Re: Why use OpenGL (was Native Mode Handling)

Kendall Bennett wrote:
> Brian Paul <brian-CdwZJljFklH+2FeEXyspIVaTQe2KTcn/@public.gmane.org> wrote:
> 
> 
>>Sure, but we want to go beyond traditional 2D X server graphics.
> 
> 
> Ok.
> 
> 
>>>smaller than a complete OpenGL rendering pipeline. You don't need
>>>mip-mapping, multi-texturing, vertex shaders, pixel shaders, display
>>>lists, selection, picking, stencil buffers etc for a 2D window manager. 
>>
>>Actually, I can anticipate uses for multi-texture, mipmapping,
>>pixel shaders, etc. in the window system. 
> 
> 
> I can't think of any reasons myself, but then again I am sure people will 
> come up with stuff.
> 
> I guess my biggest concerns with this is:
> 
> 1. The memory overheads for the new system, but with machines that have 
> 128Meg+ of memory, I guess that is not a big deal. 
> 
> 2. The complexity of developing good 2D programs with OpenGL. Programming 
> in OpenGL has a higher learning curve than just a simple 2D rendering 
> API. 
> 
> Thinking about this some more it would seem to me that perhaps what you 
> need is to make sure there is always a good 2D API available that is 
> implemented in terms of 3D functionality. Make sure it is easy to use (or 
> backwards compatible at least), and make sure it can be done *fast*. Like 
> I mentioned before, bitmap support in OpenGL sucks -

Can you elaborate?  I've heard this said before, but I never see much 
in the way of concrete information.


> it would be nice to 
> define some extensions to better handle 2D bitmaps via the OpenGL drivers 
> so the 2D API's can interface more cleanly to the hardware in an 
> efficient manner.
> 
> One way of thinking about this is that as a 2D programmer, if I want to 
> draw a blended 2D bitmap, I don't want to have to set up a geometry 
> pipeline, load a texture map, bind the texture map, set up the 3D 
> rendering engine state and then finally draw some 3D triangles to get my 
> blended bitmap on the screen. Rather I just want to call something like 
> BlendBitmap() that will take my bitmap and blend it onto the screen. 
> Whether the internal implementaiton does all of the above is irrelevant, 
> so long as the 2D programmer does not have to deal with all the 3D cruft.

What's wrong with this:

glEnable(GL_BLEND);
glWindowPos2i(x,y);
glDrawPixels( my_image );

-Brian