Re: drawables and refresh rates [solved I think]

[Rob Benton <rob benton conwaycorp net>]

Carl Nygard wrote:
> On Mon, 2004-12-06 at 15:54, Rob Benton wrote:
>
> > Thanks to everyone who helped me with this.  I think I have it figured 
> > out but would appreciate it if someone would double-check my logic.
> >
> >
> > (Draw an arc on top of a circle using input from a scale widget)
> > ======================================================================
> > _drawarea.signal_realize().connect(&drawingarea_realize);
> > _drawarea.signal_expose_event().connect(&drawingarea_expose_event);
> > _hscale.signal_value_changed().connect(&update_drawingarea);
> >
> > void drawingarea_realize()
> > {
> > 	Glib::RefPtr<Gdk::Window> window = _drawarea.get_window();
> > 	window->clear();
> > 	window->draw_arc( /* blue circle */ );
> > 	window->draw_arc( /* red arc */ );
> > 	_pixmap = Gdk::Pixmap::create(window, width, height);
> > }
>
>
> void drawingarea_realize()
> {
>   	Glib::RefPtr<Gdk::Window> window = _drawarea.get_window();
> 	_pixmap = Gdk::Pixmap::create(window, width, height);
> 	update_drawingarea();
> }
>
>
> > bool drawingarea_expose_event(GdkEventExpose * e)
> > {
> > 	update_drawingarea();
> > 	return true;
> > }
>
>
> bool drawingarea_expose_event(GdkEventExpose* e)
> {
> 	Glib::RefPtr<Gdk::Window> window = _drawarea.get_window();
> 	window->draw_drawable(_gc, _pixmap, e->x, e->y, e->width, e->height);  
> // Guessing at e->* but you get the idea
> }
>
>
> > void update_drawingarea()
> > {
> > 	Glib::RefPtr<Gdk::Window> window = _drawarea.get_window();
> > 	_pixmap->draw_drawable(_gc, window, 0, 0, 0, 0);
> > 	_pixmap->draw_arc( /* blue circle */ );
> > 	_pixmap->draw_arc( /* red arc */ );
> > 	window->draw_drawable(_gc, _pixmap, 0, 0, 0, 0);
> > }
>
>
> void update_drawingarea()
> {
> 	_pixmap->draw_rectangle(// args here, set color beforehand);
> 	_pixmap->draw_arc( /* blue circle */ );
> 	_pixmap->draw_arc( /* red arc */ );
> 	_drawarea->queue_draw();
> }
I let background be transparent in my Gtk::DrawingArea.  Is there a way 
to capture that color to send to the pixmap so that I don't screw up the 
user's gtk theme?

> > ======================================================================
> >
> > Now I only have 2 questions:
> >
> > 1. Is there anything like Gdk::Window::clear() for Gdk::Pixmap?  Right 
> > now I'm copying the Gtk::DrawingArea into it before I do anything, 
> > otherwise the pixmap will have random junk in it.  This seems kind of 
> > inefficient.
> >
> > 2. Can I emit the expose_event signal on the Gtk::DrawingArea from the 
> > Gtk::HScale value_changed callback?  That would eliminate my 3rd function.
> >
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