Implement drawing mode (\p)

Finally implement the drawing mode, which allows drawing of custom
vector graphics.  Drawings are intercepted in ass_render_event; a hash
of the drawing string is generated which is then used for looking
up drawings and bitmaps of drawings in the cache.  The drawings
itself are "fake" glyphs.  They are created by parsing the simple
drawing description language, evaluating the curves described (lines,
cubic beziers and/or a special kind of b-splines) and creating vector
outlines.  Afterwards, these drawings are (with a few exceptions, e.g.
ascender/descender) exactly handled like regular glyphs.

Support for vector clippings is still missing, but otherwise the
implementation should be complete and compatible with VSFilter.

The libass integration of the drawing parsing/processing code is still a
bit sketchy and should be refactored.

History:
WIP: Drawing mode infrastructure
WIP: Drawing tokenizer
WIP: Parse drawing tokens, call evaluators
WIP: Bezier/b-spline evaluator
WIP: Final pieces for the drawing mode
WIP: Heavy modifications to the drawing parser/tokenizer
WIP: Dynamic outline memory allocation
WIP: Drawing position fixes
WIP: more drawing position fixup (similar to VSFilter now)
WIP: Lots of cleanup and fixes for drawings.
WIP: Drawing mode integration into ass_render_event

1 files changed, 477 insertions, 0 deletions

diff --git a/libass/ass_drawing.c b/libass/ass_drawing.c
new file mode 100644
index 0000000..30d742f
--- /dev/null
+++ b/libass/ass_drawing.c
@@ -0,0 +1,477 @@
+/*
+ * Copyright (C) 2009 Grigori Goronzy <greg@geekmind.org>
+ *
+ * This file is part of libass.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <ft2build.h>
+#include FT_GLYPH_H
+#include FT_OUTLINE_H
+#include FT_BBOX_H
+#include <math.h>
+
+#include "ass_utils.h"
+#include "ass_font.h"
+#include "ass_drawing.h"
+
+#define CURVE_ACCURACY 64.0
+#define GLYPH_INITIAL_POINTS 100
+#define GLYPH_INITIAL_CONTOURS 5
+
+/*
+ * \brief Get and prepare a FreeType glyph
+ */
+static void drawing_make_glyph(ass_drawing_t *drawing, void *fontconfig_priv,
+                               ass_font_t *font, ass_hinting_t hint)
+{
+    FT_OutlineGlyph glyph;
+
+    // This is hacky...
+    glyph = (FT_OutlineGlyph) ass_font_get_glyph(fontconfig_priv, font,
+                                                 (uint32_t) ' ', hint);
+
+    FT_Outline_Done(drawing->ftlibrary, &glyph->outline);
+    FT_Outline_New(drawing->ftlibrary, GLYPH_INITIAL_POINTS,
+                   GLYPH_INITIAL_CONTOURS, &glyph->outline);
+
+    glyph->outline.n_contours = 0;
+    glyph->outline.n_points = 0;
+    glyph->root.advance.x = glyph->root.advance.y = 0;
+    drawing->glyph = glyph;
+}
+
+/*
+ * \brief Add a single point to a contour.
+ */
+static inline void drawing_add_point(ass_drawing_t *drawing,
+                                     FT_Vector *point)
+{
+    FT_Outline *ol = &drawing->glyph->outline;
+
+    if (ol->n_points >= drawing->max_points) {
+        drawing->max_points *= 2;
+        ol->points = realloc(ol->points, sizeof(FT_Vector) *
+                             drawing->max_points);
+        ol->tags = realloc(ol->tags, drawing->max_points);
+    }
+
+    ol->points[ol->n_points].x = point->x;
+    ol->points[ol->n_points].y = point->y;
+    ol->tags[ol->n_points] = 1;
+    ol->n_points++;
+}
+
+/*
+ * \brief Close a contour and check glyph size overflow.
+ */
+static inline void drawing_close_shape(ass_drawing_t *drawing)
+{
+    FT_Outline *ol = &drawing->glyph->outline;
+
+    if (ol->n_contours >= drawing->max_contours) {
+        drawing->max_contours *= 2;
+        ol->contours = realloc(ol->contours, sizeof(short) *
+                               drawing->max_contours);
+    }
+
+    ol->contours[ol->n_contours] = ol->n_points - 1;
+    ol->n_contours++;
+}
+
+/*
+ * \brief Prepare drawing for parsing.  This just sets a few parameters.
+ */
+static void drawing_prepare(ass_drawing_t *drawing)
+{
+    // Scaling parameters
+    drawing->point_scale_x = drawing->scale_x *
+                             64.0 / (1 << (drawing->scale - 1));
+    drawing->point_scale_y = drawing->scale_y *
+                             64.0 / (1 << (drawing->scale - 1));
+}
+
+/*
+ * \brief Finish a drawing.  This only sets the horizontal advance according
+ * to the glyph's bbox at the moment.
+ */
+static void drawing_finish(ass_drawing_t *drawing)
+{
+    int i, offset;
+    FT_BBox bbox;
+    FT_Outline *ol = &drawing->glyph->outline;
+
+    // Close the last contour
+    drawing_close_shape(drawing);
+
+#if 0
+    // Dump points
+    for (i = 0; i < ol->n_points; i++) {
+        printf("point (%d, %d)\n", (int) ol->points[i].x,
+               (int) ol->points[i].y);
+    }
+
+    // Dump contours
+    for (i = 0; i < ol->n_contours; i++)
+        printf("contour %d\n", ol->contours[i]);
+#endif
+
+    FT_Outline_Get_CBox(&drawing->glyph->outline, &bbox);
+    drawing->glyph->root.advance.x = d6_to_d16(bbox.xMax - bbox.xMin);
+
+    drawing->desc = double_to_d6(-drawing->pbo * drawing->scale_y);
+    drawing->asc = bbox.yMax - bbox.yMin + drawing->desc;
+
+    // Place it onto the baseline
+    offset = (bbox.yMax - bbox.yMin) + double_to_d6(-drawing->pbo *
+                                                    drawing->scale_y);
+    for (i = 0; i < ol->n_points; i++)
+        ol->points[i].y += offset;
+}
+
+/*
+ * \brief Check whether a number of items on the list is available
+ */
+static int token_check_values(ass_drawing_token_t *token, int i, int type)
+{
+    int j;
+    for (j = 0; j < i; j++) {
+        if (!token || token->type != type) return 0;
+        token = token->next;
+    }
+
+    return 1;
+}
+
+/*
+ * \brief Tokenize a drawing string into a list of ass_drawing_token_t
+ * This also expands points for closing b-splines
+ */
+static ass_drawing_token_t *drawing_tokenize(char *str)
+{
+    char *p = str;
+    int i, val, type = -1, is_set = 0;
+    FT_Vector point = {0, 0};
+
+    ass_drawing_token_t *root = NULL, *tail = NULL, *spline_start = NULL;
+
+    while (*p) {
+        if (*p == 'c' && spline_start) {
+            // Close b-splines: add the first three points of the b-spline
+            // back to the end
+            if (token_check_values(spline_start->next, 2, TOKEN_B_SPLINE)) {
+                for (i = 0; i < 3; i++) {
+                    tail->next = calloc(1, sizeof(ass_drawing_token_t));
+                    tail->next->prev = tail;
+                    tail = tail->next;
+                    tail->type = TOKEN_B_SPLINE;
+                    tail->point = spline_start->point;
+                    spline_start = spline_start->next;
+                }
+                spline_start = NULL;
+            }
+        } else if (!is_set && mystrtoi(&p, &val)) {
+            point.x = val;
+            is_set = 1;
+            p--;
+        } else if (is_set == 1 && mystrtoi(&p, &val)) {
+            point.y = val;
+            is_set = 2;
+            p--;
+        } else if (*p == 'm')
+            type = TOKEN_MOVE;
+        else if (*p == 'n')
+            type = TOKEN_MOVE_NC;
+        else if (*p == 'l')
+            type = TOKEN_LINE;
+        else if (*p == 'b')
+            type = TOKEN_CUBIC_BEZIER;
+        else if (*p == 'q')
+            type = TOKEN_CONIC_BEZIER;
+        else if (*p == 's')
+            type = TOKEN_B_SPLINE;
+        // We're simply ignoring TOKEN_EXTEND_B_SPLINE here.
+        // This is not harmful at all, since it can be ommitted with
+        // similar result (the spline is extended anyway).
+
+        if (type != -1 && is_set == 2) {
+            if (root) {
+                tail->next = calloc(1, sizeof(ass_drawing_token_t));
+                tail->next->prev = tail;
+                tail = tail->next;
+            } else
+                root = tail = calloc(1, sizeof(ass_drawing_token_t));
+            tail->type = type;
+            tail->point = point;
+            is_set = 0;
+            if (type == TOKEN_B_SPLINE && !spline_start)
+                spline_start = tail->prev;
+        }
+        p++;
+    }
+
+#if 0
+    // Check tokens
+    ass_drawing_token_t *t = root;
+    while(t) {
+        printf("token %d point (%d, %d)\n", t->type, t->point.x, t->point.y);
+        t = t->next;
+    }
+#endif
+
+    return root;
+}
+
+/*
+ * \brief Free a list of tokens
+ */
+static void drawing_free_tokens(ass_drawing_token_t *token)
+{
+    while (token) {
+        ass_drawing_token_t *at = token;
+        token = token->next;
+        free(at);
+    }
+}
+
+/*
+ * \brief Translate and scale a point coordinate according to baseline
+ * offset and scale.
+ */
+static inline void translate_point(ass_drawing_t *drawing, FT_Vector *point)
+{
+    point->x = drawing->point_scale_x * point->x;
+    point->y = drawing->point_scale_y * -point->y;
+}
+
+/*
+ * \brief Evaluate a curve into lines
+ * This curve evaluator is also used in VSFilter (RTS.cpp); it's a simple
+ * implementation of the De Casteljau algorithm.
+ */
+static void drawing_evaluate_curve(ass_drawing_t *drawing,
+                                   ass_drawing_token_t *token, char spline,
+                                   int started)
+{
+    double cx3, cx2, cx1, cx0, cy3, cy2, cy1, cy0;
+    double t, h, max_accel, max_accel1, max_accel2;
+    FT_Vector cur = {0, 0};
+
+    cur = token->point;
+    translate_point(drawing, &cur);
+    int x0 = cur.x;
+    int y0 = cur.y;
+    token = token->next;
+    cur = token->point;
+    translate_point(drawing, &cur);
+    int x1 = cur.x;
+    int y1 = cur.y;
+    token = token->next;
+    cur = token->point;
+    translate_point(drawing, &cur);
+    int x2 = cur.x;
+    int y2 = cur.y;
+    token = token->next;
+    cur = token->point;
+    translate_point(drawing, &cur);
+    int x3 = cur.x;
+    int y3 = cur.y;
+
+    if (spline) {
+        // 1   [-1 +3 -3 +1]
+        // - * [+3 -6 +3  0]
+        // 6   [-3  0 +3  0]
+        //	   [+1 +4 +1  0]
+
+        double div6 = 1.0/6.0;
+
+        cx3 = div6*(-  x0+3*x1-3*x2+x3);
+        cx2 = div6*( 3*x0-6*x1+3*x2);
+        cx1 = div6*(-3*x0	   +3*x2);
+        cx0 = div6*(   x0+4*x1+1*x2);
+
+        cy3 = div6*(-  y0+3*y1-3*y2+y3);
+        cy2 = div6*( 3*y0-6*y1+3*y2);
+        cy1 = div6*(-3*y0     +3*y2);
+        cy0 = div6*(   y0+4*y1+1*y2);
+    } else {
+        // [-1 +3 -3 +1]
+        // [+3 -6 +3  0]
+        // [-3 +3  0  0]
+        // [+1  0  0  0]
+
+        cx3 = -  x0+3*x1-3*x2+x3;
+        cx2 =  3*x0-6*x1+3*x2;
+        cx1 = -3*x0+3*x1;
+        cx0 =    x0;
+
+        cy3 = -  y0+3*y1-3*y2+y3;
+        cy2 =  3*y0-6*y1+3*y2;
+        cy1 = -3*y0+3*y1;
+        cy0 =    y0;
+    }
+
+    max_accel1 = fabs(2 * cy2) + fabs(6 * cy3);
+    max_accel2 = fabs(2 * cx2) + fabs(6 * cx3);
+
+    max_accel = FFMAX(max_accel1, max_accel2);
+    h = 1.0;
+
+    if (max_accel > CURVE_ACCURACY)
+        h = sqrt(CURVE_ACCURACY / max_accel);
+
+    if (!started) {
+        cur.x = cx0;
+        cur.y = cy0;
+        drawing_add_point(drawing, &cur);
+    }
+
+    for (t = 0; t < 1.0; t += h) {
+        cur.x = cx0 + t * (cx1 + t * (cx2 + t * cx3));
+        cur.y = cy0 + t * (cy1 + t * (cy2 + t * cy3));
+        drawing_add_point(drawing, &cur);
+    }
+
+    cur.x = cx0 + cx1 + cx2 + cx3;
+    cur.y = cy0 + cy1 + cy2 + cy3;
+    drawing_add_point(drawing, &cur);
+}
+
+/*
+ * \brief Create and initialize a new drawing and return it
+ */
+ass_drawing_t *ass_drawing_new(void *fontconfig_priv, ass_font_t *font,
+                               ass_hinting_t hint, FT_Library lib)
+{
+    ass_drawing_t* drawing;
+
+    drawing = calloc(1, sizeof(*drawing));
+    drawing->text = malloc(DRAWING_INITIAL_SIZE);
+    drawing->size = DRAWING_INITIAL_SIZE;
+
+    drawing->ftlibrary = lib;
+    drawing_make_glyph(drawing, fontconfig_priv, font, hint);
+
+    drawing->scale_x = 1.;
+    drawing->scale_y = 1.;
+    drawing->max_contours = GLYPH_INITIAL_CONTOURS;
+    drawing->max_points = GLYPH_INITIAL_POINTS;
+
+    return drawing;
+}
+
+/*
+ * \brief Free a drawing
+ */
+void ass_drawing_free(ass_drawing_t* drawing)
+{
+    free(drawing->text);
+    free(drawing);
+}
+
+/*
+ * \brief Add one ASCII character to the drawing text buffer
+ */
+void ass_drawing_add_char(ass_drawing_t* drawing, char symbol)
+{
+    drawing->text[drawing->i++] = symbol;
+    drawing->text[drawing->i] = 0;
+
+    if (drawing->i + 1 >= drawing->size) {
+        drawing->size *= 2;
+        drawing->text = realloc(drawing->text, drawing->size);
+    }
+}
+
+/*
+ * \brief Create a hashcode for the drawing
+ * XXX: To avoid collisions a better hash algorithm might be useful.
+ */
+void ass_drawing_hash(ass_drawing_t* drawing)
+{
+    drawing->hash = fnv_32a_str(drawing->text, FNV1_32A_INIT);
+}
+
+/*
+ * \brief Convert token list to outline.  Calls the line and curve evaluators.
+ */
+FT_OutlineGlyph *ass_drawing_parse(ass_drawing_t *drawing)
+{
+    int started = 0;
+    ass_drawing_token_t *token;
+    FT_Vector pen = {0, 0};
+
+    drawing->tokens = drawing_tokenize(drawing->text);
+    drawing_prepare(drawing);
+
+    token = drawing->tokens;
+    while (token) {
+        // Draw something according to current command
+        switch (token->type) {
+        case TOKEN_MOVE_NC:
+            pen = token->point;
+            translate_point(drawing, &pen);
+            token = token->next;
+            break;
+        case TOKEN_MOVE:
+            pen = token->point;
+            translate_point(drawing, &pen);
+            if (started) {
+                drawing_close_shape(drawing);
+                started = 0;
+            }
+            token = token->next;
+            break;
+        case TOKEN_LINE: {
+            FT_Vector to;
+            to = token->point;
+            translate_point(drawing, &to);
+            if (!started) drawing_add_point(drawing, &pen);
+            drawing_add_point(drawing, &to);
+            started = 1;
+            token = token->next;
+            break;
+        }
+        case TOKEN_CUBIC_BEZIER:
+            if (token_check_values(token, 3, TOKEN_CUBIC_BEZIER) &&
+                token->prev) {
+                drawing_evaluate_curve(drawing, token->prev, 0, started);
+                token = token->next;
+                token = token->next;
+                token = token->next;
+                started = 1;
+            } else
+                token = token->next;
+            break;
+        case TOKEN_B_SPLINE:
+            if (token_check_values(token, 3, TOKEN_B_SPLINE) &&
+                token->prev) {
+                drawing_evaluate_curve(drawing, token->prev, 1, started);
+                token = token->next;
+                started = 1;
+            } else
+                token = token->next;
+            break;
+        default:
+            token = token->next;
+            break;
+        }
+    }
+
+    drawing_finish(drawing);
+    drawing_free_tokens(drawing->tokens);
+    return &drawing->glyph;
+}
+
+