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>
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>
This adds an internal function to get the type of the underlying
hardware texture for any CoglTexture. It can return one of three
values to represent 2D textures, 3D textures or rectangle textures.
The idea is that this can be used as a replacement for
cogl_texture_get_gl_texture when only the target is required to make
it a bit less GL-centric. The implementation adds a new virtual
function which all of the texture backends now implement.
The enum is in a public header because a later patch will want to use
it from the CoglPipeline API. We may want to consider making the
function public too later.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
Since we've had several developers from admirable projects say they
would like to use Cogl but would really prefer not to pull in
gobject,gmodule and glib as extra dependencies we are investigating if
we can get to the point where glib is only an optional dependency.
Actually we feel like we only make minimal use of glib anyway, so it may
well be quite straightforward to achieve this.
This adds a --disable-glib configure option that can be used to disable
features that depend on glib.
Actually --disable-glib doesn't strictly disable glib at this point
because it's more helpful if cogl continues to build as we make
incremental progress towards this.
The first use of glib that this patch tackles is the use of
g_return_val_if_fail and g_return_if_fail which have been replaced with
equivalent _COGL_RETURN_VAL_IF_FAIL and _COGL_RETURN_IF_FAIL macros.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
CoglMetaTexture is an interface for dealing with high level textures
that may be comprised of one or more low-level textures internally. The
interface allows the development of primitive drawing APIs that can draw
with high-level textures (such as atlas textures) even though the
GPU doesn't natively understand these texture types.
There is currently just one function that's part of this interface:
cogl_meta_texture_foreach_in_region() which allows an application to
resolve the internal, low-level textures of a high-level texture.
cogl_rectangle() uses this API for example so that it can easily emulate
the _REPEAT wrap mode for textures that the hardware can't natively
handle repeating of.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
Instead of using integers to represent spans we now use floats instead.
This means we are no longer forced to iterate using non-normalized
coordinates so we should hopefully be able to avoid numerous redundant
unnormalize/normalize steps when using the spans api.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
Since we can assume that all slices are CoglTexture2D textures we don't
need to chain on our implementation of _foreach_sub_texture_in_region
by calling _cogl_texture_foreach_sub_texture_in_region() for each slice.
We now simply determine the normalized virtual coordinates for the
current span inline and call the given callback inline too.
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>
To save users of the api having to manually check if each iterated span
intersects the region of interest we now guarantee that any span
iterated implicitly intersects the region of interest.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This make the CoglTexture2DSliced type public and adds
cogl_texture_2d_sliced_new_with_size() as an experimental API that can
be used to construct a sliced texture without any initial data.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
As part of the on going, incremental effort to purge the non type safe
CoglHandle type from the Cogl API this patch tackles most of the
CoglHandle uses relating to textures.
We'd postponed making this change for quite a while because we wanted to
have a clearer understanding of how we wanted to evolve the texture APIs
towards Cogl 2.0 before exposing type safety here which would be
difficult to change later since it would imply breaking APIs.
The basic idea that we are steering towards now is that CoglTexture
can be considered to be the most primitive interface we have for any
object representing a texture. The texture interface would provide
roughly these methods:
cogl_texture_get_width
cogl_texture_get_height
cogl_texture_can_repeat
cogl_texture_can_mipmap
cogl_texture_generate_mipmap;
cogl_texture_get_format
cogl_texture_set_region
cogl_texture_get_region
Besides the texture interface we will then start to expose types
corresponding to specific texture types: CoglTexture2D,
CoglTexture3D, CoglTexture2DSliced, CoglSubTexture, CoglAtlasTexture and
CoglTexturePixmapX11.
We will then also expose an interface for the high-level texture types
we have (such as CoglTexture2DSlice, CoglSubTexture and
CoglAtlasTexture) called CoglMetaTexture. CoglMetaTexture is an
additional interface that lets you iterate a virtual region of a meta
texture and get mappings of primitive textures to sub-regions of that
virtual region. Internally we already have this kind of abstraction for
dealing with sliced texture, sub-textures and atlas textures in a
consistent way, so this will just make that abstraction public. The aim
here is to clarify that there is a difference between primitive textures
(CoglTexture2D/3D) and some of the other high-level textures, and also
enable developers to implement primitives that can support meta textures
since they can only be used with the cogl_rectangle API currently.
The thing that's not so clean-cut with this are the texture constructors
we have currently; such as cogl_texture_new_from_file which no longer
make sense when CoglTexture is considered to be an interface. These
will basically just become convenient factory functions and it's just a
bit unusual that they are within the cogl_texture namespace. It's worth
noting here that all the texture type APIs will also have their own type
specific constructors so these functions will only be used for the
convenience of being able to create a texture without really wanting to
know the details of what type of texture you need. Longer term for 2.0
we may come up with replacement names for these factory functions or the
other thing we are considering is designing some asynchronous factory
functions instead since it's so often detrimental to application
performance to be blocked waiting for a texture to be uploaded to the
GPU.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
Instead of calling _cogl_texutre_prepare_for_upload in
cogl_texture_set_region_from_bitmap the call is now deferred to the
implementation of the virtual for set_region. This is needed if the
texture backend is using a different format for the actual GL texture
than what is reported by cogl_texture_get_format. This happens for
example with atlas textures which report the original internal format
specified when the texture was created but actually always store the
data in an RGBA texture.
Also when creating an atlas texture from a bitmap it was preparing the
bitmap to be uploaded to the original format instead of the format of
the actual texture used for the atlas. Then it was using
cogl_texture_set_region_from_bitmap to upload the 5 pieces to make the
copies of the edge pixels. This would end up converting the image to
the actual format 5 times. The atlas textures have now been changed to
prepare the bitmap for the right format.
https://bugzilla.gnome.org/show_bug.cgi?id=657840
Reviewed-by: Robert Bragg <robert@linux.intel.com>
This exposes 2 experimental functions that make it possible to upload a
subregion of a texture from a CoglBuffer by first wrapping the buffer as
a CoglBitmap and then allowing uploading of a subregion from a
CoglBitmap. The new functions are:
cogl_bitmap_new_from_buffer() and
cogl_texture_set_region_from_bitmap()
Actually for now we are exporting this API for practical reasons since
we already had this API internally and it enables a specific feature
that was requested, but it is worth nothing that it's quite likely we
will replace these with functions that don't involve the CoglBitmap API
at some point.
For reference: The CoglBitmap API was actually removed from the 2.0
experimental API reference manual some time ago because the hope was
that we'd come up with a neater replacement. It doesn't seem entirely
clear what the scope of the CoglBitmap api is so it has became a bit of
a dumping ground. CoglBitmap is used for image loading, as a means to
represent the layout of image data and also internally deals with format
conversions.
Note: Because we are avoiding including CoglBitmap as part of the 2.0
API these functions aren't currently included in the 2.0 reference
manual.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
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.
This exposes a CoglTexture2D typedef and adds the following experimental
API:
cogl_is_texture_2d
cogl_texture_2d_new_with_size
cogl_texture_2d_new_from_data
cogl_texture_2d_new_from_foreign
Since this is experimental API you need to define
COGL_ENABLE_EXPERIMENTAL_API before including cogl.h.
Note: With these new entrypoints we now expect a CoglContext pointer to
be passed in, instead of assuming there is a default context. The aim is
that for Cogl 2.0 we won't have a default context so this is a step in
that direction.
Instead of having a single journal per context, we now have a
CoglJournal object for each CoglFramebuffer. This means we now don't
have to flush the journal when switching/pushing/popping between
different framebuffers so for example a Clutter scene that involves some
ClutterEffect actors that transiently redirect to an FBO can still be
batched.
This also allows us to track state in the journal that relates to the
current frame of its associated framebuffer which we'll need for our
optimization for using the CPU to handle reading a single pixel back
from a framebuffer when we know the whole scene is currently comprised
of simple rectangles in a journal.
* cogl_texture_get_data() is converted to use
_cogl_texture_foreach_sub_texture_in_region() to iterate
through the underlying textures.
* When we need to read only a portion of the underlying
texture, we set up a FBO and use _cogl_read_pixels()
to read the portion we need. This is enormously more
efficient for reading a small portion of a large atlas
texture.
* The CoglAtlasTexture, CoglSubTexture, and CoglTexture2dSliced
implementation of get_texture() are removed.
http://bugzilla.clutter-project.org/show_bug.cgi?id=2414
There's no longer any need to use the GL handle in the callback for
_cogl_texture_foreach_sub_texture_in_region because it can now work in
terms of primitive cogl textures so it has now been removed. This
would be helpful if we ever want to make the foreach function public
so that apps could implement their own primitives using sliced
textures.
The cogl_texture_foreach_sub_texture_in_region virtual for the sliced
texture backend was previously passing the CoglHandle of the sliced
texture to the callback. Since d5634e37 the slice texture backend now
works in terms of 2D textures so it's possible to pass the underlying
slice texture as a handle too. This makes all of the foreach callbacks
consistent in that they pass a CoglHandle of the primitive texture
type that matches the GL handle.
When converting the virtual coordinates of the underlying texture for
a slice to virtual coordinates for the whole texture it was using the
size and offset of the intersection as the size of the child
texture. This would be incorrect if the texture contains waste or the
texture coordinates are not the default. Instead the sliced foreach
function now passes the CoglSpan to the callback instead of the
intersection.
http://bugzilla.clutter-project.org/show_bug.cgi?id=2398
This applies an API naming change that's been deliberated over for a
while now which is to rename CoglMaterial to CoglPipeline.
For now the new pipeline API is marked as experimental and public
headers continue to talk about materials not pipelines. The CoglMaterial
API is now maintained in terms of the cogl_pipeline API internally.
Currently this API is targeting Cogl 2.0 so we will have time to
integrate it properly with other upcoming Cogl 2.0 work.
The basic reasons for the rename are:
- That the term "material" implies to many people that they are
constrained to fragment processing; perhaps as some kind of high-level
texture abstraction.
- In Clutter they get exposed by ClutterTexture actors which may be
re-inforcing this misconception.
- When comparing how other frameworks use the term material, a material
sometimes describes a multi-pass fragment processing technique which
isn't the case in Cogl.
- In code, "CoglPipeline" will hopefully be a much more self documenting
summary of what these objects represent; a full GPU pipeline
configuration including, for example, vertex processing, fragment
processing and blending.
- When considering the API documentation story, at some point we need a
document introducing developers to how the "GPU pipeline" works so it
should become intuitive that CoglPipeline maps back to that
description of the GPU pipeline.
- This is consistent in terminology and concept to OpenGL 4's new
pipeline object which is a container for program objects.
Note: The cogl-material.[ch] files have been renamed to
cogl-material-compat.[ch] because otherwise git doesn't seem to treat
the change as a moving the old cogl-material.c->cogl-pipeline.c and so
we loose all our git-blame history.
Instead of directly manipulating GL textures itself,
CoglTexture2DSliced now works in terms of CoglHandles. It creates the
texture slices using cogl_texture_new_with_size which should always
end up creating a CoglTexture2D because the size should fit. This
allows us to avoid replicating some code such as the first pixel
mipmap tracking and it better enforces the separation that each
texture backend is the only place that contains code dealing with each
texture target.
When picking a size for the last slice in a texture, Cogl would always
pick the biggest power of two size that doesn't create too much
waste and is less than or equal to the previous slice size. However
this can end up creating a texture that is bigger than needed if there
is a smaller power of two.
For example, if the maximum waste is 127 (the current default) and we
try to create a texture that is 257 pixels wide it will decide that
the next power of two (512) is too much waste (255) so it will create
the first slice at 256 pixels wide. Then we only have 1 pixel left to
allocate but Cogl would pick the next smaller size that has a small
enough waste which is 128. But of course 1 is already a power of two
so that's redundantly oversized by 127.
This patch fixes it so that whenever it finds a size that would be big
enough, instead of using exactly that it picks the next power of two
up from the size we need to fill.
http://bugzilla.clutter-project.org/show_bug.cgi?id=2355
Both of the cogl_texture_2d_sliced_new functions called the
slices_create function which creates the underlying GL
textures. However this was also called by init_base so the textures
would end up being created twice. This would make it leak the GL
textures and the arrays which point to them.
cogl_util_next_p2 is declared in cogl-util.h which is a private header
so it shouldn't be possible for an application to use it. It's
probably not a function we'd like to export from Cogl so it seems
better to keep it private. This patch renames it to _cogl_util_next_p2
so that it won't be exported from the shared library.
The documentation for the function is also slightly wrong because it
stated that the function returned the next power greater than
'a'. However the code would actually return 'a' if it's already a
power of two. I think the actual behaviour is more useful so this
patch changes the documentation rather than the code.
The CoglBitmap struct is now only defined within cogl-bitmap.c so that
all of its members can now only be accessed with accessor
functions. To get to the data pointer for the bitmap image you must
first call _cogl_bitmap_map and later call _cogl_bitmap_unmap. The map
function takes the same arguments as cogl_pixel_array_map so that
eventually we can make a bitmap optionally internally divert to a
pixel array.
There is a _cogl_bitmap_new_from_data function which constructs a new
bitmap object and takes ownership of the data pointer. The function
gets passed a destroy callback which gets called when the bitmap is
freed. This is similar to how gdk_pixbuf_new_from_data
works. Alternatively NULL can be passed for the destroy function which
means that the caller will manage the life of the pointer (but must
guarantee that it stays alive at least until the bitmap is
freed). This mechanism is used instead of the old approach of creating
a CoglBitmap struct on the stack and manually filling in the
members. It could also later be used to create a CoglBitmap that owns
a GdkPixbuf ref so that we don't necessarily have to copy the
GdkPixbuf data when converting to a bitmap.
There is also _cogl_bitmap_new_shared. This creates a bitmap using a
reference to another CoglBitmap for the data. This is a bit of a hack
but it is needed by the atlas texture backend which wants to divert
the set_region virtual to another texture but it needs to override the
format of the bitmap to ignore the premult flag.
The 'format' member of CoglTexture2DSliced is returned by
cogl_texture_get_format. All of the other backends return the internal
format of the GL texture in this case. However the sliced backend was
returning the format of the image data used to create the texture. It
doesn't make any sense to retain this information because it doesn't
necessarily indicate the format of the actual texture. This patch
changes it to store the internal format instead.
In general cogl-material.c has become far to large to manage in one
source file. As one of the ways to try and break it down this patch
starts to move some of lower level texture unit state management out
into cogl-material-opengl.c. The naming is such because the plan is to
follow up and migrate the very GL specific state flushing code into the
same file.
Using 'r' to name the third component is problematic because that is
commonly used to represent the red component of a vector representing
a color. Under GLSL this is awkward because the texture swizzling for
a vector uses a single letter for each component and the names for
colors, textures and positions are synonymous. GLSL works around this
by naming the components of the texture s, t, p and q. Cogl already
effectively already exposes this naming because it exposes GLSL so it
makes sense to use that naming consistently. Another alternative could
be u, v and w. This is what Blender and Direct3D use. However the w
component conflicts with the w component of a position vertex.
This adds a COGL_OBJECT_INTERNAL_DEFINE macro and friends that are the
same as COGL_OBJECT_DEFINE except that they prefix the cogl_is_*
function with an underscore so that it doesn't get exported in the
shared library.
There was a lot of common code that was copied to all of the backends
to convert the data to a suitable format and wrap it into a CoglBitmap
so that it can be passed to _cogl_texture_driver_upload_subregion_to_gl.
This patch moves the common code to cogl-texture.c so that the virtual
just takes a CoglBitmap that is already in the right format.
Previously cogl_texture_get_data would pretty much directly pass on to
the get_data texture virtual function. This ended up with a lot of
common code that was copied to all of the backends. For example, the
method is expected to return the required data size if the data
pointer is NULL and to calculate its own rowstride if the rowstride is
0. Also it needs to convert the downloaded data if GL can't support
that format directly.
This patch moves the common code to cogl-texture.c so the virtual is
always called with a format that can be downloaded directly by GL and
with a valid rowstride. If the download fails then the virtual can
return FALSE in which case cogl-texture will use the draw and read
fallback.
Instead of the ensure_mipmaps virtual that is only called whenever the
texture is about to be rendered with a min filter that needs the
mipmap, there is now a pre_paint virtual that is always called when
the texture is about to be painted in any way. It has a flags
parameter which is used to specify whether the mipmap will be needed.
This is useful for CoglTexturePixmapX11 because it needs to do stuff
before painting that is unrelated to mipmapping.
Instead of having a hardcoded series of if-statements in
cogl_is_texture to determine which types should appear as texture
subclasses, they are now stored in a GSList attached to the Cogl
context. The list is amended to using a new cogl_texture_register_type
function. There is a convenience macro called COGL_TEXTURE_DEFINE
which uses COGL_HANDLE_DEFINE_WITH_CODE to register the texture type
when the _get_type() function is first called.
For sliced 2D textures, _cogl_texture_2d_sliced_get_data() uses the
bitmap width, instead of the rowstride, when memcpy()ing into the
dest buffer.
Signed-off-by: Robert Bragg <robert@linux.intel.com>
This adds a _cogl_bind_gl_texture_transient function that should be used
instead of glBindTexture so we can have a consistent cache of the
textures bound to each texture unit so we can avoid some redundant
binding.
While this is totally fine (0 in the pointer context will be converted
in the right internal NULL representation, which could be a value with
some bits to 1), I believe it's clearer to use NULL in the pointer
context.
It seems that, in most case, it's more an overlook than a deliberate
choice to use FALSE/0 as NULL, eg. copying a _COGL_GET_CONTEXT (ctx, 0)
or a g_return_val_if_fail (cond, 0) from a function returning a
gboolean.
When uploading texture data the cogl-texture-2d-sliced backend was
using _cogl_texture_prepare_for_upload to create a bitmap suitable for
upload but then it was using the original bitmap instead of the new
bitmap for the data. This was causing any format conversions performed
by cogl_texture_prepare_for_upload to be ignored.
http://bugzilla.openedhand.com/show_bug.cgi?id=2059
Previously, Cogl's texture coordinate system was effectively always
GL_REPEAT so that if an application specifies coordinates outside the
range 0→1 it would get repeated copies of the texture. It would
however change the mode to GL_CLAMP_TO_EDGE if all of the coordinates
are in the range 0→1 so that in the common case that the whole texture
is being drawn with linear filtering it will not blend in edge pixels
from the opposite sides.
This patch adds the option for applications to change the wrap mode
per layer. There are now three wrap modes: 'repeat', 'clamp-to-edge'
and 'automatic'. The automatic map mode is the default and it
implements the previous behaviour. The wrap mode can be changed for
the s and t coordinates independently. I've tried to make the
internals support setting the r coordinate but as we don't support 3D
textures yet I haven't exposed any public API for it.
The texture backends still have a set_wrap_mode virtual but this value
is intended to be transitory and it will be changed whenever the
material is flushed (although the backends are expected to cache it so
that it won't use too many GL calls). In my understanding this value
was always meant to be transitory and all primitives were meant to set
the value before drawing. However there were comments suggesting that
this is not the expected behaviour. In particular the vertex buffer
drawing code never set a wrap mode so it would end up with whatever
the texture was previously used for. These issues are now fixed
because the material will always set the wrap modes.
There is code to manually implement clamp-to-edge for textures that
can't be hardware repeated. However this doesn't fully work because it
relies on being able to draw the stretched parts using quads with the
same values for tx1 and tx2. The texture iteration code doesn't
support this so it breaks. This is a separate bug and it isn't
trivially solved.
When flushing a material there are now extra options to set wrap mode
overrides. The overrides are an array of values for each layer that
specifies an override for the s, t or r coordinates. The primitives
use this to implement the automatic wrap mode. cogl_polygon also uses
it to set GL_CLAMP_TO_BORDER mode for its trick to render sliced
textures. Although this code has been added it looks like the sliced
trick has been broken for a while and I haven't attempted to fix it
here.
I've added a constant to represent the maximum number of layers that a
material supports so that I can size the overrides array. I've set it
to 32 because as far as I can tell we have that limit imposed anyway
because the other flush options use a guint32 to store a flag about
each layer. The overrides array ends up adding 32 bytes to each flush
options struct which may be a concern.
http://bugzilla.openedhand.com/show_bug.cgi?id=2063
GL supports setting different wrap modes for the s, t and r
coordinates so we should design the backend interface to support that
also. The r coordinate is not currently used by any of the backends
but we might as well have it to make life easier if we ever add
support for 3D textures.
http://bugzilla.openedhand.com/show_bug.cgi?id=2063
Add a return result from CoglTexture.transform_quad_coords_to_gl(),
so that we can properly determine the nature of repeats in
the face of GL_TEXTURE_RECTANGLE_ARB, where the returned
coordinates are not normalized.
The comment "We also work out whether any of the texture
coordinates are outside the range [0.0,1.0]. We need to do
this after calling transform_coords_to_gl in case the texture
backend is munging the coordinates (such as in the sub texture
backend)." is disregarded and removed, since it's actually
the virtual coordinates that determine whether we repeat,
not the GL coordinates.
Warnings about disregarded layers are used in all cases where
applicable, including for subtextures.
http://bugzilla.openedhand.com/show_bug.cgi?id=2016
Signed-off-by: Neil Roberts <neil@linux.intel.com>
In _cogl_texture_2d_sliced_foreach_sub_texture_in_region(), don't
assert that the target is GL_TEXTURE_2D; instead conditionalize
normalization on the target.
http://bugzilla.openedhand.com/show_bug.cgi?id=2015
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
