Re: Resizing contexts

[Frank C <li...@si...>]

On 7-Aug-04, at 12:03 AM, Frank C wrote:

> On 6-Aug-04, at 10:41 PM, James W. Walker wrote:
>
>> On Aug 6, 2004, at 4:17 PM, Frank C wrote:
>>
>>> It appears Quesa rebuilds the GL context whenever it's resized,  
>>> which can take a good _long_ while if you have a lot of textures  
>>> loaded (pretty much rules out using live-resize windows on OS X).  
>>> Would it be reasonable to have a GLDrawContext_UpdateSize function  
>>> to avoid rebuilding textures for a resize event? I'm fairly certain  
>>> all you have to do is update the viewport and clipping rect -  
>>> trashing the context isn't needed or desirable.
>>>
>>> Comments?
>>
>> On the Mac, you would also need to call aglUpdateContext, i think.
>
> That would be part of updating the clipping rect. On Mac OS, you would  
> have to grab the context port dimensions, update AGL_BUFFER_RECT,  
> update glViewport, and finally call aglUpdateContext. The first two  
> steps can be ignored for offscreen contexts.
>
>> I do not see any analogous wgl call for Windows.  I don't know if  
>> that means that the wgl layer does not need to be informed of a  
>> window resize, or if it means that you must recreate the context.
>
> Ya, it looks like GLDrawContext_UpdateWindowClip does nothing on  
> platforms other than Mac OS so perhaps updates are automatic, but I  
> can't offer any more insight. glViewport would certainly need to be  
> updated in all cases however.
>
> I hacked in support for the Mac at this point and it's a whole lot  
> nicer when using freely resizable windows, but I ran into a bit of  
> roadblock in IRRenderer_StartFrame. It seems the context flags get  
> trashed before getting there when a resize is pending (forcing a  
> rebuild), but I can't see where that happens. I traced one such case  
> to e3drawcontext_mac_update but it still occurs after modifying that  
> function. I'll look at it some more over the weekend...

Scratch that e3drawcontext_mac_update remark - it's Qut's fault. I've  
submitted a bug with more details:  
<http://sourceforge.net/tracker/index.php? 
func=detail&aid=1005268&group_id=45158&atid=442052>

I can offer up some code that seems to work on Mac OS X, but I suspect  
someone with more intimate knowledge of Quesa should tackle this, as  
I'm not sure how best to handle offscreen contexts or other platforms.  
One thing I noticed is that AGL_BUFFER_RECT is always enabled from the  
get-go, but really doesn't need to be for full-window contexts. I doubt  
there's any sort of performance penalty, but it would make resizing  
easier for contexts attached to window ports if AGL_BUFFER_RECT simply  
wasn't enabled.

Frank.