I need help understanding why I am getting very poor frame rates when I use pycairo to move a large image around the screen on an olpc XO. When I use pycairo to draw a rectangle of the same size on an XO, I get great performance! This is confusing to me because in my experience on other platforms, redrawing vector graphics is much, much slower than blitzing bitmaps to the screen. <div> </div><div>Is there something particular about the XO hardware, its software stack, or cairo which retards the performance of displaying images? The same test case runs fine on my desktop machine.</div><div> </div><div>Thank you! Below is testing code and here is a link if you'd like to try it yourself in the gnome desktop on an XO (the same performance problems also occur when run as part of a sugar activity):</div><div> <a href="http://alumni.media.mit.edu/%7Eerikb/tmp/test.zip" target="_blank">http://alumni.media.mit.edu/~erikb/tmp/test.zip</a></div> <div> </div><div>software notes: click to change the rectangle paint mode. Green is a cairo vector rectangle. Red-1 is a cairo image surface created by loading a png. Blue is a cairo generated image_surface. Red-1 is a gdk pixbuf created by loading a png. import gtk, gobject import cairo class DragTest( gtk.DrawingArea ): __gsignals__ = { "expose-event": "override", "on-mouse-move": (gobject.SIGNAL_RUN_LAST, gobject.TYPE_NONE, (gobject.TYPE_PYOBJECT,)), "on-mouse-down": (gobject.SIGNAL_RUN_LAST, gobject.TYPE_NONE, (gobject.TYPE_PYOBJECT,)), } def __init__(self): gtk.DrawingArea.__init__(self) self.set_events(gtk.gdk.POINTER_MOTION_MASK | gtk.gdk.BUTTON_PRESS_MASK) self.connect("motion_notify_event", self.__on_mouse_move) self.connect("button_press_event", self.__on_button_press) self.box_w = 1210 self.box_h = 910 self.box_type = 0 self.box_x = 0 self.box_y = 0 self.cairo_img = cairo.ImageSurface( cairo.FORMAT_ARGB32, self.box_w, self.box_h ) ctx = cairo.Context( self.cairo_img ) ctx.set_source_rgb( 0, 0, 1 ) ctx.rectangle( 0, 0, self.box_w, self.box_h ) ctx.fill( ) self.cairo_file_img = cairo.ImageSurface.create_from_png( "bg.png" ) self.pixbuf = gtk.gdk.pixbuf_new_from_file( "bg.png" ) def __on_mouse_move(self, area, event): self.box_x, self.box_y, mods = self.get_window().get_pointer() self.queue_draw( ) def __on_button_press(self, area, event): self.box_type += 1 if (self.box_type > 3): self.box_type = 0 self.queue_draw( ) def do_expose_event(self, event): context = self.window.cairo_create() # clip to the visible part context.rectangle(event.area.x, event.area.y, event.area.width, event.area.height) context.clip() if (self.box_type == 0): context.set_source_rgb( 0, 1, 0 ) elif (self.box_type == 1): context.set_source_surface( self.cairo_file_img, self.box_x, self.box_y ) elif (self.box_type == 2): context.set_source_surface( self.cairo_img, self.box_x, self.box_y ) elif (self.box_type == 3): context.set_source_pixbuf( self.pixbuf, self.box_x, self.box_y ) context.rectangle( self.box_x, self.box_y, self.box_w, self.box_h ) context.fill( ) window = gtk.Window() window.set_size_request( 1210, 910 ) window.connect( "delete_event", lambda *args: gtk.main_quit() ) window.add( DragTest() ) window.show_all() gtk.main() </div> <div> </div>