Use MGLGetProcAddress to access OpenGL functions

Use MGLGetProcAddress to access OpenGL functions

Rather than calling GL functions directly, use MGLGetProcAddress to
retrieve the functions dynamically at runtime.

BUG= https://github.com/domokit/mojo/issues/396
R=jamesr@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/8ca6db920bdb15381f09cdb58d797123e8165ef6

[jamesr, 2015-10-21 19:58:53]

https://codereview.chromium.org/1416133002/diff/1/examples/spinning_cube/spin...
File examples/spinning_cube/spinning_cube.cc (right):

https://codereview.chromium.org/1416133002/diff/1/examples/spinning_cube/spin...
examples/spinning_cube/spinning_cube.cc:31: typedef ReturnType (*Function##Type)
PARAMETERS;
nit: i find 'using' easier to read for function typedefs

https://codereview.chromium.org/1416133002/diff/1/examples/spinning_cube/spin...
examples/spinning_cube/spinning_cube.cc:36: private:
style guide has an order for public / private, this should go lower

[Petr Hosek, 2015-10-21 21:12:04]

https://codereview.chromium.org/1416133002/diff/1/examples/spinning_cube/spin...
File examples/spinning_cube/spinning_cube.cc (right):

https://codereview.chromium.org/1416133002/diff/1/examples/spinning_cube/spin...
examples/spinning_cube/spinning_cube.cc:31: typedef ReturnType (*Function##Type)
PARAMETERS;
On 2015/10/21 19:58:53, jamesr wrote:
> nit: i find 'using' easier to read for function typedefs

Done.

https://codereview.chromium.org/1416133002/diff/1/examples/spinning_cube/spin...
examples/spinning_cube/spinning_cube.cc:36: private:
On 2015/10/21 19:58:53, jamesr wrote:
> style guide has an order for public / private, this should go lower

I need this to be defined before I declare the members. Shall I use multiple
public/private sections?

[jamesr, 2015-10-21 23:06:28]

https://codereview.chromium.org/1416133002/diff/20001/examples/spinning_cube/...
File examples/spinning_cube/spinning_cube.cc (right):

https://codereview.chromium.org/1416133002/diff/20001/examples/spinning_cube/...
examples/spinning_cube/spinning_cube.cc:38: template <typename T> class
GLProcPtr {
Hmm, now that I understand this a bit better I'm skeptical of its value -
wouldn't it be cleaner to have a bunch of Function##Type members that you
null-initialize in the constructor?

[Petr Hosek, 2015-10-21 23:17:57]

https://codereview.chromium.org/1416133002/diff/20001/examples/spinning_cube/...
File examples/spinning_cube/spinning_cube.cc (right):

https://codereview.chromium.org/1416133002/diff/20001/examples/spinning_cube/...
examples/spinning_cube/spinning_cube.cc:38: template <typename T> class
GLProcPtr {
On 2015/10/21 23:06:28, jamesr wrote:
> Hmm, now that I understand this a bit better I'm skeptical of its value -
> wouldn't it be cleaner to have a bunch of Function##Type members that you
> null-initialize in the constructor?

Done.

[jamesr, 2015-10-21 23:28:55]

lgtm

https://codereview.chromium.org/1416133002/diff/40001/examples/spinning_cube/...
File examples/spinning_cube/spinning_cube.cc (right):

https://codereview.chromium.org/1416133002/diff/40001/examples/spinning_cube/...
examples/spinning_cube/spinning_cube.cc:39: Function = nullptr;
imo this would be slightly cleaner as an initializer list entry, i.e.

GLInterface() :
#macro voodo
    Function(),
#lalala
{}

but it doesn't really matter much

https://codereview.chromium.org/1416133002/diff/40001/examples/spinning_cube/...
File examples/spinning_cube/spinning_cube.h (right):

https://codereview.chromium.org/1416133002/diff/40001/examples/spinning_cube/...
examples/spinning_cube/spinning_cube.h:16: class GLInterface;
this can be private (or even better a separate type and not an inner class,
inner classes are icky)

[Petr Hosek, 2015-10-21 23:32:55]

https://codereview.chromium.org/1416133002/diff/40001/examples/spinning_cube/...
File examples/spinning_cube/spinning_cube.cc (right):

https://codereview.chromium.org/1416133002/diff/40001/examples/spinning_cube/...
examples/spinning_cube/spinning_cube.cc:39: Function = nullptr;
On 2015/10/21 23:28:55, jamesr wrote:
> imo this would be slightly cleaner as an initializer list entry, i.e.
> 
> GLInterface() :
> #macro voodo
>     Function(),
> #lalala
> {}
> 
> but it doesn't really matter much

That's what I tried initially but compiler doesn't like that, presumably because
the last item ends with a comma. I could put a dummy item there to work around
this but that's really icky.

[jamesr, 2015-10-21 23:36:23]

On 2015/10/21 at 23:32:55, phosek wrote:
>
https://codereview.chromium.org/1416133002/diff/40001/examples/spinning_cube/...
> File examples/spinning_cube/spinning_cube.cc (right):
> 
>
https://codereview.chromium.org/1416133002/diff/40001/examples/spinning_cube/...
> examples/spinning_cube/spinning_cube.cc:39: Function = nullptr;
> On 2015/10/21 23:28:55, jamesr wrote:
> > imo this would be slightly cleaner as an initializer list entry, i.e.
> > 
> > GLInterface() :
> > #macro voodo
> >     Function(),
> > #lalala
> > {}
> > 
> > but it doesn't really matter much
> 
> That's what I tried initially but compiler doesn't like that, presumably
because the last item ends with a comma. I could put a dummy item there to work
around this but that's really icky.

Blah, never mind then.

[Petr Hosek, 2015-10-21 23:38:49]

On 2015/10/21 23:36:23, jamesr wrote:
> On 2015/10/21 at 23:32:55, phosek wrote:
> >
>
https://codereview.chromium.org/1416133002/diff/40001/examples/spinning_cube/...
> > File examples/spinning_cube/spinning_cube.cc (right):
> > 
> >
>
https://codereview.chromium.org/1416133002/diff/40001/examples/spinning_cube/...
> > examples/spinning_cube/spinning_cube.cc:39: Function = nullptr;
> > On 2015/10/21 23:28:55, jamesr wrote:
> > > imo this would be slightly cleaner as an initializer list entry, i.e.
> > > 
> > > GLInterface() :
> > > #macro voodo
> > >     Function(),
> > > #lalala
> > > {}
> > > 
> > > but it doesn't really matter much
> > 
> > That's what I tried initially but compiler doesn't like that, presumably
> because the last item ends with a comma. I could put a dummy item there to
work
> around this but that's really icky.
> 
> Blah, never mind then.

Someone is trying to get this fixed in C++ standard, see
https://groups.google.com/a/isocpp.org/forum/#!topic/std-proposals/I8N_75J9ZB8,
but it's only going to be supported in the next C++ version :)

[Petr Hosek, 2015-10-21 23:40:33]

https://codereview.chromium.org/1416133002/diff/40001/examples/spinning_cube/...
File examples/spinning_cube/spinning_cube.h (right):

https://codereview.chromium.org/1416133002/diff/40001/examples/spinning_cube/...
examples/spinning_cube/spinning_cube.h:16: class GLInterface;
On 2015/10/21 23:28:55, jamesr wrote:
> this can be private (or even better a separate type and not an inner class,
> inner classes are icky)

Done.

[Petr Hosek, 2015-10-21 23:55:02]

Committed patchset #4 (id:60001) manually as
8ca6db920bdb15381f09cdb58d797123e8165ef6 (presubmit successful).