82860b5d5a
The name of the argument in the header must match the name in the function implementation, for gtk-doc to work properly.
884 lines
22 KiB
C
884 lines
22 KiB
C
/*
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* Clutter.
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*
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* An OpenGL based 'interactive canvas' library.
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*
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* Authored By Matthew Allum <mallum@openedhand.com>
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* Jorn Baayen <jorn@openedhand.com>
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* Emmanuele Bassi <ebassi@openedhand.com>
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* Tomas Frydrych <tf@openedhand.com>
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*
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* Copyright (C) 2006, 2007 OpenedHand
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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/**
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* SECTION:clutter-alpha
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* @short_description: A class for calculating an alpha value as a function
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* of time.
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*
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* #ClutterAlpha is a class for calculating an integer value between
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* 0 and %CLUTTER_ALPHA_MAX_ALPHA as a function of time. You should
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* provide a #ClutterTimeline and bind it to the #ClutterAlpha object;
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* you should also provide a function returning the alpha value depending
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* on the position inside the timeline; this function will be executed
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* each time a new frame in the #ClutterTimeline is reached. Since the
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* alpha function is controlled by the timeline instance, you can pause
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* or stop the #ClutterAlpha from calling the alpha function by controlling
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* the #ClutterTimeline object.
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*
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* #ClutterAlpha is used to "drive" a #ClutterBehaviour instance.
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*
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* Since: 0.2
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <math.h>
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#include "clutter-alpha.h"
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#include "clutter-main.h"
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#include "clutter-marshal.h"
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#include "clutter-private.h"
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#include "clutter-debug.h"
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G_DEFINE_TYPE (ClutterAlpha, clutter_alpha, G_TYPE_OBJECT);
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struct _ClutterAlphaPrivate
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{
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ClutterTimeline *timeline;
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guint timeline_new_frame_id;
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guint32 alpha;
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ClutterAlphaFunc func;
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gpointer data;
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GDestroyNotify destroy;
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};
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enum
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{
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PROP_0,
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PROP_TIMELINE,
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PROP_ALPHA
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};
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static void
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timeline_new_frame_cb (ClutterTimeline *timeline,
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guint current_frame_num,
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ClutterAlpha *alpha)
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{
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ClutterAlphaPrivate *priv = alpha->priv;
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/* Update alpha value and notify */
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if (priv->func)
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{
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g_object_ref (alpha);
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priv->alpha = priv->func (alpha, priv->data);
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g_object_notify (G_OBJECT (alpha), "alpha");
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g_object_unref (alpha);
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}
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}
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static void
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clutter_alpha_set_property (GObject *object,
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guint prop_id,
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const GValue *value,
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GParamSpec *pspec)
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{
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ClutterAlpha *alpha;
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ClutterAlphaPrivate *priv;
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alpha = CLUTTER_ALPHA (object);
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priv = alpha->priv;
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switch (prop_id)
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{
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case PROP_TIMELINE:
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clutter_alpha_set_timeline (alpha, g_value_get_object (value));
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break;
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default:
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G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
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break;
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}
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}
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static void
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clutter_alpha_get_property (GObject *object,
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guint prop_id,
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GValue *value,
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GParamSpec *pspec)
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{
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ClutterAlpha *alpha;
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ClutterAlphaPrivate *priv;
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alpha = CLUTTER_ALPHA (object);
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priv = alpha->priv;
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switch (prop_id)
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{
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case PROP_TIMELINE:
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g_value_set_object (value, priv->timeline);
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break;
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case PROP_ALPHA:
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g_value_set_uint (value, priv->alpha);
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break;
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default:
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G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
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break;
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}
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}
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static void
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clutter_alpha_finalize (GObject *object)
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{
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ClutterAlphaPrivate *priv = CLUTTER_ALPHA (object)->priv;
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if (priv->destroy)
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{
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priv->destroy (priv->data);
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priv->destroy = NULL;
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priv->data = NULL;
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priv->func = NULL;
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}
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G_OBJECT_CLASS (clutter_alpha_parent_class)->finalize (object);
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}
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static void
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clutter_alpha_dispose (GObject *object)
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{
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ClutterAlpha *self = CLUTTER_ALPHA(object);
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clutter_alpha_set_timeline (self, NULL);
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G_OBJECT_CLASS (clutter_alpha_parent_class)->dispose (object);
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}
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static void
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clutter_alpha_class_init (ClutterAlphaClass *klass)
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{
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GObjectClass *object_class = G_OBJECT_CLASS (klass);
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object_class->set_property = clutter_alpha_set_property;
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object_class->get_property = clutter_alpha_get_property;
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object_class->finalize = clutter_alpha_finalize;
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object_class->dispose = clutter_alpha_dispose;
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g_type_class_add_private (klass, sizeof (ClutterAlphaPrivate));
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/**
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* ClutterAlpha:timeline:
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*
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* A #ClutterTimeline instance used to drive the alpha function.
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*
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* Since: 0.2
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*/
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g_object_class_install_property (object_class,
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PROP_TIMELINE,
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g_param_spec_object ("timeline",
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"Timeline",
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"Timeline",
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CLUTTER_TYPE_TIMELINE,
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CLUTTER_PARAM_READWRITE));
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/**
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* ClutterAlpha:alpha:
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*
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* The alpha value as computed by the alpha function.
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*
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* Since: 0.2
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*/
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g_object_class_install_property (object_class,
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PROP_ALPHA,
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g_param_spec_uint ("alpha",
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"Alpha value",
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"Alpha value",
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0,
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CLUTTER_ALPHA_MAX_ALPHA,
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0,
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CLUTTER_PARAM_READABLE));
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}
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static void
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clutter_alpha_init (ClutterAlpha *self)
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{
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self->priv = G_TYPE_INSTANCE_GET_PRIVATE (self,
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CLUTTER_TYPE_ALPHA,
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ClutterAlphaPrivate);
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}
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/**
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* clutter_alpha_get_alpha:
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* @alpha: A #ClutterAlpha
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*
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* Query the current alpha value.
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*
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* Return Value: The current alpha value for the alpha
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*
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* Since: 0.2
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*/
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guint32
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clutter_alpha_get_alpha (ClutterAlpha *alpha)
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{
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g_return_val_if_fail (CLUTTER_IS_ALPHA (alpha), FALSE);
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return alpha->priv->alpha;
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}
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/**
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* clutter_alpha_set_func:
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* @alpha: A #ClutterAlpha
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* @func: A #ClutterAlphaAlphaFunc
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* @data: user data to be passed to the alpha function, or %NULL
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* @destroy: notify function used when disposing the alpha function
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*
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* Sets the #ClutterAlphaFunc function used to compute
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* the alpha value at each frame of the #ClutterTimeline
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* bound to @alpha.
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*
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* Since: 0.2
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*/
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void
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clutter_alpha_set_func (ClutterAlpha *alpha,
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ClutterAlphaFunc func,
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gpointer data,
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GDestroyNotify destroy)
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{
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ClutterAlphaPrivate *priv;
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g_return_if_fail (CLUTTER_IS_ALPHA (alpha));
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priv = alpha->priv;
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if (priv->destroy)
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{
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priv->destroy (priv->data);
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priv->func = NULL;
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priv->data = NULL;
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priv->destroy = NULL;
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}
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priv->func = func;
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priv->data = data;
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priv->destroy = destroy;
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}
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/**
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* clutter_alpha_set_timeline:
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* @alpha: A #ClutterAlpha
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* @timeline: A #ClutterTimeline
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*
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* Binds @alpha to @timeline.
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*
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* Since: 0.2
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*/
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void
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clutter_alpha_set_timeline (ClutterAlpha *alpha,
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ClutterTimeline *timeline)
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{
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ClutterAlphaPrivate *priv;
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g_return_if_fail (CLUTTER_IS_ALPHA (alpha));
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g_return_if_fail (timeline == NULL || CLUTTER_IS_TIMELINE (timeline));
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priv = alpha->priv;
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if (priv->timeline)
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{
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g_signal_handlers_disconnect_by_func (priv->timeline,
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timeline_new_frame_cb,
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alpha);
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g_object_unref (priv->timeline);
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priv->timeline = NULL;
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}
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if (timeline)
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{
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priv->timeline = g_object_ref (timeline);
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g_signal_connect (priv->timeline, "new-frame",
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G_CALLBACK (timeline_new_frame_cb),
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alpha);
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}
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}
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/**
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* clutter_alpha_get_timeline:
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* @alpha: A #ClutterAlpha
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*
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* Gets the #ClutterTimeline bound to @alpha.
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*
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* Return value: a #ClutterTimeline instance
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*
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* Since: 0.2
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*/
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ClutterTimeline *
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clutter_alpha_get_timeline (ClutterAlpha *alpha)
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{
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g_return_val_if_fail (CLUTTER_IS_ALPHA (alpha), NULL);
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return alpha->priv->timeline;
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}
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/**
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* clutter_alpha_new:
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*
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* Creates a new #ClutterAlpha instance. You must set a function
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* to compute the alpha value using clutter_alpha_set_func() and
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* bind a #ClutterTimeline object to the #ClutterAlpha instance
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* using clutter_alpha_set_timeline().
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*
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* You should use the newly created #ClutterAlpha instance inside
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* a #ClutterBehaviour object.
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*
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* Return value: the newly created empty #ClutterAlpha instance.
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*
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* Since: 0.2
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*/
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ClutterAlpha *
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clutter_alpha_new (void)
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{
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return g_object_new (CLUTTER_TYPE_ALPHA, NULL);
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}
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/**
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* clutter_alpha_new_full:
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* @timeline: #ClutterTimeline timeline
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* @func: #ClutterAlphaFunc alpha function
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* @data: data to be passed to the alpha function
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* @destroy: notify to be called when removing the alpha function
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*
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* Creates a new #ClutterAlpha instance and sets the timeline
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* and alpha function.
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*
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* Return Value: the newly created #ClutterAlpha
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*
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* Since: 0.2
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*/
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ClutterAlpha *
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clutter_alpha_new_full (ClutterTimeline *timeline,
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ClutterAlphaFunc func,
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gpointer data,
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GDestroyNotify destroy)
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{
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ClutterAlpha *retval;
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g_return_val_if_fail (CLUTTER_IS_TIMELINE (timeline), NULL);
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g_return_val_if_fail (func != NULL, NULL);
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retval = clutter_alpha_new ();
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clutter_alpha_set_timeline (retval, timeline);
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clutter_alpha_set_func (retval, func, data, destroy);
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return retval;
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}
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/**
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* clutter_ramp_inc_func:
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* @alpha: a #ClutterAlpha
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* @dummy: unused argument
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*
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* Convenience alpha function for a monotonic increasing ramp. You
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* can use this function as the alpha function for clutter_alpha_set_func().
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*
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* Return value: an alpha value.
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*
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* Since: 0.2
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*/
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guint32
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clutter_ramp_inc_func (ClutterAlpha *alpha,
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gpointer dummy)
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{
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ClutterTimeline *timeline;
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gint current_frame_num, n_frames;
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timeline = clutter_alpha_get_timeline (alpha);
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current_frame_num = clutter_timeline_get_current_frame (timeline);
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n_frames = clutter_timeline_get_n_frames (timeline);
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return (current_frame_num * CLUTTER_ALPHA_MAX_ALPHA) / n_frames;
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}
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/**
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* clutter_ramp_dec_func:
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* @alpha: a #ClutterAlpha
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* @dummy: unused argument
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*
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* Convenience alpha function for a monotonic decreasing ramp. You
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* can use this function as the alpha function for clutter_alpha_set_func().
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*
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* Return value: an alpha value.
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*
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* Since: 0.2
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*/
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guint32
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clutter_ramp_dec_func (ClutterAlpha *alpha,
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gpointer dummy)
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{
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ClutterTimeline *timeline;
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gint current_frame_num, n_frames;
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timeline = clutter_alpha_get_timeline (alpha);
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current_frame_num = clutter_timeline_get_current_frame (timeline);
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n_frames = clutter_timeline_get_n_frames (timeline);
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return (n_frames - current_frame_num)
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* CLUTTER_ALPHA_MAX_ALPHA
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/ n_frames;
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}
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/**
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* clutter_ramp_func:
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* @alpha: a #ClutterAlpha
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* @dummy: unused argument
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*
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* Convenience alpha function for a full ramp function (increase for
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* half the time, decrease for the remaining half). You can use this
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* function as the alpha function for clutter_alpha_set_func().
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*
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* Return value: an alpha value.
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*
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* Since: 0.2
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*/
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guint32
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clutter_ramp_func (ClutterAlpha *alpha,
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gpointer dummy)
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{
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ClutterTimeline *timeline;
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gint current_frame_num, n_frames;
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timeline = clutter_alpha_get_timeline (alpha);
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current_frame_num = clutter_timeline_get_current_frame (timeline);
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n_frames = clutter_timeline_get_n_frames (timeline);
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if (current_frame_num > (n_frames / 2))
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{
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return (n_frames - current_frame_num)
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* CLUTTER_ALPHA_MAX_ALPHA
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/ (n_frames / 2);
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}
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else
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{
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return current_frame_num
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* CLUTTER_ALPHA_MAX_ALPHA
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/ (n_frames / 2);
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}
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}
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static guint32
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sincx1024_func (ClutterAlpha *alpha,
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ClutterAngle angle,
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ClutterFixed offset)
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{
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ClutterTimeline *timeline;
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gint current_frame_num, n_frames;
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ClutterAngle x;
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unsigned int sine;
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timeline = clutter_alpha_get_timeline (alpha);
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current_frame_num = clutter_timeline_get_current_frame (timeline);
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n_frames = clutter_timeline_get_n_frames (timeline);
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x = angle * current_frame_num / n_frames;
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x -= (512 * 512 / angle);
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sine = ((clutter_sini (x) + offset)/2) * CLUTTER_ALPHA_MAX_ALPHA;
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sine = sine >> CFX_Q;
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return sine;
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}
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#if 0
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/*
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* The following two functions are left in place for reference
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* purposes.
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*/
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static guint32
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sincx_func (ClutterAlpha *alpha,
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ClutterFixed angle,
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ClutterFixed offset)
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{
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ClutterTimeline *timeline;
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gint current_frame_num, n_frames;
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ClutterFixed x, sine;
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timeline = clutter_alpha_get_timeline (alpha);
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current_frame_num = clutter_timeline_get_current_frame (timeline);
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n_frames = clutter_timeline_get_n_frames (timeline);
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x = angle * current_frame_num / n_frames;
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x = CLUTTER_FIXED_MUL (x, CFX_PI) - CLUTTER_FIXED_DIV (CFX_PI, angle);
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sine = (clutter_fixed_sin (x) + offset)/2;
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CLUTTER_NOTE (ALPHA, "sine: %2f\n", CLUTTER_FIXED_TO_DOUBLE (sine));
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return CLUTTER_FIXED_INT (sine * CLUTTER_ALPHA_MAX_ALPHA);
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}
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/* NB: angle is not in radians but in muliples of PI, i.e., 2.0
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* represents full circle.
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*/
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static guint32
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sinc_func (ClutterAlpha *alpha,
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float angle,
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float offset)
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{
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ClutterTimeline *timeline;
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gint current_frame_num, n_frames;
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gdouble x, sine;
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timeline = clutter_alpha_get_timeline (alpha);
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current_frame_num = clutter_timeline_get_current_frame (timeline);
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n_frames = clutter_timeline_get_n_frames (timeline);
|
|
|
|
/* FIXME: fixed point, and fixed point sine() */
|
|
|
|
x = (gdouble) (current_frame_num * angle * M_PI) / n_frames ;
|
|
sine = (sin (x - (M_PI / angle)) + offset) * 0.5f;
|
|
|
|
CLUTTER_NOTE (ALPHA, "sine: %2f\n",sine);
|
|
|
|
return CLUTTER_FLOAT_TO_INT ((sine * (gdouble) CLUTTER_ALPHA_MAX_ALPHA));
|
|
}
|
|
#endif
|
|
|
|
/**
|
|
* clutter_sine_func:
|
|
* @alpha: a #ClutterAlpha
|
|
* @dummy: unused argument
|
|
*
|
|
* Convenience alpha function for a sine wave. You can use this
|
|
* function as the alpha function for clutter_alpha_set_func().
|
|
*
|
|
* Return value: an alpha value.
|
|
*
|
|
* Since: 0.2
|
|
*/
|
|
guint32
|
|
clutter_sine_func (ClutterAlpha *alpha,
|
|
gpointer dummy)
|
|
{
|
|
#if 0
|
|
return sinc_func (alpha, 2.0, 1.0);
|
|
#else
|
|
/* 2.0 above represents full circle */
|
|
return sincx1024_func (alpha, 1024, CFX_ONE);
|
|
#endif
|
|
}
|
|
|
|
/**
|
|
* clutter_sine_inc_func:
|
|
* @alpha: a #ClutterAlpha
|
|
* @dummy: unused argument
|
|
*
|
|
* Convenience alpha function for a sine wave over interval [0, pi / 2].
|
|
* You can use this function as the alpha function for
|
|
* clutter_alpha_set_func().
|
|
*
|
|
* Return value: an alpha value.
|
|
*
|
|
* Since: 0.2
|
|
*/
|
|
guint32
|
|
clutter_sine_inc_func (ClutterAlpha *alpha,
|
|
gpointer dummy)
|
|
{
|
|
ClutterTimeline * timeline;
|
|
gint frame;
|
|
gint n_frames;
|
|
ClutterAngle x;
|
|
ClutterFixed sine;
|
|
|
|
timeline = clutter_alpha_get_timeline (alpha);
|
|
frame = clutter_timeline_get_current_frame (timeline);
|
|
n_frames = clutter_timeline_get_n_frames (timeline);
|
|
|
|
x = 256 * frame / n_frames;
|
|
|
|
sine = clutter_sini (x) * CLUTTER_ALPHA_MAX_ALPHA;
|
|
|
|
return ((guint32)sine) >> CFX_Q;
|
|
}
|
|
|
|
/**
|
|
* clutter_sine_dec_func:
|
|
* @alpha: a #ClutterAlpha
|
|
* @dummy: unused argument
|
|
*
|
|
* Convenience alpha function for a sine wave over interval [pi / 2, pi].
|
|
* You can use this function as the alpha function for
|
|
* clutter_alpha_set_func().
|
|
*
|
|
* Return value: an alpha value.
|
|
*
|
|
* Since: 0.4
|
|
*/
|
|
guint32
|
|
clutter_sine_dec_func (ClutterAlpha *alpha,
|
|
gpointer dummy)
|
|
{
|
|
ClutterTimeline * timeline;
|
|
gint frame;
|
|
gint n_frames;
|
|
ClutterAngle x;
|
|
ClutterFixed sine;
|
|
|
|
timeline = clutter_alpha_get_timeline (alpha);
|
|
frame = clutter_timeline_get_current_frame (timeline);
|
|
n_frames = clutter_timeline_get_n_frames (timeline);
|
|
|
|
x = 256 * frame / n_frames + 256;
|
|
|
|
sine = clutter_sini (x) * CLUTTER_ALPHA_MAX_ALPHA;
|
|
|
|
return ((guint32)sine) >> CFX_Q;
|
|
}
|
|
|
|
/**
|
|
* clutter_sine_half_func:
|
|
* @alpha: a #ClutterAlpha
|
|
* @dummy: unused argument
|
|
*
|
|
* Convenience alpha function for a sine wave over interval [0, pi].
|
|
* You can use this function as the alpha function for
|
|
* clutter_alpha_set_func().
|
|
*
|
|
* Return value: an alpha value.
|
|
*
|
|
* Since: 0.4
|
|
*/
|
|
guint32
|
|
clutter_sine_half_func (ClutterAlpha *alpha,
|
|
gpointer dummy)
|
|
{
|
|
ClutterTimeline * timeline;
|
|
gint frame;
|
|
gint n_frames;
|
|
ClutterAngle x;
|
|
ClutterFixed sine;
|
|
|
|
timeline = clutter_alpha_get_timeline (alpha);
|
|
frame = clutter_timeline_get_current_frame (timeline);
|
|
n_frames = clutter_timeline_get_n_frames (timeline);
|
|
|
|
x = 512 * frame / n_frames;
|
|
|
|
sine = clutter_sini (x) * CLUTTER_ALPHA_MAX_ALPHA;
|
|
|
|
return ((guint32)sine) >> CFX_Q;
|
|
}
|
|
|
|
/**
|
|
* clutter_square_func:
|
|
* @alpha: a #ClutterAlpha
|
|
* @dummy: unused argument
|
|
*
|
|
* Convenience alpha function for a square wave. You can use this
|
|
* function as the alpha function for clutter_alpha_set_func().
|
|
*
|
|
* Return value: an alpha value
|
|
*
|
|
* Since: 0.4
|
|
*/
|
|
guint32
|
|
clutter_square_func (ClutterAlpha *alpha,
|
|
gpointer dummy)
|
|
{
|
|
ClutterTimeline *timeline;
|
|
gint current_frame_num, n_frames;
|
|
|
|
timeline = clutter_alpha_get_timeline (alpha);
|
|
|
|
current_frame_num = clutter_timeline_get_current_frame (timeline);
|
|
n_frames = clutter_timeline_get_n_frames (timeline);
|
|
|
|
return (current_frame_num > (n_frames / 2)) ? CLUTTER_ALPHA_MAX_ALPHA
|
|
: 0;
|
|
}
|
|
|
|
|
|
/**
|
|
* clutter_smoothstep_inc_func:
|
|
* @alpha: a #ClutterAlpha
|
|
* @dummy: unused
|
|
*
|
|
* Convenience alpha function for a smoothstep curve. You can use this
|
|
* function as the alpha function for clutter_alpha_set_func().
|
|
*
|
|
* Return value: an alpha value
|
|
*
|
|
* Since: 0.4
|
|
*/
|
|
guint32
|
|
clutter_smoothstep_inc_func (ClutterAlpha *alpha,
|
|
gpointer dummy)
|
|
{
|
|
ClutterTimeline *timeline;
|
|
gint frame;
|
|
gint n_frames;
|
|
gint32 r;
|
|
gint32 x;
|
|
|
|
/*
|
|
* The smoothstep function uses f(x) = -2x^3 + 3x^2 where x is from <0,1>,
|
|
* and precission is critical -- we use 8.24 fixed format for this operation.
|
|
* The earlier operations involve division, which we cannot do in 8.24 for
|
|
* numbers in <0,1> we use ClutterFixed.
|
|
*/
|
|
timeline = clutter_alpha_get_timeline (alpha);
|
|
frame = clutter_timeline_get_current_frame (timeline);
|
|
n_frames = clutter_timeline_get_n_frames (timeline);
|
|
|
|
/*
|
|
* Convert x to 8.24 for next step.
|
|
*/
|
|
x = CFX_DIV (frame, n_frames) << 8;
|
|
|
|
/*
|
|
* f(x) = -2x^3 + 3x^2
|
|
*
|
|
* Convert result to ClutterFixed to avoid overflow in next step.
|
|
*/
|
|
r = ((x >> 12) * (x >> 12) * 3 - (x >> 15) * (x >> 16) * (x >> 16)) >> 8;
|
|
|
|
return CFX_INT (r * CLUTTER_ALPHA_MAX_ALPHA);
|
|
}
|
|
|
|
/**
|
|
* clutter_smoothstep_dec_func:
|
|
* @alpha: a #ClutterAlpha
|
|
* @dummy: unused
|
|
*
|
|
* Convenience alpha function for a downward smoothstep curve. You can use
|
|
* this function as the alpha function for clutter_alpha_set_func().
|
|
*
|
|
* Return value: an alpha value
|
|
*
|
|
* Since: 0.4
|
|
*/
|
|
guint32
|
|
clutter_smoothstep_dec_func (ClutterAlpha *alpha,
|
|
gpointer dummy)
|
|
{
|
|
return CLUTTER_ALPHA_MAX_ALPHA - clutter_smoothstep_inc_func (alpha, dummy);
|
|
}
|
|
|
|
/**
|
|
* clutter_exp_inc_func:
|
|
* @alpha: a #ClutterAlpha
|
|
* @dummy: unused argument
|
|
*
|
|
* Convenience alpha function for a 2^x curve. You can use this function as the
|
|
* alpha function for clutter_alpha_set_func().
|
|
*
|
|
* Return value: an alpha value.
|
|
*
|
|
* Since: 0.4
|
|
*/
|
|
guint32
|
|
clutter_exp_inc_func (ClutterAlpha *alpha,
|
|
gpointer dummy)
|
|
{
|
|
ClutterTimeline * timeline;
|
|
gint frame;
|
|
gint n_frames;
|
|
ClutterFixed x;
|
|
ClutterFixed x_alpha_max = 0x100000;
|
|
guint32 result;
|
|
|
|
/*
|
|
* Choose x_alpha_max such that
|
|
*
|
|
* (2^x_alpha_max) - 1 == CLUTTER_ALPHA_MAX_ALPHA
|
|
*/
|
|
#if CLUTTER_ALPHA_MAX_ALPHA != 0xffff
|
|
#error Adjust x_alpha_max to match CLUTTER_ALPHA_MAX_ALPHA
|
|
#endif
|
|
|
|
timeline = clutter_alpha_get_timeline (alpha);
|
|
frame = clutter_timeline_get_current_frame (timeline);
|
|
n_frames = clutter_timeline_get_n_frames (timeline);
|
|
|
|
x = x_alpha_max * frame / n_frames;
|
|
|
|
result = clutter_pow2x (x) - 1;
|
|
|
|
return result;
|
|
}
|
|
|
|
|
|
/**
|
|
* clutter_exp_dec_func:
|
|
* @alpha: a #ClutterAlpha
|
|
* @dummy: unused argument
|
|
*
|
|
* Convenience alpha function for a decreasing 2^x curve. You can use this
|
|
* function as the alpha function for clutter_alpha_set_func().
|
|
*
|
|
* Return value: an alpha value.
|
|
*
|
|
* Since: 0.4
|
|
*/
|
|
guint32
|
|
clutter_exp_dec_func (ClutterAlpha *alpha,
|
|
gpointer dummy)
|
|
{
|
|
ClutterTimeline * timeline;
|
|
gint frame;
|
|
gint n_frames;
|
|
ClutterFixed x;
|
|
ClutterFixed x_alpha_max = 0x100000;
|
|
guint32 result;
|
|
|
|
/*
|
|
* Choose x_alpha_max such that
|
|
*
|
|
* (2^x_alpha_max) - 1 == CLUTTER_ALPHA_MAX_ALPHA
|
|
*/
|
|
#if CLUTTER_ALPHA_MAX_ALPHA != 0xffff
|
|
#error Adjust x_alpha_max to match CLUTTER_ALPHA_MAX_ALPHA
|
|
#endif
|
|
|
|
timeline = clutter_alpha_get_timeline (alpha);
|
|
frame = clutter_timeline_get_current_frame (timeline);
|
|
n_frames = clutter_timeline_get_n_frames (timeline);
|
|
|
|
x = (x_alpha_max * (n_frames - frame)) / n_frames;
|
|
|
|
result = clutter_pow2x (x) - 1;
|
|
|
|
return result;
|
|
}
|