Re: [Chromium-users] Information Request: SWAP, and FLUSH()?

[Brian P. <bri...@tu...>]

James Supancic wrote:
> I have been reading the Chromium source code, I have a couple of
> questions about it.
> 
> what is the difference between function and functionSWAP()?
> I keep seeing things like
> if(tilesort_spu.swap)
> {
> call1SWAP
> call2SWAP
> call3SWAP
> }
> else
> {
> call1
> call2
> call3
> }
> 
> Debugging indicates that I always use the non-SWAP version, What is
> going on here? What does tilesort_spu.swap indicate? Why are different
> functions needed for each one?

It's for byteswapping in the case the packer and unpacker use 
different byte orderings.


> Secondly, I have been looking at the integration of various parts of
> Chromium. I noticed that many calls (especially those in
> tilesortspu_gen.c) call similarly named functions in the state
> tracker. These state tracker functions appear to do call specific
> things to update the state to what it should be after that call, at
> which point they use FLUSH() (which ends up invoking doFlush() in the
> tilesort SPU) to send necessary differences to the Render SPUs? Is
> this correct? (ig, does FLUSH flush changes to Render SPUs as needed?)
> 
> If yes, why does FLUSH() get called before the state tracker updates
> the state? I noticed that FLUSH() is always at the beginning of the
> state tracker functions, shouldn't it be at the end?

The idea is to flush any pending/buffered drawing commands before you 
change the state.  If there's no accumulated drawing commands, the 
flush is a no-op.

-Brian