[Mesa-dev] MESA and KOTOR

Wed Mar 15 06:35:38 UTC 2017

I have created a simple stub for wglMakeContextCurrentARB in stw_wgl.c 
and stw_getprocaddress.c. It simply returns TRUE, but the good thing is 
that now the game no longer crashes because the function is missing! 
However I get a divide by zero in glu32.dll, presumably because the stub 
doesn't do jack.
I tried returning FALSE but the game has no fallback, it just ignores 
the return values and assumes that everything is fine.

 From what I've seen, there is no need to override the system's 
opengl32.dll like you did for wglCreateContext/wglDeleteContext, so it 
shouldn't be too tricky to implement the function. However, I can't seem 
to find any real documentation about what it's supposed to do. I found 
this at 
https://www.khronos.org/registry/OpenGL/extensions/ARB/WGL_ARB_make_current_read.txt 
but it's pretty vague:

The function wglMakeContextCurrentARB associates the context <hglrc>
     with the device <hDrawDC> for draws and the device <hReadDC> for
     reads.  All subsequent OpenGL calls made by the calling thread are
     drawn on the device identified by <hDrawDC> and read on the device
     identified by <hReadDC>.

How do I do that? Do I have to copy the frame buffer? Or just the 
pointer? Or am I completely off road?

Thanks for helping me out ;)

Il 2017-03-14 03:44, Brian Paul ha scritto:
> Looks like my KOTOR patch never made it to master.  I'm attaching it 
> below so you can try it.  I should commit it master.  In any case, let 
> me know if it helps.
>
> -Brian
>
> On 03/13/2017 10:55 AM, Federico Dossena wrote:
>> Hi Jose, thanks for replying, I've seen your name inside many files in
>> mesa ;)
>>
>> I have tried mesa master (previously I was using 17.0.1) but it still
>> crashes for the same null pointer.
>> Do you have a link to that patch you've mentioned for kotor?
>>
>> I have used apitrace and took traces of both the nvidia driver (which
>> runs kotor) and mesa (up until the crash).
>> Here's a link to them:
>> https://drive.google.com/file/d/0B6qj91UlSYlYa3dIM0FtaHNULW8/view?usp=sharing 
>>
>> <https://urldefense.proofpoint.com/v2/url?u=https-3A__drive.google.com_file_d_0B6qj91UlSYlYa3dIM0FtaHNULW8_view-3Fusp-3Dsharing&d=DwMDaQ&c=uilaK90D4TOVoH58JNXRgQ&r=Ie7_encNUsqxbSRbqbNgofw0ITcfE8JKfaUjIQhncGA&m=u9OxTt6a0b4XxAVoFjjG7RmQNYLAIe3smaD2NtY0mhE&s=h5NDyV1_DsR1WIruLOfH3IDrWkYTa8VEHeC3vIiucF4&e=> 
>>
>>
>> I tried reading them with the dump function but it's way above my
>> comprehension.
>>
>> I know that some applications use wglGetProcAddress to check if an
>> extension if available, but I've seen KOTOR check for the
>> WGL_ARB_render_texture, and when it's present it enables frame buffer
>> effects and soft shadows, which use wglMakeContextCurrentARB (not
>> wglBindTexImageARB, I was wrong in my previous mail), which for some
>> reason is a null pointer.
>>
>> ////
>>
>>
>> Il 2017-03-13 14:39, Jose Fonseca ha scritto:
>>> 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
>>>> _______________________________________________
>>>> mesa-dev mailing list
>>>> mesa-dev at lists.freedesktop.org
>>>> https://lists.freedesktop.org/mailman/listinfo/mesa-dev
>>>>
>>>
>>> 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
>>
>>
>>
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>>
>>
>

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