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cogl-clip-stack: Use reference counted stack entries

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The stack is now stored as a list of reference counted entries.
Instead of using a GList, each entry now contains a link with a
reference to its parent. The idea is that this would allow copying
stacks with a shared ancestry.

Previously the code flushed the state by finding the bottom of the
stack and then applying each entry by walking back up to the top. This
is slightly harder to do now because the list is no longer
doubly-linked. However I don't think it matters which order the
entries are applied so I've just changed it to apply them in reverse
order.

There was also a restriction that if ever the stencil buffer is used
then we could no longer use clip planes for any subsequent entries. I
don't think this makes sense because it should always work as long as
it doesn't attempt to use the clip planes more than once. I've
therefore removed the restriction.
This commit is contained in:
Neil Roberts 2010-04-14 13:17:26 +01:00
parent ecf65cd4a5
commit 71fdc54dde
1 changed files with 149 additions and 58 deletions
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207
cogl/cogl-clip-stack.c
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@ -42,6 +42,7 @@
typedef struct _CoglClipStack CoglClipStack;
typedef struct _CoglClipStackEntry CoglClipStackEntry;
typedef struct _CoglClipStackEntryRect CoglClipStackEntryRect;
typedef struct _CoglClipStackEntryWindowRect CoglClipStackEntryWindowRect;
typedef struct _CoglClipStackEntryPath CoglClipStackEntryPath;
@ -53,14 +54,65 @@ typedef enum
COGL_CLIP_STACK_PATH
} CoglClipStackEntryType;
/* A clip stack consists a list of entries. Each entry has a reference
* count and a link to its parent node. The child takes a reference on
* the parent and the CoglClipStack holds a reference to the top of
* the stack. There are no links back from the parent to the
* children. This allows stacks that have common ancestry to share the
* entries.
*
* For example, the following sequence of operations would generate
* the tree below:
*
* CoglHandle stack_a = _cogl_clip_stack_new ();
* _cogl_set_clip_stack (stack_a);
* cogl_clip_stack_push_rectangle (...);
* cogl_clip_stack_push_rectangle (...);
* CoglHandle stack_b = _cogl_clip_stack_copy (stack_a);
* cogl_clip_stack_push_from_path ();
* cogl_set_clip_stack (stack_b);
* cogl_clip_stack_push_window_rectangle (...);
*
* stack_a
* \ holds a ref to
* +-----------+
* | path node |
* |ref count 1|
* +-----------+
* \
* +-----------+ +-----------+
* both tops hold | rect node | | rect node |
* a ref to the |ref count 2|--|ref count 1|
* same rect node +-----------+ +-----------+
* /
* +-----------+
* | win. rect |
* |ref count 1|
* +-----------+
* / holds a ref to
* stack_b
*
*/
struct _CoglClipStack
{
GList *stack_top;
CoglClipStackEntry *stack_top;
};
struct _CoglClipStackEntry
{
CoglClipStackEntryType type;
/* This will be null if there is no parent. If it is not null then
this node must be holding a reference to the parent */
CoglClipStackEntry *parent;
unsigned int ref_count;
};
struct _CoglClipStackEntryRect
{
CoglClipStackEntryType type;
CoglClipStackEntry _parent_data;
/* The rectangle for this clip */
float x0;
@ -74,7 +126,7 @@ struct _CoglClipStackEntryRect
struct _CoglClipStackEntryWindowRect
{
CoglClipStackEntryType type;
CoglClipStackEntry _parent_data;
/* The window space rectangle for this clip */
float x0;
@ -85,7 +137,7 @@ struct _CoglClipStackEntryWindowRect
struct _CoglClipStackEntryPath
{
CoglClipStackEntryType type;
CoglClipStackEntry _parent_data;
/* The matrix that was current when the clip was set */
CoglMatrix matrix;
@ -327,6 +379,27 @@ disable_clip_planes (void)
GE( glDisable (GL_CLIP_PLANE0) );
}
static gpointer
_cogl_clip_stack_push_entry (CoglClipStack *clip_stack,
size_t size,
CoglClipStackEntryType type)
{
CoglClipStackEntry *entry = g_slice_alloc (size);
/* The new entry starts with a ref count of 1 because the stack
holds a reference to it as it is the top entry */
entry->ref_count = 1;
entry->type = type;
entry->parent = clip_stack->stack_top;
clip_stack->stack_top = entry;
/* We don't need to take a reference to the parent from the entry
because the clip_stack would have had to reference the top of
the stack and we can just steal that */
return entry;
}
void
cogl_clip_push_window_rectangle (int x_offset,
int y_offset,
@ -352,7 +425,9 @@ cogl_clip_push_window_rectangle (int x_offset,
framebuffer_height = _cogl_framebuffer_get_height (framebuffer);
entry = g_slice_new (CoglClipStackEntryWindowRect);
entry = _cogl_clip_stack_push_entry (stack,
sizeof (CoglClipStackEntryWindowRect),
COGL_CLIP_STACK_WINDOW_RECT);
/* We store the entry coordinates in OpenGL window coordinate space and so
* because Cogl defines the window origin to be top left but OpenGL defines
@ -361,7 +436,6 @@ cogl_clip_push_window_rectangle (int x_offset,
* NB: Cogl forces all offscreen rendering to be done upside down so in this
* case no conversion is needed.
*/
entry->type = COGL_CLIP_STACK_WINDOW_RECT;
entry->x0 = x_offset;
entry->x1 = x_offset + width;
if (cogl_is_offscreen (framebuffer))
@ -375,9 +449,6 @@ cogl_clip_push_window_rectangle (int x_offset,
entry->y1 = framebuffer_height - y_offset;
}
/* Store it in the stack */
stack->stack_top = g_list_prepend (stack->stack_top, entry);
clip_state->stack_dirty = TRUE;
}
@ -508,10 +579,11 @@ cogl_clip_push_rectangle (float x_1,
stack = clip_state->stacks->data;
entry = g_slice_new (CoglClipStackEntryRect);
/* Make a new entry */
entry->type = COGL_CLIP_STACK_RECT;
entry = _cogl_clip_stack_push_entry (stack,
sizeof (CoglClipStackEntryRect),
COGL_CLIP_STACK_RECT);
entry->x0 = x_1;
entry->y0 = y_1;
entry->x1 = x_2;
@ -519,9 +591,6 @@ cogl_clip_push_rectangle (float x_1,
cogl_get_modelview_matrix (&entry->matrix);
/* Store it in the stack */
stack->stack_top = g_list_prepend (stack->stack_top, entry);
clip_state->stack_dirty = TRUE;
}
@ -557,16 +626,14 @@ cogl_clip_push_from_path_preserve (void)
stack = clip_state->stacks->data;
entry = g_slice_new (CoglClipStackEntryPath);
entry = _cogl_clip_stack_push_entry (stack,
sizeof (CoglClipStackEntryPath),
COGL_CLIP_STACK_PATH);
entry->type = COGL_CLIP_STACK_PATH;
entry->path = cogl_path_copy (cogl_path_get ());
cogl_get_modelview_matrix (&entry->matrix);
/* Store it in the stack */
stack->stack_top = g_list_prepend (stack->stack_top, entry);
clip_state->stack_dirty = TRUE;
}
@ -578,12 +645,43 @@ cogl_clip_push_from_path (void)
cogl_path_new ();
}
static void
_cogl_clip_stack_entry_unref (CoglClipStackEntry *entry)
{
/* Unref all of the entries until we hit the root of the list or the
entry still has a remaining reference */
while (entry && --entry->ref_count <= 0)
{
CoglClipStackEntry *parent = entry->parent;
switch (entry->type)
{
case COGL_CLIP_STACK_RECT:
g_slice_free1 (sizeof (CoglClipStackEntryRect), entry);
break;
case COGL_CLIP_STACK_WINDOW_RECT:
g_slice_free1 (sizeof (CoglClipStackEntryWindowRect), entry);
break;
case COGL_CLIP_STACK_PATH:
cogl_handle_unref (((CoglClipStackEntryPath *) entry)->path);
g_slice_free1 (sizeof (CoglClipStackEntryPath), entry);
break;
default:
g_assert_not_reached ();
}
entry = parent;
}
}
static void
_cogl_clip_pop_real (CoglClipStackState *clip_state)
{
CoglClipStack *stack;
gpointer entry;
CoglClipStackEntryType type;
CoglClipStackEntry *entry;
/* We don't log clip stack changes in the journal so we must flush
* it before making modifications */
@ -593,22 +691,19 @@ _cogl_clip_pop_real (CoglClipStackState *clip_state)
g_return_if_fail (stack->stack_top != NULL);
entry = stack->stack_top->data;
type = *(CoglClipStackEntryType *) entry;
/* Remove the top entry from the stack */
if (type == COGL_CLIP_STACK_RECT)
g_slice_free (CoglClipStackEntryRect, entry);
else if (type == COGL_CLIP_STACK_WINDOW_RECT)
g_slice_free (CoglClipStackEntryWindowRect, entry);
else
{
cogl_handle_unref (((CoglClipStackEntryPath *) entry)->path);
g_slice_free (CoglClipStackEntryPath, entry);
}
stack->stack_top = g_list_delete_link (stack->stack_top,
stack->stack_top);
/* To pop we are moving the top of the stack to the old top's parent
node. The stack always needs to have a reference to the top entry
so we must take a reference to the new top. The stack would have
previously had a reference to the old top so we need to decrease
the ref count on that. We need to ref the new head first in case
this stack was the only thing referencing the old top. In that
case the call to _cogl_clip_stack_entry_unref will unref the
parent. */
entry = stack->stack_top;
stack->stack_top = entry->parent;
if (stack->stack_top)
stack->stack_top->ref_count++;
_cogl_clip_stack_entry_unref (entry);
clip_state->stack_dirty = TRUE;
}
@ -634,13 +729,13 @@ _cogl_flush_clip_state (CoglClipStackState *clip_state)
int has_clip_planes;
gboolean using_clip_planes = FALSE;
gboolean using_stencil_buffer = FALSE;
GList *node;
int scissor_x0 = 0;
int scissor_y0 = 0;
int scissor_x1 = G_MAXINT;
int scissor_y1 = G_MAXINT;
CoglMatrixStack *modelview_stack =
_cogl_framebuffer_get_modelview_stack (_cogl_get_framebuffer ());
CoglClipStackEntry *entry;
if (!clip_state->stack_dirty)
return;
@ -670,16 +765,13 @@ _cogl_flush_clip_state (CoglClipStackState *clip_state)
if (stack->stack_top == NULL)
return;
/* Find the bottom of the stack */
for (node = stack->stack_top; node->next; node = node->next);
/* Re-add every entry from the bottom of the stack up */
for (; node; node = node->prev)
/* Add all of the entries. This will end up adding them in the
reverse order that they were specified but as all of the clips
are intersecting it should work out the same regardless of the
order */
for (entry = stack->stack_top; entry; entry = entry->parent)
{
gpointer entry = node->data;
CoglClipStackEntryType type = *(CoglClipStackEntryType *) entry;
if (type == COGL_CLIP_STACK_PATH)
if (entry->type == COGL_CLIP_STACK_PATH)
{
CoglClipStackEntryPath *path_entry = (CoglClipStackEntryPath *) entry;
@ -693,19 +785,16 @@ _cogl_flush_clip_state (CoglClipStackState *clip_state)
_cogl_matrix_stack_pop (modelview_stack);
using_stencil_buffer = TRUE;
/* We can't use clip planes any more */
has_clip_planes = FALSE;
}
else if (type == COGL_CLIP_STACK_RECT)
else if (entry->type == COGL_CLIP_STACK_RECT)
{
CoglClipStackEntryRect *rect = (CoglClipStackEntryRect *) entry;
_cogl_matrix_stack_push (modelview_stack);
_cogl_matrix_stack_set (modelview_stack, &rect->matrix);
/* If this is the first entry and we support clip planes then use
that instead */
/* If we support clip planes and we haven't already used
them then use that instead */
if (has_clip_planes)
{
set_clip_planes (rect->x0,
@ -732,7 +821,8 @@ _cogl_flush_clip_state (CoglClipStackState *clip_state)
{
/* Get the intersection of all window space rectangles in the clip
* stack */
CoglClipStackEntryWindowRect *window_rect = entry;
CoglClipStackEntryWindowRect *window_rect =
(CoglClipStackEntryWindowRect *) entry;
scissor_x0 = MAX (scissor_x0, window_rect->x0);
scissor_y0 = MAX (scissor_y0, window_rect->y0);
scissor_x1 = MIN (scissor_x1, window_rect->x1);
@ -813,9 +903,10 @@ _cogl_clip_stack_restore_real (CoglClipStackState *clip_state)
stack = clip_state->stacks->data;
/* Empty the current stack */
while (stack->stack_top)
_cogl_clip_pop_real (clip_state);
/* Free the stack. We only need to unref the top node and this
should end up freeing all of the parents if need be */
if (stack->stack_top)
_cogl_clip_stack_entry_unref (stack->stack_top);
/* Revert to an old stack */
g_slice_free (CoglClipStack, stack);