mutter/clutter/cogl/cogl/cogl-rectangle-map.c
Neil Roberts 72029e14db cogl-rectangle-map: Record largest gap rather than the remaining space
Previously each node in the rectangle map tree would store the total
remaining space in all of its children to use as an optimization when
adding nodes. With this it could skip an entire branch of the tree if
it knew there could never be enough space for the new node in the
branch. This modifies that slightly to instead store the largest
single gap. This allows it to skip a branch earlier because often
there would be a lot of small gaps which would add up to enough a
space for the new rectangle, but the space can't be used unless it is
in a single node.

The rectangle map still needs to keep track of the total remaining
space for the whole map for the debugging output so this has been
added back in to the CoglRectangleMap struct. There is a separate
debugging function to verify this value.
2010-08-12 11:57:00 +01:00

753 lines
23 KiB
C

/*
* Cogl
*
* An object oriented GL/GLES Abstraction/Utility Layer
*
* Copyright (C) 2009 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/>.
*
*
*
* Authors:
* Neil Roberts <neil@linux.intel.com>
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <glib.h>
#include "cogl-rectangle-map.h"
#include "cogl-debug.h"
/* Implements a data structure which keeps track of unused
sub-rectangles within a larger rectangle using a binary tree
structure. The algorithm for this is based on the description here:
http://www.blackpawn.com/texts/lightmaps/default.html
*/
#ifdef COGL_ENABLE_DEBUG
/* The cairo header is only used for debugging to generate an image of
the atlas */
#include <cairo.h>
static void _cogl_rectangle_map_dump_image (CoglRectangleMap *map);
#endif /* COGL_ENABLE_DEBUG */
typedef struct _CoglRectangleMapNode CoglRectangleMapNode;
typedef struct _CoglRectangleMapStackEntry CoglRectangleMapStackEntry;
typedef void (* CoglRectangleMapInternalForeachCb) (CoglRectangleMapNode *node,
void *data);
typedef enum
{
COGL_RECTANGLE_MAP_BRANCH,
COGL_RECTANGLE_MAP_FILLED_LEAF,
COGL_RECTANGLE_MAP_EMPTY_LEAF
} CoglRectangleMapNodeType;
struct _CoglRectangleMap
{
CoglRectangleMapNode *root;
unsigned int n_rectangles;
unsigned int space_remaining;
GDestroyNotify value_destroy_func;
/* Stack used for walking the structure. This is only used during
the lifetime of a single function call but it is kept here as an
optimisation to avoid reallocating it every time it is needed */
GArray *stack;
};
struct _CoglRectangleMapNode
{
CoglRectangleMapNodeType type;
CoglRectangleMapEntry rectangle;
unsigned int largest_gap;
CoglRectangleMapNode *parent;
union
{
/* Fields used when this is a branch */
struct
{
CoglRectangleMapNode *left;
CoglRectangleMapNode *right;
} branch;
/* Field used when this is a filled leaf */
void *data;
} d;
};
struct _CoglRectangleMapStackEntry
{
/* The node to search */
CoglRectangleMapNode *node;
/* Index of next branch of this node to explore. Basically either 0
to go left or 1 to go right */
gboolean next_index;
};
static CoglRectangleMapNode *
_cogl_rectangle_map_node_new (void)
{
return g_slice_new (CoglRectangleMapNode);
}
static void
_cogl_rectangle_map_node_free (CoglRectangleMapNode *node)
{
g_slice_free (CoglRectangleMapNode, node);
}
CoglRectangleMap *
_cogl_rectangle_map_new (unsigned int width,
unsigned int height,
GDestroyNotify value_destroy_func)
{
CoglRectangleMap *map = g_new (CoglRectangleMap, 1);
CoglRectangleMapNode *root = _cogl_rectangle_map_node_new ();
root->type = COGL_RECTANGLE_MAP_EMPTY_LEAF;
root->parent = NULL;
root->rectangle.x = 0;
root->rectangle.y = 0;
root->rectangle.width = width;
root->rectangle.height = height;
root->largest_gap = width * height;
map->root = root;
map->n_rectangles = 0;
map->value_destroy_func = value_destroy_func;
map->space_remaining = width * height;
map->stack = g_array_new (FALSE, FALSE, sizeof (CoglRectangleMapStackEntry));
return map;
}
static void
_cogl_rectangle_map_stack_push (GArray *stack,
CoglRectangleMapNode *node,
gboolean next_index)
{
CoglRectangleMapStackEntry *new_entry;
g_array_set_size (stack, stack->len + 1);
new_entry = &g_array_index (stack, CoglRectangleMapStackEntry,
stack->len - 1);
new_entry->node = node;
new_entry->next_index = next_index;
}
static void
_cogl_rectangle_map_stack_pop (GArray *stack)
{
g_array_set_size (stack, stack->len - 1);
}
static CoglRectangleMapStackEntry *
_cogl_rectangle_map_stack_get_top (GArray *stack)
{
return &g_array_index (stack, CoglRectangleMapStackEntry,
stack->len - 1);
}
static CoglRectangleMapNode *
_cogl_rectangle_map_node_split_horizontally (CoglRectangleMapNode *node,
unsigned int left_width)
{
/* Splits the node horizontally (according to emacs' definition, not
vim) by converting it to a branch and adding two new leaf
nodes. The leftmost branch will have the width left_width and
will be returned. If the node is already just the right size it
won't do anything */
CoglRectangleMapNode *left_node, *right_node;
if (node->rectangle.width == left_width)
return node;
left_node = _cogl_rectangle_map_node_new ();
left_node->type = COGL_RECTANGLE_MAP_EMPTY_LEAF;
left_node->parent = node;
left_node->rectangle.x = node->rectangle.x;
left_node->rectangle.y = node->rectangle.y;
left_node->rectangle.width = left_width;
left_node->rectangle.height = node->rectangle.height;
left_node->largest_gap = (left_node->rectangle.width *
left_node->rectangle.height);
node->d.branch.left = left_node;
right_node = _cogl_rectangle_map_node_new ();
right_node->type = COGL_RECTANGLE_MAP_EMPTY_LEAF;
right_node->parent = node;
right_node->rectangle.x = node->rectangle.x + left_width;
right_node->rectangle.y = node->rectangle.y;
right_node->rectangle.width = node->rectangle.width - left_width;
right_node->rectangle.height = node->rectangle.height;
right_node->largest_gap = (right_node->rectangle.width *
right_node->rectangle.height);
node->d.branch.right = right_node;
node->type = COGL_RECTANGLE_MAP_BRANCH;
return left_node;
}
static CoglRectangleMapNode *
_cogl_rectangle_map_node_split_vertically (CoglRectangleMapNode *node,
unsigned int top_height)
{
/* Splits the node vertically (according to emacs' definition, not
vim) by converting it to a branch and adding two new leaf
nodes. The topmost branch will have the height top_height and
will be returned. If the node is already just the right size it
won't do anything */
CoglRectangleMapNode *top_node, *bottom_node;
if (node->rectangle.height == top_height)
return node;
top_node = _cogl_rectangle_map_node_new ();
top_node->type = COGL_RECTANGLE_MAP_EMPTY_LEAF;
top_node->parent = node;
top_node->rectangle.x = node->rectangle.x;
top_node->rectangle.y = node->rectangle.y;
top_node->rectangle.width = node->rectangle.width;
top_node->rectangle.height = top_height;
top_node->largest_gap = (top_node->rectangle.width *
top_node->rectangle.height);
node->d.branch.left = top_node;
bottom_node = _cogl_rectangle_map_node_new ();
bottom_node->type = COGL_RECTANGLE_MAP_EMPTY_LEAF;
bottom_node->parent = node;
bottom_node->rectangle.x = node->rectangle.x;
bottom_node->rectangle.y = node->rectangle.y + top_height;
bottom_node->rectangle.width = node->rectangle.width;
bottom_node->rectangle.height = node->rectangle.height - top_height;
bottom_node->largest_gap = (bottom_node->rectangle.width *
bottom_node->rectangle.height);
node->d.branch.right = bottom_node;
node->type = COGL_RECTANGLE_MAP_BRANCH;
return top_node;
}
#ifdef COGL_ENABLE_DEBUG
static unsigned int
_cogl_rectangle_map_verify_recursive (CoglRectangleMapNode *node)
{
/* This is just used for debugging the data structure. It
recursively walks the tree to verify that the largest gap values
all add up */
switch (node->type)
{
case COGL_RECTANGLE_MAP_BRANCH:
{
int sum =
_cogl_rectangle_map_verify_recursive (node->d.branch.left) +
_cogl_rectangle_map_verify_recursive (node->d.branch.right);
g_assert (node->largest_gap ==
MAX (node->d.branch.left->largest_gap,
node->d.branch.right->largest_gap));
return sum;
}
case COGL_RECTANGLE_MAP_EMPTY_LEAF:
g_assert (node->largest_gap ==
node->rectangle.width * node->rectangle.height);
return 0;
case COGL_RECTANGLE_MAP_FILLED_LEAF:
g_assert (node->largest_gap == 0);
return 1;
}
return 0;
}
static unsigned int
_cogl_rectangle_map_get_space_remaining_recursive (CoglRectangleMapNode *node)
{
/* This is just used for debugging the data structure. It
recursively walks the tree to verify that the remaining space
value adds up */
switch (node->type)
{
case COGL_RECTANGLE_MAP_BRANCH:
{
CoglRectangleMapNode *l = node->d.branch.left;
CoglRectangleMapNode *r = node->d.branch.right;
return (_cogl_rectangle_map_get_space_remaining_recursive (l) +
_cogl_rectangle_map_get_space_remaining_recursive (r));
}
case COGL_RECTANGLE_MAP_EMPTY_LEAF:
return node->rectangle.width * node->rectangle.height;
case COGL_RECTANGLE_MAP_FILLED_LEAF:
return 0;
}
return 0;
}
static void
_cogl_rectangle_map_verify (CoglRectangleMap *map)
{
unsigned int actual_n_rectangles =
_cogl_rectangle_map_verify_recursive (map->root);
unsigned int actual_space_remaining =
_cogl_rectangle_map_get_space_remaining_recursive (map->root);
g_assert_cmpuint (actual_n_rectangles, ==, map->n_rectangles);
g_assert_cmpuint (actual_space_remaining, ==, map->space_remaining);
}
#endif /* COGL_ENABLE_DEBUG */
gboolean
_cogl_rectangle_map_add (CoglRectangleMap *map,
unsigned int width,
unsigned int height,
void *data,
CoglRectangleMapEntry *rectangle)
{
unsigned int rectangle_size = width * height;
/* Stack of nodes to search in */
GArray *stack = map->stack;
CoglRectangleMapNode *found_node = NULL;
/* Zero-sized rectangles break the algorithm for removing rectangles
so we'll disallow them */
g_return_val_if_fail (width > 0 && height > 0, FALSE);
/* Start with the root node */
g_array_set_size (stack, 0);
_cogl_rectangle_map_stack_push (stack, map->root, FALSE);
/* Depth-first search for an empty node that is big enough */
while (stack->len > 0)
{
CoglRectangleMapStackEntry *stack_top;
CoglRectangleMapNode *node;
int next_index;
/* Pop an entry off the stack */
stack_top = _cogl_rectangle_map_stack_get_top (stack);
node = stack_top->node;
next_index = stack_top->next_index;
_cogl_rectangle_map_stack_pop (stack);
/* Regardless of the type of the node, there's no point
descending any further if the new rectangle won't fit within
it */
if (node->rectangle.width >= width &&
node->rectangle.height >= height &&
node->largest_gap >= rectangle_size)
{
if (node->type == COGL_RECTANGLE_MAP_EMPTY_LEAF)
{
/* We've found a node we can use */
found_node = node;
break;
}
else if (node->type == COGL_RECTANGLE_MAP_BRANCH)
{
if (next_index)
/* Try the right branch */
_cogl_rectangle_map_stack_push (stack,
node->d.branch.right,
0);
else
{
/* Make sure we remember to try the right branch once
we've finished descending the left branch */
_cogl_rectangle_map_stack_push (stack,
node,
1);
/* Try the left branch */
_cogl_rectangle_map_stack_push (stack,
node->d.branch.left,
0);
}
}
}
}
if (found_node)
{
CoglRectangleMapNode *node;
/* Split according to whichever axis will leave us with the
largest space */
if (found_node->rectangle.width - width >
found_node->rectangle.height - height)
{
found_node =
_cogl_rectangle_map_node_split_horizontally (found_node, width);
found_node =
_cogl_rectangle_map_node_split_vertically (found_node, height);
}
else
{
found_node =
_cogl_rectangle_map_node_split_vertically (found_node, height);
found_node =
_cogl_rectangle_map_node_split_horizontally (found_node, width);
}
found_node->type = COGL_RECTANGLE_MAP_FILLED_LEAF;
found_node->d.data = data;
found_node->largest_gap = 0;
if (rectangle)
*rectangle = found_node->rectangle;
/* Walk back up the tree and update the stored largest gap for
the node's sub tree */
for (node = found_node->parent; node; node = node->parent)
{
/* This node is a parent so it should always be a branch */
g_assert (node->type == COGL_RECTANGLE_MAP_BRANCH);
node->largest_gap = MAX (node->d.branch.left->largest_gap,
node->d.branch.right->largest_gap);
}
/* There is now an extra rectangle in the map */
map->n_rectangles++;
/* and less space */
map->space_remaining -= rectangle_size;
#ifdef COGL_ENABLE_DEBUG
if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_DUMP_ATLAS_IMAGE))
{
_cogl_rectangle_map_dump_image (map);
/* Dumping the rectangle map is really slow so we might as well
verify the space remaining here as it is also quite slow */
_cogl_rectangle_map_verify (map);
}
#endif
return TRUE;
}
else
return FALSE;
}
void
_cogl_rectangle_map_remove (CoglRectangleMap *map,
const CoglRectangleMapEntry *rectangle)
{
CoglRectangleMapNode *node = map->root;
unsigned int rectangle_size = rectangle->width * rectangle->height;
/* We can do a binary-chop down the search tree to find the rectangle */
while (node->type == COGL_RECTANGLE_MAP_BRANCH)
{
CoglRectangleMapNode *left_node = node->d.branch.left;
/* If and only if the rectangle is in the left node then the x,y
position of the rectangle will be within the node's
rectangle */
if (rectangle->x < left_node->rectangle.x + left_node->rectangle.width &&
rectangle->y < left_node->rectangle.y + left_node->rectangle.height)
/* Go left */
node = left_node;
else
/* Go right */
node = node->d.branch.right;
}
/* Make sure we found the right node */
if (node->type != COGL_RECTANGLE_MAP_FILLED_LEAF ||
node->rectangle.x != rectangle->x ||
node->rectangle.y != rectangle->y ||
node->rectangle.width != rectangle->width ||
node->rectangle.height != rectangle->height)
/* This should only happen if someone tried to remove a rectangle
that was not in the map so something has gone wrong */
g_return_if_reached ();
else
{
/* Convert the node back to an empty node */
if (map->value_destroy_func)
map->value_destroy_func (node->d.data);
node->type = COGL_RECTANGLE_MAP_EMPTY_LEAF;
node->largest_gap = rectangle_size;
/* Walk back up the tree combining branch nodes that have two
empty leaves back into a single empty leaf */
for (node = node->parent; node; node = node->parent)
{
/* This node is a parent so it should always be a branch */
g_assert (node->type == COGL_RECTANGLE_MAP_BRANCH);
if (node->d.branch.left->type == COGL_RECTANGLE_MAP_EMPTY_LEAF &&
node->d.branch.right->type == COGL_RECTANGLE_MAP_EMPTY_LEAF)
{
_cogl_rectangle_map_node_free (node->d.branch.left);
_cogl_rectangle_map_node_free (node->d.branch.right);
node->type = COGL_RECTANGLE_MAP_EMPTY_LEAF;
node->largest_gap = (node->rectangle.width *
node->rectangle.height);
}
else
break;
}
/* Reduce the amount of space remaining in all of the parents
further up the chain */
for (; node; node = node->parent)
node->largest_gap = MAX (node->d.branch.left->largest_gap,
node->d.branch.right->largest_gap);
/* There is now one less rectangle */
g_assert (map->n_rectangles > 0);
map->n_rectangles--;
/* and more space */
map->space_remaining += rectangle_size;
}
#ifdef COGL_ENABLE_DEBUG
if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_DUMP_ATLAS_IMAGE))
{
_cogl_rectangle_map_dump_image (map);
/* Dumping the rectangle map is really slow so we might as well
verify the space remaining here as it is also quite slow */
_cogl_rectangle_map_verify (map);
}
#endif
}
unsigned int
_cogl_rectangle_map_get_width (CoglRectangleMap *map)
{
return map->root->rectangle.width;
}
unsigned int
_cogl_rectangle_map_get_height (CoglRectangleMap *map)
{
return map->root->rectangle.height;
}
unsigned int
_cogl_rectangle_map_get_remaining_space (CoglRectangleMap *map)
{
return map->space_remaining;
}
unsigned int
_cogl_rectangle_map_get_n_rectangles (CoglRectangleMap *map)
{
return map->n_rectangles;
}
static void
_cogl_rectangle_map_internal_foreach (CoglRectangleMap *map,
CoglRectangleMapInternalForeachCb func,
void *data)
{
/* Stack of nodes to search in */
GArray *stack = map->stack;
/* Start with the root node */
g_array_set_size (stack, 0);
_cogl_rectangle_map_stack_push (stack, map->root, 0);
/* Iterate all nodes depth-first */
while (stack->len > 0)
{
CoglRectangleMapStackEntry *stack_top =
_cogl_rectangle_map_stack_get_top (stack);
CoglRectangleMapNode *node = stack_top->node;
switch (node->type)
{
case COGL_RECTANGLE_MAP_BRANCH:
if (stack_top->next_index == 0)
{
/* Next time we come back to this node, go to the right */
stack_top->next_index = 1;
/* Explore the left branch next */
_cogl_rectangle_map_stack_push (stack,
node->d.branch.left,
0);
}
else if (stack_top->next_index == 1)
{
/* Next time we come back to this node, stop processing it */
stack_top->next_index = 2;
/* Explore the right branch next */
_cogl_rectangle_map_stack_push (stack,
node->d.branch.right,
0);
}
else
{
/* We're finished with this node so we can call the callback */
func (node, data);
_cogl_rectangle_map_stack_pop (stack);
}
break;
default:
/* Some sort of leaf node, just call the callback */
func (node, data);
_cogl_rectangle_map_stack_pop (stack);
break;
}
}
/* The stack should now be empty */
g_assert (stack->len == 0);
}
typedef struct _CoglRectangleMapForeachClosure
{
CoglRectangleMapCallback callback;
void *data;
} CoglRectangleMapForeachClosure;
static void
_cogl_rectangle_map_foreach_cb (CoglRectangleMapNode *node, void *data)
{
CoglRectangleMapForeachClosure *closure = data;
if (node->type == COGL_RECTANGLE_MAP_FILLED_LEAF)
closure->callback (&node->rectangle, node->d.data, closure->data);
}
void
_cogl_rectangle_map_foreach (CoglRectangleMap *map,
CoglRectangleMapCallback callback,
void *data)
{
CoglRectangleMapForeachClosure closure;
closure.callback = callback;
closure.data = data;
_cogl_rectangle_map_internal_foreach (map,
_cogl_rectangle_map_foreach_cb,
&closure);
}
static void
_cogl_rectangle_map_free_cb (CoglRectangleMapNode *node, void *data)
{
CoglRectangleMap *map = data;
if (node->type == COGL_RECTANGLE_MAP_FILLED_LEAF && map->value_destroy_func)
map->value_destroy_func (node->d.data);
_cogl_rectangle_map_node_free (node);
}
void
_cogl_rectangle_map_free (CoglRectangleMap *map)
{
_cogl_rectangle_map_internal_foreach (map,
_cogl_rectangle_map_free_cb,
map);
g_array_free (map->stack, TRUE);
g_free (map);
}
#ifdef COGL_ENABLE_DEBUG
static void
_cogl_rectangle_map_dump_image_cb (CoglRectangleMapNode *node, void *data)
{
cairo_t *cr = data;
if (node->type == COGL_RECTANGLE_MAP_FILLED_LEAF ||
node->type == COGL_RECTANGLE_MAP_EMPTY_LEAF)
{
/* Fill the rectangle using a different colour depending on
whether the rectangle is used */
if (node->type == COGL_RECTANGLE_MAP_FILLED_LEAF)
cairo_set_source_rgb (cr, 0.0, 0.0, 1.0);
else
cairo_set_source_rgb (cr, 0.0, 0.0, 0.0);
cairo_rectangle (cr,
node->rectangle.x,
node->rectangle.y,
node->rectangle.width,
node->rectangle.height);
cairo_fill_preserve (cr);
/* Draw a white outline around the rectangle */
cairo_set_source_rgb (cr, 1.0, 1.0, 1.0);
cairo_stroke (cr);
}
}
static void
_cogl_rectangle_map_dump_image (CoglRectangleMap *map)
{
/* This dumps a png to help visualize the map. Each leaf rectangle
is drawn with a white outline. Unused leaves are filled in black
and used leaves are blue */
cairo_surface_t *surface =
cairo_image_surface_create (CAIRO_FORMAT_RGB24,
_cogl_rectangle_map_get_width (map),
_cogl_rectangle_map_get_height (map));
cairo_t *cr = cairo_create (surface);
_cogl_rectangle_map_internal_foreach (map,
_cogl_rectangle_map_dump_image_cb,
cr);
cairo_destroy (cr);
cairo_surface_write_to_png (surface, "cogl-rectangle-map-dump.png");
cairo_surface_destroy (surface);
}
#endif /* COGL_ENABLE_DEBUG */