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Diffstat (limited to 'src/cairo-clip-tor-scan-converter.c')
| -rw-r--r-- | src/cairo-clip-tor-scan-converter.c | 1845 |
1 files changed, 1845 insertions, 0 deletions
diff --git a/src/cairo-clip-tor-scan-converter.c b/src/cairo-clip-tor-scan-converter.c new file mode 100644 index 000000000..e32a5a9d9 --- /dev/null +++ b/src/cairo-clip-tor-scan-converter.c @@ -0,0 +1,1845 @@ +/* -*- 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 <assert.h> +#include <stdlib.h> +#include <string.h> +#include <limits.h> +#include <setjmp.h> + +/* 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<<GLITTER_INPUT_BITS. */ +#ifndef GLITTER_INPUT_BITS +# define GLITTER_INPUT_BITS 8 +#endif +#define GLITTER_INPUT_SCALE (1<<GLITTER_INPUT_BITS) +typedef int glitter_input_scaled_t; + +/* Opaque type for scan converting. */ +typedef struct glitter_scan_converter glitter_scan_converter_t; + +/*------------------------------------------------------------------------- + * glitter-paths.c: Implementation internal types + */ +#include <stdlib.h> +#include <string.h> +#include <limits.h> + +/* 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); +} + |