/* -*- 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 #include #include #include /*------------------------------------------------------------------------- * cairo specific config */ #define I static /* Prefer cairo's status type. */ #define GLITTER_HAVE_STATUS_T 1 #define GLITTER_STATUS_SUCCESS CAIRO_STATUS_SUCCESS #define GLITTER_STATUS_NO_MEMORY CAIRO_STATUS_NO_MEMORY typedef cairo_status_t glitter_status_t; /* 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; static glitter_status_t blit_with_span_renderer( struct cell_list *coverages, cairo_span_renderer_t *span_renderer, struct pool *span_pool, int y, int xmin, int xmax); #define GLITTER_BLIT_COVERAGES_ARGS \ cairo_span_renderer_t *span_renderer, \ struct pool *span_pool #define GLITTER_BLIT_COVERAGES(cells, y, xmin, xmax) do { \ cairo_status_t status = blit_with_span_renderer (cells, \ span_renderer, \ span_pool, \ y, xmin, xmax); \ if (unlikely (status)) \ return status; \ } while (0) /*------------------------------------------------------------------------- * 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)) >> 9) #else # define GRID_AREA_TO_ALPHA(c) ((c)*255 / GRID_XY) /* tweak me for rounding */ #endif #define UNROLL3(x) x x x struct quorem { int quo; int 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. */ unsigned char data[0]; }; /* 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; /* 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; }; /* 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 { 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; }; /* 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 { /* Points to the left-most cell in the scan line. */ struct cell *head; /* Cursor state for iterating through the cell list. Points to * a pointer to the current cell: either &cell_list->head or the next * field of the previous cell. */ 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_x_t xmin, xmax; 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 void _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; } static struct _pool_chunk * _pool_chunk_create( struct _pool_chunk *prev_chunk, size_t size) { struct _pool_chunk *p; size_t size_with_head = size + sizeof(struct _pool_chunk); if (size_with_head < size) return NULL; p = malloc(size_with_head); if (p) _pool_chunk_init(p, prev_chunk, size); return p; } static void pool_init( struct pool *pool, size_t default_capacity, size_t embedded_capacity) { 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); pool_init(pool, 0, 0); } /* 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->current, capacity); if (NULL == chunk) return NULL; } pool->current = chunk; obj = &chunk->data[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 = &chunk->data[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 && tail->x > x) { cell_list_rewind(cells); } } static void cell_list_init(struct cell_list *cells) { pool_init(cells->cell_pool.base, 256*sizeof(struct cell), sizeof(cells->cell_pool.embedded)); cells->head = NULL; cell_list_rewind(cells); } static void cell_list_fini(struct cell_list *cells) { pool_fini(cells->cell_pool.base); cell_list_init(cells); } /* 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 = NULL; pool_reset(cells->cell_pool.base); } /* 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 **cursor = cells->cursor; struct cell *tail; while (1) { UNROLL3({ tail = *cursor; if (NULL == tail || tail->x >= x) { break; } cursor = &tail->next; }); } cells->cursor = cursor; if (tail && tail->x == x) { return tail; } else { struct cell *cell = pool_alloc( cells->cell_pool.base, sizeof(struct cell)); if (NULL == cell) return NULL; *cursor = cell; cell->next = tail; cell->x = x; cell->uncovered_area = 0; cell->covered_height = 0; return cell; } } /* 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_find2(struct cell_list *cells, int x1, int x2) { struct cell_pair pair; struct cell **cursor = cells->cursor; struct cell *cell1; struct cell *cell2; struct cell *newcell; /* Find first cell at x1. */ while (1) { UNROLL3({ cell1 = *cursor; if (NULL == cell1 || cell1->x > x1) break; if (cell1->x == x1) goto found_first; cursor = &cell1->next; }); } /* New first cell at x1. */ newcell = pool_alloc( cells->cell_pool.base, sizeof(struct cell)); if (NULL != newcell) { *cursor = newcell; newcell->next = cell1; newcell->x = x1; newcell->uncovered_area = 0; newcell->covered_height = 0; } cell1 = newcell; found_first: /* Find second cell at x2. */ while (1) { UNROLL3({ cell2 = *cursor; if (NULL == cell2 || cell2->x > x2) break; if (cell2->x == x2) goto found_second; cursor = &cell2->next; }); } /* New second cell at x2. */ newcell = pool_alloc( cells->cell_pool.base, sizeof(struct cell)); if (NULL != newcell) { *cursor = newcell; newcell->next = cell2; newcell->x = x2; newcell->uncovered_area = 0; newcell->covered_height = 0; } cell2 = newcell; found_second: cells->cursor = cursor; pair.cell1 = cell1; pair.cell2 = cell2; return pair; } /* Add an unbounded subpixel span covering subpixels >= x to the * coverage cells. */ static glitter_status_t cell_list_add_unbounded_subspan( struct cell_list *cells, grid_scaled_x_t x) { struct cell *cell; int ix, fx; GRID_X_TO_INT_FRAC(x, ix, fx); cell = cell_list_find(cells, ix); if (cell) { cell->uncovered_area += 2*fx; cell->covered_height++; return GLITTER_STATUS_SUCCESS; } return GLITTER_STATUS_NO_MEMORY; } /* Add a subpixel span covering [x1, x2) to the coverage cells. */ inline static glitter_status_t 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_find2(cells, ix1, ix2); if (p.cell1 && p.cell2) { p.cell1->uncovered_area += 2*fx1; ++p.cell1->covered_height; p.cell2->uncovered_area -= 2*fx2; --p.cell2->covered_height; return GLITTER_STATUS_SUCCESS; } } else { struct cell *cell = cell_list_find(cells, ix1); if (cell) { cell->uncovered_area += 2*(fx1-fx2); return GLITTER_STATUS_SUCCESS; } } return GLITTER_STATUS_NO_MEMORY; } /* 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 glitter_status_t cell_list_render_edge( struct cell_list *cells, struct edge *edge, int sign) { struct quorem x1 = edge->x; struct quorem x2 = x1; grid_scaled_y_t y1, y2, dy; grid_scaled_x_t dx; int ix1, ix2; grid_scaled_x_t fx1, fx2; 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); if (NULL == cell) return GLITTER_STATUS_NO_MEMORY; cell->covered_height += sign*GRID_Y; cell->uncovered_area += sign*(fx1 + fx2)*GRID_Y; return GLITTER_STATUS_SUCCESS; } /* 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_find2(cells, ix1, ix1+1); if (!pair.cell1 || !pair.cell2) return GLITTER_STATUS_NO_MEMORY; 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); if (NULL == cell) return GLITTER_STATUS_NO_MEMORY; } while (ix1 != ix2); pair.cell2 = cell; } pair.cell2->uncovered_area += sign*(y2 - y.quo)*fx2; pair.cell2->covered_height += sign*(y2 - y.quo); } return GLITTER_STATUS_SUCCESS; } static void polygon_init(struct polygon *polygon) { polygon->ymin = polygon->ymax = 0; polygon->y_buckets = NULL; pool_init(polygon->edge_pool.base, (8192 - sizeof(struct _pool_chunk))/sizeof(struct edge), sizeof(polygon->edge_pool.embedded)); } static void polygon_fini(struct polygon *polygon) { free(polygon->y_buckets); pool_fini(polygon->edge_pool.base); polygon_init(polygon); } static void * realloc_and_clear(void *p, size_t a, size_t b) { size_t total = a*b; if (b && total / b != a) return NULL; p = realloc(p, total); if (p) memset(p, 0, total); return p; } /* 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 glitter_status_t polygon_reset( struct polygon *polygon, grid_scaled_y_t ymin, grid_scaled_y_t ymax) { void *p; 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 (h > 0x7FFFFFFFU - EDGE_Y_BUCKET_HEIGHT) goto bail_no_mem; /* even if you could, you wouldn't want to. */ if (num_buckets > 0) { p = realloc_and_clear( polygon->y_buckets, num_buckets, sizeof(struct edge*)); if (NULL == p) goto bail_no_mem; } else { free(polygon->y_buckets); p = NULL; } polygon->y_buckets = p; polygon->ymin = ymin; polygon->ymax = ymax; return GLITTER_STATUS_SUCCESS; bail_no_mem: free(polygon->y_buckets); polygon->y_buckets = NULL; polygon->ymin = 0; polygon->ymax = 0; return GLITTER_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 glitter_status_t polygon_add_edge( struct polygon *polygon, int x0, int y0, int x1, int y1, int dir) { 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; if (y0 == y1) return GLITTER_STATUS_SUCCESS; if (y0 > y1) { int tmp; tmp = x0; x0 = x1; x1 = tmp; tmp = y0; y0 = y1; y1 = tmp; dir = -dir; } if (y0 >= ymax || y1 <= ymin) return GLITTER_STATUS_SUCCESS; e = pool_alloc(polygon->edge_pool.base, sizeof(struct edge)); if (NULL == e) return GLITTER_STATUS_NO_MEMORY; dx = x1 - x0; dy = y1 - y0; e->dy = dy; e->dxdy = floored_divrem(dx, dy); if (ymin <= y0) { ytop = y0; e->x.quo = x0; e->x.rem = 0; } else { ytop = ymin; e->x = floored_muldivrem(ymin - y0, dx, dy); e->x.quo += x0; } e->dir = dir; e->ytop = ytop; ybot = y1 < ymax ? y1 : ymax; e->height_left = ybot - ytop; 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. */ return GLITTER_STATUS_SUCCESS; } 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); } static void active_list_fini( struct active_list *active) { active_list_reset(active); } /* Merge the edges in an unsorted list of edges into a sorted * list. The sort order is edges ascending by edge->x.quo. Returns * the new head of the sorted list. */ static struct edge * merge_unsorted_edges(struct edge *sorted_head, struct edge *unsorted_head) { struct edge *head = unsorted_head; struct edge **cursor = &sorted_head; int x; while (NULL != head) { struct edge *prev = *cursor; struct edge *next = head->next; x = head->x.quo; if (NULL == prev || x < prev->x.quo) { cursor = &sorted_head; } while (1) { UNROLL3({ prev = *cursor; if (NULL == prev || prev->x.quo >= x) break; cursor = &prev->next; }); } head->next = *cursor; *cursor = head; head = next; } return sorted_head; } /* 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) { /* Recomputes the minimum height of all edges on the active * list if we have been dropping edges. */ if (active->min_height <= 0) { struct edge *e = active->head; int min_height = INT_MAX; while (NULL != e) { if (e->height_left < min_height) min_height = e->height_left; e = e->next; } active->min_height = min_height; } /* Check for intersections only if no edges end during the next * row. */ if (active->min_height >= GRID_Y) { grid_scaled_x_t prev_x = INT_MIN; struct edge *e = active->head; while (NULL != e) { struct quorem x = e->x; 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; } return 0; } /* 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, grid_scaled_y_t y, struct polygon *polygon) { /* Split off the edges on the current subrow and merge them into * the active list. */ unsigned ix = EDGE_Y_BUCKET_INDEX(y, polygon->ymin); int min_height = active->min_height; struct edge *subrow_edges = NULL; struct edge **ptail = &polygon->y_buckets[ix]; while (1) { struct edge *tail = *ptail; if (NULL == tail) break; if (y == tail->ytop) { *ptail = tail->next; tail->next = subrow_edges; subrow_edges = tail; if (tail->height_left < min_height) min_height = tail->height_left; } else { ptail = &tail->next; } } active->head = merge_unsorted_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; while (1) { struct edge *edge; UNROLL3({ edge = *cursor; if (NULL == edge) break; if (0 != --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 = edge->next; edge->next = unsorted; unsorted = edge; } else { prev_x = edge->x.quo; cursor = &edge->next; } } else { *cursor = edge->next; } }); } if (unsorted) active->head = merge_unsorted_edges(active->head, unsorted); } inline static glitter_status_t 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; int status; cell_list_rewind(coverages); while (NULL != edge) { xstart = edge->x.quo; winding = edge->dir; while (1) { edge = edge->next; if (NULL == edge) { return cell_list_add_unbounded_subspan( coverages, xstart); } winding += edge->dir; if (0 == winding) break; } xend = edge->x.quo; status = cell_list_add_subspan(coverages, xstart, xend); if (status) return status; edge = edge->next; } return GLITTER_STATUS_SUCCESS; } static glitter_status_t apply_evenodd_fill_rule_for_subrow( struct active_list *active, struct cell_list *coverages) { struct edge *edge = active->head; int xstart; int xend; int status; cell_list_rewind(coverages); while (NULL != edge) { xstart = edge->x.quo; edge = edge->next; if (NULL == edge) { return cell_list_add_unbounded_subspan( coverages, xstart); } xend = edge->x.quo; status = cell_list_add_subspan(coverages, xstart, xend); if (status) return status; edge = edge->next; } return GLITTER_STATUS_SUCCESS; } static glitter_status_t apply_nonzero_fill_rule_and_step_edges( struct active_list *active, struct cell_list *coverages) { struct edge **cursor = &active->head; struct edge *left_edge; int status; 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) { return cell_list_render_edge( coverages, left_edge, +1); } 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) break; 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; } } status = cell_list_render_edge( coverages, left_edge, +1); if (status) return status; status = cell_list_render_edge( coverages, right_edge, -1); if (status) return status; left_edge = *cursor; } return GLITTER_STATUS_SUCCESS; } static glitter_status_t apply_evenodd_fill_rule_and_step_edges( struct active_list *active, struct cell_list *coverages) { struct edge **cursor = &active->head; struct edge *left_edge; int status; 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; } right_edge = *cursor; if (NULL == right_edge) { return cell_list_render_edge( coverages, left_edge, +1); } right_edge->height_left -= GRID_Y; if (right_edge->height_left) { cursor = &right_edge->next; } else { *cursor = right_edge->next; } status = cell_list_render_edge( coverages, left_edge, +1); if (status) return status; status = cell_list_render_edge( coverages, right_edge, -1); if (status) return status; left_edge = *cursor; } return GLITTER_STATUS_SUCCESS; } /* If the user hasn't configured a coverage blitter, use a default one * that blits spans directly to an A8 raster. */ #ifndef GLITTER_BLIT_COVERAGES inline static void blit_span( unsigned char *row_pixels, int x, unsigned len, grid_area_t coverage) { int alpha = GRID_AREA_TO_ALPHA(coverage); if (1 == len) { row_pixels[x] = alpha; } else { memset(row_pixels + x, alpha, len); } } #define GLITTER_BLIT_COVERAGES(coverages, y, xmin, xmax) \ blit_cells(coverages, raster_pixels + (y)*raster_stride, xmin, xmax) static void blit_cells( struct cell_list *cells, unsigned char *row_pixels, int xmin, int xmax) { struct cell *cell = cells->head; int prev_x = xmin; int coverage = 0; if (NULL == cell) return; while (NULL != cell && cell->x < xmin) { coverage += cell->covered_height; cell = cell->next; } coverage *= GRID_X*2; for (; NULL != cell; cell = cell->next) { int x = cell->x; int area; if (x >= xmax) break; if (x > prev_x && 0 != coverage) { blit_span(row_pixels, prev_x, x - prev_x, coverage); } coverage += cell->covered_height * GRID_X*2; area = coverage - cell->uncovered_area; if (area) { blit_span(row_pixels, x, 1, area); } prev_x = x+1; } if (0 != coverage && prev_x < xmax) { blit_span(row_pixels, prev_x, xmax - prev_x, coverage); } } #endif /* GLITTER_BLIT_COVERAGES */ static void _glitter_scan_converter_init(glitter_scan_converter_t *converter) { polygon_init(converter->polygon); active_list_init(converter->active); cell_list_init(converter->coverages); converter->xmin=0; converter->ymin=0; converter->xmax=0; converter->ymax=0; } static void _glitter_scan_converter_fini(glitter_scan_converter_t *converter) { polygon_fini(converter->polygon); active_list_fini(converter->active); cell_list_fini(converter->coverages); converter->xmin=0; converter->ymin=0; converter->xmax=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) I glitter_status_t glitter_scan_converter_reset( glitter_scan_converter_t *converter, int xmin, int ymin, int xmax, int ymax) { glitter_status_t status; converter->xmin = 0; converter->xmax = 0; converter->ymin = 0; converter->ymax = 0; xmin = int_to_grid_scaled_x(xmin); ymin = int_to_grid_scaled_y(ymin); xmax = int_to_grid_scaled_x(xmax); 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->xmin = xmin; converter->xmax = xmax; converter->ymin = ymin; converter->ymax = ymax; return GLITTER_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) I glitter_status_t glitter_scan_converter_add_edge( glitter_scan_converter_t *converter, glitter_input_scaled_t x1, glitter_input_scaled_t y1, glitter_input_scaled_t x2, glitter_input_scaled_t y2, int dir) { /* XXX: possible overflows if GRID_X/Y > 2**GLITTER_INPUT_BITS */ grid_scaled_y_t sx1, sy1; grid_scaled_y_t sx2, sy2; INPUT_TO_GRID_Y(y1, sy1); INPUT_TO_GRID_Y(y2, sy2); if (sy1 == sy2) return GLITTER_STATUS_SUCCESS; INPUT_TO_GRID_X(x1, sx1); INPUT_TO_GRID_X(x2, sx2); return polygon_add_edge( converter->polygon, sx1, sy1, sx2, sy2, dir); } #ifndef GLITTER_BLIT_COVERAGES_BEGIN # define GLITTER_BLIT_COVERAGES_BEGIN #endif #ifndef GLITTER_BLIT_COVERAGES_END # define GLITTER_BLIT_COVERAGES_END #endif #ifndef GLITTER_BLIT_COVERAGES_EMPTY # define GLITTER_BLIT_COVERAGES_EMPTY(y, xmin, xmax) #endif I glitter_status_t glitter_scan_converter_render( glitter_scan_converter_t *converter, int nonzero_fill, GLITTER_BLIT_COVERAGES_ARGS) { int i; int ymax_i = converter->ymax / GRID_Y; int ymin_i = converter->ymin / GRID_Y; int xmin_i, xmax_i; int h = ymax_i - ymin_i; struct polygon *polygon = converter->polygon; struct cell_list *coverages = converter->coverages; struct active_list *active = converter->active; xmin_i = converter->xmin / GRID_X; xmax_i = converter->xmax / GRID_X; if (xmin_i >= xmax_i) return GLITTER_STATUS_SUCCESS; /* Let the coverage blitter initialise itself. */ GLITTER_BLIT_COVERAGES_BEGIN; /* Render each pixel row. */ for (i=0; iy_buckets[i]) { if (!active->head) { GLITTER_BLIT_COVERAGES_EMPTY(i+ymin_i, xmin_i, xmax_i); continue; } do_full_step = active_list_can_step_full_row(active); } cell_list_reset(coverages); if (do_full_step) { /* Step by a full pixel row's worth. */ if (nonzero_fill) { status = apply_nonzero_fill_rule_and_step_edges( active, coverages); } else { status = apply_evenodd_fill_rule_and_step_edges( active, coverages); } } else { /* Subsample this row. */ grid_scaled_y_t suby; for (suby = 0; suby < GRID_Y; suby++) { grid_scaled_y_t y = (i+ymin_i)*GRID_Y + suby; active_list_merge_edges_from_polygon( active, y, polygon); if (nonzero_fill) status |= apply_nonzero_fill_rule_for_subrow( active, coverages); else status |= apply_evenodd_fill_rule_for_subrow( active, coverages); active_list_substep_edges(active); } } if (status) return status; GLITTER_BLIT_COVERAGES(coverages, i+ymin_i, xmin_i, xmax_i); if (!active->head) { active->min_height = INT_MAX; } else { active->min_height -= GRID_Y; } } /* Clean up the coverage blitter. */ GLITTER_BLIT_COVERAGES_END; return GLITTER_STATUS_SUCCESS; } /*------------------------------------------------------------------------- * cairo specific implementation: the coverage blitter and * scan converter subclass. */ static glitter_status_t blit_with_span_renderer( struct cell_list *cells, cairo_span_renderer_t *renderer, struct pool *span_pool, int y, int xmin, int xmax) { struct cell *cell = cells->head; int prev_x = xmin; int cover = 0; cairo_half_open_span_t *spans; unsigned num_spans; if (cell == NULL) return CAIRO_STATUS_SUCCESS; /* Skip cells to the left of the clip region. */ while (cell != NULL && cell->x < xmin) { cover += cell->covered_height; cell = cell->next; } cover *= GRID_X*2; /* Count number of cells remaining. */ { struct cell *next = cell; num_spans = 0; while (next) { next = next->next; ++num_spans; } num_spans = 2*num_spans + 1; } /* Allocate enough spans for the row. */ pool_reset (span_pool); spans = pool_alloc (span_pool, sizeof(spans[0])*num_spans); if (spans == NULL) return GLITTER_STATUS_NO_MEMORY; num_spans = 0; /* Form the spans from the coverages and areas. */ for (; cell != NULL; cell = cell->next) { int x = cell->x; int area; if (x >= xmax) break; if (x > prev_x) { spans[num_spans].x = prev_x; spans[num_spans].coverage = GRID_AREA_TO_ALPHA (cover); ++num_spans; } cover += cell->covered_height*GRID_X*2; area = cover - cell->uncovered_area; spans[num_spans].x = x; spans[num_spans].coverage = GRID_AREA_TO_ALPHA (area); ++num_spans; prev_x = x+1; } if (prev_x < xmax) { spans[num_spans].x = prev_x; spans[num_spans].coverage = GRID_AREA_TO_ALPHA (cover); ++num_spans; } /* Dump them into the renderer. */ return renderer->render_row (renderer, y, spans, num_spans); } struct _cairo_tor_scan_converter { cairo_scan_converter_t base; glitter_scan_converter_t converter[1]; cairo_fill_rule_t fill_rule; struct { struct pool base[1]; cairo_half_open_span_t embedded[32]; } span_pool; }; typedef struct _cairo_tor_scan_converter cairo_tor_scan_converter_t; static void _cairo_tor_scan_converter_destroy(void *abstract_converter) { cairo_tor_scan_converter_t *self = abstract_converter; if (self == NULL) { return; } _glitter_scan_converter_fini (self->converter); pool_fini (self->span_pool.base); free(self); } static cairo_status_t _cairo_tor_scan_converter_add_edge( void *abstract_converter, cairo_fixed_t x1, cairo_fixed_t y1, cairo_fixed_t x2, cairo_fixed_t y2) { cairo_tor_scan_converter_t *self = abstract_converter; cairo_status_t status; status = glitter_scan_converter_add_edge ( self->converter, x1, y1, x2, y2, +1); if (status) { return _cairo_scan_converter_set_error (self, _cairo_error (status)); } return CAIRO_STATUS_SUCCESS; } static cairo_status_t _cairo_tor_scan_converter_generate( void *abstract_converter, cairo_span_renderer_t *renderer) { cairo_tor_scan_converter_t *self = abstract_converter; cairo_status_t status = glitter_scan_converter_render ( self->converter, self->fill_rule == CAIRO_FILL_RULE_WINDING, renderer, self->span_pool.base); if (status) { return _cairo_scan_converter_set_error (self, _cairo_error (status)); } return CAIRO_STATUS_SUCCESS; } cairo_scan_converter_t * _cairo_tor_scan_converter_create( int xmin, int ymin, int xmax, int ymax, cairo_fill_rule_t fill_rule) { cairo_status_t status; cairo_tor_scan_converter_t *self = calloc (1, sizeof(struct _cairo_tor_scan_converter)); if (self == NULL) goto bail_nomem; self->base.destroy = &_cairo_tor_scan_converter_destroy; self->base.add_edge = &_cairo_tor_scan_converter_add_edge; self->base.generate = &_cairo_tor_scan_converter_generate; pool_init (self->span_pool.base, 250 * sizeof(self->span_pool.embedded[0]), sizeof(self->span_pool.embedded)); _glitter_scan_converter_init (self->converter); status = glitter_scan_converter_reset ( self->converter, xmin, ymin, xmax, ymax); if (status != CAIRO_STATUS_SUCCESS) goto bail; self->fill_rule = fill_rule; return &self->base; bail: self->base.destroy(&self->base); bail_nomem: return _cairo_scan_converter_create_in_error (CAIRO_STATUS_NO_MEMORY); }