Instead of having _cogl_get/set_clip stack which reference the global
CoglContext this instead makes those into CoglClipState method functions
named _cogl_clip_state_get/set_stack that take an explicit pointer to a
CoglClipState.
This also adds _cogl_framebuffer_get/set_clip_stack convenience
functions that avoid having to first get the ClipState from a
framebuffer then the stack from that - so we can maintain the
convenience of _cogl_get_clip_stack.
Previously we tracked whether the clip stack needs flushing as part of
the CoglClipState which is part of the CoglFramebuffer state. This is
a bit odd because most of the clipping state (such as the clip planes
and the scissor) are part of the GL context's state rather than the
framebuffer. We were marking the clip state on the framebuffer dirty
every time we change the framebuffer anyway so it seems to make more
sense to have the dirtiness be part of the global context.
Instead of a just a single boolean to record whether the state needs
flushing, the CoglContext now holds a reference to the clip stack that
was flushed. That way we can flush arbitrary stack states and if it
happens to be the same as the state already flushed then Cogl will do
nothing. This will be useful if we log the clip stack in the journal
because then we will need to flush unrelated clip stack states for
each batch.
Instead of having a separate CoglHandle for CoglClipStack the code is
now expected to directly hold a pointer to the top entry on the
stack. The empty stack is then the NULL pointer. This saves an
allocation when we want to copy the stack because we can just take a
reference on a stack entry. The idea is that this will make it
possible to store the clip stack in the journal without any extra
allocations.
The _cogl_get_clip_stack and set functions now take a CoglClipStack
pointer instead of a handle so it would no longer make sense to make
them public. However I think the only reason we would have wanted that
in the first place would be to save the clip state between switching
FBOs and that is no longer necessary.
This adds three new internal API functions which can be used to retain
the clip stack state and restore it later:
_cogl_get_clip_stack
_cogl_set_clip_stack
_cogl_clip_stack_copy
The functions are currently internal and not yet used but we may want
to make them public in future to replace the cogl_clip_stack_save()
and cogl_clip_stack_restore() APIs.
The get function just returns the handle to the clip stack at the top
of the stack of stacks and the set function just replaces it.
The copy function makes a cheap copy of an existing stack by taking a
reference to the top stack entry. This ends up working like a deep
copy because there is no way to modify entries of a stack but it
doesn't actually copy the data.
CoglClipStackState has now been renamed to CoglClipState and is moved
to a separate file. CoglClipStack now just maintains a stack and
doesn't worry about the rest of the state. CoglClipStack sill contains
the code to flush the stack to GL.
