approach is to use the COGL_FLAGS_ macros which lets us handle bitmasks
without a size limit and we change the public api to accept individual
feature enums instead of a mask. This way there is no limit on the
number of features we can add to Cogl.
Instead of using cogl_features_available() there is a new
cogl_has_feature() function and for checking multiple features there is
cogl_has_features() which takes a zero terminated vararg list of
features.
In addition to being able to check for individual features this also
adds a way to query all the features currently available via
cogl_foreach_feature() which will call a callback for each feature.
Since the new functions take an explicit context pointer there is also
no longer any ambiguity over when users can first start to query
features.
Reviewed-by: Neil Roberts <neil@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 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>
Previously, _cogl_get_proc_address had a fallback to resolve the
symbol using g_module_open(NULL) to get the symbol from anywhere in
the address space. The EGL backend ends up using this on some drivers
because eglGetProcAddress isn't meant to return a pointer for core
functions. This causes problems if something in the process is linking
against a different GL library, for example Cairo may be linking
against libGL itself. In this case it may end up resolving symbols
from the GL library even if GLES is being used.
This patch removes the fallback. The EGL version now has its own
fallback instead which passes the existing libgl_module from the
renderer to g_module_symbol so that it should only get symbols from
that library or its dependency chain. The GLX and WGL winsys only call
glXGetProcAddress and wglGetProcAddress. The stub winsys does however
continue using the global symbol lookup.
The internal _cogl_get_proc_address function has been renamed to
_cogl_renderer_get_proc_address because it needs a connected renderer
to work so it could be considered to be a renderer method. The pointer
to the renderer is passed down to the winsys backends so that it can
use the data attached to the renderer to get the module pointers.
https://bugzilla.gnome.org/show_bug.cgi?id=655412
Reviewed-by: Robert Bragg <robert@linux.intel.com>
When we moved all the GL function pointers to be part of CoglContext in
commit dae02a99a5 we made a mistake and started to OR in the private
COGL_PRIVATE_FEATURE_TEXTURE_2D_FROM_EGL_IMAGE feature flag into the non
private flags which would mean cogl would think the GL_OES_EGL_image
extension wasn't supported.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
The _cogl_context_check_gl_version function is meant to be called once
Cogl has a GL context so that it can check whether the context found
is supported by Cogl. However, only the stub winsys was calling this
and it was doing it before Cogl had a chance to retrieve the function
pointer for glString so it would just crash. This patch combines the
two functions into one so that _cogl_context_update_features returns a
gboolean and a GError. Then it can just check the context itself.
https://bugzilla.gnome.org/show_bug.cgi?id=654440
Reviewed-by: Robert Bragg <robert@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
The texture driver functions are now accessed through a vtable pointed
to by a struct in the CoglContext so that eventually it will be
possible to compile both the GL and GLES texture drivers into a single
binary and then select between them at runtime.
Since the GL function pointers have move to the root of CoglContext,
the driver specific data for GLES became empty and the GL data had
only one varible which apparently nothing was using. It's therefore
convenient to remove the private driver data to make it easier to have
a build of Cogl which enables both GL and GLES support. If we ever
need driver private data later we might want to use
cogl_object_set_user_data instead.
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.
Instead of storing all of the feature function pointers in the driver
specific data of the CoglContext they are now all stored directly in
CoglContext. There is a single header containing the description of
the functions which gets included by cogl-context.h. There is a single
function in cogl-feature-private.c to check for all of these
functions.
The name of the function pointer variables have been changed from
ctx->drv.pf_glWhatever to just ctx->glWhatever.
The feature flags that get set when an extension is available are now
separated from the table of extensions. This is necessary because
different extensions can mean different things on GLES and GL. For
example, having access to glMapBuffer implies read and write support
on GL but only write support on GLES. The flags are instead set in the
driver specific init function by checking whether the function
pointers were successfully resolved.
_cogl_feature_check has been changed to assume the feature is
supported if any of the listed extensions are available instead of
requiring all of them. This makes it more convenient to specify
alternate names for the extension. Nothing else had previously listed
more than one name for an extension so this shouldn't cause any
problems.
The function declarations for the GL_OES_EGL_image extension were
using the wrong name for the GLeglImageOES type so it was getting
build errors when compiling for GLES.
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.
Instead of simply extending the cogl_pipeline_ namespace to add api for
controlling the depth testing state we now break the api out. This adds
a CoglDepthState type that can be stack allocated. The members of the
structure are private but we have the following API to setup the state:
cogl_depth_state_init
cogl_depth_state_set_test_enabled
cogl_depth_state_get_test_enabled
cogl_depth_state_set_test_function
cogl_depth_state_get_test_function
cogl_depth_state_set_writing_enabled
cogl_depth_state_get_writing_enabled
cogl_depth_state_set_range
cogl_depth_state_get_range
This removes the following experimental API which is now superseded:
cogl_material_set_depth_test_enabled
cogl_material_get_depth_test_enabled
cogl_material_set_depth_test_function
cogl_material_get_depth_test_function
cogl_material_set_depth_writing_enabled
cogl_material_get_depth_writing_enabled
cogl_material_set_depth_range
cogl_material_get_depth_range
Once a CoglDepthState structure is setup it can be set on a pipeline
using cogl_pipeline_set_depth_state().
Older drivers for PowerVR SGX hardware have the vendor-specific
GL_IMG_TEXTURE_NPOT extension instead of the
functionally-equivalent GL_OES_TEXTURE_NPOT extension.
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.
This moves the functionality of _cogl_create_context_driver from
driver/{gl,gles}/cogl-context-driver-{gl,gles}.c into
driver/{gl,gles}/cogl-{gl,gles}.c as a static function called
initialize_context_driver.
cogl-context-driver-{gl,gles}.[ch] have now been removed.
This extension is the GLES equivalent of the GL_EXT_framebuffer_blit
extension except that it has some extra restrictions. We need to check
for some extension that provides glBlitFramebuffer so that we can
unconditionally use ctx->drv.pf_glBlitFramebuffer in both GL and GLES
code. Even with the restrictions, the extension provides enough
features for what Cogl needs.
GLES has an extension called GL_OES_mapbuffer to support mapping
buffer objects but only for writing. Cogl now has two new feature
flags to advertise whether mapping for reading and writing is
supported. Under OpenGL, these features are always set if the VBO
extension is advertised and under GLES only the write flag is set if
the GL_OES_mapbuffer extension is advertised.
When uploading data for GLES we need to deal with cases where the
rowstride is too large to be described only by GL_UNPACK_ALIGNMENT
because there is no GL_UNPACK_ROW_LENGTH. Previously for the
sub-region uploading code it would always copy the bitmap and for the
code to upload the whole image it would copy the bitmap unless the
rowstride == bpp*width. Neither paths took into account that we don't
need to copy if the rowstride is just an alignment of bpp*width. This
moves the bitmap copying code to a separate function that is used by
both upload methods. It only copies the bitmap if the rowstride is not
just an alignment of bpp*width.
http://bugzilla.clutter-project.org/show_bug.cgi?id=2491
The GLES2 wrapper is no longer needed because the shader generation is
done within the GLSL fragend and vertend and any functions that are
different for GLES2 are now guarded by #ifdefs.
Once the GLES2 wrapper is removed we won't be able to upload the
matrices with the fixed function API any more. The fixed function API
gives a global state for setting the matrix but if a custom shader
uniform is used for the matrices then the state is per
program. _cogl_matrix_stack_flush_to_gl is called in a few places and
it is assumed the current pipeline doesn't need to be flushed before
it is called. To allow these semantics to continue to work, on GLES2
the matrix flush now just stores a reference to the matrix stack in
the CoglContext. A pre_paint virtual is added to the progend which is
called whenever a pipeline is flushed, even if the same pipeline was
flushed already. This gives the GLSL progend a chance to upload the
matrices to the uniforms. The combined modelview/projection matrix is
only calculated if it is used. The generated programs end up never
using the modelview or projection matrix so it usually only has to
upload the combined matrix. When a matrix stack is flushed a reference
is taked to it by the pipeline progend and the age is stored so that
if the same state is used with the same program again then we don't
need to reupload the uniform.
