I am trying to write a program that shows a moving circle with pthread and a
custom libsigc++ signal to learn how to update a drawing. I use a similar
method of cairo clock in gtkmm example. If I compile and run the program the
terminal shows the following error message if I click on the window after
seeing a moving circle for a while (64 iterations of the loop in
thread_function).
Fatal IO error 11 (Resource temporarily unavailable) on X server :0.0.
If I comment out win->process_updates( false ); in function
SpecArea::on_new_data, the circle doesn't move until the mouse cursor hovers
over the area.
I will greatly appreciate it if anybody points out the problem. And I also
wonder if this is the right way of updating drawing with pthread.
I am using ubuntu 9.04 64bit, kernel : 2.6.28-16-generic
Here is the code.
#include <unistd.h>
#include <cstdlib>
#include <pthread.h>
#include <gtkmm/main.h>
#include <gtkmm/window.h>
#include <gtkmm/drawingarea.h>
#include <cairomm/context.h>
#include <iostream>
void *thread_function( void *arg );
class SpecArea : public Gtk::DrawingArea
{
double xc, yc;
public:
SpecArea();
virtual ~SpecArea();
protected:
virtual bool on_expose_event( GdkEventExpose* event );
void on_new_data( double x, double y );
};
sigc::signal<void, double, double> signal_new_data;
int main( int argc, char** argv )
{
Gtk::Main kit( argc, argv );
Gtk::Window win;
win.set_title( "Spectrum analyzer" );
SpecArea area;
win.add( area );
area.show();
pthread_t thread;
pthread_create( &thread, NULL, thread_function, NULL );
Gtk::Main::run( win );
pthread_join ( thread, NULL );
return 0;
}
void *thread_function( void *arg )
{
usleep(100000);
for( int i=1; i<=100; ++i )
{
std::cout << i << '\n';
usleep(10000);
signal_new_data( i/100., i/100. );
}
return NULL;
}
SpecArea::SpecArea() : xc(0.), yc(0.)
{
signal_new_data.connect( sigc::mem_fun( *this, &SpecArea::on_new_data )
);
#ifndef GLIBMM_DEFAULT_SIGNAL_HANDLERS_ENABLED
//Connect the signal handler if it isn't already a virtual method
override:
signal_expose_event().connect( sigc::mem_fun( *this,
&SpecArea::on_expose_event ), false );
#endif //GLIBMM_DEFAULT_SIGNAL_HANDLERS_ENABLED
}
SpecArea::~SpecArea() { }
bool SpecArea::on_expose_event( GdkEventExpose* event )
{
Glib::RefPtr<Gdk::Window> window = get_window();
if(window)
{
Gtk::Allocation allocation = get_allocation();
const int width = allocation.get_width();
const int height = allocation.get_height();
int lesser = MIN(width, height);
Cairo::RefPtr<Cairo::Context> cr =
window->create_cairo_context();
cr->set_line_width(lesser * 0.01);
cr->rectangle( event->area.x, event->area.y, event->area.width,
event->area.height );
cr->clip();
cr->save();
cr->arc( xc*width, yc*height, 0.1*lesser, 0.0, 2.0 * M_PI );
cr->set_source_rgb( 0.9, 0.0, 0.0);
cr->fill_preserve();
cr->restore();
cr->stroke();
}
return true;
}
void SpecArea::on_new_data( double x, double y )
{
xc = x;
yc = y;
Glib::RefPtr<Gdk::Window> win = get_window();
if( win )
{
Gdk::Rectangle rec( 0, 0, get_allocation().get_width(),
get_allocation().get_height() );
win->invalidate_rect( rec, false );
//win->process_updates( false );
}
}
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