void
_clutter_paint_volume_get_stage_paint_box (ClutterPaintVolume *pv,
ClutterStage *stage,
ClutterActorBox *box)
{
ClutterPaintVolume projected_pv;
CoglMatrix modelview;
CoglMatrix projection;
float viewport[4];
_clutter_paint_volume_copy_static (pv, &projected_pv);
cogl_matrix_init_identity (&modelview);
/* If the paint volume isn't already in eye coordinates... */
if (pv->actor)
_clutter_actor_apply_relative_transformation_matrix (pv->actor, NULL,
&modelview);
_clutter_stage_get_projection_matrix (stage, &projection);
_clutter_stage_get_viewport (stage,
&viewport[0],
&viewport[1],
&viewport[2],
&viewport[3]);
_clutter_paint_volume_project (&projected_pv,
&modelview,
&projection,
viewport);
_clutter_paint_volume_get_bounding_box (&projected_pv, box);
_clutter_actor_box_enlarge_for_effects (box);
clutter_paint_volume_free (&projected_pv);
}
void
_clutter_paint_volume_get_stage_paint_box (ClutterPaintVolume *pv,
ClutterStage *stage,
ClutterActorBox *box)
{
ClutterPaintVolume projected_pv;
CoglMatrix modelview;
CoglMatrix projection;
float viewport[4];
float width;
float height;
_clutter_paint_volume_copy_static (pv, &projected_pv);
cogl_matrix_init_identity (&modelview);
/* If the paint volume isn't already in eye coordinates... */
if (pv->actor)
_clutter_actor_apply_relative_transformation_matrix (pv->actor, NULL,
&modelview);
_clutter_stage_get_projection_matrix (stage, &projection);
_clutter_stage_get_viewport (stage,
&viewport[0],
&viewport[1],
&viewport[2],
&viewport[3]);
_clutter_paint_volume_project (&projected_pv,
&modelview,
&projection,
viewport);
_clutter_paint_volume_get_bounding_box (&projected_pv, box);
/* The aim here is that for a given rectangle defined with floating point
* coordinates we want to determine a stable quantized size in pixels
* that doesn't vary due to the original box's sub-pixel position.
*
* The reason this is important is because effects will use this
* API to determine the size of offscreen framebuffers and so for
* a fixed-size object that may be animated accross the screen we
* want to make sure that the stage paint-box has an equally stable
* size so that effects aren't made to continuously re-allocate
* a corresponding fbo.
*
* The other thing we consider is that the calculation of this box is
* subject to floating point precision issues that might be slightly
* different to the precision issues involved with actually painting the
* actor, which might result in painting slightly leaking outside the
* user's calculated paint-volume. For this we simply aim to pad out the
* paint-volume by at least half a pixel all the way around.
*/
width = box->x2 - box->x1;
height = box->y2 - box->y1;
width = CLUTTER_NEARBYINT (width);
height = CLUTTER_NEARBYINT (height);
/* XXX: NB the width/height may now be up to 0.5px too small so we
* must also pad by 0.25px all around to account for this. In total we
* must padd by at least 0.75px around all sides. */
/* XXX: The furthest that we can overshoot the bottom right corner by
* here is 1.75px in total if you consider that the 0.75 padding could
* just cross an integer boundary and so ceil will effectively add 1.
*/
box->x2 = ceilf (box->x2 + 0.75);
box->y2 = ceilf (box->y2 + 0.75);
/* Now we redefine the top-left relative to the bottom right based on the
* rounded width/height determined above + a constant so that the overall
* size of the box will be stable and not dependant on the box's
* position.
*
* Adding 3px to the width/height will ensure we cover the maximum of
* 1.75px padding on the bottom/right and still ensure we have > 0.75px
* padding on the top/left.
*/
box->x1 = box->x2 - width - 3;
box->y1 = box->y2 - height - 3;
clutter_paint_volume_free (&projected_pv);
}
