Sorry sorry sorry for not being able to answer sooner!

Shortly after I proclaimed that my Internet connection was back, I lost 
it again. This time I won't say a word. Perhaps right now you are a 
reading a letter delivered by a pigeon, who knows.


Carsten Haitzler (The Rasterman) wrote:
> On Fri, 15 Dec 2006 19:17:53 +0100 (CET) [EMAIL PROTECTED] babbled:H
>> Why is creation of OpenGL rendering context handled by Evas (or whoever it
>> is) itself? The user has a fine control of creation of X11 resources,
>> therefore in my eyes it would seem a natural extension to this frame of
>> mind that the user can control how GL resources should be handled also.
>>     
>
> because a gl context is global. evas has no idea what the current context 
> color
> is, texture, multitexture mode, currently bound fragment shader, etc. etc. 
> etc.
>
> because it is a state engine that you change the state of - if evas comes in
> not knowing the state when drawing, it will have to either reset every 
> possible
> known state value each time, or, as it does currently, manage its own state.
>
>   
>> My motivation for asking lies in the concept I proposed last I wrote,
>> namely a video-processing framework based on a shared OpenGL context (i.e.
>> indirect rendering which will make it possible to use textures,
>> shader-programs etc shared between processes).
>>     
>
> ok. now to this. the problem with this is that evas is meant to be INDEPENDENT
> of its rendering engine at the api level. i am very loathe to expose the 
> engine
> to the evas api if i can. this means an evas program can change engines at 
> will
> and "just work" (tm).
>   
I was fishing for this answer way back. Figured someone would come clear 
eventually. Anyway, you are absolutely right. A videoframework shouldn't 
depend on a GUI.
In the audio world JACK (an out-of-process sound stream system) has 
taken a different course, namely to let every node in the processing 
graph (e.g. a sound filter adding echo to a signal) run as a separate 
process with the GUI of its own choice, Gtk, Qt etc. So each node owns 
an XWindow of it's own. Of course it puts a heavier load on the Window 
Manager, since it now becomes in charge of giving the user a chance to 
find his way through a lot of windows.
DSSI (an in-process plugin-system) also lets the plugin handle it's own 
GUI, which run in it's own thread.

I'll stick to this model.

> what you want is basically evas as a gl front-end for yourself, not as a
> display independent canvas. now there is nothing wrong with that - but it is
> not one of the goals of evas to do that. that is why you will not find the gl
> context exposed and find it very hard to get TO internals. it's all nicely
> abstracted away. now i do know what you want - you want to be able to place a
> gl rendered scene (3d maybe) in a canvas. if its 3d you want - then we are
> talking major nasty work as we then need to expose EVERY engine, all the 
> engine
> capabilities and ways in and out of that sanely. if its just 2d - maybe its
> something that needs to go into evas anyway. i have been considering filter
> objects for example that would provide filtering like gaussian blur, sharpen,
> etc. etc. so maybe what you want is somewhere on the todo in a more generic 
> way?
>   

I can positively say that even just the basic needs skyrockets past what 
any reasonably ordinary canvas engine needs to handle. 3D, 2D, dedicated 
mask-generation, motion tracking and so on. The list is endless. It 
would cause you more trouble than good to do that. But thanks for offering.

Regards, Rene Jensen




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