/* -*- Mode: c; tab-width: 8; c-basic-offset: 4; indent-tabs-mode: t; -*- */ /* glitter-paths - polygon scan converter * * Copyright (c) 2008 M Joonas Pihlaja * Copyright (c) 2007 David Turner * * Permission is hereby granted, free of charge, to any person * obtaining a copy of this software and associated documentation * files (the "Software"), to deal in the Software without * restriction, including without limitation the rights to use, * copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following * conditions: * * The above copyright notice and this permission notice shall be * included in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR * OTHER DEALINGS IN THE SOFTWARE. */ /* This is the Glitter paths scan converter incorporated into cairo. * The source is from commit 734c53237a867a773640bd5b64816249fa1730f8 * of * * http://gitweb.freedesktop.org/?p=users/joonas/glitter-paths */ /* Glitter-paths is a stand alone polygon rasteriser derived from * David Turner's reimplementation of Tor Anderssons's 15x17 * supersampling rasteriser from the Apparition graphics library. The * main new feature here is cheaply choosing per-scan line between * doing fully analytical coverage computation for an entire row at a * time vs. using a supersampling approach. * * David Turner's code can be found at * * http://david.freetype.org/rasterizer-shootout/raster-comparison-20070813.tar.bz2 * * In particular this file incorporates large parts of ftgrays_tor10.h * from raster-comparison-20070813.tar.bz2 */ /* Overview * * A scan converter's basic purpose to take polygon edges and convert * them into an RLE compressed A8 mask. This one works in two phases: * gathering edges and generating spans. * * 1) As the user feeds the scan converter edges they are vertically * clipped and bucketted into a _polygon_ data structure. The edges * are also snapped from the user's coordinates to the subpixel grid * coordinates used during scan conversion. * * user * | * | edges * V * polygon buckets * * 2) Generating spans works by performing a vertical sweep of pixel * rows from top to bottom and maintaining an _active_list_ of edges * that intersect the row. From the active list the fill rule * determines which edges are the left and right edges of the start of * each span, and their contribution is then accumulated into a pixel * coverage list (_cell_list_) as coverage deltas. Once the coverage * deltas of all edges are known we can form spans of constant pixel * coverage by summing the deltas during a traversal of the cell list. * At the end of a pixel row the cell list is sent to a coverage * blitter for rendering to some target surface. * * The pixel coverages are computed by either supersampling the row * and box filtering a mono rasterisation, or by computing the exact * coverages of edges in the active list. The supersampling method is * used whenever some edge starts or stops within the row or there are * edge intersections in the row. * * polygon bucket for \ * current pixel row | * | | * | activate new edges | Repeat GRID_Y times if we * V \ are supersampling this row, * active list / or just once if we're computing * | | analytical coverage. * | coverage deltas | * V | * pixel coverage list / * | * V * coverage blitter */ #include "cairoint.h" #include "cairo-spans-private.h" #include "cairo-error-private.h" #include #include #include #include #include /* The input coordinate scale and the rasterisation grid scales. */ #define GLITTER_INPUT_BITS CAIRO_FIXED_FRAC_BITS #define GRID_X_BITS CAIRO_FIXED_FRAC_BITS #define GRID_Y 15 /* Set glitter up to use a cairo span renderer to do the coverage * blitting. */ struct pool; struct cell_list; /*------------------------------------------------------------------------- * glitter-paths.h */ /* "Input scaled" numbers are fixed precision reals with multiplier * 2**GLITTER_INPUT_BITS. Input coordinates are given to glitter as * pixel scaled numbers. These get converted to the internal grid * scaled numbers as soon as possible. Internal overflow is possible * if GRID_X/Y inside glitter-paths.c is larger than * 1< #include #include /* All polygon coordinates are snapped onto a subsample grid. "Grid * scaled" numbers are fixed precision reals with multiplier GRID_X or * GRID_Y. */ typedef int grid_scaled_t; typedef int grid_scaled_x_t; typedef int grid_scaled_y_t; /* Default x/y scale factors. * You can either define GRID_X/Y_BITS to get a power-of-two scale * or define GRID_X/Y separately. */ #if !defined(GRID_X) && !defined(GRID_X_BITS) # define GRID_X_BITS 8 #endif #if !defined(GRID_Y) && !defined(GRID_Y_BITS) # define GRID_Y 15 #endif /* Use GRID_X/Y_BITS to define GRID_X/Y if they're available. */ #ifdef GRID_X_BITS # define GRID_X (1 << GRID_X_BITS) #endif #ifdef GRID_Y_BITS # define GRID_Y (1 << GRID_Y_BITS) #endif /* The GRID_X_TO_INT_FRAC macro splits a grid scaled coordinate into * integer and fractional parts. The integer part is floored. */ #if defined(GRID_X_TO_INT_FRAC) /* do nothing */ #elif defined(GRID_X_BITS) # define GRID_X_TO_INT_FRAC(x, i, f) \ _GRID_TO_INT_FRAC_shift(x, i, f, GRID_X_BITS) #else # define GRID_X_TO_INT_FRAC(x, i, f) \ _GRID_TO_INT_FRAC_general(x, i, f, GRID_X) #endif #define _GRID_TO_INT_FRAC_general(t, i, f, m) do { \ (i) = (t) / (m); \ (f) = (t) % (m); \ if ((f) < 0) { \ --(i); \ (f) += (m); \ } \ } while (0) #define _GRID_TO_INT_FRAC_shift(t, i, f, b) do { \ (f) = (t) & ((1 << (b)) - 1); \ (i) = (t) >> (b); \ } while (0) /* A grid area is a real in [0,1] scaled by 2*GRID_X*GRID_Y. We want * to be able to represent exactly areas of subpixel trapezoids whose * vertices are given in grid scaled coordinates. The scale factor * comes from needing to accurately represent the area 0.5*dx*dy of a * triangle with base dx and height dy in grid scaled numbers. */ typedef int grid_area_t; #define GRID_XY (2*GRID_X*GRID_Y) /* Unit area on the grid. */ /* GRID_AREA_TO_ALPHA(area): map [0,GRID_XY] to [0,255]. */ #if GRID_XY == 510 # define GRID_AREA_TO_ALPHA(c) (((c)+1) >> 1) #elif GRID_XY == 255 # define GRID_AREA_TO_ALPHA(c) (c) #elif GRID_XY == 64 # define GRID_AREA_TO_ALPHA(c) (((c) << 2) | -(((c) & 0x40) >> 6)) #elif GRID_XY == 128 # define GRID_AREA_TO_ALPHA(c) ((((c) << 1) | -((c) >> 7)) & 255) #elif GRID_XY == 256 # define GRID_AREA_TO_ALPHA(c) (((c) | -((c) >> 8)) & 255) #elif GRID_XY == 15 # define GRID_AREA_TO_ALPHA(c) (((c) << 4) + (c)) #elif GRID_XY == 2*256*15 # define GRID_AREA_TO_ALPHA(c) (((c) + ((c)<<4) + 256) >> 9) #else # define GRID_AREA_TO_ALPHA(c) (((c)*255 + GRID_XY/2) / GRID_XY) #endif #define UNROLL3(x) x x x struct quorem { int32_t quo; int32_t rem; }; /* Header for a chunk of memory in a memory pool. */ struct _pool_chunk { /* # bytes used in this chunk. */ size_t size; /* # bytes total in this chunk */ size_t capacity; /* Pointer to the previous chunk or %NULL if this is the sentinel * chunk in the pool header. */ struct _pool_chunk *prev_chunk; /* Actual data starts here. Well aligned for pointers. */ }; /* A memory pool. This is supposed to be embedded on the stack or * within some other structure. It may optionally be followed by an * embedded array from which requests are fulfilled until * malloc needs to be called to allocate a first real chunk. */ struct pool { /* Chunk we're allocating from. */ struct _pool_chunk *current; jmp_buf *jmp; /* Free list of previously allocated chunks. All have >= default * capacity. */ struct _pool_chunk *first_free; /* The default capacity of a chunk. */ size_t default_capacity; /* Header for the sentinel chunk. Directly following the pool * struct should be some space for embedded elements from which * the sentinel chunk allocates from. */ struct _pool_chunk sentinel[1]; }; /* A polygon edge. */ struct edge { /* Next in y-bucket or active list. */ struct edge *next; /* Current x coordinate while the edge is on the active * list. Initialised to the x coordinate of the top of the * edge. The quotient is in grid_scaled_x_t units and the * remainder is mod dy in grid_scaled_y_t units.*/ struct quorem x; /* Advance of the current x when moving down a subsample line. */ struct quorem dxdy; /* Advance of the current x when moving down a full pixel * row. Only initialised when the height of the edge is large * enough that there's a chance the edge could be stepped by a * full row's worth of subsample rows at a time. */ struct quorem dxdy_full; /* The clipped y of the top of the edge. */ grid_scaled_y_t ytop; /* y2-y1 after orienting the edge downwards. */ grid_scaled_y_t dy; /* Number of subsample rows remaining to scan convert of this * edge. */ grid_scaled_y_t height_left; /* Original sign of the edge: +1 for downwards, -1 for upwards * edges. */ int dir; int vertical; int clip; }; /* Number of subsample rows per y-bucket. Must be GRID_Y. */ #define EDGE_Y_BUCKET_HEIGHT GRID_Y #define EDGE_Y_BUCKET_INDEX(y, ymin) (((y) - (ymin))/EDGE_Y_BUCKET_HEIGHT) /* A collection of sorted and vertically clipped edges of the polygon. * Edges are moved from the polygon to an active list while scan * converting. */ struct polygon { /* The vertical clip extents. */ grid_scaled_y_t ymin, ymax; /* Array of edges all starting in the same bucket. An edge is put * into bucket EDGE_BUCKET_INDEX(edge->ytop, polygon->ymin) when * it is added to the polygon. */ struct edge **y_buckets; struct edge *y_buckets_embedded[64]; struct { struct pool base[1]; struct edge embedded[32]; } edge_pool; }; /* A cell records the effect on pixel coverage of polygon edges * passing through a pixel. It contains two accumulators of pixel * coverage. * * Consider the effects of a polygon edge on the coverage of a pixel * it intersects and that of the following one. The coverage of the * following pixel is the height of the edge multiplied by the width * of the pixel, and the coverage of the pixel itself is the area of * the trapezoid formed by the edge and the right side of the pixel. * * +-----------------------+-----------------------+ * | | | * | | | * |_______________________|_______________________| * | \...................|.......................|\ * | \..................|.......................| | * | \.................|.......................| | * | \....covered.....|.......................| | * | \....area.......|.......................| } covered height * | \..............|.......................| | * |uncovered\.............|.......................| | * | area \............|.......................| | * |___________\...........|.......................|/ * | | | * | | | * | | | * +-----------------------+-----------------------+ * * Since the coverage of the following pixel will always be a multiple * of the width of the pixel, we can store the height of the covered * area instead. The coverage of the pixel itself is the total * coverage minus the area of the uncovered area to the left of the * edge. As it's faster to compute the uncovered area we only store * that and subtract it from the total coverage later when forming * spans to blit. * * The heights and areas are signed, with left edges of the polygon * having positive sign and right edges having negative sign. When * two edges intersect they swap their left/rightness so their * contribution above and below the intersection point must be * computed separately. */ struct cell { struct cell *next; int x; grid_area_t uncovered_area; grid_scaled_y_t covered_height; grid_scaled_y_t clipped_height; }; /* A cell list represents the scan line sparsely as cells ordered by * ascending x. It is geared towards scanning the cells in order * using an internal cursor. */ struct cell_list { /* Sentinel nodes */ struct cell head, tail; /* Cursor state for iterating through the cell list. */ struct cell *cursor; /* Cells in the cell list are owned by the cell list and are * allocated from this pool. */ struct { struct pool base[1]; struct cell embedded[32]; } cell_pool; }; struct cell_pair { struct cell *cell1; struct cell *cell2; }; /* The active list contains edges in the current scan line ordered by * the x-coordinate of the intercept of the edge and the scan line. */ struct active_list { /* Leftmost edge on the current scan line. */ struct edge *head; /* A lower bound on the height of the active edges is used to * estimate how soon some active edge ends. We can't advance the * scan conversion by a full pixel row if an edge ends somewhere * within it. */ grid_scaled_y_t min_height; }; struct glitter_scan_converter { struct polygon polygon[1]; struct active_list active[1]; struct cell_list coverages[1]; /* Clip box. */ grid_scaled_y_t ymin, ymax; }; /* Compute the floored division a/b. Assumes / and % perform symmetric * division. */ inline static struct quorem floored_divrem(int a, int b) { struct quorem qr; qr.quo = a/b; qr.rem = a%b; if ((a^b)<0 && qr.rem) { qr.quo -= 1; qr.rem += b; } return qr; } /* Compute the floored division (x*a)/b. Assumes / and % perform symmetric * division. */ static struct quorem floored_muldivrem(int x, int a, int b) { struct quorem qr; long long xa = (long long)x*a; qr.quo = xa/b; qr.rem = xa%b; if ((xa>=0) != (b>=0) && qr.rem) { qr.quo -= 1; qr.rem += b; } return qr; } static struct _pool_chunk * _pool_chunk_init( struct _pool_chunk *p, struct _pool_chunk *prev_chunk, size_t capacity) { p->prev_chunk = prev_chunk; p->size = 0; p->capacity = capacity; return p; } static struct _pool_chunk * _pool_chunk_create(struct pool *pool, size_t size) { struct _pool_chunk *p; p = malloc(size + sizeof(struct _pool_chunk)); if (unlikely (NULL == p)) longjmp (*pool->jmp, _cairo_error (CAIRO_STATUS_NO_MEMORY)); return _pool_chunk_init(p, pool->current, size); } static void pool_init(struct pool *pool, jmp_buf *jmp, size_t default_capacity, size_t embedded_capacity) { pool->jmp = jmp; pool->current = pool->sentinel; pool->first_free = NULL; pool->default_capacity = default_capacity; _pool_chunk_init(pool->sentinel, NULL, embedded_capacity); } static void pool_fini(struct pool *pool) { struct _pool_chunk *p = pool->current; do { while (NULL != p) { struct _pool_chunk *prev = p->prev_chunk; if (p != pool->sentinel) free(p); p = prev; } p = pool->first_free; pool->first_free = NULL; } while (NULL != p); } /* Satisfy an allocation by first allocating a new large enough chunk * and adding it to the head of the pool's chunk list. This function * is called as a fallback if pool_alloc() couldn't do a quick * allocation from the current chunk in the pool. */ static void * _pool_alloc_from_new_chunk( struct pool *pool, size_t size) { struct _pool_chunk *chunk; void *obj; size_t capacity; /* If the allocation is smaller than the default chunk size then * try getting a chunk off the free list. Force alloc of a new * chunk for large requests. */ capacity = size; chunk = NULL; if (size < pool->default_capacity) { capacity = pool->default_capacity; chunk = pool->first_free; if (chunk) { pool->first_free = chunk->prev_chunk; _pool_chunk_init(chunk, pool->current, chunk->capacity); } } if (NULL == chunk) chunk = _pool_chunk_create (pool, capacity); pool->current = chunk; obj = ((unsigned char*)chunk + sizeof(*chunk) + chunk->size); chunk->size += size; return obj; } /* Allocate size bytes from the pool. The first allocated address * returned from a pool is aligned to sizeof(void*). Subsequent * addresses will maintain alignment as long as multiples of void* are * allocated. Returns the address of a new memory area or %NULL on * allocation failures. The pool retains ownership of the returned * memory. */ inline static void * pool_alloc (struct pool *pool, size_t size) { struct _pool_chunk *chunk = pool->current; if (size <= chunk->capacity - chunk->size) { void *obj = ((unsigned char*)chunk + sizeof(*chunk) + chunk->size); chunk->size += size; return obj; } else { return _pool_alloc_from_new_chunk(pool, size); } } /* Relinquish all pool_alloced memory back to the pool. */ static void pool_reset (struct pool *pool) { /* Transfer all used chunks to the chunk free list. */ struct _pool_chunk *chunk = pool->current; if (chunk != pool->sentinel) { while (chunk->prev_chunk != pool->sentinel) { chunk = chunk->prev_chunk; } chunk->prev_chunk = pool->first_free; pool->first_free = pool->current; } /* Reset the sentinel as the current chunk. */ pool->current = pool->sentinel; pool->sentinel->size = 0; } /* Rewinds the cell list's cursor to the beginning. After rewinding * we're good to cell_list_find() the cell any x coordinate. */ inline static void cell_list_rewind (struct cell_list *cells) { cells->cursor = &cells->head; } /* Rewind the cell list if its cursor has been advanced past x. */ inline static void cell_list_maybe_rewind (struct cell_list *cells, int x) { struct cell *tail = cells->cursor; if (tail->x > x) cell_list_rewind (cells); } static void cell_list_init(struct cell_list *cells, jmp_buf *jmp) { pool_init(cells->cell_pool.base, jmp, 256*sizeof(struct cell), sizeof(cells->cell_pool.embedded)); cells->tail.next = NULL; cells->tail.x = INT_MAX; cells->head.x = INT_MIN; cells->head.next = &cells->tail; cell_list_rewind (cells); } static void cell_list_fini(struct cell_list *cells) { pool_fini (cells->cell_pool.base); } /* Empty the cell list. This is called at the start of every pixel * row. */ inline static void cell_list_reset (struct cell_list *cells) { cell_list_rewind (cells); cells->head.next = &cells->tail; pool_reset (cells->cell_pool.base); } static struct cell * cell_list_alloc (struct cell_list *cells, struct cell *tail, int x) { struct cell *cell; cell = pool_alloc (cells->cell_pool.base, sizeof (struct cell)); cell->next = tail->next; tail->next = cell; cell->x = x; cell->uncovered_area = 0; cell->covered_height = 0; cell->clipped_height = 0; return cell; } /* Find a cell at the given x-coordinate. Returns %NULL if a new cell * needed to be allocated but couldn't be. Cells must be found with * non-decreasing x-coordinate until the cell list is rewound using * cell_list_rewind(). Ownership of the returned cell is retained by * the cell list. */ inline static struct cell * cell_list_find (struct cell_list *cells, int x) { struct cell *tail = cells->cursor; while (1) { UNROLL3({ if (tail->next->x > x) break; tail = tail->next; }); } if (tail->x != x) tail = cell_list_alloc (cells, tail, x); return cells->cursor = tail; } /* Find two cells at x1 and x2. This is exactly equivalent * to * * pair.cell1 = cell_list_find(cells, x1); * pair.cell2 = cell_list_find(cells, x2); * * except with less function call overhead. */ inline static struct cell_pair cell_list_find_pair(struct cell_list *cells, int x1, int x2) { struct cell_pair pair; pair.cell1 = cells->cursor; while (1) { UNROLL3({ if (pair.cell1->next->x > x1) break; pair.cell1 = pair.cell1->next; }); } if (pair.cell1->x != x1) { struct cell *cell = pool_alloc (cells->cell_pool.base, sizeof (struct cell)); cell->x = x1; cell->uncovered_area = 0; cell->covered_height = 0; cell->clipped_height = 0; cell->next = pair.cell1->next; pair.cell1->next = cell; pair.cell1 = cell; } pair.cell2 = pair.cell1; while (1) { UNROLL3({ if (pair.cell2->next->x > x2) break; pair.cell2 = pair.cell2->next; }); } if (pair.cell2->x != x2) { struct cell *cell = pool_alloc (cells->cell_pool.base, sizeof (struct cell)); cell->uncovered_area = 0; cell->covered_height = 0; cell->clipped_height = 0; cell->x = x2; cell->next = pair.cell2->next; pair.cell2->next = cell; pair.cell2 = cell; } cells->cursor = pair.cell2; return pair; } /* Add a subpixel span covering [x1, x2) to the coverage cells. */ inline static void cell_list_add_subspan(struct cell_list *cells, grid_scaled_x_t x1, grid_scaled_x_t x2) { int ix1, fx1; int ix2, fx2; GRID_X_TO_INT_FRAC(x1, ix1, fx1); GRID_X_TO_INT_FRAC(x2, ix2, fx2); if (ix1 != ix2) { struct cell_pair p; p = cell_list_find_pair(cells, ix1, ix2); p.cell1->uncovered_area += 2*fx1; ++p.cell1->covered_height; p.cell2->uncovered_area -= 2*fx2; --p.cell2->covered_height; } else { struct cell *cell = cell_list_find(cells, ix1); cell->uncovered_area += 2*(fx1-fx2); } } /* Adds the analytical coverage of an edge crossing the current pixel * row to the coverage cells and advances the edge's x position to the * following row. * * This function is only called when we know that during this pixel row: * * 1) The relative order of all edges on the active list doesn't * change. In particular, no edges intersect within this row to pixel * precision. * * 2) No new edges start in this row. * * 3) No existing edges end mid-row. * * This function depends on being called with all edges from the * active list in the order they appear on the list (i.e. with * non-decreasing x-coordinate.) */ static void cell_list_render_edge( struct cell_list *cells, struct edge *edge, int sign) { grid_scaled_y_t y1, y2, dy; grid_scaled_x_t dx; int ix1, ix2; grid_scaled_x_t fx1, fx2; struct quorem x1 = edge->x; struct quorem x2 = x1; if (! edge->vertical) { x2.quo += edge->dxdy_full.quo; x2.rem += edge->dxdy_full.rem; if (x2.rem >= 0) { ++x2.quo; x2.rem -= edge->dy; } edge->x = x2; } GRID_X_TO_INT_FRAC(x1.quo, ix1, fx1); GRID_X_TO_INT_FRAC(x2.quo, ix2, fx2); /* Edge is entirely within a column? */ if (ix1 == ix2) { /* We always know that ix1 is >= the cell list cursor in this * case due to the no-intersections precondition. */ struct cell *cell = cell_list_find(cells, ix1); cell->covered_height += sign*GRID_Y; cell->uncovered_area += sign*(fx1 + fx2)*GRID_Y; return; } /* Orient the edge left-to-right. */ dx = x2.quo - x1.quo; if (dx >= 0) { y1 = 0; y2 = GRID_Y; } else { int tmp; tmp = ix1; ix1 = ix2; ix2 = tmp; tmp = fx1; fx1 = fx2; fx2 = tmp; dx = -dx; sign = -sign; y1 = GRID_Y; y2 = 0; } dy = y2 - y1; /* Add coverage for all pixels [ix1,ix2] on this row crossed * by the edge. */ { struct cell_pair pair; struct quorem y = floored_divrem((GRID_X - fx1)*dy, dx); /* When rendering a previous edge on the active list we may * advance the cell list cursor past the leftmost pixel of the * current edge even though the two edges don't intersect. * e.g. consider two edges going down and rightwards: * * --\_+---\_+-----+-----+---- * \_ \_ | | * | \_ | \_ | | * | \_| \_| | * | \_ \_ | * ----+-----+-\---+-\---+---- * * The left edge touches cells past the starting cell of the * right edge. Fortunately such cases are rare. * * The rewinding is never necessary if the current edge stays * within a single column because we've checked before calling * this function that the active list order won't change. */ cell_list_maybe_rewind(cells, ix1); pair = cell_list_find_pair(cells, ix1, ix1+1); pair.cell1->uncovered_area += sign*y.quo*(GRID_X + fx1); pair.cell1->covered_height += sign*y.quo; y.quo += y1; if (ix1+1 < ix2) { struct quorem dydx_full = floored_divrem(GRID_X*dy, dx); struct cell *cell = pair.cell2; ++ix1; do { grid_scaled_y_t y_skip = dydx_full.quo; y.rem += dydx_full.rem; if (y.rem >= dx) { ++y_skip; y.rem -= dx; } y.quo += y_skip; y_skip *= sign; cell->uncovered_area += y_skip*GRID_X; cell->covered_height += y_skip; ++ix1; cell = cell_list_find(cells, ix1); } while (ix1 != ix2); pair.cell2 = cell; } pair.cell2->uncovered_area += sign*(y2 - y.quo)*fx2; pair.cell2->covered_height += sign*(y2 - y.quo); } } static void polygon_init (struct polygon *polygon, jmp_buf *jmp) { polygon->ymin = polygon->ymax = 0; polygon->y_buckets = polygon->y_buckets_embedded; pool_init (polygon->edge_pool.base, jmp, 8192 - sizeof (struct _pool_chunk), sizeof (polygon->edge_pool.embedded)); } static void polygon_fini (struct polygon *polygon) { if (polygon->y_buckets != polygon->y_buckets_embedded) free (polygon->y_buckets); pool_fini (polygon->edge_pool.base); } /* Empties the polygon of all edges. The polygon is then prepared to * receive new edges and clip them to the vertical range * [ymin,ymax). */ static cairo_status_t polygon_reset (struct polygon *polygon, grid_scaled_y_t ymin, grid_scaled_y_t ymax) { unsigned h = ymax - ymin; unsigned num_buckets = EDGE_Y_BUCKET_INDEX(ymax + EDGE_Y_BUCKET_HEIGHT-1, ymin); pool_reset(polygon->edge_pool.base); if (unlikely (h > 0x7FFFFFFFU - EDGE_Y_BUCKET_HEIGHT)) goto bail_no_mem; /* even if you could, you wouldn't want to. */ if (polygon->y_buckets != polygon->y_buckets_embedded) free (polygon->y_buckets); polygon->y_buckets = polygon->y_buckets_embedded; if (num_buckets > ARRAY_LENGTH (polygon->y_buckets_embedded)) { polygon->y_buckets = _cairo_malloc_ab (num_buckets, sizeof (struct edge *)); if (unlikely (NULL == polygon->y_buckets)) goto bail_no_mem; } memset (polygon->y_buckets, 0, num_buckets * sizeof (struct edge *)); polygon->ymin = ymin; polygon->ymax = ymax; return CAIRO_STATUS_SUCCESS; bail_no_mem: polygon->ymin = 0; polygon->ymax = 0; return CAIRO_STATUS_NO_MEMORY; } static void _polygon_insert_edge_into_its_y_bucket( struct polygon *polygon, struct edge *e) { unsigned ix = EDGE_Y_BUCKET_INDEX(e->ytop, polygon->ymin); struct edge **ptail = &polygon->y_buckets[ix]; e->next = *ptail; *ptail = e; } inline static void polygon_add_edge (struct polygon *polygon, const cairo_edge_t *edge, int clip) { struct edge *e; grid_scaled_x_t dx; grid_scaled_y_t dy; grid_scaled_y_t ytop, ybot; grid_scaled_y_t ymin = polygon->ymin; grid_scaled_y_t ymax = polygon->ymax; assert (edge->bottom > edge->top); if (unlikely (edge->top >= ymax || edge->bottom <= ymin)) return; e = pool_alloc (polygon->edge_pool.base, sizeof (struct edge)); dx = edge->line.p2.x - edge->line.p1.x; dy = edge->line.p2.y - edge->line.p1.y; e->dy = dy; e->dir = edge->dir; e->clip = clip; ytop = edge->top >= ymin ? edge->top : ymin; ybot = edge->bottom <= ymax ? edge->bottom : ymax; e->ytop = ytop; e->height_left = ybot - ytop; if (dx == 0) { e->vertical = TRUE; e->x.quo = edge->line.p1.x; e->x.rem = 0; e->dxdy.quo = 0; e->dxdy.rem = 0; e->dxdy_full.quo = 0; e->dxdy_full.rem = 0; } else { e->vertical = FALSE; e->dxdy = floored_divrem (dx, dy); if (ytop == edge->line.p1.y) { e->x.quo = edge->line.p1.x; e->x.rem = 0; } else { e->x = floored_muldivrem (ytop - edge->line.p1.y, dx, dy); e->x.quo += edge->line.p1.x; } if (e->height_left >= GRID_Y) { e->dxdy_full = floored_muldivrem (GRID_Y, dx, dy); } else { e->dxdy_full.quo = 0; e->dxdy_full.rem = 0; } } _polygon_insert_edge_into_its_y_bucket (polygon, e); e->x.rem -= dy; /* Bias the remainder for faster * edge advancement. */ } static void active_list_reset (struct active_list *active) { active->head = NULL; active->min_height = 0; } static void active_list_init(struct active_list *active) { active_list_reset(active); } /* * Merge two sorted edge lists. * Input: * - head_a: The head of the first list. * - head_b: The head of the second list; head_b cannot be NULL. * Output: * Returns the head of the merged list. * * Implementation notes: * To make it fast (in particular, to reduce to an insertion sort whenever * one of the two input lists only has a single element) we iterate through * a list until its head becomes greater than the head of the other list, * then we switch their roles. As soon as one of the two lists is empty, we * just attach the other one to the current list and exit. * Writes to memory are only needed to "switch" lists (as it also requires * attaching to the output list the list which we will be iterating next) and * to attach the last non-empty list. */ static struct edge * merge_sorted_edges (struct edge *head_a, struct edge *head_b) { struct edge *head, **next; int32_t x; if (head_a == NULL) return head_b; next = &head; if (head_a->x.quo <= head_b->x.quo) { head = head_a; } else { head = head_b; goto start_with_b; } do { x = head_b->x.quo; while (head_a != NULL && head_a->x.quo <= x) { next = &head_a->next; head_a = head_a->next; } *next = head_b; if (head_a == NULL) return head; start_with_b: x = head_a->x.quo; while (head_b != NULL && head_b->x.quo <= x) { next = &head_b->next; head_b = head_b->next; } *next = head_a; if (head_b == NULL) return head; } while (1); } /* * Sort (part of) a list. * Input: * - list: The list to be sorted; list cannot be NULL. * - limit: Recursion limit. * Output: * - head_out: The head of the sorted list containing the first 2^(level+1) elements of the * input list; if the input list has fewer elements, head_out be a sorted list * containing all the elements of the input list. * Returns the head of the list of unprocessed elements (NULL if the sorted list contains * all the elements of the input list). * * Implementation notes: * Special case single element list, unroll/inline the sorting of the first two elements. * Some tail recursion is used since we iterate on the bottom-up solution of the problem * (we start with a small sorted list and keep merging other lists of the same size to it). */ static struct edge * sort_edges (struct edge *list, unsigned int level, struct edge **head_out) { struct edge *head_other, *remaining; unsigned int i; head_other = list->next; /* Single element list -> return */ if (head_other == NULL) { *head_out = list; return NULL; } /* Unroll the first iteration of the following loop (halves the number of calls to merge_sorted_edges): * - Initialize remaining to be the list containing the elements after the second in the input list. * - Initialize *head_out to be the sorted list containing the first two element. */ remaining = head_other->next; if (list->x.quo <= head_other->x.quo) { *head_out = list; /* list->next = head_other; */ /* The input list is already like this. */ head_other->next = NULL; } else { *head_out = head_other; head_other->next = list; list->next = NULL; } for (i = 0; i < level && remaining; i++) { /* Extract a sorted list of the same size as *head_out * (2^(i+1) elements) from the list of remaining elements. */ remaining = sort_edges (remaining, i, &head_other); *head_out = merge_sorted_edges (*head_out, head_other); } /* *head_out now contains (at most) 2^(level+1) elements. */ return remaining; } /* Test if the edges on the active list can be safely advanced by a * full row without intersections or any edges ending. */ inline static int active_list_can_step_full_row (struct active_list *active) { const struct edge *e; int prev_x = INT_MIN; /* Recomputes the minimum height of all edges on the active * list if we have been dropping edges. */ if (active->min_height <= 0) { int min_height = INT_MAX; e = active->head; while (NULL != e) { if (e->height_left < min_height) min_height = e->height_left; e = e->next; } active->min_height = min_height; } if (active->min_height < GRID_Y) return 0; /* Check for intersections as no edges end during the next row. */ e = active->head; while (NULL != e) { struct quorem x = e->x; if (! e->vertical) { x.quo += e->dxdy_full.quo; x.rem += e->dxdy_full.rem; if (x.rem >= 0) ++x.quo; } if (x.quo <= prev_x) return 0; prev_x = x.quo; e = e->next; } return 1; } /* Merges edges on the given subpixel row from the polygon to the * active_list. */ inline static void active_list_merge_edges_from_polygon(struct active_list *active, struct edge **ptail, grid_scaled_y_t y, struct polygon *polygon) { /* Split off the edges on the current subrow and merge them into * the active list. */ int min_height = active->min_height; struct edge *subrow_edges = NULL; struct edge *tail = *ptail; do { struct edge *next = tail->next; if (y == tail->ytop) { tail->next = subrow_edges; subrow_edges = tail; if (tail->height_left < min_height) min_height = tail->height_left; *ptail = next; } else ptail = &tail->next; tail = next; } while (tail); if (subrow_edges) { sort_edges (subrow_edges, UINT_MAX, &subrow_edges); active->head = merge_sorted_edges (active->head, subrow_edges); active->min_height = min_height; } } /* Advance the edges on the active list by one subsample row by * updating their x positions. Drop edges from the list that end. */ inline static void active_list_substep_edges(struct active_list *active) { struct edge **cursor = &active->head; grid_scaled_x_t prev_x = INT_MIN; struct edge *unsorted = NULL; struct edge *edge = *cursor; do { UNROLL3({ struct edge *next; if (NULL == edge) break; next = edge->next; if (--edge->height_left) { edge->x.quo += edge->dxdy.quo; edge->x.rem += edge->dxdy.rem; if (edge->x.rem >= 0) { ++edge->x.quo; edge->x.rem -= edge->dy; } if (edge->x.quo < prev_x) { *cursor = next; edge->next = unsorted; unsorted = edge; } else { prev_x = edge->x.quo; cursor = &edge->next; } } else { *cursor = next; } edge = next; }) } while (1); if (unsorted) { sort_edges (unsorted, UINT_MAX, &unsorted); active->head = merge_sorted_edges (active->head, unsorted); } } inline static void apply_nonzero_fill_rule_for_subrow (struct active_list *active, struct cell_list *coverages) { struct edge *edge = active->head; int winding = 0; int xstart; int xend; cell_list_rewind (coverages); while (NULL != edge) { xstart = edge->x.quo; winding = edge->dir; while (1) { edge = edge->next; if (NULL == edge) { ASSERT_NOT_REACHED; return; } winding += edge->dir; if (0 == winding) { if (edge->next == NULL || edge->next->x.quo != edge->x.quo) break; } } xend = edge->x.quo; cell_list_add_subspan (coverages, xstart, xend); edge = edge->next; } } static void apply_evenodd_fill_rule_for_subrow (struct active_list *active, struct cell_list *coverages) { struct edge *edge = active->head; int xstart; int xend; cell_list_rewind (coverages); while (NULL != edge) { xstart = edge->x.quo; while (1) { edge = edge->next; if (NULL == edge) { ASSERT_NOT_REACHED; return; } if (edge->next == NULL || edge->next->x.quo != edge->x.quo) break; edge = edge->next; } xend = edge->x.quo; cell_list_add_subspan (coverages, xstart, xend); edge = edge->next; } } static void apply_nonzero_fill_rule_and_step_edges (struct active_list *active, struct cell_list *coverages) { struct edge **cursor = &active->head; struct edge *left_edge; left_edge = *cursor; while (NULL != left_edge) { struct edge *right_edge; int winding = left_edge->dir; left_edge->height_left -= GRID_Y; if (left_edge->height_left) cursor = &left_edge->next; else *cursor = left_edge->next; while (1) { right_edge = *cursor; if (NULL == right_edge) { cell_list_render_edge (coverages, left_edge, +1); return; } right_edge->height_left -= GRID_Y; if (right_edge->height_left) cursor = &right_edge->next; else *cursor = right_edge->next; winding += right_edge->dir; if (0 == winding) { if (right_edge->next == NULL || right_edge->next->x.quo != right_edge->x.quo) { break; } } if (! right_edge->vertical) { right_edge->x.quo += right_edge->dxdy_full.quo; right_edge->x.rem += right_edge->dxdy_full.rem; if (right_edge->x.rem >= 0) { ++right_edge->x.quo; right_edge->x.rem -= right_edge->dy; } } } cell_list_render_edge (coverages, left_edge, +1); cell_list_render_edge (coverages, right_edge, -1); left_edge = *cursor; } } static void apply_evenodd_fill_rule_and_step_edges (struct active_list *active, struct cell_list *coverages) { struct edge **cursor = &active->head; struct edge *left_edge; left_edge = *cursor; while (NULL != left_edge) { struct edge *right_edge; left_edge->height_left -= GRID_Y; if (left_edge->height_left) cursor = &left_edge->next; else *cursor = left_edge->next; while (1) { right_edge = *cursor; if (NULL == right_edge) { cell_list_render_edge (coverages, left_edge, +1); return; } right_edge->height_left -= GRID_Y; if (right_edge->height_left) cursor = &right_edge->next; else *cursor = right_edge->next; if (right_edge->next == NULL || right_edge->next->x.quo != right_edge->x.quo) { break; } if (! right_edge->vertical) { right_edge->x.quo += right_edge->dxdy_full.quo; right_edge->x.rem += right_edge->dxdy_full.rem; if (right_edge->x.rem >= 0) { ++right_edge->x.quo; right_edge->x.rem -= right_edge->dy; } } } cell_list_render_edge (coverages, left_edge, +1); cell_list_render_edge (coverages, right_edge, -1); left_edge = *cursor; } } static void _glitter_scan_converter_init(glitter_scan_converter_t *converter, jmp_buf *jmp) { polygon_init(converter->polygon, jmp); active_list_init(converter->active); cell_list_init(converter->coverages, jmp); converter->ymin=0; converter->ymax=0; } static void _glitter_scan_converter_fini(glitter_scan_converter_t *converter) { polygon_fini(converter->polygon); cell_list_fini(converter->coverages); converter->ymin=0; converter->ymax=0; } static grid_scaled_t int_to_grid_scaled(int i, int scale) { /* Clamp to max/min representable scaled number. */ if (i >= 0) { if (i >= INT_MAX/scale) i = INT_MAX/scale; } else { if (i <= INT_MIN/scale) i = INT_MIN/scale; } return i*scale; } #define int_to_grid_scaled_x(x) int_to_grid_scaled((x), GRID_X) #define int_to_grid_scaled_y(x) int_to_grid_scaled((x), GRID_Y) static cairo_status_t glitter_scan_converter_reset(glitter_scan_converter_t *converter, int ymin, int ymax) { cairo_status_t status; converter->ymin = 0; converter->ymax = 0; ymin = int_to_grid_scaled_y(ymin); ymax = int_to_grid_scaled_y(ymax); active_list_reset(converter->active); cell_list_reset(converter->coverages); status = polygon_reset(converter->polygon, ymin, ymax); if (status) return status; converter->ymin = ymin; converter->ymax = ymax; return CAIRO_STATUS_SUCCESS; } /* INPUT_TO_GRID_X/Y (in_coord, out_grid_scaled, grid_scale) * These macros convert an input coordinate in the client's * device space to the rasterisation grid. */ /* Gah.. this bit of ugly defines INPUT_TO_GRID_X/Y so as to use * shifts if possible, and something saneish if not. */ #if !defined(INPUT_TO_GRID_Y) && defined(GRID_Y_BITS) && GRID_Y_BITS <= GLITTER_INPUT_BITS # define INPUT_TO_GRID_Y(in, out) (out) = (in) >> (GLITTER_INPUT_BITS - GRID_Y_BITS) #else # define INPUT_TO_GRID_Y(in, out) INPUT_TO_GRID_general(in, out, GRID_Y) #endif #if !defined(INPUT_TO_GRID_X) && defined(GRID_X_BITS) && GRID_X_BITS <= GLITTER_INPUT_BITS # define INPUT_TO_GRID_X(in, out) (out) = (in) >> (GLITTER_INPUT_BITS - GRID_X_BITS) #else # define INPUT_TO_GRID_X(in, out) INPUT_TO_GRID_general(in, out, GRID_X) #endif #define INPUT_TO_GRID_general(in, out, grid_scale) do { \ long long tmp__ = (long long)(grid_scale) * (in); \ tmp__ >>= GLITTER_INPUT_BITS; \ (out) = tmp__; \ } while (0) static void glitter_scan_converter_add_edge (glitter_scan_converter_t *converter, const cairo_edge_t *edge, int clip) { cairo_edge_t e; INPUT_TO_GRID_Y (edge->top, e.top); INPUT_TO_GRID_Y (edge->bottom, e.bottom); if (e.top >= e.bottom) return; /* XXX: possible overflows if GRID_X/Y > 2**GLITTER_INPUT_BITS */ INPUT_TO_GRID_Y (edge->line.p1.y, e.line.p1.y); INPUT_TO_GRID_Y (edge->line.p2.y, e.line.p2.y); if (e.line.p1.y == e.line.p2.y) return; INPUT_TO_GRID_X (edge->line.p1.x, e.line.p1.x); INPUT_TO_GRID_X (edge->line.p2.x, e.line.p2.x); e.dir = edge->dir; polygon_add_edge (converter->polygon, &e, clip); } static cairo_bool_t active_list_is_vertical (struct active_list *active) { struct edge *e; for (e = active->head; e != NULL; e = e->next) { if (! e->vertical) return FALSE; } return TRUE; } static void step_edges (struct active_list *active, int count) { struct edge **cursor = &active->head; struct edge *edge; for (edge = *cursor; edge != NULL; edge = *cursor) { edge->height_left -= GRID_Y * count; if (edge->height_left) cursor = &edge->next; else *cursor = edge->next; } } static cairo_status_t blit_coverages (struct cell_list *cells, cairo_span_renderer_t *renderer, struct pool *span_pool, int y, int height) { struct cell *cell = cells->head.next; int prev_x = -1; int cover = 0, last_cover = 0; int clip = 0; cairo_half_open_span_t *spans; unsigned num_spans; assert (cell != &cells->tail); /* Count number of cells remaining. */ { struct cell *next = cell; num_spans = 2; while (next->next) { next = next->next; ++num_spans; } num_spans = 2*num_spans; } /* Allocate enough spans for the row. */ pool_reset (span_pool); spans = pool_alloc (span_pool, sizeof(spans[0])*num_spans); num_spans = 0; /* Form the spans from the coverages and areas. */ for (; cell->next; cell = cell->next) { int x = cell->x; int area; if (x > prev_x && cover != last_cover) { spans[num_spans].x = prev_x; spans[num_spans].coverage = GRID_AREA_TO_ALPHA (cover); spans[num_spans].inverse = 0; last_cover = cover; ++num_spans; } cover += cell->covered_height*GRID_X*2; clip += cell->covered_height*GRID_X*2; area = cover - cell->uncovered_area; if (area != last_cover) { spans[num_spans].x = x; spans[num_spans].coverage = GRID_AREA_TO_ALPHA (area); spans[num_spans].inverse = 0; last_cover = area; ++num_spans; } prev_x = x+1; } /* Dump them into the renderer. */ return renderer->render_rows (renderer, y, height, spans, num_spans); } static void glitter_scan_converter_render(glitter_scan_converter_t *converter, int nonzero_fill, cairo_span_renderer_t *span_renderer, struct pool *span_pool) { int i, j; int ymax_i = converter->ymax / GRID_Y; int ymin_i = converter->ymin / GRID_Y; int h = ymax_i - ymin_i; struct polygon *polygon = converter->polygon; struct cell_list *coverages = converter->coverages; struct active_list *active = converter->active; /* Render each pixel row. */ for (i = 0; i < h; i = j) { int do_full_step = 0; j = i + 1; /* Determine if we can ignore this row or use the full pixel * stepper. */ if (GRID_Y == EDGE_Y_BUCKET_HEIGHT && ! polygon->y_buckets[i]) { if (! active->head) { for (; j < h && ! polygon->y_buckets[j]; j++) ; continue; } do_full_step = active_list_can_step_full_row (active); } if (do_full_step) { /* Step by a full pixel row's worth. */ if (nonzero_fill) apply_nonzero_fill_rule_and_step_edges (active, coverages); else apply_evenodd_fill_rule_and_step_edges (active, coverages); if (active_list_is_vertical (active)) { while (j < h && polygon->y_buckets[j] == NULL && active->min_height >= 2*GRID_Y) { active->min_height -= GRID_Y; j++; } if (j != i + 1) step_edges (active, j - (i + 1)); } } else { grid_scaled_y_t suby; /* Subsample this row. */ for (suby = 0; suby < GRID_Y; suby++) { grid_scaled_y_t y = (i+ymin_i)*GRID_Y + suby; if (polygon->y_buckets[i]) { active_list_merge_edges_from_polygon (active, &polygon->y_buckets[i], y, polygon); } if (nonzero_fill) apply_nonzero_fill_rule_for_subrow (active, coverages); else apply_evenodd_fill_rule_for_subrow (active, coverages); active_list_substep_edges(active); } } blit_coverages (coverages, span_renderer, span_pool, i+ymin_i, j -i); cell_list_reset (coverages); if (! active->head) active->min_height = INT_MAX; else active->min_height -= GRID_Y; } } struct _cairo_clip_tor_scan_converter { cairo_scan_converter_t base; glitter_scan_converter_t converter[1]; cairo_fill_rule_t fill_rule; cairo_antialias_t antialias; cairo_fill_rule_t clip_fill_rule; cairo_antialias_t clip_antialias; jmp_buf jmp; struct { struct pool base[1]; cairo_half_open_span_t embedded[32]; } span_pool; }; typedef struct _cairo_clip_tor_scan_converter cairo_clip_tor_scan_converter_t; static void _cairo_clip_tor_scan_converter_destroy (void *converter) { cairo_clip_tor_scan_converter_t *self = converter; if (self == NULL) { return; } _glitter_scan_converter_fini (self->converter); pool_fini (self->span_pool.base); free(self); } static cairo_status_t _cairo_clip_tor_scan_converter_generate (void *converter, cairo_span_renderer_t *renderer) { cairo_clip_tor_scan_converter_t *self = converter; cairo_status_t status; if ((status = setjmp (self->jmp))) return _cairo_scan_converter_set_error (self, _cairo_error (status)); glitter_scan_converter_render (self->converter, self->fill_rule == CAIRO_FILL_RULE_WINDING, renderer, self->span_pool.base); return CAIRO_STATUS_SUCCESS; } cairo_scan_converter_t * _cairo_clip_tor_scan_converter_create (cairo_clip_t *clip, cairo_polygon_t *polygon, cairo_fill_rule_t fill_rule, cairo_antialias_t antialias) { cairo_clip_tor_scan_converter_t *self; cairo_polygon_t clipper; cairo_status_t status; int i; self = calloc (1, sizeof(struct _cairo_clip_tor_scan_converter)); if (unlikely (self == NULL)) { status = _cairo_error (CAIRO_STATUS_NO_MEMORY); goto bail_nomem; } self->base.destroy = _cairo_clip_tor_scan_converter_destroy; self->base.generate = _cairo_clip_tor_scan_converter_generate; pool_init (self->span_pool.base, &self->jmp, 250 * sizeof(self->span_pool.embedded[0]), sizeof(self->span_pool.embedded)); _glitter_scan_converter_init (self->converter, &self->jmp); status = glitter_scan_converter_reset (self->converter, clip->extents.y, clip->extents.y + clip->extents.height); if (unlikely (status)) goto bail; self->fill_rule = fill_rule; self->antialias = antialias; for (i = 0; i < polygon->num_edges; i++) glitter_scan_converter_add_edge (self->converter, &polygon->edges[i], FALSE); status = _cairo_clip_get_polygon (clip, &clipper, &self->clip_fill_rule, &self->clip_antialias); if (unlikely (status)) goto bail; for (i = 0; i < clipper.num_edges; i++) glitter_scan_converter_add_edge (self->converter, &clipper.edges[i], TRUE); _cairo_polygon_fini (&clipper); return &self->base; bail: self->base.destroy(&self->base); bail_nomem: return _cairo_scan_converter_create_in_error (status); }