Milosz Derezynski wrote:
It does not seem neccessary to create 2 separate Cairo Contexts:
class MyArea : public Gtk::DrawingArea
{
public:
virtual ~MyArea();
protected:
//Override default signal handler:
virtual bool on_expose_event(
GdkEventExpose* event);
};
MyArea::MyArea()
{
}
MyArea::~MyArea()
{
}
bool MyArea::on_expose_event(GdkEventExpose* event)
{
// This is where we draw on the window
Cairo::RefPtr<Cairo::Context> cr = window->create_cairo_context();
cr->set_line_width(10.0);
cr->move_to(0, 0);
cr->line_to(100, 100);
cr->stroke();
return true;
}
This will work equally well. Is there any specific reason why you want
to keep the surface member in the class and use it the way you wrote
it in the preceding mail?
M.
2008/12/3 BC Zhu <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>
Now i am using Gtkmm. I want to maintain a reference to
Cairo::Context or Cairo::Surface, so i can draw something on it
anywhere.
I am trying to do this , but failed.
With following code , i am trying to keep a reference to
Cairo:::Surface，but when on_expose_event was called secondly , it
will fail.
And i have tried to maintain a reference to Cairo::Context too,
but failed either.
Could some body give me an advice?
Thanks in advance!
class MyArea : public Gtk::DrawingArea
{
public:
virtual ~MyArea();
protected:
//Override default signal handler:
virtual bool on_expose_event(GdkEventExpose* event);
private:
Cairo::RefPtr<Cairo::Surface> surf_;
};
MyArea::MyArea()
{
}
MyArea::~MyArea()
{
}
bool MyArea::on_expose_event(GdkEventExpose* event)
{
// This is where we draw on the window
if(!surf_){
Glib::RefPtr<Gdk::Window> window = get_window();
Cairo::RefPtr<Cairo::Context> cr =
window->create_cairo_context();
surf_ = cr->get_target();
}
Cairo::RefPtr<Cairo::Context> cr = Cairo::Context::create(surf_);
cr->set_line_width(10.0);
cr->move_to(0, 0);
cr->line_to(100, 100);
cr->stroke();
return true;
}
--
Best Regards
Bicen.Zhu
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Hi,
I also have this problem, my reason to keep the context (or surface) is
that i want to draw and i don't want to loose the previous drawings i
made in the context.
The last code works fine but when you call
Cairo::RefPtr<Cairo::Context> cr = window->create_cairo_context();
in the on_expose_event(), you are creating a new context, an empty context.
My solution was drawing in a context i create and then copy this context
over the one i get from the component, the problem is that this method
is _very_ inefficient.
Regards,
Diego A. Fons.
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