Re: drawables and refresh rates [solved I think]

[Carl Nygard <cjnygard fast net>]

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();
}

> ======================================================================
> 
> 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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