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effect: Add OffscreenEffect

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The OffscreenEffect class is meant to be used to implement Effect
sub-classes that create an offscreen framebuffer and redirect the
actor's paint sequence there. The OffscreenEffect is useful for
effects using fragment shaders.

Any shader-based effect being applied to an actor through an offscreen
buffer should be used before painting the resulting target material and
not for every actor. This means that doing:

       pre_paint: cogl_program_use(program)
                  set up offscreen buffer
           paint: [ actors ] → offscreen buffer → target material
      post_paint: paint target material
                  cogl_program_use(null)

Is not correct. Unfortunately, we cannot really do:

      post_paint: cogl_program_use(program)
                  paint target material
                  cogl_program_use(null)

Because the OffscreenEffect::post_paint() implementation also pops the
offscreen buffer and re-instates the previous framebuffer:

      post_paint: cogl_program_use(program)
                  change frame buffer ← ouch!
                  paint target material
                  cogl_program_use(null)

One way to fix it is to allow using the shader right before painting
the target material - which means adding a new virtual inside the
OffscreenEffect class vtable in additions to the ones defined by the
parent Effect class.

The newly-added paint_target() virtual allows the correct sequence of
actions by adding an entry point for sub-classes to wrap the "paint
target material" operation with custom code, in order to implement the
case above correctly as:

      post_paint: change frame buffer
                  cogl_program_use(program)
                  paint target material
                  cogl_program_use(null)

The added upside is that sub-classes of OffscreenEffect involving
shaders really just need to override the prepare() and paint_target()
virtuals, since the pre_paint() and post_paint() do all that's needed.
This commit is contained in:
Emmanuele Bassi 2010-05-17 11:39:27 +01:00
parent a86f1b45bb
commit c3ab32ae68
4 changed files with 435 additions and 0 deletions
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2
clutter/Makefile.am
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@ -113,6 +113,7 @@ source_h = \
$(srcdir)/clutter-main.h \
$(srcdir)/clutter-media.h \
$(srcdir)/clutter-model.h \
$(srcdir)/clutter-offscreen-effect.h \
$(srcdir)/clutter-path.h \
$(srcdir)/clutter-rectangle.h \
$(srcdir)/clutter-score.h \
@ -197,6 +198,7 @@ source_c = \
$(srcdir)/clutter-master-clock.c \
$(srcdir)/clutter-media.c \
$(srcdir)/clutter-model.c \
$(srcdir)/clutter-offscreen-effect.c \
$(srcdir)/clutter-path.c \
$(srcdir)/clutter-rectangle.c \
$(srcdir)/clutter-score.c \

336
clutter/clutter-offscreen-effect.c Normal file
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@ -0,0 +1,336 @@
/*
* Clutter.
*
* An OpenGL based 'interactive canvas' library.
*
* Copyright (C) 2010 Intel Corporation.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see <http://www.gnu.org/licenses/>.
*
* Author:
* Emmanuele Bassi <ebassi@linux.intel.com>
*/
/**
* SECTION:clutter-offscreen-effect
* @short_description: Base class for effects using offscreen buffers
* @see_also: #ClutterBlurEffect, #ClutterEffect
*
* #ClutterOffscreenEffect is an abstract class that can be used by
* #ClutterEffect sub-classes requiring access to an offscreen buffer.
*
* Some effects, like the fragment shader based effects, can only use GL
* textures, and in order to apply those effects to any kind of actor they
* require that all drawing operations are applied to an offscreen framebuffer
* that gets redirected to a texture.
*
* #ClutterOffscreenEffect provides all the heavy-lifting for creating the
* offscreen framebuffer, the redirection and the final paint of the texture on
* the desired stage.
*
* <refsect2 id="ClutterOffscreenEffect-implementing">
* <title>Implementing a ClutterOffscreenEffect</title>
* <para>Creating a sub-class of #ClutterOffscreenEffect requires, in case
* of overriding the #ClutterEffect virtual functions, to chain up to the
* #ClutterOffscreenEffect's implementation.</para>
* <para>On top of the #ClutterEffect's virtual functions,
* #ClutterOffscreenEffect also provides a <function>paint_target()</function>
* function, which encapsulates the effective painting of the texture that
* contains the result of the offscreen redirection.</para>
* </refsect2>
*
* #ClutterOffscreenEffect is available since Clutter 1.4
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "clutter-offscreen-effect.h"
#include "cogl/cogl.h"
#include "clutter-debug.h"
#include "clutter-private.h"
struct _ClutterOffscreenEffectPrivate
{
CoglHandle offscreen;
CoglHandle target;
ClutterActor *actor;
};
G_DEFINE_ABSTRACT_TYPE (ClutterOffscreenEffect,
clutter_offscreen_effect,
CLUTTER_TYPE_EFFECT);
static void
clutter_offscreen_effect_set_actor (ClutterActorMeta *meta,
ClutterActor *actor)
{
ClutterOffscreenEffect *self = CLUTTER_OFFSCREEN_EFFECT (meta);
ClutterOffscreenEffectPrivate *priv = self->priv;
ClutterActorMetaClass *meta_class;
ClutterPerspective perspective;
gfloat width, height, z_camera;
ClutterActorBox allocation;
gfloat fb_width, fb_height;
ClutterActor *stage;
CoglHandle texture;
CoglMatrix matrix;
meta_class = CLUTTER_ACTOR_META_CLASS (clutter_offscreen_effect_parent_class);
meta_class->set_actor (meta, actor);
/* clear out the previous state */
if (priv->offscreen != COGL_INVALID_HANDLE)
{
cogl_handle_unref (priv->offscreen);
priv->offscreen = COGL_INVALID_HANDLE;
}
if (priv->target != COGL_INVALID_HANDLE)
{
cogl_handle_unref (priv->target);
priv->target = COGL_INVALID_HANDLE;
}
/* we keep a back pointer here, to avoid going through the ActorMeta */
priv->actor = clutter_actor_meta_get_actor (meta);
if (priv->actor == NULL)
return;
stage = clutter_actor_get_stage (priv->actor);
if (stage == NULL)
{
CLUTTER_NOTE (MISC, "The actor '%s' is not part of a stage",
clutter_actor_get_name (actor) == NULL
? G_OBJECT_TYPE_NAME (actor)
: clutter_actor_get_name (actor));
/* we forcibly disable the effect here */
clutter_actor_meta_set_enabled (meta, FALSE);
return;
}
clutter_stage_get_perspective (CLUTTER_STAGE (stage), &perspective);
clutter_actor_get_allocation_box (stage, &allocation);
clutter_actor_box_get_size (&allocation, &fb_width, &fb_height);
clutter_actor_get_allocation_box (priv->actor, &allocation);
clutter_actor_box_get_size (&allocation, &width, &height);
priv->target = cogl_material_new ();
texture = cogl_texture_new_with_size (MAX (width, 1), MAX (height, 1),
COGL_TEXTURE_NO_SLICING,
COGL_PIXEL_FORMAT_RGBA_8888_PRE);
cogl_material_set_layer (priv->target, 0, texture);
cogl_handle_unref (texture);
cogl_material_set_layer_filters (priv->target, 0,
COGL_MATERIAL_FILTER_LINEAR,
COGL_MATERIAL_FILTER_LINEAR);
priv->offscreen = cogl_offscreen_new_to_texture (texture);
if (priv->offscreen == COGL_INVALID_HANDLE)
{
g_warning ("%s: Unable to create an Offscreen buffer", G_STRLOC);
/* we forcibly disable the effect here */
clutter_actor_meta_set_enabled (meta, FALSE);
return;
}
cogl_push_framebuffer (priv->offscreen);
width = cogl_texture_get_width (texture);
height = cogl_texture_get_height (texture);
fb_width /= fb_width / width;
fb_height /= fb_height / height;
cogl_set_viewport (0, 0, width, height);
cogl_perspective (perspective.fovy,
perspective.aspect,
perspective.z_near,
perspective.z_far);
cogl_get_projection_matrix (&matrix);
z_camera = 0.5 * matrix.xx;
cogl_matrix_init_identity (&matrix);
cogl_matrix_translate (&matrix, -0.5f, -0.5f, -z_camera);
cogl_matrix_scale (&matrix,
1.0f / fb_width,
-1.0f / fb_height,
1.0f / fb_width);
cogl_matrix_translate (&matrix, 0.0f, -1.0f * fb_height, 0.0f);
cogl_set_modelview_matrix (&matrix);
cogl_pop_framebuffer ();
}
static gboolean
clutter_offscreen_effect_pre_paint (ClutterEffect *effect)
{
ClutterOffscreenEffect *self = CLUTTER_OFFSCREEN_EFFECT (effect);
ClutterOffscreenEffectPrivate *priv = self->priv;
if (!clutter_actor_meta_get_enabled (CLUTTER_ACTOR_META (effect)))
return FALSE;
if (priv->offscreen != COGL_INVALID_HANDLE)
{
CoglColor transparent;
cogl_push_framebuffer (priv->offscreen);
cogl_push_matrix ();
cogl_color_set_from_4ub (&transparent, 0, 0, 0, 0);
cogl_clear (&transparent,
COGL_BUFFER_BIT_COLOR |
COGL_BUFFER_BIT_STENCIL |
COGL_BUFFER_BIT_DEPTH);
return TRUE;
}
return FALSE;
}
static void
clutter_offscreen_effect_real_paint_target (ClutterOffscreenEffect *effect)
{
ClutterOffscreenEffectPrivate *priv = effect->priv;
ClutterActorBox allocation;
gfloat width, height;
guint8 paint_opacity;
paint_opacity = clutter_actor_get_paint_opacity (priv->actor);
clutter_actor_get_allocation_box (priv->actor, &allocation);
clutter_actor_box_get_size (&allocation, &width, &height);
cogl_material_set_color4ub (priv->target,
paint_opacity,
paint_opacity,
paint_opacity,
paint_opacity);
cogl_set_source (priv->target);
cogl_rectangle_with_texture_coords (0, 0, width, height,
0.0, 0.0,
1.0, 1.0);
}
static void
clutter_offscreen_effect_post_paint (ClutterEffect *effect)
{
ClutterOffscreenEffect *self = CLUTTER_OFFSCREEN_EFFECT (effect);
ClutterOffscreenEffectPrivate *priv = self->priv;
if (priv->offscreen != COGL_INVALID_HANDLE &&
priv->target != COGL_INVALID_HANDLE &&
priv->actor != NULL)
{
cogl_pop_matrix ();
cogl_pop_framebuffer ();
/* paint the target material; this is virtualized for
* sub-classes that require special hand-holding
*/
clutter_offscreen_effect_paint_target (self);
}
}
static void
clutter_offscreen_effect_finalize (GObject *gobject)
{
ClutterOffscreenEffect *self = CLUTTER_OFFSCREEN_EFFECT (gobject);
ClutterOffscreenEffectPrivate *priv = self->priv;
if (priv->offscreen)
cogl_handle_unref (priv->offscreen);
if (priv->target)
cogl_handle_unref (priv->target);
G_OBJECT_CLASS (clutter_offscreen_effect_parent_class)->finalize (gobject);
}
static void
clutter_offscreen_effect_class_init (ClutterOffscreenEffectClass *klass)
{
ClutterActorMetaClass *meta_class = CLUTTER_ACTOR_META_CLASS (klass);
ClutterEffectClass *effect_class = CLUTTER_EFFECT_CLASS (klass);
GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
g_type_class_add_private (klass, sizeof (ClutterOffscreenEffectPrivate));
klass->paint_target = clutter_offscreen_effect_real_paint_target;
meta_class->set_actor = clutter_offscreen_effect_set_actor;
effect_class->pre_paint = clutter_offscreen_effect_pre_paint;
effect_class->post_paint = clutter_offscreen_effect_post_paint;
gobject_class->finalize = clutter_offscreen_effect_finalize;
}
static void
clutter_offscreen_effect_init (ClutterOffscreenEffect *self)
{
self->priv = G_TYPE_INSTANCE_GET_PRIVATE (self,
CLUTTER_TYPE_OFFSCREEN_EFFECT,
ClutterOffscreenEffectPrivate);
}
/**
* clutter_offscreen_effect_get_target:
* @effect: a #ClutterOffscreenEffect
*
* Retrieves the material used as a render target for the offscreen
* buffer created by @effect
*
* Return value: (transfer none): a handle for a #CoglMaterial, or
* %COGL_INVALID_HANDLE. The returned handle is owned by Clutter
* and it should not be modified or freed
*
* Since: 1.4
*/
CoglHandle
clutter_offscreen_effect_get_target (ClutterOffscreenEffect *effect)
{
g_return_val_if_fail (CLUTTER_IS_OFFSCREEN_EFFECT (effect),
COGL_INVALID_HANDLE);
return effect->priv->target;
}
/**
* clutter_offscreen_effect_paint_target:
* @effect: a #ClutterOffscreenEffect
*
* Calls the paint_target() virtual function of the @effect
*
* Since: 1.4
*/
void
clutter_offscreen_effect_paint_target (ClutterOffscreenEffect *effect)
{
g_return_if_fail (CLUTTER_IS_OFFSCREEN_EFFECT (effect));
CLUTTER_OFFSCREEN_EFFECT_GET_CLASS (effect)->paint_target (effect);
}

96
clutter/clutter-offscreen-effect.h Normal file
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@ -0,0 +1,96 @@
/*
* Clutter.
*
* An OpenGL based 'interactive canvas' library.
*
* Copyright (C) 2010 Intel Corporation.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see <http://www.gnu.org/licenses/>.
*
* Author:
* Emmanuele Bassi <ebassi@linux.intel.com>
*/
#if !defined(__CLUTTER_H_INSIDE__) && !defined(CLUTTER_COMPILATION)
#error "Only <clutter/clutter.h> can be included directly."
#endif
#ifndef __CLUTTER_OFFSCREEN_EFFECT_H__
#define __CLUTTER_OFFSCREEN_EFFECT_H__
#include <clutter/clutter-effect.h>
G_BEGIN_DECLS
#define CLUTTER_TYPE_OFFSCREEN_EFFECT (clutter_offscreen_effect_get_type ())
#define CLUTTER_OFFSCREEN_EFFECT(o) (G_TYPE_CHECK_INSTANCE_CAST ((o), CLUTTER_TYPE_OFFSCREEN_EFFECT, ClutterOffscreenEffect))
#define CLUTTER_IS_OFFSCREEN_EFFECT(o) (G_TYPE_CHECK_INSTANCE_TYPE ((o), CLUTTER_TYPE_OFFSCREEN_EFFECT))
#define CLUTTER_OFFSCREEN_EFFECT_CLASS(k) (G_TYPE_CHECK_CLASS_CAST ((k), CLUTTER_TYPE_OFFSCREEN_EFFECT, ClutterOffscreenEffectClass))
#define CLUTTER_IS_OFFSCREEN_EFFECT_CLASS(k) (G_TYPE_CHECK_CLASS_TYPE ((k), CLUTTER_TYPE_OFFSCREEN_EFFECT))
#define CLUTTER_OFFSCREEN_EFFECT_GET_CLASS(o) (G_TYPE_INSTANCE_GET_CLASS ((o), CLUTTER_TYPE_OFFSCREEN_EFFECT, ClutterOffscreenEffectClass))
typedef struct _ClutterOffscreenEffect ClutterOffscreenEffect;
typedef struct _ClutterOffscreenEffectPrivate ClutterOffscreenEffectPrivate;
typedef struct _ClutterOffscreenEffectClass ClutterOffscreenEffectClass;
/**
* ClutterOffscreenEffect:
*
* The #ClutterOffscreenEffect structure contains only private data
* and should be accessed using the provided API
*
* Since: 1.4
*/
struct _ClutterOffscreenEffect
{
/*< private >*/
ClutterEffect parent_instance;
ClutterOffscreenEffectPrivate *priv;
};
/**
* ClutterOffscreenEffectClass:
* @paint_target: virtual function
*
* The #ClutterOffscreenEffectClass structure contains only private data
*
* Since: 1.4
*/
struct _ClutterOffscreenEffectClass
{
/*< private >*/
ClutterEffectClass parent_class;
/*< public >*/
void (* paint_target) (ClutterOffscreenEffect *effect);
/*< private >*/
void (* _clutter_offscreen1) (void);
void (* _clutter_offscreen2) (void);
void (* _clutter_offscreen3) (void);
void (* _clutter_offscreen4) (void);
void (* _clutter_offscreen5) (void);
void (* _clutter_offscreen6) (void);
void (* _clutter_offscreen7) (void);
};
GType clutter_offscreen_effect_get_type (void) G_GNUC_CONST;
CoglHandle clutter_offscreen_effect_get_target (ClutterOffscreenEffect *effect);
void clutter_offscreen_effect_paint_target (ClutterOffscreenEffect *effect);
G_END_DECLS
#endif /* __CLUTTER_OFFSCREEN_EFFECT_H__ */

1
clutter/clutter.h
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@ -76,6 +76,7 @@
#include "clutter-main.h"
#include "clutter-media.h"
#include "clutter-model.h"
#include "clutter-offscreen-effect.h"
#include "clutter-path.h"
#include "clutter-rectangle.h"
#include "clutter-score.h"