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Clutter::Cookbook.3pm

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)