[crossfire] just a comment for SDL (was RE: Release of 1.11 in a week or two)

[Mark Wedel]

Olivier Huet wrote:
> Hello,
> 
> 
> Just for SDL, there is perhaps a better chance to have hardware acceleration
> with it than with OpenGL only : I don't know SDL but looking a little
> sources and documentations, I think that it do try several ways to have
> hardware acceleration available on hosting operating system (DirectX &
> OpenGL for Windows, DGA & OpenGL on Linux + XFree86, etc.). 

  Maybe.  For whatever reason, on my system, SDL didn't offer much in way of 
acceleration over pixmap, while opengl does (unfortunately, it isn't a direct 
apples to apples type of thing, as there may have been other changes I made to 
my system).

> 
> For a little example, on Windows, OpenGL drivers are not always directly
> installed on recent laptop with "modified for laptop" video cards : you have
> to wait to have some new drivers or to use some tricks to install standard
> drivers (thoses normally for non laptop but that do works perfectly with
> laptops :-) ).

  Right - which is one reason I'm not really suggesting it by the only drawing 
mode (pixmap could be used for that edge case).  I imagine even in such cases as 
no hardware driver yet, there may also be software driver to do it, but 
performance on that may be quite bad.

> 
> When I used to use Linux, there was almost never hardware OpenGL driver
> available. I hope it did change now :-) but you probably have more recent
> news than me on that subject.

  It sort of depends.  If you're a firm believer in only using open source 
drivers, support may be limited or lacking.

  If you don't mind using binary only drivers, both nvidia and ati provide 
those, and that probably covers 90% of the cards out there.

  I _think_ that for older models of both ATI & Nvidia cards, there may also be 
3D drivers for that.  There are also rumors (or maybe it has happened - can't 
remember) that ATI (amd) is going to release detailed specs for their cards to 
the public, so that should make it possible to write good opengl drivers.


> But on the other hand, I do know a good proverb in computer science : the
> less "external library" you use, the more stable your application will be
> :-)
> --> so regarding what you say and this proverb, it's perhaps a good idea to
> remove SDL mode, in benefit to adding more functionalities in OpenGL mode
> :-)

  The real issue is that having 3 drawing modes really seems excessive to me. 
And from what I see, with SDL, it is really up to the application to define the 
bits (including lighting effects, etc) and SDL can blit those bits, but in 
itself, it doesn't have any way to do much than 'here are some bits - draw them 
to the screen'.  Opengl as lots of more advanced features (I keep thinking about 
adding a zoom out feature to the map, so one could see areas that were visible 
but now fogged off - very easy to do with opengl, as it will handle rescaling of 
all the image data internally for example).