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  1. /* -*- Mode: c; tab-width: 8; c-basic-offset: 4; indent-tabs-mode: t; -*- */
  2. /* glitter-paths - polygon scan converter
  3.  *
  4.  * Copyright (c) 2008  M Joonas Pihlaja
  5.  * Copyright (c) 2007  David Turner
  6.  *
  7.  * Permission is hereby granted, free of charge, to any person
  8.  * obtaining a copy of this software and associated documentation
  9.  * files (the "Software"), to deal in the Software without
  10.  * restriction, including without limitation the rights to use,
  11.  * copy, modify, merge, publish, distribute, sublicense, and/or sell
  12.  * copies of the Software, and to permit persons to whom the
  13.  * Software is furnished to do so, subject to the following
  14.  * conditions:
  15.  *
  16.  * The above copyright notice and this permission notice shall be
  17.  * included in all copies or substantial portions of the Software.
  18.  *
  19.  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  20.  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
  21.  * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  22.  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
  23.  * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
  24.  * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  25.  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  26.  * OTHER DEALINGS IN THE SOFTWARE.
  27.  */
  28. /* This is the Glitter paths scan converter incorporated into cairo.
  29.  * The source is from commit 734c53237a867a773640bd5b64816249fa1730f8
  30.  * of
  31.  *
  32.  *   http://gitweb.freedesktop.org/?p=users/joonas/glitter-paths
  33.  */
  34. /* Glitter-paths is a stand alone polygon rasteriser derived from
  35.  * David Turner's reimplementation of Tor Anderssons's 15x17
  36.  * supersampling rasteriser from the Apparition graphics library.  The
  37.  * main new feature here is cheaply choosing per-scan line between
  38.  * doing fully analytical coverage computation for an entire row at a
  39.  * time vs. using a supersampling approach.
  40.  *
  41.  * David Turner's code can be found at
  42.  *
  43.  *   http://david.freetype.org/rasterizer-shootout/raster-comparison-20070813.tar.bz2
  44.  *
  45.  * In particular this file incorporates large parts of ftgrays_tor10.h
  46.  * from raster-comparison-20070813.tar.bz2
  47.  */
  48. /* Overview
  49.  *
  50.  * A scan converter's basic purpose to take polygon edges and convert
  51.  * them into an RLE compressed A8 mask.  This one works in two phases:
  52.  * gathering edges and generating spans.
  53.  *
  54.  * 1) As the user feeds the scan converter edges they are vertically
  55.  * clipped and bucketted into a _polygon_ data structure.  The edges
  56.  * are also snapped from the user's coordinates to the subpixel grid
  57.  * coordinates used during scan conversion.
  58.  *
  59.  *     user
  60.  *      |
  61.  *      | edges
  62.  *      V
  63.  *    polygon buckets
  64.  *
  65.  * 2) Generating spans works by performing a vertical sweep of pixel
  66.  * rows from top to bottom and maintaining an _active_list_ of edges
  67.  * that intersect the row.  From the active list the fill rule
  68.  * determines which edges are the left and right edges of the start of
  69.  * each span, and their contribution is then accumulated into a pixel
  70.  * coverage list (_cell_list_) as coverage deltas.  Once the coverage
  71.  * deltas of all edges are known we can form spans of constant pixel
  72.  * coverage by summing the deltas during a traversal of the cell list.
  73.  * At the end of a pixel row the cell list is sent to a coverage
  74.  * blitter for rendering to some target surface.
  75.  *
  76.  * The pixel coverages are computed by either supersampling the row
  77.  * and box filtering a mono rasterisation, or by computing the exact
  78.  * coverages of edges in the active list.  The supersampling method is
  79.  * used whenever some edge starts or stops within the row or there are
  80.  * edge intersections in the row.
  81.  *
  82.  *   polygon bucket for       \
  83.  *   current pixel row        |
  84.  *      |                     |
  85.  *      | activate new edges  |  Repeat GRID_Y times if we
  86.  *      V                     \  are supersampling this row,
  87.  *   active list              /  or just once if we're computing
  88.  *      |                     |  analytical coverage.
  89.  *      | coverage deltas     |
  90.  *      V                     |
  91.  *   pixel coverage list     /
  92.  *      |
  93.  *      V
  94.  *   coverage blitter
  95.  */
  96. #include "cairoint.h"
  97. #include "cairo-spans-private.h"
  98. #include "cairo-error-private.h"
  99.  
  100. #include <stdlib.h>
  101. #include <string.h>
  102. #include <limits.h>
  103. #include <setjmp.h>
  104.  
  105. /*-------------------------------------------------------------------------
  106.  * cairo specific config
  107.  */
  108. #define I static
  109.  
  110. /* Prefer cairo's status type. */
  111. #define GLITTER_HAVE_STATUS_T 1
  112. #define GLITTER_STATUS_SUCCESS CAIRO_STATUS_SUCCESS
  113. #define GLITTER_STATUS_NO_MEMORY CAIRO_STATUS_NO_MEMORY
  114. typedef cairo_status_t glitter_status_t;
  115.  
  116. /* The input coordinate scale and the rasterisation grid scales. */
  117. #define GLITTER_INPUT_BITS CAIRO_FIXED_FRAC_BITS
  118. //#define GRID_X_BITS CAIRO_FIXED_FRAC_BITS
  119. //#define GRID_Y 15
  120. #define GRID_X_BITS 2
  121. #define GRID_Y_BITS 2
  122.  
  123. /* Set glitter up to use a cairo span renderer to do the coverage
  124.  * blitting. */
  125. struct pool;
  126. struct cell_list;
  127.  
  128. /*-------------------------------------------------------------------------
  129.  * glitter-paths.h
  130.  */
  131.  
  132. /* "Input scaled" numbers are fixed precision reals with multiplier
  133.  * 2**GLITTER_INPUT_BITS.  Input coordinates are given to glitter as
  134.  * pixel scaled numbers.  These get converted to the internal grid
  135.  * scaled numbers as soon as possible. Internal overflow is possible
  136.  * if GRID_X/Y inside glitter-paths.c is larger than
  137.  * 1<<GLITTER_INPUT_BITS. */
  138. #ifndef GLITTER_INPUT_BITS
  139. #  define GLITTER_INPUT_BITS 8
  140. #endif
  141. #define GLITTER_INPUT_SCALE (1<<GLITTER_INPUT_BITS)
  142. typedef int glitter_input_scaled_t;
  143.  
  144. #if !GLITTER_HAVE_STATUS_T
  145. typedef enum {
  146.     GLITTER_STATUS_SUCCESS = 0,
  147.     GLITTER_STATUS_NO_MEMORY
  148. } glitter_status_t;
  149. #endif
  150.  
  151. #ifndef I
  152. # define I /*static*/
  153. #endif
  154.  
  155. /* Opaque type for scan converting. */
  156. typedef struct glitter_scan_converter glitter_scan_converter_t;
  157.  
  158. /* Reset a scan converter to accept polygon edges and set the clip box
  159.  * in pixels.  Allocates O(ymax-ymin) bytes of memory.  The clip box
  160.  * is set to integer pixel coordinates xmin <= x < xmax, ymin <= y <
  161.  * ymax. */
  162. I glitter_status_t
  163. glitter_scan_converter_reset(
  164.     glitter_scan_converter_t *converter,
  165.     int xmin, int ymin,
  166.     int xmax, int ymax);
  167.  
  168. /* Render the polygon in the scan converter to the given A8 format
  169.  * image raster.  Only the pixels accessible as pixels[y*stride+x] for
  170.  * x,y inside the clip box are written to, where xmin <= x < xmax,
  171.  * ymin <= y < ymax.  The image is assumed to be clear on input.
  172.  *
  173.  * If nonzero_fill is true then the interior of the polygon is
  174.  * computed with the non-zero fill rule.  Otherwise the even-odd fill
  175.  * rule is used.
  176.  *
  177.  * The scan converter must be reset or destroyed after this call. */
  178.  
  179. /*-------------------------------------------------------------------------
  180.  * glitter-paths.c: Implementation internal types
  181.  */
  182. #include <stdlib.h>
  183. #include <string.h>
  184. #include <limits.h>
  185.  
  186. /* All polygon coordinates are snapped onto a subsample grid. "Grid
  187.  * scaled" numbers are fixed precision reals with multiplier GRID_X or
  188.  * GRID_Y. */
  189. typedef int grid_scaled_t;
  190. typedef int grid_scaled_x_t;
  191. typedef int grid_scaled_y_t;
  192.  
  193. /* Default x/y scale factors.
  194.  *  You can either define GRID_X/Y_BITS to get a power-of-two scale
  195.  *  or define GRID_X/Y separately. */
  196. #if !defined(GRID_X) && !defined(GRID_X_BITS)
  197. #  define GRID_X_BITS 8
  198. #endif
  199. #if !defined(GRID_Y) && !defined(GRID_Y_BITS)
  200. #  define GRID_Y 15
  201. #endif
  202.  
  203. /* Use GRID_X/Y_BITS to define GRID_X/Y if they're available. */
  204. #ifdef GRID_X_BITS
  205. #  define GRID_X (1 << GRID_X_BITS)
  206. #endif
  207. #ifdef GRID_Y_BITS
  208. #  define GRID_Y (1 << GRID_Y_BITS)
  209. #endif
  210.  
  211. /* The GRID_X_TO_INT_FRAC macro splits a grid scaled coordinate into
  212.  * integer and fractional parts. The integer part is floored. */
  213. #if defined(GRID_X_TO_INT_FRAC)
  214.   /* do nothing */
  215. #elif defined(GRID_X_BITS)
  216. #  define GRID_X_TO_INT_FRAC(x, i, f) \
  217.         _GRID_TO_INT_FRAC_shift(x, i, f, GRID_X_BITS)
  218. #else
  219. #  define GRID_X_TO_INT_FRAC(x, i, f) \
  220.         _GRID_TO_INT_FRAC_general(x, i, f, GRID_X)
  221. #endif
  222.  
  223. #define _GRID_TO_INT_FRAC_general(t, i, f, m) do {      \
  224.     (i) = (t) / (m);                                    \
  225.     (f) = (t) % (m);                                    \
  226.     if ((f) < 0) {                                      \
  227.         --(i);                                          \
  228.         (f) += (m);                                     \
  229.     }                                                   \
  230. } while (0)
  231.  
  232. #define _GRID_TO_INT_FRAC_shift(t, i, f, b) do {        \
  233.     (f) = (t) & ((1 << (b)) - 1);                       \
  234.     (i) = (t) >> (b);                                   \
  235. } while (0)
  236.  
  237. /* A grid area is a real in [0,1] scaled by 2*GRID_X*GRID_Y.  We want
  238.  * to be able to represent exactly areas of subpixel trapezoids whose
  239.  * vertices are given in grid scaled coordinates.  The scale factor
  240.  * comes from needing to accurately represent the area 0.5*dx*dy of a
  241.  * triangle with base dx and height dy in grid scaled numbers. */
  242. #define GRID_XY (2*GRID_X*GRID_Y) /* Unit area on the grid. */
  243.  
  244. /* GRID_AREA_TO_ALPHA(area): map [0,GRID_XY] to [0,255]. */
  245. #if GRID_XY == 510
  246. #  define GRID_AREA_TO_ALPHA(c)   (((c)+1) >> 1)
  247. #elif GRID_XY == 255
  248. #  define  GRID_AREA_TO_ALPHA(c)  (c)
  249. #elif GRID_XY == 64
  250. #  define  GRID_AREA_TO_ALPHA(c)  (((c) << 2) | -(((c) & 0x40) >> 6))
  251. #elif GRID_XY == 32
  252. #  define  GRID_AREA_TO_ALPHA(c)  (((c) << 3) | -(((c) & 0x20) >> 5))
  253. #elif GRID_XY == 128
  254. #  define  GRID_AREA_TO_ALPHA(c)  ((((c) << 1) | -((c) >> 7)) & 255)
  255. #elif GRID_XY == 256
  256. #  define  GRID_AREA_TO_ALPHA(c)  (((c) | -((c) >> 8)) & 255)
  257. #elif GRID_XY == 15
  258. #  define  GRID_AREA_TO_ALPHA(c)  (((c) << 4) + (c))
  259. #elif GRID_XY == 2*256*15
  260. #  define  GRID_AREA_TO_ALPHA(c)  (((c) + ((c)<<4) + 256) >> 9)
  261. #else
  262. #  define  GRID_AREA_TO_ALPHA(c)  (((c)*255 + GRID_XY/2) / GRID_XY)
  263. #endif
  264.  
  265. #define UNROLL3(x) x x x
  266.  
  267. struct quorem {
  268.     int32_t quo;
  269.     int32_t rem;
  270. };
  271.  
  272. /* Header for a chunk of memory in a memory pool. */
  273. struct _pool_chunk {
  274.     /* # bytes used in this chunk. */
  275.     size_t size;
  276.  
  277.     /* # bytes total in this chunk */
  278.     size_t capacity;
  279.  
  280.     /* Pointer to the previous chunk or %NULL if this is the sentinel
  281.      * chunk in the pool header. */
  282.     struct _pool_chunk *prev_chunk;
  283.  
  284.     /* Actual data starts here.  Well aligned for pointers. */
  285. };
  286.  
  287. /* A memory pool.  This is supposed to be embedded on the stack or
  288.  * within some other structure.  It may optionally be followed by an
  289.  * embedded array from which requests are fulfilled until
  290.  * malloc needs to be called to allocate a first real chunk. */
  291. struct pool {
  292.     /* Chunk we're allocating from. */
  293.     struct _pool_chunk *current;
  294.  
  295.     jmp_buf *jmp;
  296.  
  297.     /* Free list of previously allocated chunks.  All have >= default
  298.      * capacity. */
  299.     struct _pool_chunk *first_free;
  300.  
  301.     /* The default capacity of a chunk. */
  302.     size_t default_capacity;
  303.  
  304.     /* Header for the sentinel chunk.  Directly following the pool
  305.      * struct should be some space for embedded elements from which
  306.      * the sentinel chunk allocates from. */
  307.     struct _pool_chunk sentinel[1];
  308. };
  309.  
  310. /* A polygon edge. */
  311. struct edge {
  312.     /* Next in y-bucket or active list. */
  313.     struct edge *next, *prev;
  314.  
  315.     /* Number of subsample rows remaining to scan convert of this
  316.      * edge. */
  317.     grid_scaled_y_t height_left;
  318.  
  319.     /* Original sign of the edge: +1 for downwards, -1 for upwards
  320.      * edges.  */
  321.     int dir;
  322.     int vertical;
  323.  
  324.     /* Current x coordinate while the edge is on the active
  325.      * list. Initialised to the x coordinate of the top of the
  326.      * edge. The quotient is in grid_scaled_x_t units and the
  327.      * remainder is mod dy in grid_scaled_y_t units.*/
  328.     struct quorem x;
  329.  
  330.     /* Advance of the current x when moving down a subsample line. */
  331.     struct quorem dxdy;
  332.  
  333.     /* The clipped y of the top of the edge. */
  334.     grid_scaled_y_t ytop;
  335.  
  336.     /* y2-y1 after orienting the edge downwards.  */
  337.     grid_scaled_y_t dy;
  338. };
  339.  
  340. #define EDGE_Y_BUCKET_INDEX(y, ymin) (((y) - (ymin))/GRID_Y)
  341.  
  342. /* A collection of sorted and vertically clipped edges of the polygon.
  343.  * Edges are moved from the polygon to an active list while scan
  344.  * converting. */
  345. struct polygon {
  346.     /* The vertical clip extents. */
  347.     grid_scaled_y_t ymin, ymax;
  348.  
  349.     /* Array of edges all starting in the same bucket.  An edge is put
  350.      * into bucket EDGE_BUCKET_INDEX(edge->ytop, polygon->ymin) when
  351.      * it is added to the polygon. */
  352.     struct edge **y_buckets;
  353.     struct edge *y_buckets_embedded[64];
  354.  
  355.     struct {
  356.         struct pool base[1];
  357.         struct edge embedded[32];
  358.     } edge_pool;
  359. };
  360.  
  361. /* A cell records the effect on pixel coverage of polygon edges
  362.  * passing through a pixel.  It contains two accumulators of pixel
  363.  * coverage.
  364.  *
  365.  * Consider the effects of a polygon edge on the coverage of a pixel
  366.  * it intersects and that of the following one.  The coverage of the
  367.  * following pixel is the height of the edge multiplied by the width
  368.  * of the pixel, and the coverage of the pixel itself is the area of
  369.  * the trapezoid formed by the edge and the right side of the pixel.
  370.  *
  371.  * +-----------------------+-----------------------+
  372.  * |                       |                       |
  373.  * |                       |                       |
  374.  * |_______________________|_______________________|
  375.  * |   \...................|.......................|\
  376.  * |    \..................|.......................| |
  377.  * |     \.................|.......................| |
  378.  * |      \....covered.....|.......................| |
  379.  * |       \....area.......|.......................| } covered height
  380.  * |        \..............|.......................| |
  381.  * |uncovered\.............|.......................| |
  382.  * |  area    \............|.......................| |
  383.  * |___________\...........|.......................|/
  384.  * |                       |                       |
  385.  * |                       |                       |
  386.  * |                       |                       |
  387.  * +-----------------------+-----------------------+
  388.  *
  389.  * Since the coverage of the following pixel will always be a multiple
  390.  * of the width of the pixel, we can store the height of the covered
  391.  * area instead.  The coverage of the pixel itself is the total
  392.  * coverage minus the area of the uncovered area to the left of the
  393.  * edge.  As it's faster to compute the uncovered area we only store
  394.  * that and subtract it from the total coverage later when forming
  395.  * spans to blit.
  396.  *
  397.  * The heights and areas are signed, with left edges of the polygon
  398.  * having positive sign and right edges having negative sign.  When
  399.  * two edges intersect they swap their left/rightness so their
  400.  * contribution above and below the intersection point must be
  401.  * computed separately. */
  402. struct cell {
  403.     struct cell         *next;
  404.     int                  x;
  405.     int16_t              uncovered_area;
  406.     int16_t              covered_height;
  407. };
  408.  
  409. /* A cell list represents the scan line sparsely as cells ordered by
  410.  * ascending x.  It is geared towards scanning the cells in order
  411.  * using an internal cursor. */
  412. struct cell_list {
  413.     /* Sentinel nodes */
  414.     struct cell head, tail;
  415.  
  416.     /* Cursor state for iterating through the cell list. */
  417.     struct cell *cursor, *rewind;
  418.  
  419.     /* Cells in the cell list are owned by the cell list and are
  420.      * allocated from this pool.  */
  421.     struct {
  422.         struct pool base[1];
  423.         struct cell embedded[32];
  424.     } cell_pool;
  425. };
  426.  
  427. struct cell_pair {
  428.     struct cell *cell1;
  429.     struct cell *cell2;
  430. };
  431.  
  432. /* The active list contains edges in the current scan line ordered by
  433.  * the x-coordinate of the intercept of the edge and the scan line. */
  434. struct active_list {
  435.     /* Leftmost edge on the current scan line. */
  436.     struct edge head, tail;
  437.  
  438.     /* A lower bound on the height of the active edges is used to
  439.      * estimate how soon some active edge ends.  We can't advance the
  440.      * scan conversion by a full pixel row if an edge ends somewhere
  441.      * within it. */
  442.     grid_scaled_y_t min_height;
  443.     int is_vertical;
  444. };
  445.  
  446. struct glitter_scan_converter {
  447.     struct polygon      polygon[1];
  448.     struct active_list  active[1];
  449.     struct cell_list    coverages[1];
  450.  
  451.     cairo_half_open_span_t *spans;
  452.     cairo_half_open_span_t spans_embedded[64];
  453.  
  454.     /* Clip box. */
  455.     grid_scaled_x_t xmin, xmax;
  456.     grid_scaled_y_t ymin, ymax;
  457. };
  458.  
  459. /* Compute the floored division a/b. Assumes / and % perform symmetric
  460.  * division. */
  461. inline static struct quorem
  462. floored_divrem(int a, int b)
  463. {
  464.     struct quorem qr;
  465.     qr.quo = a/b;
  466.     qr.rem = a%b;
  467.     if ((a^b)<0 && qr.rem) {
  468.         qr.quo -= 1;
  469.         qr.rem += b;
  470.     }
  471.     return qr;
  472. }
  473.  
  474. /* Compute the floored division (x*a)/b. Assumes / and % perform symmetric
  475.  * division. */
  476. static struct quorem
  477. floored_muldivrem(int x, int a, int b)
  478. {
  479.     struct quorem qr;
  480.     long long xa = (long long)x*a;
  481.     qr.quo = xa/b;
  482.     qr.rem = xa%b;
  483.     if ((xa>=0) != (b>=0) && qr.rem) {
  484.         qr.quo -= 1;
  485.         qr.rem += b;
  486.     }
  487.     return qr;
  488. }
  489.  
  490. static struct _pool_chunk *
  491. _pool_chunk_init(
  492.     struct _pool_chunk *p,
  493.     struct _pool_chunk *prev_chunk,
  494.     size_t capacity)
  495. {
  496.     p->prev_chunk = prev_chunk;
  497.     p->size = 0;
  498.     p->capacity = capacity;
  499.     return p;
  500. }
  501.  
  502. static struct _pool_chunk *
  503. _pool_chunk_create(struct pool *pool, size_t size)
  504. {
  505.     struct _pool_chunk *p;
  506.  
  507.     p = malloc(size + sizeof(struct _pool_chunk));
  508.     if (unlikely (NULL == p))
  509.         longjmp (*pool->jmp, _cairo_error (CAIRO_STATUS_NO_MEMORY));
  510.  
  511.     return _pool_chunk_init(p, pool->current, size);
  512. }
  513.  
  514. static void
  515. pool_init(struct pool *pool,
  516.           jmp_buf *jmp,
  517.           size_t default_capacity,
  518.           size_t embedded_capacity)
  519. {
  520.     pool->jmp = jmp;
  521.     pool->current = pool->sentinel;
  522.     pool->first_free = NULL;
  523.     pool->default_capacity = default_capacity;
  524.     _pool_chunk_init(pool->sentinel, NULL, embedded_capacity);
  525. }
  526.  
  527. static void
  528. pool_fini(struct pool *pool)
  529. {
  530.     struct _pool_chunk *p = pool->current;
  531.     do {
  532.         while (NULL != p) {
  533.             struct _pool_chunk *prev = p->prev_chunk;
  534.             if (p != pool->sentinel)
  535.                 free(p);
  536.             p = prev;
  537.         }
  538.         p = pool->first_free;
  539.         pool->first_free = NULL;
  540.     } while (NULL != p);
  541. }
  542.  
  543. /* Satisfy an allocation by first allocating a new large enough chunk
  544.  * and adding it to the head of the pool's chunk list. This function
  545.  * is called as a fallback if pool_alloc() couldn't do a quick
  546.  * allocation from the current chunk in the pool. */
  547. static void *
  548. _pool_alloc_from_new_chunk(
  549.     struct pool *pool,
  550.     size_t size)
  551. {
  552.     struct _pool_chunk *chunk;
  553.     void *obj;
  554.     size_t capacity;
  555.  
  556.     /* If the allocation is smaller than the default chunk size then
  557.      * try getting a chunk off the free list.  Force alloc of a new
  558.      * chunk for large requests. */
  559.     capacity = size;
  560.     chunk = NULL;
  561.     if (size < pool->default_capacity) {
  562.         capacity = pool->default_capacity;
  563.         chunk = pool->first_free;
  564.         if (chunk) {
  565.             pool->first_free = chunk->prev_chunk;
  566.             _pool_chunk_init(chunk, pool->current, chunk->capacity);
  567.         }
  568.     }
  569.  
  570.     if (NULL == chunk)
  571.         chunk = _pool_chunk_create (pool, capacity);
  572.     pool->current = chunk;
  573.  
  574.     obj = ((unsigned char*)chunk + sizeof(*chunk) + chunk->size);
  575.     chunk->size += size;
  576.     return obj;
  577. }
  578.  
  579. /* Allocate size bytes from the pool.  The first allocated address
  580.  * returned from a pool is aligned to sizeof(void*).  Subsequent
  581.  * addresses will maintain alignment as long as multiples of void* are
  582.  * allocated.  Returns the address of a new memory area or %NULL on
  583.  * allocation failures.  The pool retains ownership of the returned
  584.  * memory. */
  585. inline static void *
  586. pool_alloc (struct pool *pool, size_t size)
  587. {
  588.     struct _pool_chunk *chunk = pool->current;
  589.  
  590.     if (size <= chunk->capacity - chunk->size) {
  591.         void *obj = ((unsigned char*)chunk + sizeof(*chunk) + chunk->size);
  592.         chunk->size += size;
  593.         return obj;
  594.     } else {
  595.         return _pool_alloc_from_new_chunk(pool, size);
  596.     }
  597. }
  598.  
  599. /* Relinquish all pool_alloced memory back to the pool. */
  600. static void
  601. pool_reset (struct pool *pool)
  602. {
  603.     /* Transfer all used chunks to the chunk free list. */
  604.     struct _pool_chunk *chunk = pool->current;
  605.     if (chunk != pool->sentinel) {
  606.         while (chunk->prev_chunk != pool->sentinel) {
  607.             chunk = chunk->prev_chunk;
  608.         }
  609.         chunk->prev_chunk = pool->first_free;
  610.         pool->first_free = pool->current;
  611.     }
  612.     /* Reset the sentinel as the current chunk. */
  613.     pool->current = pool->sentinel;
  614.     pool->sentinel->size = 0;
  615. }
  616.  
  617. /* Rewinds the cell list's cursor to the beginning.  After rewinding
  618.  * we're good to cell_list_find() the cell any x coordinate. */
  619. inline static void
  620. cell_list_rewind (struct cell_list *cells)
  621. {
  622.     cells->cursor = &cells->head;
  623. }
  624.  
  625. inline static void
  626. cell_list_maybe_rewind (struct cell_list *cells, int x)
  627. {
  628.     if (x < cells->cursor->x) {
  629.         cells->cursor = cells->rewind;
  630.         if (x < cells->cursor->x)
  631.             cells->cursor = &cells->head;
  632.     }
  633. }
  634.  
  635. inline static void
  636. cell_list_set_rewind (struct cell_list *cells)
  637. {
  638.     cells->rewind = cells->cursor;
  639. }
  640.  
  641. static void
  642. cell_list_init(struct cell_list *cells, jmp_buf *jmp)
  643. {
  644.     pool_init(cells->cell_pool.base, jmp,
  645.               256*sizeof(struct cell),
  646.               sizeof(cells->cell_pool.embedded));
  647.     cells->tail.next = NULL;
  648.     cells->tail.x = INT_MAX;
  649.     cells->head.x = INT_MIN;
  650.     cells->head.next = &cells->tail;
  651.     cell_list_rewind (cells);
  652. }
  653.  
  654. static void
  655. cell_list_fini(struct cell_list *cells)
  656. {
  657.     pool_fini (cells->cell_pool.base);
  658. }
  659.  
  660. /* Empty the cell list.  This is called at the start of every pixel
  661.  * row. */
  662. inline static void
  663. cell_list_reset (struct cell_list *cells)
  664. {
  665.     cell_list_rewind (cells);
  666.     cells->head.next = &cells->tail;
  667.     pool_reset (cells->cell_pool.base);
  668. }
  669.  
  670. inline static struct cell *
  671. cell_list_alloc (struct cell_list *cells,
  672.                  struct cell *tail,
  673.                  int x)
  674. {
  675.     struct cell *cell;
  676.  
  677.     cell = pool_alloc (cells->cell_pool.base, sizeof (struct cell));
  678.     cell->next = tail->next;
  679.     tail->next = cell;
  680.     cell->x = x;
  681.     *(uint32_t *)&cell->uncovered_area = 0;
  682.  
  683.     return cell;
  684. }
  685.  
  686. /* Find a cell at the given x-coordinate.  Returns %NULL if a new cell
  687.  * needed to be allocated but couldn't be.  Cells must be found with
  688.  * non-decreasing x-coordinate until the cell list is rewound using
  689.  * cell_list_rewind(). Ownership of the returned cell is retained by
  690.  * the cell list. */
  691. inline static struct cell *
  692. cell_list_find (struct cell_list *cells, int x)
  693. {
  694.     struct cell *tail = cells->cursor;
  695.  
  696.     if (tail->x == x)
  697.         return tail;
  698.  
  699.     while (1) {
  700.         UNROLL3({
  701.                 if (tail->next->x > x)
  702.                         break;
  703.                 tail = tail->next;
  704.         });
  705.     }
  706.  
  707.     if (tail->x != x)
  708.         tail = cell_list_alloc (cells, tail, x);
  709.     return cells->cursor = tail;
  710.  
  711. }
  712.  
  713. /* Find two cells at x1 and x2.  This is exactly equivalent
  714.  * to
  715.  *
  716.  *   pair.cell1 = cell_list_find(cells, x1);
  717.  *   pair.cell2 = cell_list_find(cells, x2);
  718.  *
  719.  * except with less function call overhead. */
  720. inline static struct cell_pair
  721. cell_list_find_pair(struct cell_list *cells, int x1, int x2)
  722. {
  723.     struct cell_pair pair;
  724.  
  725.     pair.cell1 = cells->cursor;
  726.     while (1) {
  727.         UNROLL3({
  728.                 if (pair.cell1->next->x > x1)
  729.                         break;
  730.                 pair.cell1 = pair.cell1->next;
  731.         });
  732.     }
  733.     if (pair.cell1->x != x1)
  734.         pair.cell1 = cell_list_alloc (cells, pair.cell1, x1);
  735.  
  736.     pair.cell2 = pair.cell1;
  737.     while (1) {
  738.         UNROLL3({
  739.                 if (pair.cell2->next->x > x2)
  740.                         break;
  741.                 pair.cell2 = pair.cell2->next;
  742.         });
  743.     }
  744.     if (pair.cell2->x != x2)
  745.         pair.cell2 = cell_list_alloc (cells, pair.cell2, x2);
  746.  
  747.     cells->cursor = pair.cell2;
  748.     return pair;
  749. }
  750.  
  751. /* Add a subpixel span covering [x1, x2) to the coverage cells. */
  752. inline static void
  753. cell_list_add_subspan(struct cell_list *cells,
  754.                       grid_scaled_x_t x1,
  755.                       grid_scaled_x_t x2)
  756. {
  757.     int ix1, fx1;
  758.     int ix2, fx2;
  759.  
  760.     if (x1 == x2)
  761.         return;
  762.  
  763.     GRID_X_TO_INT_FRAC(x1, ix1, fx1);
  764.     GRID_X_TO_INT_FRAC(x2, ix2, fx2);
  765.  
  766.     if (ix1 != ix2) {
  767.         struct cell_pair p;
  768.         p = cell_list_find_pair(cells, ix1, ix2);
  769.         p.cell1->uncovered_area += 2*fx1;
  770.         ++p.cell1->covered_height;
  771.         p.cell2->uncovered_area -= 2*fx2;
  772.         --p.cell2->covered_height;
  773.     } else {
  774.         struct cell *cell = cell_list_find(cells, ix1);
  775.         cell->uncovered_area += 2*(fx1-fx2);
  776.     }
  777. }
  778.  
  779. /* Adds the analytical coverage of an edge crossing the current pixel
  780.  * row to the coverage cells and advances the edge's x position to the
  781.  * following row.
  782.  *
  783.  * This function is only called when we know that during this pixel row:
  784.  *
  785.  * 1) The relative order of all edges on the active list doesn't
  786.  * change.  In particular, no edges intersect within this row to pixel
  787.  * precision.
  788.  *
  789.  * 2) No new edges start in this row.
  790.  *
  791.  * 3) No existing edges end mid-row.
  792.  *
  793.  * This function depends on being called with all edges from the
  794.  * active list in the order they appear on the list (i.e. with
  795.  * non-decreasing x-coordinate.)  */
  796. static void
  797. cell_list_render_edge(struct cell_list *cells,
  798.                       struct edge *edge,
  799.                       int sign)
  800. {
  801.     grid_scaled_x_t fx;
  802.     struct cell *cell;
  803.     int ix;
  804.  
  805.     GRID_X_TO_INT_FRAC(edge->x.quo, ix, fx);
  806.  
  807.     /* We always know that ix1 is >= the cell list cursor in this
  808.      * case due to the no-intersections precondition.  */
  809.     cell = cell_list_find(cells, ix);
  810.     cell->covered_height += sign*GRID_Y;
  811.     cell->uncovered_area += sign*2*fx*GRID_Y;
  812. }
  813.  
  814. static void
  815. polygon_init (struct polygon *polygon, jmp_buf *jmp)
  816. {
  817.     polygon->ymin = polygon->ymax = 0;
  818.     polygon->y_buckets = polygon->y_buckets_embedded;
  819.     pool_init (polygon->edge_pool.base, jmp,
  820.                8192 - sizeof (struct _pool_chunk),
  821.                sizeof (polygon->edge_pool.embedded));
  822. }
  823.  
  824. static void
  825. polygon_fini (struct polygon *polygon)
  826. {
  827.     if (polygon->y_buckets != polygon->y_buckets_embedded)
  828.         free (polygon->y_buckets);
  829.  
  830.     pool_fini (polygon->edge_pool.base);
  831. }
  832.  
  833. /* Empties the polygon of all edges. The polygon is then prepared to
  834.  * receive new edges and clip them to the vertical range
  835.  * [ymin,ymax). */
  836. static glitter_status_t
  837. polygon_reset (struct polygon *polygon,
  838.                grid_scaled_y_t ymin,
  839.                grid_scaled_y_t ymax)
  840. {
  841.     unsigned h = ymax - ymin;
  842.     unsigned num_buckets = EDGE_Y_BUCKET_INDEX(ymax + GRID_Y-1, ymin);
  843.  
  844.     pool_reset(polygon->edge_pool.base);
  845.  
  846.     if (unlikely (h > 0x7FFFFFFFU - GRID_Y))
  847.         goto bail_no_mem; /* even if you could, you wouldn't want to. */
  848.  
  849.     if (polygon->y_buckets != polygon->y_buckets_embedded)
  850.         free (polygon->y_buckets);
  851.  
  852.     polygon->y_buckets =  polygon->y_buckets_embedded;
  853.     if (num_buckets > ARRAY_LENGTH (polygon->y_buckets_embedded)) {
  854.         polygon->y_buckets = _cairo_malloc_ab (num_buckets,
  855.                                                sizeof (struct edge *));
  856.         if (unlikely (NULL == polygon->y_buckets))
  857.             goto bail_no_mem;
  858.     }
  859.     memset (polygon->y_buckets, 0, num_buckets * sizeof (struct edge *));
  860.  
  861.     polygon->ymin = ymin;
  862.     polygon->ymax = ymax;
  863.     return GLITTER_STATUS_SUCCESS;
  864.  
  865. bail_no_mem:
  866.     polygon->ymin = 0;
  867.     polygon->ymax = 0;
  868.     return GLITTER_STATUS_NO_MEMORY;
  869. }
  870.  
  871. static void
  872. _polygon_insert_edge_into_its_y_bucket(struct polygon *polygon,
  873.                                        struct edge *e)
  874. {
  875.     unsigned ix = EDGE_Y_BUCKET_INDEX(e->ytop, polygon->ymin);
  876.     struct edge **ptail = &polygon->y_buckets[ix];
  877.     e->next = *ptail;
  878.     *ptail = e;
  879. }
  880.  
  881. inline static void
  882. polygon_add_edge (struct polygon *polygon,
  883.                   const cairo_edge_t *edge)
  884. {
  885.     struct edge *e;
  886.     grid_scaled_x_t dx;
  887.     grid_scaled_y_t dy;
  888.     grid_scaled_y_t ytop, ybot;
  889.     grid_scaled_y_t ymin = polygon->ymin;
  890.     grid_scaled_y_t ymax = polygon->ymax;
  891.  
  892.     if (unlikely (edge->top >= ymax || edge->bottom <= ymin))
  893.         return;
  894.  
  895.     e = pool_alloc (polygon->edge_pool.base, sizeof (struct edge));
  896.  
  897.     dx = edge->line.p2.x - edge->line.p1.x;
  898.     dy = edge->line.p2.y - edge->line.p1.y;
  899.     e->dy = dy;
  900.     e->dir = edge->dir;
  901.  
  902.     ytop = edge->top >= ymin ? edge->top : ymin;
  903.     ybot = edge->bottom <= ymax ? edge->bottom : ymax;
  904.     e->ytop = ytop;
  905.     e->height_left = ybot - ytop;
  906.  
  907.     if (dx == 0) {
  908.         e->vertical = TRUE;
  909.         e->x.quo = edge->line.p1.x;
  910.         e->x.rem = 0;
  911.         e->dxdy.quo = 0;
  912.         e->dxdy.rem = 0;
  913.     } else {
  914.         e->vertical = FALSE;
  915.         e->dxdy = floored_divrem (dx, dy);
  916.         if (ytop == edge->line.p1.y) {
  917.             e->x.quo = edge->line.p1.x;
  918.             e->x.rem = 0;
  919.         } else {
  920.             e->x = floored_muldivrem (ytop - edge->line.p1.y, dx, dy);
  921.             e->x.quo += edge->line.p1.x;
  922.         }
  923.     }
  924.  
  925.     _polygon_insert_edge_into_its_y_bucket (polygon, e);
  926.  
  927.     e->x.rem -= dy;             /* Bias the remainder for faster
  928.                                  * edge advancement. */
  929. }
  930.  
  931. static void
  932. active_list_reset (struct active_list *active)
  933. {
  934.     active->head.vertical = 1;
  935.     active->head.height_left = INT_MAX;
  936.     active->head.x.quo = INT_MIN;
  937.     active->head.prev = NULL;
  938.     active->head.next = &active->tail;
  939.     active->tail.prev = &active->head;
  940.     active->tail.next = NULL;
  941.     active->tail.x.quo = INT_MAX;
  942.     active->tail.height_left = INT_MAX;
  943.     active->tail.vertical = 1;
  944.     active->min_height = 0;
  945.     active->is_vertical = 1;
  946. }
  947.  
  948. static void
  949. active_list_init(struct active_list *active)
  950. {
  951.     active_list_reset(active);
  952. }
  953.  
  954. /*
  955.  * Merge two sorted edge lists.
  956.  * Input:
  957.  *  - head_a: The head of the first list.
  958.  *  - head_b: The head of the second list; head_b cannot be NULL.
  959.  * Output:
  960.  * Returns the head of the merged list.
  961.  *
  962.  * Implementation notes:
  963.  * To make it fast (in particular, to reduce to an insertion sort whenever
  964.  * one of the two input lists only has a single element) we iterate through
  965.  * a list until its head becomes greater than the head of the other list,
  966.  * then we switch their roles. As soon as one of the two lists is empty, we
  967.  * just attach the other one to the current list and exit.
  968.  * Writes to memory are only needed to "switch" lists (as it also requires
  969.  * attaching to the output list the list which we will be iterating next) and
  970.  * to attach the last non-empty list.
  971.  */
  972. static struct edge *
  973. merge_sorted_edges (struct edge *head_a, struct edge *head_b)
  974. {
  975.     struct edge *head, **next, *prev;
  976.     int32_t x;
  977.  
  978.     prev = head_a->prev;
  979.     next = &head;
  980.     if (head_a->x.quo <= head_b->x.quo) {
  981.         head = head_a;
  982.     } else {
  983.         head = head_b;
  984.         head_b->prev = prev;
  985.         goto start_with_b;
  986.     }
  987.  
  988.     do {
  989.         x = head_b->x.quo;
  990.         while (head_a != NULL && head_a->x.quo <= x) {
  991.             prev = head_a;
  992.             next = &head_a->next;
  993.             head_a = head_a->next;
  994.         }
  995.  
  996.         head_b->prev = prev;
  997.         *next = head_b;
  998.         if (head_a == NULL)
  999.             return head;
  1000.  
  1001. start_with_b:
  1002.         x = head_a->x.quo;
  1003.         while (head_b != NULL && head_b->x.quo <= x) {
  1004.             prev = head_b;
  1005.             next = &head_b->next;
  1006.             head_b = head_b->next;
  1007.         }
  1008.  
  1009.         head_a->prev = prev;
  1010.         *next = head_a;
  1011.         if (head_b == NULL)
  1012.             return head;
  1013.     } while (1);
  1014. }
  1015.  
  1016. /*
  1017.  * Sort (part of) a list.
  1018.  * Input:
  1019.  *  - list: The list to be sorted; list cannot be NULL.
  1020.  *  - limit: Recursion limit.
  1021.  * Output:
  1022.  *  - head_out: The head of the sorted list containing the first 2^(level+1) elements of the
  1023.  *              input list; if the input list has fewer elements, head_out be a sorted list
  1024.  *              containing all the elements of the input list.
  1025.  * Returns the head of the list of unprocessed elements (NULL if the sorted list contains
  1026.  * all the elements of the input list).
  1027.  *
  1028.  * Implementation notes:
  1029.  * Special case single element list, unroll/inline the sorting of the first two elements.
  1030.  * Some tail recursion is used since we iterate on the bottom-up solution of the problem
  1031.  * (we start with a small sorted list and keep merging other lists of the same size to it).
  1032.  */
  1033. static struct edge *
  1034. sort_edges (struct edge *list,
  1035.             unsigned int level,
  1036.             struct edge **head_out)
  1037. {
  1038.     struct edge *head_other, *remaining;
  1039.     unsigned int i;
  1040.  
  1041.     head_other = list->next;
  1042.  
  1043.     if (head_other == NULL) {
  1044.         *head_out = list;
  1045.         return NULL;
  1046.     }
  1047.  
  1048.     remaining = head_other->next;
  1049.     if (list->x.quo <= head_other->x.quo) {
  1050.         *head_out = list;
  1051.         head_other->next = NULL;
  1052.     } else {
  1053.         *head_out = head_other;
  1054.         head_other->prev = list->prev;
  1055.         head_other->next = list;
  1056.         list->prev = head_other;
  1057.         list->next = NULL;
  1058.     }
  1059.  
  1060.     for (i = 0; i < level && remaining; i++) {
  1061.         remaining = sort_edges (remaining, i, &head_other);
  1062.         *head_out = merge_sorted_edges (*head_out, head_other);
  1063.     }
  1064.  
  1065.     return remaining;
  1066. }
  1067.  
  1068. static struct edge *
  1069. merge_unsorted_edges (struct edge *head, struct edge *unsorted)
  1070. {
  1071.     sort_edges (unsorted, UINT_MAX, &unsorted);
  1072.     return merge_sorted_edges (head, unsorted);
  1073. }
  1074.  
  1075. /* Test if the edges on the active list can be safely advanced by a
  1076.  * full row without intersections or any edges ending. */
  1077. inline static int
  1078. can_do_full_row (struct active_list *active)
  1079. {
  1080.     const struct edge *e;
  1081.  
  1082.     /* Recomputes the minimum height of all edges on the active
  1083.      * list if we have been dropping edges. */
  1084.     if (active->min_height <= 0) {
  1085.         int min_height = INT_MAX;
  1086.         int is_vertical = 1;
  1087.  
  1088.         e = active->head.next;
  1089.         while (NULL != e) {
  1090.             if (e->height_left < min_height)
  1091.                 min_height = e->height_left;
  1092.             is_vertical &= e->vertical;
  1093.             e = e->next;
  1094.         }
  1095.  
  1096.         active->is_vertical = is_vertical;
  1097.         active->min_height = min_height;
  1098.     }
  1099.  
  1100.     if (active->min_height < GRID_Y)
  1101.         return 0;
  1102.  
  1103.     return active->is_vertical;
  1104. }
  1105.  
  1106. /* Merges edges on the given subpixel row from the polygon to the
  1107.  * active_list. */
  1108. inline static void
  1109. active_list_merge_edges_from_bucket(struct active_list *active,
  1110.                                     struct edge *edges)
  1111. {
  1112.     active->head.next = merge_unsorted_edges (active->head.next, edges);
  1113. }
  1114.  
  1115. inline static void
  1116. polygon_fill_buckets (struct active_list *active,
  1117.                       struct edge *edge,
  1118.                       int y,
  1119.                       struct edge **buckets)
  1120. {
  1121.     grid_scaled_y_t min_height = active->min_height;
  1122.     int is_vertical = active->is_vertical;
  1123.  
  1124.     while (edge) {
  1125.         struct edge *next = edge->next;
  1126.         int suby = edge->ytop - y;
  1127.         if (buckets[suby])
  1128.             buckets[suby]->prev = edge;
  1129.         edge->next = buckets[suby];
  1130.         edge->prev = NULL;
  1131.         buckets[suby] = edge;
  1132.         if (edge->height_left < min_height)
  1133.             min_height = edge->height_left;
  1134.         is_vertical &= edge->vertical;
  1135.         edge = next;
  1136.     }
  1137.  
  1138.     active->is_vertical = is_vertical;
  1139.     active->min_height = min_height;
  1140. }
  1141.  
  1142. inline static void
  1143. sub_row (struct active_list *active,
  1144.          struct cell_list *coverages,
  1145.          unsigned int mask)
  1146. {
  1147.     struct edge *edge = active->head.next;
  1148.     int xstart = INT_MIN, prev_x = INT_MIN;
  1149.     int winding = 0;
  1150.  
  1151.     cell_list_rewind (coverages);
  1152.  
  1153.     while (&active->tail != edge) {
  1154.         struct edge *next = edge->next;
  1155.         int xend = edge->x.quo;
  1156.  
  1157.         if (--edge->height_left) {
  1158.             edge->x.quo += edge->dxdy.quo;
  1159.             edge->x.rem += edge->dxdy.rem;
  1160.             if (edge->x.rem >= 0) {
  1161.                 ++edge->x.quo;
  1162.                 edge->x.rem -= edge->dy;
  1163.             }
  1164.  
  1165.             if (edge->x.quo < prev_x) {
  1166.                 struct edge *pos = edge->prev;
  1167.                 pos->next = next;
  1168.                 next->prev = pos;
  1169.                 do {
  1170.                     pos = pos->prev;
  1171.                 } while (edge->x.quo < pos->x.quo);
  1172.                 pos->next->prev = edge;
  1173.                 edge->next = pos->next;
  1174.                 edge->prev = pos;
  1175.                 pos->next = edge;
  1176.             } else
  1177.                 prev_x = edge->x.quo;
  1178.         } else {
  1179.             edge->prev->next = next;
  1180.             next->prev = edge->prev;
  1181.         }
  1182.  
  1183.         winding += edge->dir;
  1184.         if ((winding & mask) == 0) {
  1185.             if (next->x.quo != xend) {
  1186.                 cell_list_add_subspan (coverages, xstart, xend);
  1187.                 xstart = INT_MIN;
  1188.             }
  1189.         } else if (xstart == INT_MIN)
  1190.             xstart = xend;
  1191.  
  1192.         edge = next;
  1193.     }
  1194. }
  1195.  
  1196. inline static void dec (struct edge *e, int h)
  1197. {
  1198.     e->height_left -= h;
  1199.     if (e->height_left == 0) {
  1200.         e->prev->next = e->next;
  1201.         e->next->prev = e->prev;
  1202.     }
  1203. }
  1204.  
  1205. static void
  1206. full_row (struct active_list *active,
  1207.           struct cell_list *coverages,
  1208.           unsigned int mask)
  1209. {
  1210.     struct edge *left = active->head.next;
  1211.  
  1212.     while (&active->tail != left) {
  1213.         struct edge *right;
  1214.         int winding;
  1215.  
  1216.         dec (left, GRID_Y);
  1217.  
  1218.         winding = left->dir;
  1219.         right = left->next;
  1220.         do {
  1221.             dec (right, GRID_Y);
  1222.  
  1223.             winding += right->dir;
  1224.             if ((winding & mask) == 0 && right->next->x.quo != right->x.quo)
  1225.                 break;
  1226.  
  1227.             right = right->next;
  1228.         } while (1);
  1229.  
  1230.         cell_list_set_rewind (coverages);
  1231.         cell_list_render_edge (coverages, left, +1);
  1232.         cell_list_render_edge (coverages, right, -1);
  1233.  
  1234.         left = right->next;
  1235.     }
  1236. }
  1237.  
  1238. static void
  1239. _glitter_scan_converter_init(glitter_scan_converter_t *converter, jmp_buf *jmp)
  1240. {
  1241.     polygon_init(converter->polygon, jmp);
  1242.     active_list_init(converter->active);
  1243.     cell_list_init(converter->coverages, jmp);
  1244.     converter->xmin=0;
  1245.     converter->ymin=0;
  1246.     converter->xmax=0;
  1247.     converter->ymax=0;
  1248. }
  1249.  
  1250. static void
  1251. _glitter_scan_converter_fini(glitter_scan_converter_t *self)
  1252. {
  1253.     if (self->spans != self->spans_embedded)
  1254.         free (self->spans);
  1255.  
  1256.     polygon_fini(self->polygon);
  1257.     cell_list_fini(self->coverages);
  1258.  
  1259.     self->xmin=0;
  1260.     self->ymin=0;
  1261.     self->xmax=0;
  1262.     self->ymax=0;
  1263. }
  1264.  
  1265. static grid_scaled_t
  1266. int_to_grid_scaled(int i, int scale)
  1267. {
  1268.     /* Clamp to max/min representable scaled number. */
  1269.     if (i >= 0) {
  1270.         if (i >= INT_MAX/scale)
  1271.             i = INT_MAX/scale;
  1272.     }
  1273.     else {
  1274.         if (i <= INT_MIN/scale)
  1275.             i = INT_MIN/scale;
  1276.     }
  1277.     return i*scale;
  1278. }
  1279.  
  1280. #define int_to_grid_scaled_x(x) int_to_grid_scaled((x), GRID_X)
  1281. #define int_to_grid_scaled_y(x) int_to_grid_scaled((x), GRID_Y)
  1282.  
  1283. I glitter_status_t
  1284. glitter_scan_converter_reset(
  1285.                              glitter_scan_converter_t *converter,
  1286.                              int xmin, int ymin,
  1287.                              int xmax, int ymax)
  1288. {
  1289.     glitter_status_t status;
  1290.  
  1291.     converter->xmin = 0; converter->xmax = 0;
  1292.     converter->ymin = 0; converter->ymax = 0;
  1293.  
  1294.     if (xmax - xmin > ARRAY_LENGTH(converter->spans_embedded)) {
  1295.         converter->spans = _cairo_malloc_ab (xmax - xmin,
  1296.                                              sizeof (cairo_half_open_span_t));
  1297.         if (unlikely (converter->spans == NULL))
  1298.             return _cairo_error (CAIRO_STATUS_NO_MEMORY);
  1299.     } else
  1300.         converter->spans = converter->spans_embedded;
  1301.  
  1302.     xmin = int_to_grid_scaled_x(xmin);
  1303.     ymin = int_to_grid_scaled_y(ymin);
  1304.     xmax = int_to_grid_scaled_x(xmax);
  1305.     ymax = int_to_grid_scaled_y(ymax);
  1306.  
  1307.     active_list_reset(converter->active);
  1308.     cell_list_reset(converter->coverages);
  1309.     status = polygon_reset(converter->polygon, ymin, ymax);
  1310.     if (status)
  1311.         return status;
  1312.  
  1313.     converter->xmin = xmin;
  1314.     converter->xmax = xmax;
  1315.     converter->ymin = ymin;
  1316.     converter->ymax = ymax;
  1317.     return GLITTER_STATUS_SUCCESS;
  1318. }
  1319.  
  1320. /* INPUT_TO_GRID_X/Y (in_coord, out_grid_scaled, grid_scale)
  1321.  *   These macros convert an input coordinate in the client's
  1322.  *   device space to the rasterisation grid.
  1323.  */
  1324. /* Gah.. this bit of ugly defines INPUT_TO_GRID_X/Y so as to use
  1325.  * shifts if possible, and something saneish if not.
  1326.  */
  1327. #if !defined(INPUT_TO_GRID_Y) && defined(GRID_Y_BITS) && GRID_Y_BITS <= GLITTER_INPUT_BITS
  1328. #  define INPUT_TO_GRID_Y(in, out) (out) = (in) >> (GLITTER_INPUT_BITS - GRID_Y_BITS)
  1329. #else
  1330. #  define INPUT_TO_GRID_Y(in, out) INPUT_TO_GRID_general(in, out, GRID_Y)
  1331. #endif
  1332.  
  1333. #if !defined(INPUT_TO_GRID_X) && defined(GRID_X_BITS) && GRID_X_BITS <= GLITTER_INPUT_BITS
  1334. #  define INPUT_TO_GRID_X(in, out) (out) = (in) >> (GLITTER_INPUT_BITS - GRID_X_BITS)
  1335. #else
  1336. #  define INPUT_TO_GRID_X(in, out) INPUT_TO_GRID_general(in, out, GRID_X)
  1337. #endif
  1338.  
  1339. #define INPUT_TO_GRID_general(in, out, grid_scale) do {         \
  1340.     long long tmp__ = (long long)(grid_scale) * (in);   \
  1341.     tmp__ >>= GLITTER_INPUT_BITS;                               \
  1342.     (out) = tmp__;                                              \
  1343. } while (0)
  1344.  
  1345. /* Add a new polygon edge from pixel (x1,y1) to (x2,y2) to the scan
  1346.  * converter.  The coordinates represent pixel positions scaled by
  1347.  * 2**GLITTER_PIXEL_BITS.  If this function fails then the scan
  1348.  * converter should be reset or destroyed.  Dir must be +1 or -1,
  1349.  * with the latter reversing the orientation of the edge. */
  1350. I void
  1351. glitter_scan_converter_add_edge (glitter_scan_converter_t *converter,
  1352.                                  const cairo_edge_t *edge)
  1353. {
  1354.     cairo_edge_t e;
  1355.  
  1356.     INPUT_TO_GRID_Y (edge->top, e.top);
  1357.     INPUT_TO_GRID_Y (edge->bottom, e.bottom);
  1358.     if (e.top >= e.bottom)
  1359.         return;
  1360.  
  1361.     /* XXX: possible overflows if GRID_X/Y > 2**GLITTER_INPUT_BITS */
  1362.     INPUT_TO_GRID_Y (edge->line.p1.y, e.line.p1.y);
  1363.     INPUT_TO_GRID_Y (edge->line.p2.y, e.line.p2.y);
  1364.     if (e.line.p1.y == e.line.p2.y)
  1365.         e.line.p2.y++; /* Fudge to prevent div-by-zero */
  1366.  
  1367.     INPUT_TO_GRID_X (edge->line.p1.x, e.line.p1.x);
  1368.     INPUT_TO_GRID_X (edge->line.p2.x, e.line.p2.x);
  1369.  
  1370.     e.dir = edge->dir;
  1371.  
  1372.     polygon_add_edge (converter->polygon, &e);
  1373. }
  1374.  
  1375. static void
  1376. step_edges (struct active_list *active, int count)
  1377. {
  1378.     struct edge *edge;
  1379.  
  1380.     count *= GRID_Y;
  1381.     for (edge = active->head.next; edge != &active->tail; edge = edge->next) {
  1382.         edge->height_left -= count;
  1383.         if (! edge->height_left) {
  1384.             edge->prev->next = edge->next;
  1385.             edge->next->prev = edge->prev;
  1386.         }
  1387.     }
  1388. }
  1389.  
  1390. static glitter_status_t
  1391. blit_a8 (struct cell_list *cells,
  1392.          cairo_span_renderer_t *renderer,
  1393.          cairo_half_open_span_t *spans,
  1394.          int y, int height,
  1395.          int xmin, int xmax)
  1396. {
  1397.     struct cell *cell = cells->head.next;
  1398.     int prev_x = xmin, last_x = -1;
  1399.     int16_t cover = 0, last_cover = 0;
  1400.     unsigned num_spans;
  1401.  
  1402.     if (cell == &cells->tail)
  1403.         return CAIRO_STATUS_SUCCESS;
  1404.  
  1405.     /* Skip cells to the left of the clip region. */
  1406.     while (cell->x < xmin) {
  1407.         cover += cell->covered_height;
  1408.         cell = cell->next;
  1409.     }
  1410.     cover *= GRID_X*2;
  1411.  
  1412.     /* Form the spans from the coverages and areas. */
  1413.     num_spans = 0;
  1414.     for (; cell->x < xmax; cell = cell->next) {
  1415.         int x = cell->x;
  1416.         int16_t area;
  1417.  
  1418.         if (x > prev_x && cover != last_cover) {
  1419.             spans[num_spans].x = prev_x;
  1420.             spans[num_spans].coverage = GRID_AREA_TO_ALPHA (cover);
  1421.             last_cover = cover;
  1422.             last_x = prev_x;
  1423.             ++num_spans;
  1424.         }
  1425.  
  1426.         cover += cell->covered_height*GRID_X*2;
  1427.         area = cover - cell->uncovered_area;
  1428.  
  1429.         if (area != last_cover) {
  1430.             spans[num_spans].x = x;
  1431.             spans[num_spans].coverage = GRID_AREA_TO_ALPHA (area);
  1432.             last_cover = area;
  1433.             last_x = x;
  1434.             ++num_spans;
  1435.         }
  1436.  
  1437.         prev_x = x+1;
  1438.     }
  1439.  
  1440.     if (prev_x <= xmax && cover != last_cover) {
  1441.         spans[num_spans].x = prev_x;
  1442.         spans[num_spans].coverage = GRID_AREA_TO_ALPHA (cover);
  1443.         last_cover = cover;
  1444.         last_x = prev_x;
  1445.         ++num_spans;
  1446.     }
  1447.  
  1448.     if (last_x < xmax && last_cover) {
  1449.         spans[num_spans].x = xmax;
  1450.         spans[num_spans].coverage = 0;
  1451.         ++num_spans;
  1452.     }
  1453.  
  1454.     /* Dump them into the renderer. */
  1455.     return renderer->render_rows (renderer, y, height, spans, num_spans);
  1456. }
  1457.  
  1458. #define GRID_AREA_TO_A1(A)  ((GRID_AREA_TO_ALPHA (A) > 127) ? 255 : 0)
  1459. static glitter_status_t
  1460. blit_a1 (struct cell_list *cells,
  1461.          cairo_span_renderer_t *renderer,
  1462.          cairo_half_open_span_t *spans,
  1463.          int y, int height,
  1464.          int xmin, int xmax)
  1465. {
  1466.     struct cell *cell = cells->head.next;
  1467.     int prev_x = xmin, last_x = -1;
  1468.     int16_t cover = 0;
  1469.     uint8_t coverage, last_cover = 0;
  1470.     unsigned num_spans;
  1471.  
  1472.     if (cell == &cells->tail)
  1473.         return CAIRO_STATUS_SUCCESS;
  1474.  
  1475.     /* Skip cells to the left of the clip region. */
  1476.     while (cell->x < xmin) {
  1477.         cover += cell->covered_height;
  1478.         cell = cell->next;
  1479.     }
  1480.     cover *= GRID_X*2;
  1481.  
  1482.     /* Form the spans from the coverages and areas. */
  1483.     num_spans = 0;
  1484.     for (; cell->x < xmax; cell = cell->next) {
  1485.         int x = cell->x;
  1486.         int16_t area;
  1487.  
  1488.         coverage = GRID_AREA_TO_A1 (cover);
  1489.         if (x > prev_x && coverage != last_cover) {
  1490.             last_x = spans[num_spans].x = prev_x;
  1491.             last_cover = spans[num_spans].coverage = coverage;
  1492.             ++num_spans;
  1493.         }
  1494.  
  1495.         cover += cell->covered_height*GRID_X*2;
  1496.         area = cover - cell->uncovered_area;
  1497.  
  1498.         coverage = GRID_AREA_TO_A1 (area);
  1499.         if (coverage != last_cover) {
  1500.             last_x = spans[num_spans].x = x;
  1501.             last_cover = spans[num_spans].coverage = coverage;
  1502.             ++num_spans;
  1503.         }
  1504.  
  1505.         prev_x = x+1;
  1506.     }
  1507.  
  1508.     coverage = GRID_AREA_TO_A1 (cover);
  1509.     if (prev_x <= xmax && coverage != last_cover) {
  1510.         last_x = spans[num_spans].x = prev_x;
  1511.         last_cover = spans[num_spans].coverage = coverage;
  1512.         ++num_spans;
  1513.     }
  1514.  
  1515.     if (last_x < xmax && last_cover) {
  1516.         spans[num_spans].x = xmax;
  1517.         spans[num_spans].coverage = 0;
  1518.         ++num_spans;
  1519.     }
  1520.     if (num_spans == 1)
  1521.         return CAIRO_STATUS_SUCCESS;
  1522.  
  1523.     /* Dump them into the renderer. */
  1524.     return renderer->render_rows (renderer, y, height, spans, num_spans);
  1525. }
  1526.  
  1527.  
  1528. I void
  1529. glitter_scan_converter_render(glitter_scan_converter_t *converter,
  1530.                               unsigned int winding_mask,
  1531.                               int antialias,
  1532.                               cairo_span_renderer_t *renderer)
  1533. {
  1534.     int i, j;
  1535.     int ymax_i = converter->ymax / GRID_Y;
  1536.     int ymin_i = converter->ymin / GRID_Y;
  1537.     int xmin_i, xmax_i;
  1538.     int h = ymax_i - ymin_i;
  1539.     struct polygon *polygon = converter->polygon;
  1540.     struct cell_list *coverages = converter->coverages;
  1541.     struct active_list *active = converter->active;
  1542.     struct edge *buckets[GRID_Y] = { 0 };
  1543.  
  1544.     xmin_i = converter->xmin / GRID_X;
  1545.     xmax_i = converter->xmax / GRID_X;
  1546.     if (xmin_i >= xmax_i)
  1547.         return;
  1548.  
  1549.     /* Render each pixel row. */
  1550.     for (i = 0; i < h; i = j) {
  1551.         int do_full_row = 0;
  1552.  
  1553.         j = i + 1;
  1554.  
  1555.         /* Determine if we can ignore this row or use the full pixel
  1556.          * stepper. */
  1557.         if (! polygon->y_buckets[i]) {
  1558.             if (active->head.next == &active->tail) {
  1559.                 active->min_height = INT_MAX;
  1560.                 active->is_vertical = 1;
  1561.                 for (; j < h && ! polygon->y_buckets[j]; j++)
  1562.                     ;
  1563.                 continue;
  1564.             }
  1565.  
  1566.             do_full_row = can_do_full_row (active);
  1567.         }
  1568.  
  1569.         if (do_full_row) {
  1570.             /* Step by a full pixel row's worth. */
  1571.             full_row (active, coverages, winding_mask);
  1572.  
  1573.             if (active->is_vertical) {
  1574.                 while (j < h &&
  1575.                        polygon->y_buckets[j] == NULL &&
  1576.                        active->min_height >= 2*GRID_Y)
  1577.                 {
  1578.                     active->min_height -= GRID_Y;
  1579.                     j++;
  1580.                 }
  1581.                 if (j != i + 1)
  1582.                     step_edges (active, j - (i + 1));
  1583.             }
  1584.         } else {
  1585.             int sub;
  1586.  
  1587.             polygon_fill_buckets (active,
  1588.                                   polygon->y_buckets[i],
  1589.                                   (i+ymin_i)*GRID_Y,
  1590.                                   buckets);
  1591.  
  1592.             /* Subsample this row. */
  1593.             for (sub = 0; sub < GRID_Y; sub++) {
  1594.                 if (buckets[sub]) {
  1595.                     active_list_merge_edges_from_bucket (active, buckets[sub]);
  1596.                     buckets[sub] = NULL;
  1597.                 }
  1598.  
  1599.                 sub_row (active, coverages, winding_mask);
  1600.             }
  1601.         }
  1602.  
  1603.         if (antialias)
  1604.             blit_a8 (coverages, renderer, converter->spans,
  1605.                      i+ymin_i, j-i, xmin_i, xmax_i);
  1606.         else
  1607.             blit_a1 (coverages, renderer, converter->spans,
  1608.                      i+ymin_i, j-i, xmin_i, xmax_i);
  1609.         cell_list_reset (coverages);
  1610.  
  1611.         active->min_height -= GRID_Y;
  1612.     }
  1613. }
  1614.  
  1615. struct _cairo_tor22_scan_converter {
  1616.     cairo_scan_converter_t base;
  1617.  
  1618.     glitter_scan_converter_t converter[1];
  1619.     cairo_fill_rule_t fill_rule;
  1620.     cairo_antialias_t antialias;
  1621.  
  1622.     jmp_buf jmp;
  1623. };
  1624.  
  1625. typedef struct _cairo_tor22_scan_converter cairo_tor22_scan_converter_t;
  1626.  
  1627. static void
  1628. _cairo_tor22_scan_converter_destroy (void *converter)
  1629. {
  1630.     cairo_tor22_scan_converter_t *self = converter;
  1631.     if (self == NULL) {
  1632.         return;
  1633.     }
  1634.     _glitter_scan_converter_fini (self->converter);
  1635.     free(self);
  1636. }
  1637.  
  1638. cairo_status_t
  1639. _cairo_tor22_scan_converter_add_polygon (void           *converter,
  1640.                                        const cairo_polygon_t *polygon)
  1641. {
  1642.     cairo_tor22_scan_converter_t *self = converter;
  1643.     int i;
  1644.  
  1645. #if 0
  1646.     FILE *file = fopen ("polygon.txt", "w");
  1647.     _cairo_debug_print_polygon (file, polygon);
  1648.     fclose (file);
  1649. #endif
  1650.  
  1651.     for (i = 0; i < polygon->num_edges; i++)
  1652.          glitter_scan_converter_add_edge (self->converter, &polygon->edges[i]);
  1653.  
  1654.     return CAIRO_STATUS_SUCCESS;
  1655. }
  1656.  
  1657. static cairo_status_t
  1658. _cairo_tor22_scan_converter_generate (void                      *converter,
  1659.                                     cairo_span_renderer_t       *renderer)
  1660. {
  1661.     cairo_tor22_scan_converter_t *self = converter;
  1662.     cairo_status_t status;
  1663.  
  1664.     if ((status = setjmp (self->jmp)))
  1665.         return _cairo_scan_converter_set_error (self, _cairo_error (status));
  1666.  
  1667.     glitter_scan_converter_render (self->converter,
  1668.                                    self->fill_rule == CAIRO_FILL_RULE_WINDING ? ~0 : 1,
  1669.                                    self->antialias != CAIRO_ANTIALIAS_NONE,
  1670.                                    renderer);
  1671.     return CAIRO_STATUS_SUCCESS;
  1672. }
  1673.  
  1674. cairo_scan_converter_t *
  1675. _cairo_tor22_scan_converter_create (int                 xmin,
  1676.                                   int                   ymin,
  1677.                                   int                   xmax,
  1678.                                   int                   ymax,
  1679.                                   cairo_fill_rule_t     fill_rule,
  1680.                                   cairo_antialias_t     antialias)
  1681. {
  1682.     cairo_tor22_scan_converter_t *self;
  1683.     cairo_status_t status;
  1684.  
  1685.     self = malloc (sizeof(struct _cairo_tor22_scan_converter));
  1686.     if (unlikely (self == NULL)) {
  1687.         status = _cairo_error (CAIRO_STATUS_NO_MEMORY);
  1688.         goto bail_nomem;
  1689.     }
  1690.  
  1691.     self->base.destroy = _cairo_tor22_scan_converter_destroy;
  1692.     self->base.generate = _cairo_tor22_scan_converter_generate;
  1693.  
  1694.     _glitter_scan_converter_init (self->converter, &self->jmp);
  1695.     status = glitter_scan_converter_reset (self->converter,
  1696.                                            xmin, ymin, xmax, ymax);
  1697.     if (unlikely (status))
  1698.         goto bail;
  1699.  
  1700.     self->fill_rule = fill_rule;
  1701.     self->antialias = antialias;
  1702.  
  1703.     return &self->base;
  1704.  
  1705.  bail:
  1706.     self->base.destroy(&self->base);
  1707.  bail_nomem:
  1708.     return _cairo_scan_converter_create_in_error (status);
  1709. }
  1710.