[Scummvm-devel] Non-hardcoded gameids

Max Horn max at quendi.de
Wed May 31 14:49:01 CEST 2006


Am 31.05.2006 um 23:34 schrieb David Given:

> Max Horn wrote:
> [...]
>>> So if the overlay doesn't support alpha, how does the user see  
>>> the game
>>> canvas through it? There must be some way of preventing parts (or  
>>> all)
>>> of it from being drawn.
>>
>> It's done by implementing the alpha blending manually. Not a big  
>> problem
>> since things are drawn over a static background when the overlay  
>> is active.
>
> Sorry, that's not quite what I meant --- if the overlay's colour  
> format
> doesn't have an alpha channel, how do you tell the compositor which  
> bits
> should be transparent or not? Or does the colour format *always*  
> have an alpha
> channel?

As I said: You do all the blending manually. There is no "compositor"  
in the backends (well, with the exception of the DC backend, which  
supports real alpha blending). That's a conscious design decision --  
we support various platforms that are 8 bit only, and forcing these  
system to emulate some kind of "alpha blending" would tax them  
enormously.

>
> (And the GUI is all drawn on the overlay, right?)

Aye.

Bye,
Max





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