[Development] QT5 OpenGL question

[Jiergir Ogoerg]

Also,
QOpenGLFunctions doesn't have a glClear() function while being advertised
as "The QOpenGLFunctions class provides cross-platform access to the
OpenGL/ES 2.0 API" but GLES2.0 does have a glClear() function.

Is it a bug?

Other classes like QOpenGLFunctions_2_1 and QOpenGLFunctions_3_2_Core do
have such a function.



On Fri, Aug 2, 2013 at 9:35 PM, Jiergir Ogoerg <f35f22fan at gmail.com> wrote:

> Thanks both of you, I see now, GL is old (1993 I guess) and it shows, e.g.
> it requires creating a context on windows before even being able to query
> GL info etc.
>
> What do you think of the new Linux GL ABI proposal from Nvidia:
> https://github.com/aritger/linux-opengl-abi-proposal
>
> I recall doing some WebGL work a month ago (I forgot about) and I ran into
> the same issue - couldn't use the same "gl" on multiple GL canvas on an
> html5 page,
> but in WebGL the function names are stripped of the "gl" prefix so you
> don't have to repeat yourself like gl.glUseProgram, just gl.UseProgram -
> with
> Qt5 I'd have to use the former, unfortunately, but not a big deal.
>
>
>
> On Fri, Aug 2, 2013 at 3:21 PM, Sean Harmer <sean.harmer at kdab.com> wrote:
>
>> Hi,
>>
>> On Friday 02 August 2013 15:01:05 Jiergir Ogoerg wrote:
>> > Thanks, but it's better to use functions wrapped in namespaces when it's
>> > possible (for example - according to Google's C++ coding style) instead
>> of
>> > static methods in classes or methods of class instances or any other
>> > solution when you can just use functions wrapped in namespaces.
>> > And no, Qt5 doesn't allow using glew.
>> >
>> > On your later point - could you please elaborate on why you need the GL
>> > function addresses to be context-specific? I've used freeglut and GLFW
>> > before and never cared of had issues with this.
>>
>> Please see:
>>
>> http://www.opengl.org/wiki/Load_OpenGL_Functions
>>
>> and
>>
>>
>> http://msdn.microsoft.com/en-us/library/windows/desktop/dd374386(v=vs.85).aspx
>>
>> Cheers,
>>
>> Sean
>>
>> >
>> > On Fri, Aug 2, 2013 at 1:44 PM, Sean Harmer <sean.harmer at kdab.com>
>> wrote:
>> > > On Friday 02 August 2013 10:05:56 Sze Howe Koh wrote:
>> > > > On 2 August 2013 08:16, Jiergir Ogoerg <f35f22fan at gmail.com> wrote:
>> > > > > Hi,
>> > > > > I'm willing to switch to QT5 with GL,
>> > > > > afaik in Qt5 the GL functions are encapsulated into a class that
>> > >
>> > > extends
>> > >
>> > > > > QAbstractOpenGLFunctions and you can't use the GL calls outside
>> that
>> > >
>> > > class
>> > >
>> > > > > unless you pass each time a reference to this class.
>> > > > >
>> > > > > Why doesn't it publish the GL functions publicly (not inside a
>> class
>> > > > > instance) like glew and other tools do?
>> > > > >
>> > > > > I'm asking because I have a lib of mine that uses GL calls, what
>> > >
>> > > should I
>> > >
>> > > > > do, pass an instance of OpenGLFunctions class to each method in
>> the
>> > >
>> > > lib? -
>> > >
>> > > > > that's cumbersome.
>> > > >
>> > > > Hi,
>> > > >
>> > > > To answer your second question, you could use a global pointer to a
>> > > > QOpenGLFunctions_X object -- no need to pass it as around as an
>> > > > argument.
>> > >
>> > > Or set it as a member variable in that class. Or inherit your class
>> from
>> > > QOpenGLFunctions_blah. Or you could resolve global functions
>> yourself. Or
>> > > maybe use GLEW - although I've not tried that with Qt for a while now.
>> > >
>> > > The reason we have these functions on a class rather than globally is
>> that
>> > > the
>> > > function addresses can be context-specific.
>> > >
>> > > Cheers,
>> > >
>> > > Sean
>> > > --
>> > > Join us in October at Qt Developer Days 2013 -
>> https://devdays.kdab.com
>> > >
>> > > Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
>> > > Klarälvdalens Datakonsult AB, a KDAB Group company
>> > > Tel. Sweden (HQ) +46-563-540090, USA +1-866-777-KDAB(5322)
>> > > KDAB - Qt Experts - Platform-independent software solutions
>> --
>> Join us in October at Qt Developer Days 2013 - https://devdays.kdab.com
>>
>> Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
>> Klarälvdalens Datakonsult AB, a KDAB Group company
>> Tel. Sweden (HQ) +46-563-540090, USA +1-866-777-KDAB(5322)
>> KDAB - Qt Experts - Platform-independent software solutions
>>
>
>
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