From f83d5a9d20c9bcaf80d2e808daafecbdda841c28 Mon Sep 17 00:00:00 2001 From: Matthias Clasen Date: Tue, 24 Nov 2020 20:01:07 -0500 Subject: [PATCH] path: Implement gsk_path_parse Implement the SVG path syntax to read back the strings that we generate when serializing paths. The tests for this code are taken from librsvg. This includes an elliptical arc implementation according to the SVG spec. The code is mostly taken from librsvg, but pretty directly follows the SVG spec implementation notes. We don't export this, since the parametrization is inconvenient. We do want an arc_to API, but these are not the arcs we are looking for. --- gsk/gskpath.c | 498 ++++++++++++++++++++++++++++++++++++++++++++++++++ gsk/gskpath.h | 4 + 2 files changed, 502 insertions(+) diff --git a/gsk/gskpath.c b/gsk/gskpath.c index 660fb98245..156bb038e0 100644 --- a/gsk/gskpath.c +++ b/gsk/gskpath.c @@ -1990,3 +1990,501 @@ gsk_path_foreach_with_tolerance (GskPath *self, return TRUE; } +/* path parser and utilities */ + +static void +skip_whitespace (const char **p) +{ + while (g_ascii_isspace (**p)) + (*p)++; +} + +static void +skip_optional_comma (const char **p) +{ + skip_whitespace (p); + if (**p == ',') + (*p)++; +} + +static gboolean +parse_number (const char **p, + double *c) +{ + char *e; + *c = g_ascii_strtod (*p, &e); + if (e == *p) + return FALSE; + *p = e; + skip_optional_comma (p); + return TRUE; +} + +static gboolean +parse_coordinate (const char **p, + double *c) +{ + return parse_number (p, c); +} + +static gboolean +parse_coordinate_pair (const char **p, + double *x, + double *y) +{ + double xx, yy; + const char *o = *p; + + if (!parse_coordinate (p, &xx)) + { + *p = o; + return FALSE; + } + if (!parse_coordinate (p, &yy)) + { + *p = o; + return FALSE; + } + + *x = xx; + *y = yy; + + return TRUE; +} + +static gboolean +parse_nonnegative_number (const char **p, + double *x) +{ + const char *o = *p; + double n; + + if (!parse_number (p, &n)) + return FALSE; + + if (n < 0) + { + *p = o; + return FALSE; + } + + *x = n; + + return TRUE; +} + +static gboolean +parse_flag (const char **p, + gboolean *f) +{ + skip_whitespace (p); + if (strchr ("01", **p)) + { + *f = **p == '1'; + (*p)++; + skip_optional_comma (p); + return TRUE; + } + + return FALSE; +} + +static gboolean +parse_command (const char **p, + char *cmd) +{ + char *s; + const char *allowed; + + if (*cmd == 'X') + allowed = "mM"; + else + allowed = "mMhHvVzZlLcCsStTqQaA"; + + skip_whitespace (p); + s = strchr (allowed, **p); + if (s) + { + *cmd = *s; + (*p)++; + return TRUE; + } + return FALSE; +} + +/** + * gsk_path_parse: + * @string: a string + * + * This is a convenience function that constructs a #GskPath + * from a serialized form. The string is expected to be in + * [SVG path syntax](https://www.w3.org/TR/SVG11/paths.html#PathData), + * as e.g. produced by gsk_path_to_string(). + * + * Returns: (nullable): a new #GskPath, or %NULL if @string could not be parsed + **/ +GskPath * +gsk_path_parse (const char *string) +{ + GskPathBuilder *builder; + double x, y; + double prev_x1, prev_y1; + double path_x, path_y; + const char *p; + char cmd; + char prev_cmd; + gboolean after_comma; + gboolean repeat; + + builder = gsk_path_builder_new (); + + cmd = 'X'; + path_x = path_y = 0; + x = y = 0; + prev_x1 = prev_y1 = 0; + after_comma = FALSE; + + p = string; + while (*p) + { + prev_cmd = cmd; + repeat = !parse_command (&p, &cmd); + + if (after_comma && !repeat) + goto error; + + switch (cmd) + { + case 'X': + goto error; + + case 'Z': + case 'z': + if (repeat) + goto error; + else + { + gsk_path_builder_close (builder); + x = path_x; + y = path_y; + } + break; + + case 'M': + case 'm': + { + double x1, y1; + + if (parse_coordinate_pair (&p, &x1, &y1)) + { + if (cmd == 'm') + { + x1 += x; + y1 += y; + } + if (repeat) + gsk_path_builder_line_to (builder, x1, y1); + else + { + gsk_path_builder_move_to (builder, x1, y1); + if (strchr ("zZX", prev_cmd)) + { + path_x = x1; + path_y = y1; + } + } + x = x1; + y = y1; + } + else + goto error; + } + break; + + case 'L': + case 'l': + { + double x1, y1; + + if (parse_coordinate_pair (&p, &x1, &y1)) + { + if (cmd == 'l') + { + x1 += x; + y1 += y; + } + + if (strchr ("zZ", prev_cmd)) + { + gsk_path_builder_move_to (builder, x, y); + path_x = x; + path_y = y; + } + gsk_path_builder_line_to (builder, x1, y1); + x = x1; + y = y1; + } + else + goto error; + } + break; + + case 'H': + case 'h': + { + double x1; + + if (parse_coordinate (&p, &x1)) + { + if (cmd == 'h') + x1 += x; + if (strchr ("zZ", prev_cmd)) + { + gsk_path_builder_move_to (builder, x, y); + path_x = x; + path_y = y; + } + gsk_path_builder_line_to (builder, x1, y); + x = x1; + } + else + goto error; + } + break; + + case 'V': + case 'v': + { + double y1; + + if (parse_coordinate (&p, &y1)) + { + if (cmd == 'v') + y1 += y; + if (strchr ("zZ", prev_cmd)) + { + gsk_path_builder_move_to (builder, x, y); + path_x = x; + path_y = y; + } + gsk_path_builder_line_to (builder, x, y1); + y = y1; + } + else + goto error; + } + break; + + case 'C': + case 'c': + { + double x0, y0, x1, y1, x2, y2; + + if (parse_coordinate_pair (&p, &x0, &y0) && + parse_coordinate_pair (&p, &x1, &y1) && + parse_coordinate_pair (&p, &x2, &y2)) + { + if (cmd == 'c') + { + x0 += x; + y0 += y; + x1 += x; + y1 += y; + x2 += x; + y2 += y; + } + if (strchr ("zZ", prev_cmd)) + { + gsk_path_builder_move_to (builder, x, y); + path_x = x; + path_y = y; + } + gsk_path_builder_curve_to (builder, x0, y0, x1, y1, x2, y2); + prev_x1 = x1; + prev_y1 = y1; + x = x2; + y = y2; + } + else + goto error; + } + break; + + case 'S': + case 's': + { + double x0, y0, x1, y1, x2, y2; + + if (parse_coordinate_pair (&p, &x1, &y1) && + parse_coordinate_pair (&p, &x2, &y2)) + { + if (cmd == 's') + { + x1 += x; + y1 += y; + x2 += x; + y2 += y; + } + if (strchr ("CcSs", prev_cmd)) + { + x0 = 2 * x - prev_x1; + y0 = 2 * y - prev_y1; + } + else + { + x0 = x; + y0 = y; + } + if (strchr ("zZ", prev_cmd)) + { + gsk_path_builder_move_to (builder, x, y); + path_x = x; + path_y = y; + } + gsk_path_builder_curve_to (builder, x0, y0, x1, y1, x2, y2); + prev_x1 = x1; + prev_y1 = y1; + x = x2; + y = y2; + } + else + goto error; + } + break; + + case 'Q': + case 'q': + { + double x1, y1, x2, y2, xx1, yy1, xx2, yy2; + + if (parse_coordinate_pair (&p, &x1, &y1) && + parse_coordinate_pair (&p, &x2, &y2)) + { + if (cmd == 'q') + { + x1 += x; + y1 += y; + x2 += x; + y2 += y; + } + xx1 = (x + 2.0 * x1) / 3.0; + yy1 = (y + 2.0 * y1) / 3.0; + xx2 = (x2 + 2.0 * x1) / 3.0; + yy2 = (y2 + 2.0 * y1) / 3.0; + if (strchr ("zZ", prev_cmd)) + { + gsk_path_builder_move_to (builder, x, y); + path_x = x; + path_y = y; + } + gsk_path_builder_curve_to (builder, xx1, yy1, xx2, yy2, x2, y2); + prev_x1 = x1; + prev_y1 = y1; + x = x2; + y = y2; + } + else + goto error; + } + break; + + case 'T': + case 't': + { + double x1, y1, x2, y2, xx1, yy1, xx2, yy2; + + if (parse_coordinate_pair (&p, &x2, &y2)) + { + if (cmd == 't') + { + x2 += x; + y2 += y; + } + if (strchr ("QqTt", prev_cmd)) + { + x1 = 2 * x - prev_x1; + y1 = 2 * y - prev_y1; + } + else + { + x1 = x; + y1 = y; + } + xx1 = (x + 2.0 * x1) / 3.0; + yy1 = (y + 2.0 * y1) / 3.0; + xx2 = (x2 + 2.0 * x1) / 3.0; + yy2 = (y2 + 2.0 * y1) / 3.0; + if (strchr ("zZ", prev_cmd)) + { + gsk_path_builder_move_to (builder, x, y); + path_x = x; + path_y = y; + } + gsk_path_builder_curve_to (builder, xx1, yy1, xx2, yy2, x2, y2); + prev_x1 = x1; + prev_y1 = y1; + x = x2; + y = y2; + } + else + goto error; + } + break; + + case 'A': + case 'a': + { + double rx, ry; + double x_axis_rotation; + int large_arc, sweep; + double x1, y1; + + if (parse_nonnegative_number (&p, &rx) && + parse_nonnegative_number (&p, &ry) && + parse_number (&p, &x_axis_rotation) && + parse_flag (&p, &large_arc) && + parse_flag (&p, &sweep) && + parse_coordinate_pair (&p, &x1, &y1)) + { + if (cmd == 'a') + { + x1 += x; + y1 += y; + } + + if (strchr ("zZ", prev_cmd)) + { + gsk_path_builder_move_to (builder, x, y); + path_x = x; + path_y = y; + } + gsk_path_builder_svg_arc_to (builder, + rx, ry, x_axis_rotation, + large_arc, sweep, + x1, y1); + x = x1; + y = y1; + } + else + goto error; + } + break; + + default: + goto error; + } + + after_comma = (p > string) && p[-1] == ','; + } + + if (after_comma) + goto error; + + return gsk_path_builder_free_to_path (builder); + +error: + //g_warning ("Can't parse string '%s' as GskPath, error at %ld", string, p - string); + gsk_path_builder_unref (builder); + + return NULL; +} diff --git a/gsk/gskpath.h b/gsk/gskpath.h index dc678fe09c..3abde79534 100644 --- a/gsk/gskpath.h +++ b/gsk/gskpath.h @@ -64,6 +64,10 @@ void gsk_path_print (GskPath GString *string); GDK_AVAILABLE_IN_ALL char * gsk_path_to_string (GskPath *self); + +GDK_AVAILABLE_IN_ALL +GskPath * gsk_path_parse (const char *string); + GDK_AVAILABLE_IN_ALL void gsk_path_to_cairo (GskPath *self, cairo_t *cr);