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Thread: OpenVG VG_NO_CONTEXT_ERROR

  1. #1
    Junior Member
    Join Date
    Nov 2011
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    2

    OpenVG VG_NO_CONTEXT_ERROR

    Hi All,

    I am relatively new to OpenVG and currently am just experimenting with some code. The following scenario led me to ask this question:

    - I am currently working on EFL Port of Webkit in Linux env (ubuntu 11.04)
    - spc requirement is to try to enable OpenVG in EFL webkit port.
    - I have all the needed libraries installed (EGL/Mesa etc and Amanith VG ).
    - When the EGL calls are being made, i am able to creat the pbuffer surface.

    --> When i am trying to call vgCreatePath, getting stuck with VG_NO_CONTEXT_ERROR.
    I had gone through OpenVG specs, where its mentioned "If no context is current at the time vgGetError is called, the error code VG_NO_CONTEXT_ERROR is returned". I could not get much out of this statement while running the code .

    Any pointers, links , help would be highly appreciated.

    PS: Being new to OpenVG, I may have missed out on providing more relevant information for the problem statement , which I would be more than happy to provide.

    Thanks,

  2. #2

    Re: OpenVG VG_NO_CONTEXT_ERROR

    Quote Originally Posted by sammy
    Hi All,

    I am relatively new to OpenVG and currently am just experimenting with some code. The following scenario led me to ask this question:

    - I am currently working on EFL Port of Webkit in Linux env (ubuntu 11.04)
    - spc requirement is to try to enable OpenVG in EFL webkit port.
    - I have all the needed libraries installed (EGL/Mesa etc and Amanith VG ).
    - When the EGL calls are being made, i am able to creat the pbuffer surface.

    --> When i am trying to call vgCreatePath, getting stuck with VG_NO_CONTEXT_ERROR.
    I had gone through OpenVG specs, where its mentioned "If no context is current at the time vgGetError is called, the error code VG_NO_CONTEXT_ERROR is returned". I could not get much out of this statement while running the code .

    Any pointers, links , help would be highly appreciated.

    PS: Being new to OpenVG, I may have missed out on providing more relevant information for the problem statement , which I would be more than happy to provide.

    Thanks,
    Hi sammy,

    I'm Matteo Muratori, the main coder of AmanithVG.
    In order to use AmanithVG GLE, you must:

    1) instantiate (and make it current) a valid OpenGL / OpenGL ES context + surface; such surface must "contain" a color buffer and a depth buffer (or stencil buffer). So I suggest you to include the following attributes when you create the pbuffer surface: EGL_BUFFER_SIZE, 32, EGL_DEPTH_SIZE, 24, EGL_STENCIL_SIZE, 8

    2) make the GL surface and context current, using eglMakeCurrent

    3) initialize AmanithVG GLE driver, creating an OpenVG context + surface:
    Code :
    void *vgContext = NULL;
    void *vgSurface = NULL;
    VGboolean initOpenVG(const VGint width, const VGint height) {
        vgContext = vgPrivContextCreateMZT(NULL);
        if (!vgContext)
            return VG_FALSE;
        vgSurface = vgPrivSurfaceCreateMZT(width, height, VG_FALSE, VG_TRUE);
        if (!vgSurface) {
            vgPrivContextDestroyMZT(vgContext);
            return VG_FALSE;
        }
        if (vgPrivMakeCurrentMZT(vgContext, vgSurface) == VG_FALSE) {
            vgPrivSurfaceDestroyMZT(vgSurface);
            vgPrivContextDestroyMZT(vgContext);
            return VG_FALSE;
        }
        return VG_TRUE;
    }

    The vgPrivMakeCurrentMZT call can fail if your current GL surface has no depth buffer nor stencil buffer attached. In such case, VG_FALSE is returned and every OpenVG function returns VG_NO_CONTEXT_ERROR.
    Anyway, if you are going to use AmanithVG in conjunction with Webkit, I would suggest to have a try with AmanithVG SRE, that is more suitable for high quality rendering, and it includes an EGL 1.4 layer too (so you can totally exclude Mesa/OpenGL).

    If you need more details, please feel free to contact me via private message.

    Kind Regards,
    Matteo.
    AmanithVG Lead Programmer

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