[maemo-developers] Smooth animation

[From: Kimmo Hämäläinen]

On Wed, 2009-12-30 at 10:46 +0100, ext Mark Clarkson wrote:
> Hi, I am writing an app for the n900 which requires smooth animation
>  within a subwindow. I want to retain the top toolbar and make use of
>  hildon's themed widgets - I want to keep, as much as possible, the
>  maemo 5 look and feel.

By "top toolbar" you mean the menu/title bar and close button?

> I have tried cairo animation and clutter (bug #7459), neither of which provide smooth tear/flicker free animation.
> 
> As a beginner maemo developer, excited with the possibilities of this new device, is there a way to achieve this goal?

We don't have vsync (unless you use OpenGL directly and enable it
yourself and disable the compositor [which is not using it]), so the
best you can do is to:

1) try to render every frame so that it's all contained in one damage
event (so that the compositor will do it all in one OpenGL update).
2) try to render every frame as fast as possible to keep animations
smooth.

The xresponse utility is a good tool to see how long the screen updates
take and how many damage events are generated for the compositor.

This is easier to do in a fullscreen application because then you can
disable the compositor and draw to the screen directly (which allows for
better FPS, and damage events do not matter anymore).

-Kimmo

> 
> Cheers
> Mark.
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