Search code examples
animationgtkpygtk

Smooth animations using GTK+

I'm creating a network animator (similar to nam, if you have used it before).

Basically, I have nodes represented as small dots on a GTK+ DrawingArea, and I update the positions of these nodes and redraw the DrawingArea in a loop.

The resulting animation is fast, but not smooth (there's a lot of flicker). This is probably because I fill the DrawingArea with a solid color before each frame.

How do you think I can best tackle this problem? Should I pre-render the frames onto Pixbufs? Is there a better solution?

Here's my current drawing code (using PyGTK):

rect  = self.drawing_area.get_allocation()
style = self.drawing_area.get_style()

pos   = [n.position_at(self.t) for n in self.nodes]

self.drawing_area.window.draw_rectangle(style.bg_gc[gtk.STATE_NORMAL], True,
                                        0, 0, rect.width, rect.height)

for p in pos:
    self.drawing_area.window.draw_arc(style.fg_gc[gtk.STATE_NORMAL], True,
                                      rect.width  * (p.x / 2400.0) - NODE_SIZE/2,
                                      rect.height * (p.y / 2400.0) - NODE_SIZE/2,
                                      NODE_SIZE, NODE_SIZE,
                                      0, 64 * 360)

where self.t is the current time, which is incremented in the loop.

Solution

  • I changed my code to render the frames onto a Pixmap, and replaced the DrawingArea with an Image.

    While this solved the flickering, now the CPU usage has peaked. The animation is still quite fast, but I don't think this method is scalable.

    Time for some optimization, I guess.

    UPDATE: It turns out using expose-event with an Image wasn't such a good idea. CPU usage is back to normal.