[waffle] [GSOC2014] Current design/implementation + the infamous corruption

[Emil Velikov]

On 06/06/14 14:00, Jose Fonseca wrote:
> 
> 
> ----- Original Message -----
>> On 05/06/14 03:19, Emil Velikov wrote:
>>> Hi all,
>>>
>>> Over the last few days I have been though some head-scratching and
>>> re-writing
>>> things, in order to resolve an "interesting" memory corruption to no avail
>>> :'(
>>>
>>> Before explaining more about the issue here is some info about the current
>>> design + where to get the patches. Let me know if you would like me to send
>>> them to the ML.
>>>
>>> Branch GSOC2014 over at
>>> https://urldefense.proofpoint.com/v1/url?u=https://github.com/evelikov/waffle&k=oIvRg1%2BdGAgOoM1BIlLLqw%3D%3D%0A&r=NMr9uy2iTjWVixC0wOcYCWEIYhfo80qKwRgdodpoDzA%3D%0A&m=a2j0YKhUfDCeKnrHMRWtbX2GGkBhvFdRuL%2BmYYiIN7g%3D%0A&s=653132e086e89788df300b121854441a78291782135936411a4a6254e6959c6a
>>>
>>> Archlinux users can use the pkgbuild script in
>>> pkg/archlinux/mingw-w64-waffle.
>>>
>>> Design by example - gl_sample.c (i.e. how to use waffle)
>>>
>>> waffle_init()
>>> waffle_display_connect()
>>> + RegisterClass()        // Registers the window class used as a "template"
>>>                          // by Windows to create the window
>>>
>>                            // Create a default/root window, config and
>>                            context
>>                            // as wglGetProcAddress needs to be executed under
>>                            // current context.
>>
>> Missed case:
>> waffle_get_proc_address()  // if (wglGetCurrentContext() == NULL) {
>>                            //     using_display_context = true;
>>                            //     wglMakeCurrent(display->hdc,
>>                            display->hglrc)
>>                            // }
>>                            // ok = wglGetProcAddress()
>>                            // if (using_display_context == true)
>>                            //     wglMakeCurrent(NULL, NULL)
>>                            // return ok;
>>
>>                            // Unbinding the current context may be an
>>                            // overkill although will help with unintentional
>>                            // misuse of waffle's API.
>>
>>                            // NOTE: Will need to change waffle's internals
>>                            // in order to get access to wcore_display.
>>                            // The API will need a change to include the
>>                            // display waffle_get_proc_address(dpy, "glHam")
>>
>>
>>> waffle_config_choose(dpy...)
>>> + CreateWindow()         // Create a window and prepend it to the
>>>                          // wgl_display::windows list.
>>>
>> Now that I look at it, I'm not entirely sure why I needed a list of all
>> windows in wgl_display. Seems like I can drop that.
>>
>>> + ChoosePixelFormat()
>>> + SetPixelFormat()       // Set the pixelformat and link the current window
>>>                          // to the wgl_config
>>>
>>> waffle_context_create(config...)
>>> + CreateContext(hDC... ) // At this point we need access to the wgl_window,
>>>                          // as hWnd/hDC (window_handle/device_context
>>>                          handle)
>>>                          // is essential.
>>>                          // This is where wgl_config::window comes into
>>>                          play.
>>>
>>> waffle_window_create(config, w, h)
>>> + wgl_window_resize()    // Reuse the window, adjusting it's dimensions, as
>>>                          // w, h used at creation time are include the
>>>                          window
>>>                          // border. AFAICK there is no way to determine the
>>>                          // correct window dimensions prior to creation.
>>>
>>> ...
>>>
>>> waffle_window_create(config, w, h)
>>> + waffle_window_resize() // Reuse the window... and boom. Any suggestions
>>> on
>>>                          // how to resolve this, or should we mandate that
>>>                          // this is not a valid usage of waffle ?
>>>
>> There is no use case in piglit + waffle{examples/utils} where one would
>> create
>> multiple windows for a single config. I might just add a lovely assert and
>> don't worry about this too much.
>>
>> With the above resolved I will take a look at handling gl profiles and alike.
>>
>>>
>>> And now back to the memory corruption:
>>>
>> Resolved, thanks to Jon Turney.
>>
>> The functions obtained by waffle_dl_sym() are part of the Windows API, which
>> uses different calling convention (stdcall vs cdecl) which causes the heap
>> corruption. 
> 
> Good catch.
> 
The mess was so deep that I've managed to bring the whole Windows down on two
occasions :)

>> Annotating properly makes the gl_basic test work like a charm.
> 
> That's great progres!
> 
Indeed I was over the moon when I saw the window contents flip through the
different colors. Kind of stuck at the next step though :\

Jose, gents,

Would you know how to convert redsize [1] to redBits/redShift [2] ?

The former format is used by ChoosePixelFormat under glx, egl and cgl which do
a lot of dancing at libGL/libEGL level, while windows delegates that to the
caller and expects the latter format.

I've been through mesa/src/glx and it's kind of making my head spin. I'm going
to see if I can make more sense from mesa/src/egl.

AFAICS I can use wglChoosePixelFormatARB/wglChoosePixelFormat(GL) over
ChoosePixelFormat (GDI), although I have seen a handful recommendations
against it - black window, excessive flickering etc.

IMHO the former should help although it's not really documented on MSDN :\


Any suggestions and links on the topic would be appreciated :)

Cheers,
Emil




[1]
https://github.com/waffle-gl/waffle/blob/master/src/waffle/core/wcore_config_attrs.h#L32

[2] http://msdn.microsoft.com/en-gb/library/windows/desktop/dd368826(v=vs.85).aspx


>>
>> AFAICS waffle_get_proc_address is in the same boat. Will need to test.
>>
>> Cheers,
>> Emil
>>
> 
> Jose
>