Re: Drawing in separate thread to Gtk::DrawingArea

[Mohith Manoj <mohith manoj skanray com>]

Hi,

You could create a Cairo::ImageSurface and operate on that from the worker thread. Have additional variables to indicate status of drawing, area updated as member variables of this class. Then use Glib::Dispatcher to notify UI thread when its time to 'Blit' something on to screen. Needless to say it requires additional memory but its far better compared to trying to synchronize worker and UI threads so that they don't end up fighting with each other!

Regards,
Mohith Manoj

On 26-07-2014 22:20, Szőke Szabolcs wrote:

Hi everybody. I found the tutorial on gtkmm developer page about multi-threading. But when I wanted to adapt for my needs, I couldn't figure out how to do it. I have a DrawingArea widget within a window and I want to do the drawing in separate thread because as the drawing became more complex, the gui thread gets locked every time when something is drawn. I know the theory: I should use a Dispatcher to send the data to gui thread, but in tutorial I saw that when the worker thread completed the job, the gui thread is notified. But I can't do that, or at least I don't know how to do that in this situation. Any help will be appreciated.

Here is the code:

#include <gtkmm.h>

class DrawingArea : public Gtk::DrawingArea

{

public:

DrawingArea()

{

this->set_hexpand();

this->set_vexpand();

}

~DrawingArea() {};

protected:

bool on_draw(const Cairo::RefPtr<Cairo::Context>& context)

{

// drawing stuff

return true;

}

};

class Window : public Gtk::Window

{

public:

Window()

{

this->set_default_size(800, 600);

this->add(this->m_drawing_area);

}

~Window() {};

protected:

DrawingArea m_drawing_area;

};

int main(int argc, char* argv[])

{

Glib::RefPtr<Gtk::Application> application = Gtk::Application::create(argc, argv, "org.draw_in_separate_thread");

Window window;

return application->run(window);

}

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