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kolibrios/programs/games/pig/trunk/dirty.c

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/*
------------------------------------------------------------
Fixed Rate Pig - a fixed logic frame rate demo
------------------------------------------------------------
* Copyright (C) 2004 David Olofson <david@olofson.net>
*
* This software is released under the terms of the GPL.
*
* Contact author for permission if you want to use this
* software, or work derived from it, under other terms.
*/
#include <stdlib.h>
#include "engine.h"
/* Approximate worth of one dirtyrect in pixels. */
#define PIG_WORST_MERGE 300
/*
* If the merged result gets at most this many percent
* bigger than the larger of the two input rects,
* accept it as Perfect.
*/
#define PIG_INSTANT_MERGE 10
PIG_dirtytable *pig_dirty_open(int size)
{
PIG_dirtytable *pdt = (PIG_dirtytable *)malloc(sizeof(PIG_dirtytable));
if(!pdt)
return NULL;
pdt->size = size;
pdt->rects = (SDL_Rect *)calloc(size, sizeof(SDL_Rect));
if(!pdt->rects)
{
free(pdt);
return NULL;
}
pdt->count = 0;
pdt->best = 0;
return pdt;
}
void pig_dirty_close(PIG_dirtytable *pdt)
{
free(pdt->rects);
free(pdt);
}
void pig_mergerect(SDL_Rect *from, SDL_Rect *to)
{
int x1 = from->x;
int y1 = from->y;
int x2 = from->x + from->w;
int y2 = from->y + from->h;
if(to->x < x1)
x1 = to->x;
if(to->y < y1)
y1 = to->y;
if(to->x + to->w > x2)
x2 = to->x + to->w;
if(to->y + to->h > y2)
y2 = to->y + to->h;
to->x = x1;
to->y = y1;
to->w = x2 - x1;
to->h = y2 - y1;
}
void pig_intersectrect(SDL_Rect *from, SDL_Rect *to)
{
int Amin, Amax, Bmin, Bmax;
Amin = to->x;
Amax = Amin + to->w;
Bmin = from->x;
Bmax = Bmin + from->w;
if(Bmin > Amin)
Amin = Bmin;
to->x = Amin;
if(Bmax < Amax)
Amax = Bmax;
to->w = Amax - Amin > 0 ? Amax - Amin : 0;
Amin = to->y;
Amax = Amin + to->h;
Bmin = from->y;
Bmax = Bmin + from->h;
if(Bmin > Amin)
Amin = Bmin;
to->y = Amin;
if(Bmax < Amax)
Amax = Bmax;
to->h = Amax - Amin > 0 ? Amax - Amin : 0;
}
void pig_dirty_add(PIG_dirtytable *pdt, SDL_Rect *dr)
{
int i, j, best_i, best_loss;
/*
* Look for merger candidates.
*
* We start right before the best match we
* had the last time around. This can give
* us large numbers of direct or quick hits
* when dealing with old/new rects for moving
* objects and the like.
*/
best_i = -1;
best_loss = 100000000;
if(pdt->count)
i = (pdt->best + pdt->count - 1) % pdt->count;
for(j = 0; j < pdt->count; ++j)
{
int a1, a2, am, ratio, loss;
SDL_Rect testr;
a1 = dr->w * dr->h;
testr = pdt->rects[i];
a2 = testr.w * testr.h;
pig_mergerect(dr, &testr);
am = testr.w * testr.h;
/* Perfect or Instant Pick? */
ratio = 100 * am / (a1 > a2 ? a1 : a2);
if(ratio < PIG_INSTANT_MERGE)
{
/* Ok, this is good enough! Stop searching. */
pig_mergerect(dr, &pdt->rects[i]);
pdt->best = i;
return;
}
loss = am - a1 - a2;
if(loss < best_loss)
{
best_i = i;
best_loss = loss;
pdt->best = i;
}
++i;
i %= pdt->count;
}
/* ...and if the best result is good enough, merge! */
if((best_i >= 0) && (best_loss < PIG_WORST_MERGE))
{
pig_mergerect(dr, &pdt->rects[best_i]);
return;
}
/* Try to add to table... */
if(pdt->count < pdt->size)
{
pdt->rects[pdt->count++] = *dr;
return;
}
/* Emergency: Table full! Grab best candidate... */
pig_mergerect(dr, &pdt->rects[best_i]);
}
void pig_dirty_merge(PIG_dirtytable *pdt, PIG_dirtytable *from)
{
int i;
for(i = 0; i < from->count; ++i)
pig_dirty_add(pdt, from->rects + i);
}