We've started seeing cases where we want to allocate lots of one-shot
primitives per-frame and the cost of allocating primitives becomes
important in this case since it can start being noticeable in profiles.
The main cost for allocating primitives was the GArray allocation
and appending the attributes to the array. This updates the code to
simply over allocate the primitive storage so we can embed the list
of attributes directly in that allocation.
If the user later sets new attributes and there isn't enough embedded
space then a separate slice allocation for the new attributes is made
but still this should be far less costly than using a GArray as before.
Most of the time we would expect when setting new attributes there will
still be the same number of attributes, so the embedded space can simple
be reused.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This is part of a broader cleanup of some of the experimental Cogl API.
One of the reasons for this particular rename is to switch away from
using the term "Array" which implies a regular, indexable layout which
isn't the case. We also want to have a strongly implied relationship
between CoglAttributes and CoglAttributeBuffers.
This adds a way to mark that a primitive is in use so that modifications
will generate a warning. The plan is to use this mechanism when batching
primitives in the journal to warn users that mid-scene modifications of
primitives is not allowed.
A CoglPrimitive is a retainable object for drawing a single primitive,
such as a triangle strip, fan or list.
CoglPrimitives build on CoglVertexAttributes and CoglIndices which
themselves build on CoglVertexArrays and CoglIndexArrays respectively.
A CoglPrimitive encapsulates enough information such that it can be
retained in a queue (e.g. the Cogl Journal, or renderlists in the
future) and drawn at some later time.
