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

[Jose Fonseca]

----- 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.

> Annotating properly makes the gl_basic test work like a charm.

That's great progres!

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

Jose