Add support for per-vertex point sizes

This adds a new function to enable per-vertex point size on a
pipeline. This can be set with
cogl_pipeline_set_per_vertex_point_size(). Once enabled the point size
can be set either by drawing with an attribute named
'cogl_point_size_in' or by writing to the 'cogl_point_size_out'
builtin from a snippet.

There is a feature flag which must be checked for before using
per-vertex point sizes. This will only be set on GL >= 2.0 or on GLES
2.0. GL will only let you set a per-vertex point size from GLSL by
writing to gl_PointSize. This is only available in GL2 and not in the
older GLSL extensions.

The per-vertex point size has its own pipeline state flag so that it
can be part of the state that affects vertex shader generation.

Having to enable the per vertex point size with a separate function is
a bit awkward. Ideally it would work like the color attribute where
you can just set it for every vertex in your primitive with
cogl_pipeline_set_color or set it per-vertex by just using the
attribute. This is harder to get working with the point size because
we need to generate a different vertex shader depending on what
attributes are bound. I think if we wanted to make this work
transparently we would still want to internally have a pipeline
property describing whether the shader was generated with per-vertex
support so that it would work with the shader cache correctly.
Potentially we could make the per-vertex property internal and
automatically make a weak pipeline whenever the attribute is bound.
However we would then also need to automatically detect when an
application is writing to cogl_point_size_out from a snippet.

Reviewed-by: Robert Bragg <robert@linux.intel.com>
Separate out CoglPath api into sub-library

This splits out the cogl_path_ api into a separate cogl-path sub-library
like cogl-pango and cogl-gst. This enables developers to build Cogl with
this sub-library disabled if they don't need it which can be useful when
its important to keep the size of an application and its dependencies
down to a minimum. The functions cogl_framebuffer_{fill,stroke}_path
have been renamed to cogl_path_{fill,stroke}.

There were a few places in core cogl and cogl-gst that referenced the
CoglPath api and these have been decoupled by using the CoglPrimitive
api instead. In the case of cogl_framebuffer_push_path_clip() the core
clip stack no longer accepts path clips directly but it's now possible
to get a CoglPrimitive for the fill of a path and so the implementation
of cogl_framebuffer_push_path_clip() now lives in cogl-path and works as
a shim that first gets a CoglPrimitive and uses
cogl_framebuffer_push_primitive_clip instead.

We may want to consider renaming cogl_framebuffer_push_path_clip to
put it in the cogl_path_ namespace.

Reviewed-by: Neil Roberts <neil@linux.intel.com>
generalize driver description and selection

This adds a table of driver descriptions to cogl-renderer.c in order of
preference and when choosing what driver to use we now iterate the table
instead of repeating boilerplate checks. For handling the "default driver"
that can be specified when building cogl and handling driver overrides
there is a foreach_driver_description() that will make sure to iterate
the default driver first or if an override has been set then nothing but
the override will be considered.

This patch introduces some driver flags that let us broadly categorize
what kind of GL driver we are currently running on. Since there are
numerous OpenGL apis with different broad feature sets and new apis
may be introduced in the future by Khronos then we should tend to
avoid using the driver id to do runtime feature checking. These flags
provide a more stable quantity for broad feature checks.

Reviewed-by: Neil Roberts <neil@linux.intel.com>
Adds "webgl" driver

This adds a COGL_DRIVER_WEBGL enum and a new driver description for
webgl in cogl-renderer.c. This also adds a COGL_DRIVER_FLAG_OPENGL_WEB
driver flag and a HAVE_COGL_WEBGL define which we can start to use to
handle special cases where webgl differs from gles2.

Reviewed-by: Neil Roberts <neil@linux.intel.com>
webgl: use DEPTH_STENCIL_ATTACHMENT

WebGL doesn't allow you to separately attach buffers to the
STENCIL_ATTACHMENT and DEPTH_ATTACHMENT framebuffer attachment points
and instead requires you to use the DEPTH_STENCIL_ATTACHMENT whenever
you want a depth and stencil buffer.

Reviewed-by: Neil Roberts <neil@linux.intel.com>
Use GModule instead of libdl to load unit test symbols

Previously the unit tests were using libdl without directly linking to
it. It looks like this ends up working because one of Cogl's
dependencies ends up pulling adding -ldl via libtool. However in some
configurations it looks like this wasn't happening.

To avoid this problem we can just use GModule to resolve the symbols.
g_module_open is documented to return a handle to the ‘main program’
when NULL is passed as the filename and looking at the code it seems
that this ends up using RTLD_DEFAULT so it will have the same effect.

The in-tree copy of glib already has the code for gmodule so this
shouldn't cause problems for --disable-glib.

Reviewed-by: Robert Bragg <robert@linux.intel.com>
renderer: assert CoglPrivateFeatureFlags fit in 32 bits

This updates the static assertion in cogl-renderer.c to only check that
the flags will fit in 32 bits instead of asserting the type has the same
size as an unsigned long.
cogl-path: Fix the uninitialised path->fill_primitive

This was not being uninitialised so it was sometimes causing a crash
when it tried to unref an invalid pointer. This was causing test-path
to fail for me.

Reviewed-by: Robert Bragg <robert@linux.intel.com>
Add test that Cogl doesn't crash when freeing unallocated texture

It looks like Cogl doesn't currently clean up an unallocated atlas
texture properly so if it fails to allocate it. It will then crash
when it is freed. This adds a conformance test to verify that all of
the various texture types can be freed without allocating them.

Reviewed-by: Robert Bragg <robert@linux.intel.com>
Fix freeing an atlas texture that hasn't been allocated

The free function for atlas textures was previously always assuming
that there will be a valid sub_texture pointer but this might not be
the case if the texture was never successfully allocated. This was
causing Cogl to crash if the application tries to make a texture that
can not fit in the atlas using the automagic texture API.

Reviewed-by: Robert Bragg <robert@linux.intel.com>
Use a GList instead of a BSD list for CoglPipelineSnippetList

Previously CoglPipelineSnippetList was using the BSD embedded list
type with a mini struct to combine the list node with a pointer to the
snippet. This is effectively equivalent to just using a GList so we
might as well do that. This will help if we eventually want to get rid
of cogl-queue.h

Reviewed-by: Robert Bragg <robert@linux.intel.com>
Use the Wayland embedded linked list implementation instead of BSD's

This removes cogl-queue.h and adds a copy of Wayland's embedded list
implementation. The advantage of the Wayland model is that it is much
simpler and so it is easier to follow. It also doesn't require
defining a typedef for every list type.

The downside is that there is only one list type which is a
doubly-linked list where the head has a pointer to both the beginning
and the end. The BSD implementation has many more combinations some of
which we were taking advantage of to reduce the size of critical
structs where we didn't need a pointer to the end of the list.

The corresponding changes to uses of cogl-queue.h are:

• COGL_STAILQ_* was used for onscreen the list of events and dirty
  notifications. This makes the size of the CoglContext grow by one
  pointer.

• COGL_TAILQ_* was used for fences.

• COGL_LIST_* for CoglClosures. In this case the list head now has an
  extra pointer which means CoglOnscreen will grow by the size of
  three pointers, but this doesn't seem like a particularly important
  struct to optimise for size anyway.

• COGL_LIST_* was used for the list of foreign GLES2 offscreens.

• COGL_TAILQ_* was used for the list of sub stacks in a
  CoglMemoryStack.

• COGL_LIST_* was used to track the list of layers that haven't had
  code generated yet while generating a fragment shader for a
  pipeline.

• COGL_LIST_* was used to track the pipeline hierarchy in CoglNode.

The last part is a bit more controversial because it increases the
size of CoglPipeline and CoglPipelineLayer by one pointer in order to
have the redundant tail pointer for the list head. Normally we try to
be very careful about the size of the CoglPipeline struct. Because
CoglPipeline is slice-allocated, this effectively ends up adding two
pointers to the size because GSlice rounds up to the size of two
pointers.

Reviewed-by: Robert Bragg <robert@linux.intel.com>
Don't handle the out-of-memory error specially for auto-textures

Previously when trying the three different texture types to create an
automagic texture it would handle the out-of-memory error specially
and bypass trying the remaining texture types. Presumably the idea is
that out-of-memory is a serious error and it can't be recovered from.
However, in the case of atlas textures, this error will be thrown if
the texture is too large to fit into an atlas. In that case it makes
sense to try another texture type so that it can fallback to using a
sliced texture. I think conceptually each different texture type will
have different memory requirements so it seems reasonable to try the
others if there is not enough memory for one of them.

This was causing cogl_texture_new_from_data to break when loading very
large textures because it wouldn't end up slicing them.

Reviewed-by: Robert Bragg <robert@linux.intel.com>
display: add _set_onscreen_template() api

Currently it's only possible to set an onscreen template on a
CoglDisplay by passing a template to cogl_display_new(). For
applications that want to deal with fallbacks then they may want to
replace the onscreen template so this adds a
cogl_display_set_onscreen_template() function.

Reviewed-by: Neil Roberts <neil@linux.intel.com>
Removes the CoglSwapChain api

The CoglSwapChain api made initializing a context more awkward than it
ought to be in the relatively common case where you want onscreen
framebuffers to have an alpha channel.

The api let you specify an explicit swap-chain length and also request
that the swap chain buffers should have an alpha component and then the
a CoglSwapChain could be used to construct a CoglOnscreenTemplate

This removes the CoglSwapChain object and apis and adds a
cogl_onscreen_template_set_has_alpha() api instead. Since we can't
normally control exactly how long the swap chain is even if we have api
to request a length this patch doesn't replace that capability.

One thing to note here is that this removes the ability to request a
single buffered CoglOnscreen framebuffer but since we have never had a
use case for that and have not generally considered the implications of
supporting single buffered rendering in Cogl's design it is probably for
the best not to imply that it's supported.

Reviewed-by: Neil Roberts <neil@linux.intel.com>