Refresh Rate

[Duncan Perrett elekta com]

Hello,

My application is required to draw to an X-window at a rate of at least 25
times per second.
I don't need any windows or widgets - I'm just using draw_gray_image() to
draw some grayscale bitmaps.
Unfortunately, I have tested a gtkmm program and it seems to take 40ms to
refresh the screen without me doing any extra work on top.
If I do some work in my program it becomes 130ms.

I tried to connect the refresh signal at 1ms but that isn't achievable.
m_RefreshPeriod = 1 ...

    Glib::signal_timeout().connect(sigc::mem_fun(*this,

&MyImageDisplay::refreshTimeoutCallback),
                                                 m_RefreshPeriod,
Glib::PRIORITY_HIGH);



bool MyImageDisplay::refreshTimeoutCallback()
{
RESET_GLOBAL_TIMER;
START_GLOBAL_TIMER;
//    GetImageArray(m_Image);                   // Transfer image matrix to
image array

    Glib::RefPtr<Gdk::Window> window = get_window();
    window->draw_gray_image(m_refGC, 0, 0, m_XRes, m_YRes,
                            Gdk::RGB_DITHER_NORMAL, (guchar*)m_Image,
m_XRes);
STOP_GLOBAL_TIMER;
DOUT("time taken :" << GET_GLOBAL_TIME_ELAPSED << std::endl);

    // never disconnect callback
    return true;
}



m_Image is declared as char m_Image[1000000] to cope with the expected
screen resolution (eg: 1024x768).

Have I picked the wrong library to use?  I realise gtkmm is probably
targeted at applications like Window Managers/GUIs.  Should I drop gtkmm
and use Xlib instead?

Thanks,

Duncan


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