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clip-stack: Adds _cogl_clip_stack_get_bounds API

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This adds an internal function to be able to query the screen space
bounding box of the current clip entries contained in a given
CoglClipStack.

This bounding box which is cheap to determine can be useful to know the
largest extents that might be updated while drawing with this clip
stack.

For example the plan is to use this as part of an optimized read-pixel
path handled on the CPU which will need to track the currently valid
extents of the last call to cogl_clear()
This commit is contained in:
Robert Bragg 2011-01-12 19:13:45 +00:00
parent 1a5a4df326
commit cf92670fbb
2 changed files with 39 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

45
cogl/cogl-clip-stack.c
View File

@ -531,16 +531,41 @@ _cogl_clip_stack_pop (CoglClipStack *stack)
return new_top;
}
void
_cogl_clip_stack_get_bounds (CoglClipStack *stack,
int *scissor_x0,
int *scissor_y0,
int *scissor_x1,
int *scissor_y1)
{
CoglClipStack *entry;
*scissor_x0 = 0;
*scissor_y0 = 0;
*scissor_x1 = G_MAXINT;
*scissor_y1 = G_MAXINT;
for (entry = stack; entry; entry = entry->parent)
{
/* Get the intersection of the current scissor and the bounding
box of this clip */
*scissor_x0 = MAX (*scissor_x0, entry->bounds_x0);
*scissor_y0 = MAX (*scissor_y0, entry->bounds_y0);
*scissor_x1 = MIN (*scissor_x1, entry->bounds_x1);
*scissor_y1 = MIN (*scissor_y1, entry->bounds_y1);
}
}
void
_cogl_clip_stack_flush (CoglClipStack *stack)
{
int has_clip_planes;
gboolean using_clip_planes = FALSE;
gboolean using_stencil_buffer = FALSE;
int scissor_x0 = 0;
int scissor_y0 = 0;
int scissor_x1 = G_MAXINT;
int scissor_y1 = G_MAXINT;
int scissor_x0;
int scissor_y0;
int scissor_x1;
int scissor_y1;
CoglMatrixStack *modelview_stack;
CoglClipStack *entry;
int scissor_y_start;
@ -581,15 +606,9 @@ _cogl_clip_stack_flush (CoglClipStack *stack)
clear the stencil buffer then the clear will be clipped to the
intersection of all of the bounding boxes. This saves having to
clear the whole stencil buffer */
for (entry = stack; entry; entry = entry->parent)
{
/* Get the intersection of the current scissor and the bounding
box of this clip */
scissor_x0 = MAX (scissor_x0, entry->bounds_x0);
scissor_y0 = MAX (scissor_y0, entry->bounds_y0);
scissor_x1 = MIN (scissor_x1, entry->bounds_x1);
scissor_y1 = MIN (scissor_y1, entry->bounds_y1);
}
_cogl_clip_stack_get_bounds (stack,
&scissor_x0, &scissor_y0,
&scissor_x1, &scissor_y1);
/* Enable scissoring as soon as possible */
if (scissor_x0 >= scissor_x1 || scissor_y0 >= scissor_y1)

7
cogl/cogl-clip-stack.h
View File

@ -170,6 +170,13 @@ _cogl_clip_stack_push_from_path (CoglClipStack *stack,
CoglClipStack *
_cogl_clip_stack_pop (CoglClipStack *stack);
void
_cogl_clip_stack_get_bounds (CoglClipStack *stack,
int *scissor_x0,
int *scissor_y0,
int *scissor_x1,
int *scissor_y1);
void
_cogl_clip_stack_flush (CoglClipStack *stack);