/* A redraw clip represents (in stage coordinates) the bounding box of
* something that needs to be redraw. Typically they are added to the
* StageWindow as a result of clutter_actor_queue_clipped_redraw() by
* actors such as ClutterGLXTexturePixmap. All redraw clips are
* discarded after the next paint.
*
* A NULL stage_clip means the whole stage needs to be redrawn.
*
* What we do with this information:
* - we keep track of the bounding box for all redraw clips
* - when we come to redraw; if the bounding box is smaller than the
* stage we scissor the redraw to that box and use
* GLX_MESA_copy_sub_buffer to present the redraw to the front
* buffer. Some heuristics are used to decide when a clipped redraw
* should be promoted into a full stage redraw.
*
* Currently we simply check that the bounding box height is < 300
* pixels.
*
* XXX: we don't have any empirical data telling us what a sensible
* thresholds is!
*
* TODO - we should use different heuristics depending on whether the
* framebuffer is on screen and not redirected by a compositor VS
* offscreen (either due to compositor redirection or because we are
* rendering to a CoglOffscreen framebuffer)
*
* When not redirected glXCopySubBuffer (on intel hardware at least)
* will block the GPU until the vertical trace is at the optimal point
* so the copy can be done without tearing. In this case we don't want
* to copy tall regions because they increase the average time spent
* blocking the GPU.
*
* When rendering offscreen (CoglOffscreen or redirected by
* compositor) then no extra synchronization is needed before the copy
* can start.
*
* In all cases we need to consider that glXCopySubBuffer implies a
* blit which may be avoided by promoting to a full stage redraw if:
* - the framebuffer is redirected offscreen or a CoglOffscreen.
* - the framebuffer is onscreen and fullscreen.
* By promoting to a full stage redraw we trade off the cost involved
* in rasterizing the extra pixels vs avoiding to use a blit to
* present the back buffer.
*
*/
static void
clutter_stage_glx_add_redraw_clip (ClutterStageWindow *stage_window,
ClutterGeometry *stage_clip)
{
ClutterStageGLX *stage_glx = CLUTTER_STAGE_GLX (stage_window);
/* If we are already forced to do a full stage redraw then bail early */
if (clutter_stage_glx_ignoring_redraw_clips (stage_window))
return;
/* A NULL stage clip means a full stage redraw has been queued and
* we keep track of this by setting a degenerate
* stage_glx->bounding_redraw_clip */
if (stage_clip == NULL)
{
stage_glx->bounding_redraw_clip.width = 0;
return;
}
/* Do nothing on an empty clip to avoid confusing with out magic-flag
* degenerate clip
*/
if (stage_clip->width == 0 || stage_clip->height == 0)
return;
if (!stage_glx->initialized_redraw_clip)
{
stage_glx->bounding_redraw_clip.x = stage_clip->x;
stage_glx->bounding_redraw_clip.y = stage_clip->y;
stage_glx->bounding_redraw_clip.width = stage_clip->width;
stage_glx->bounding_redraw_clip.height = stage_clip->height;
}
else if (stage_glx->bounding_redraw_clip.width > 0)
{
_clutter_geometry_union (&stage_glx->bounding_redraw_clip, stage_clip,
&stage_glx->bounding_redraw_clip);
}
#if 0
redraw_area = (stage_glx->bounding_redraw_clip.width *
stage_glx->bounding_redraw_clip.height);
stage_area = stage_x11->xwin_width * stage_x11->xwin_height;
/* Redrawing and blitting >70% of the stage is assumed to be more
* expensive than redrawing the additional 30% to avoid the blit.
*
* FIXME: This threshold was plucked out of thin air!
*/
if (redraw_area > (stage_area * 0.7f))
{
g_print ("DEBUG: clipped redraw too big, forcing full redraw\n");
/* Set a degenerate clip to force a full redraw */
stage_glx->bounding_redraw_clip.width = 0;
}
#endif
stage_glx->initialized_redraw_clip = TRUE;
}
/* A redraw clip represents (in stage coordinates) the bounding box of
* something that needs to be redraw. Typically they are added to the
* StageWindow as a result of clutter_actor_queue_clipped_redraw() by
* actors such as ClutterGLXTexturePixmap. All redraw clips are
* discarded after the next paint.
*
* A NULL stage_clip means the whole stage needs to be redrawn.
*
* What we do with this information:
* - we keep track of the bounding box for all redraw clips
* - when we come to redraw; if the bounding box is smaller than the
* stage we scissor the redraw to that box and use
* GLX_MESA_copy_sub_buffer to present the redraw to the front
* buffer.
*
* XXX - In theory, we should have some sort of heuristics to promote
* a clipped redraw to a full screen redraw; in reality, it turns out
* that promotion is fairly expensive. See the Clutter bug described
* at: http://bugzilla.clutter-project.org/show_bug.cgi?id=2136 .
*
* TODO - we should use different heuristics depending on whether the
* framebuffer is on screen and not redirected by a compositor VS
* offscreen (either due to compositor redirection or because we are
* rendering to a CoglOffscreen framebuffer)
*
* When not redirected glXCopySubBuffer (on intel hardware at least)
* will block the GPU until the vertical trace is at the optimal point
* so the copy can be done without tearing. In this case we don't want
* to copy tall regions because they increase the average time spent
* blocking the GPU.
*
* When rendering offscreen (CoglOffscreen or redirected by
* compositor) then no extra synchronization is needed before the copy
* can start.
*
* In all cases we need to consider that glXCopySubBuffer implies a
* blit which may be avoided by promoting to a full stage redraw if:
* - the framebuffer is redirected offscreen or a CoglOffscreen.
* - the framebuffer is onscreen and fullscreen.
* By promoting to a full stage redraw we trade off the cost involved
* in rasterizing the extra pixels vs avoiding to use a blit to
* present the back buffer.
*/
static void
clutter_stage_glx_add_redraw_clip (ClutterStageWindow *stage_window,
ClutterGeometry *stage_clip)
{
ClutterStageGLX *stage_glx = CLUTTER_STAGE_GLX (stage_window);
/* If we are already forced to do a full stage redraw then bail early */
if (clutter_stage_glx_ignoring_redraw_clips (stage_window))
return;
/* A NULL stage clip means a full stage redraw has been queued and
* we keep track of this by setting a zero width
* stage_glx->bounding_redraw_clip */
if (stage_clip == NULL)
{
stage_glx->bounding_redraw_clip.width = 0;
stage_glx->initialized_redraw_clip = TRUE;
return;
}
/* Ignore requests to add degenerate/empty clip rectangles */
if (stage_clip->width == 0 || stage_clip->height == 0)
return;
if (!stage_glx->initialized_redraw_clip)
{
stage_glx->bounding_redraw_clip.x = stage_clip->x;
stage_glx->bounding_redraw_clip.y = stage_clip->y;
stage_glx->bounding_redraw_clip.width = stage_clip->width;
stage_glx->bounding_redraw_clip.height = stage_clip->height;
}
else if (stage_glx->bounding_redraw_clip.width > 0)
{
clutter_geometry_union (&stage_glx->bounding_redraw_clip,
stage_clip,
&stage_glx->bounding_redraw_clip);
}
#if 0
redraw_area = (stage_glx->bounding_redraw_clip.width *
stage_glx->bounding_redraw_clip.height);
stage_area = stage_x11->xwin_width * stage_x11->xwin_height;
/* Redrawing and blitting >70% of the stage is assumed to be more
* expensive than redrawing the additional 30% to avoid the blit.
*
* FIXME: This threshold was plucked out of thin air!
*
* The threshold has been disabled after verifying that it indeed
* made redraws more expensive than intended; see bug reference:
*
* http://bugzilla.clutter-project.org/show_bug.cgi?id=2136
*/
if (redraw_area > (stage_area * 0.7f))
{
g_print ("DEBUG: clipped redraw too big, forcing full redraw\n");
/* Set a zero width clip to force a full redraw */
stage_glx->bounding_redraw_clip.width = 0;
}
#endif
stage_glx->initialized_redraw_clip = TRUE;
}
