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Clutter-1.002
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/ Clutter::Cookbook

NAME

Clutter::Cookbook - Examples of how to use Clutter

DESCRIPTION

This document tries to provide examples on how to perform some common tasks when building an application or a toolkit using the Clutter Perl bindings.

The original version of this document can be found on the Clutter project main site; the online version is aimed at the C API.

ACTORS

Maintaining the aspect ratio when loading a texture

Clutter::Texture already provides a property that maintains the aspect ratio of an image loaded on a texture:

Clutter::Texture:keep-aspect-ratio
  type: boolean
  default: FALSE

Usually, you just need to set it to TRUE before setting the image data:

$texture = Clutter::Texture->new();
$texture->set(keep_aspect_ratio => TRUE);
$texture->set_from_file($filename);
$texture->set_width(100);

This will set up a texture with the contents of filename, a width of 100 pixels and an height maintaining the same aspect ratio of the original image.

Clutter::Texture, like the rest of Clutter's actors, is a height-for-width actor. This means that the width will be queried first and then the height set for the given width. If you need to set the height of a texture and maintain the same aspect ratio, you will need to change the texture to be a width-for-height actor instead, by using this property:

Clutter::Actor:request-mode
  type: Clutter::RequestMode
  default: CLUTTER_REQUEST_HEIGHT_FOR_WIDTH

And then setting the height for the actor:

$texture = Clutter::Texture->new();
$texture->set(
    keep_aspect_ratio => TRUE,
    request_mode      => 'width-for-height',
);
$texture->set_from_file($filename);
$texture->set_height(100);

This will set up a texture with the contents of filename, a height of 100 pixels and a width maintaining the same aspect ratio of the original image.

ANIMATIONS

Inverting animations

If an animation is composed by two identical parts with the latter part "flipping" the animation of the former one, e.g.:

                      / scale from 2.0 to 1.0
begin                /
+--------------------|--------------------+------> time
\                                         end
 \ scale from 1.0 to 2.0

Instead of using two different effects or two different behaviours you might simply use the

Clutter::Timeline:direction
  type: Clutter::TimelineDirection
  default: CLUTTER_TIMELINE_FORWARD

Property of Clutter::Timeline. Set up the timeline duration to be the exact half of the overall animation and connect a callback to the

Clutter::Timeline::completed

Signal and change the direction property; you will also need to rewind the timeline so that the state is reset at the right frame number:

$timeline = Clutter::Timeline->new();
$timeline->set_duration(250); # 250 msecs
$timeline->signal_connect(completed => sub {
    $timeline->set_direction('backward');
    $timeline->rewind();
    $timeline->start();
});

When the timeline is complete it will be restarted from the end and go backward to the start. Any Clutter::Behaviour attached to the timeline will be reversed as well, giving you the desired effect.

AUTHOR

Emmanuele Bassi <ebassi@linux.intel.com>

COPYRIGHT

Copyright (C) 2008 Intel Corporation

SEE ALSO

perl(1), Clutter(3pm)