[Mesa-dev] MESA and KOTOR

[Jose Fonseca]

On 13/03/17 11:09, Emil Velikov wrote:
> On 11 March 2017 at 11:51, Federico Dossena <dossenus91 at gmail.com> wrote:
>> In the last week I've been trying to bring an "old" game back to life, Star
>> Wars Knights of the old republic (KOTOR, for short). It's from 2003 and uses
>> OpenGL 1.4.
>>
>> I have used Mesa, libtxc_dxtn and some trickery to decompress the textures
>> to boost performance, and right now I have it up and running smoothly with
>> Gallium on LLVMPipe, compiled on Windows. (I can upload a copy if someone is
>> interested). This took me about 2 days of compiling and figuring out stuff.
>>
>> Here's where the weirdness begins:
>> Turning on framebuffer effects or soft shadows make the game crash right
>> after the menu. Using a disassembler and debugger and what little knowledge
>> I have of reverse engineering, I managed to track down the issue to a
>> function which uses wglGetProcAddress to get the addresses of several OpenGL
>> functions. Some of these calls return a null pointer (even if there is a
>> valid context and it is current), and when the game tries to call them, it
>> crashes. The first one that makes it crash is a pointer to
>> wglBindTexImageARB, but there are a few others. NOPing the offending
>> instructions did not work, and returning a nop function just makes the game
>> display artifacts.
>>
> Strange - afaict mesa (st/wgl) exposes both wglBindTexImageARB and the
> WGL_ARB_render_texture extension.
> You can break on DrvGetProcAddress and trace where/how we end up with
> NULL function pointer.
>
> -Emil
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Federico,

You should be using latest master for this.   There have been recent 
changes/fixes to our WGL implementation.


Last fall Brian Paul fixed an issue with WGL extension seen on KOTOR. 
I'm not sure the the issue has been crossported to Mesa master yet, and 
it might be unrelated.


Generally speaking, wglGetProcAddress returning NULL by itself is not a 
problem.  Many games wrongly rely on wglGetProcAddress NULL results to 
detect whether an GL/WGL extension is present (which goes against the 
spec).  Other libraries try to bindly get every possible entrypoint 
through wglGetProcAddress, then check which ones to use based on 
supported extensions (which is actually fine by the spec.)


For the record, getting an apitrace is usually useful to debug this sort 
of issues.  One can use apitrace straigh from windows or with WINE -- 
https://github.com/apitrace/apitrace/wiki/WINE


Jose