Am 20.03.2014 um 15:04 schrieb Carlos <aarkham...@yahoo.com>:
> ...
>
> I've tried Qt 5.2 MSVC2010 32bit OpenGL and Qt 5.2 MinGW 32 bit and it fails
> in both. In Qt4 the OpenGL version is 4.3.0 and in Qt5 is 2.1.2,
Just to interrogate the Usual Suspects: you /are/ explicitly asking for an
OpenGL 4.3 "CoreProfile" context, aren't you?
If not, it might be by pure chance what the underlying OpenGL driver is
offering you.
Also, are you using the (not quite yet) deprecated "QGL" APIs (QGLWidget,
QGLFormat,...), or the new "QOpenGL" APIs such as QSurfaceFormat,
QOpenGLContext?
I remember there was an issue in some initial Qt 5 release which prevented to
create an OpenGL 3.x context, because some deprecated GL function was still
being used within Qt itself, causing the "context creation/testing" function to
fail, and hence always the default 2.x GL context was returned.
But as I said, that was on a Mac and my memory is very sketchy (and now that I
write these lines I think the problem was not creating a 3.2 context at that
time, but rather executing a GLSL 1.50 shader with QGLShaderProgram, as its
internal code was still trying to bind uniforms with a GLSL 1.20 syntax, or so
I vaguely remember...).
Anyway, you might want to start over with a quick "Hello GL" application (and
QOpenGLShaderProgram & Co. is now the way to rock these days!).
Sean's blog is probably a good point to start ;)
http://www.kdab.com/opengl-in-qt-5-1-part-1/
You will notice though that it uses QWindow instead of the good ol' QGLWidget,
and that quite some "boilerplate code" is needed to get the convenient
initializeGL/paintGL/resizeGL etc. methods back that were offered by QGLWidget.
Let alone that QWindow represents a "top-level" window, which you still need to
"wrap" into a QWidget hierarchy compatible widget (I think
QWidget::createWindowContainer does that). For a full screen game QWindow
however is probably all you need anyway.
Here is an example which uses a QWindow with an "OpenGL surface":
https://qt-project.org/doc/qt-5.0/qtgui/openglwindow.html
It's funny: this example code seems only to be available in the Qt 5.0 and 5.1
docs, but not in the current 5.2 docs. It is also not listed in the "official
Qt examples" chapter. And note that the shader code uses the "OpenGL ES 2.0"
(GLSL 1.20?) syntax and the example does not explicitly ask for an OpenGL
context, because an OpenGL ES 2.0 compatible context is probably (supposedly?)
what you get by default on most desktops anyway, if you don't ask for it
explicitly.
So take this example with care, but it should demonstrate the effort required
to get a "QGLWidget like experience".
My understanding is that the old QGLWidget /should/ still work, especially also
with more recent GL context than "OpenGL ES 2.0" (because that is what Qt
itself has to restrict itself internally!). That means you would still have to
use the old QGLContext and QGLFormat classes as to create an OpenGL 3.x or 4.x
context, but then you could (should) use the new "QOpenGL" API such as
QOpenGLShaderProgram etc. (if you use them at all).
As I just realised myself the upcoming QOpenGLWidget itself is only scheduled
for Qt 5.4 (QTBUG-36899), so that still leaves us in a somewhat weird situation
when you want to write QWidget-based OpenGL applications: either you hack away
with QWindow (and wrap it into a container), or you mix old "QGL" with new
"QOpenGL" APIs (in the hope that the former still behave nice with recent
OpenGL 4.x context).
I hope that gives you a few pointers to experiment with ;)
Cheers,
Oliver
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