[SDL] 2D API evolution (SDL 1.3/2.0)

[David Olofson]

On Thursday 17 August 2006 18:14, Torsten Giebl wrote:
> Hello !
> 
> 
> > Implementation? :)
> > Adding a feature to the existing software blitters is a daunting
> > prospect, since the complexity increases exponentially.
> 
> 
> Are the Blitters itself complicated or is it
> complicated to get the best optimum as possible ?

Well, the SDL blitters can never really be trivial, simply because 
there are quite a few required features to implement to make a useful 
backend. The supported permutations of alpha blending, full surface 
alpha, colorkey and RLE acceleration in SDL 1.2 already result in a 
bunch of specific cases that you pretty much have to implement 
specifically for anything like usable performance. Multiply that with 
three more blending modes, then multiply with three types/levels of 
scaling, and then... well, you get the idea. :-)

Now, if you want eliminate all unnecessary conditionals and expensive 
flexibility in inner loops, there are even more dimensions to add. 
Just for starters, everything will have to come in versions for at 
least 8 bit, 15/16 bit, 24 bit and 32 bit pixel formats. Add real 
time dithering (so that dithering can work with transforms, without 
throwing in an intermediate rendering buffer with higher bit depth 
than the display), and you'll need support for a bunch of useful 
combinations, such as 32->15/16, 24->15/16, 32->8 and 24->8.

Basicall, you don't even have to dive into the tricky details of 
actually optimizing the various permutations. The number of 
permutations alone quickly explodes into insane proportions.


//David Olofson - Programmer, Composer, Open Source Advocate

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