Beginnings of port to core buildsystem

svn path=/trunk/libsvgtiny/; revision=9419

1 files changed, 648 insertions, 0 deletions

diff --git a/src/svgtiny_gradient.c b/src/svgtiny_gradient.c
new file mode 100644
index 0000000..be4f256
--- /dev/null
+++ b/src/svgtiny_gradient.c
@@ -0,0 +1,648 @@
+/*
+ * This file is part of Libsvgtiny
+ * Licensed under the MIT License,
+ *                http://opensource.org/licenses/mit-license.php
+ * Copyright 2008 James Bursa <james@semichrome.net>
+ */
+
+#define _GNU_SOURCE  /* for strndup */
+#include <assert.h>
+#include <math.h>
+#include <string.h>
+#include "svgtiny.h"
+#include "svgtiny_internal.h"
+
+#undef GRADIENT_DEBUG
+
+static svgtiny_code svgtiny_parse_linear_gradient(xmlNode *linear,
+		struct svgtiny_parse_state *state);
+static float svgtiny_parse_gradient_offset(const char *s);
+static void svgtiny_path_bbox(float *p, unsigned int n,
+		float *x0, float *y0, float *x1, float *y1);
+static void svgtiny_invert_matrix(float *m, float *inv);
+
+
+/**
+ * Find a gradient by id and parse it.
+ */
+
+void svgtiny_find_gradient(const char *id, struct svgtiny_parse_state *state)
+{
+	fprintf(stderr, "svgtiny_find_gradient: id \"%s\"\n", id);
+
+	state->linear_gradient_stop_count = 0;
+	state->gradient_x1 = "0%";
+	state->gradient_y1 = "0%";
+	state->gradient_x2 = "100%";
+	state->gradient_y2 = "0%";
+	state->gradient_user_space_on_use = false;
+	state->gradient_transform.a = 1;
+	state->gradient_transform.b = 0;
+	state->gradient_transform.c = 0;
+	state->gradient_transform.d = 1;
+	state->gradient_transform.e = 0;
+	state->gradient_transform.f = 0;
+
+	xmlNode *gradient = svgtiny_find_element_by_id(
+			(xmlNode *) state->document, id);
+	fprintf(stderr, "gradient %p\n", gradient);
+	if (!gradient) {
+		fprintf(stderr, "gradient \"%s\" not found\n", id);
+		return;
+	}
+
+	fprintf(stderr, "gradient name \"%s\"\n", gradient->name);
+	if (strcmp((const char *) gradient->name, "linearGradient") == 0) {
+		svgtiny_parse_linear_gradient(gradient, state);
+	}
+}
+
+
+/**
+ * Parse a <linearGradient> element node.
+ *
+ * http://www.w3.org/TR/SVG11/pservers#LinearGradients
+ */
+
+svgtiny_code svgtiny_parse_linear_gradient(xmlNode *linear,
+		struct svgtiny_parse_state *state)
+{
+	xmlAttr *href = xmlHasProp(linear, (const xmlChar *) "href");
+	if (href && href->children->content[0] == '#')
+		svgtiny_find_gradient((const char *) href->children->content
+				+ 1, state);
+
+	for (xmlAttr *attr = linear->properties; attr; attr = attr->next) {
+		const char *name = (const char *) attr->name;
+		const char *content = (const char *) attr->children->content;
+		if (strcmp(name, "x1") == 0)
+			state->gradient_x1 = content;
+		else if (strcmp(name, "y1") == 0)
+			state->gradient_y1 = content;
+		else if (strcmp(name, "x2") == 0)
+			state->gradient_x2 = content;
+		else if (strcmp(name, "y2") == 0)
+			state->gradient_y2 = content;
+		else if (strcmp(name, "gradientUnits") == 0)
+			state->gradient_user_space_on_use =
+					strcmp(content, "userSpaceOnUse") == 0;
+		else if (strcmp(name, "gradientTransform") == 0) {
+			float a = 1, b = 0, c = 0, d = 1, e = 0, f = 0;
+			char *s = strdup(content);
+			if (!s)
+				return svgtiny_OUT_OF_MEMORY;
+			svgtiny_parse_transform(s, &a, &b, &c, &d, &e, &f);
+			free(s);
+			fprintf(stderr, "transform %g %g %g %g %g %g\n",
+					a, b, c, d, e, f);
+			state->gradient_transform.a = a;
+			state->gradient_transform.b = b;
+			state->gradient_transform.c = c;
+			state->gradient_transform.d = d;
+			state->gradient_transform.e = e;
+			state->gradient_transform.f = f;
+		}
+        }
+
+	unsigned int i = 0;
+	for (xmlNode *stop = linear->children; stop; stop = stop->next) {
+		float offset = -1;
+		svgtiny_colour color = svgtiny_TRANSPARENT;
+
+		if (stop->type != XML_ELEMENT_NODE)
+			continue;
+		if (strcmp((const char *) stop->name, "stop") != 0)
+			continue;
+
+		for (xmlAttr *attr = stop->properties; attr;
+				attr = attr->next) {
+			const char *name = (const char *) attr->name;
+			const char *content =
+					(const char *) attr->children->content;
+			if (strcmp(name, "offset") == 0)
+				offset = svgtiny_parse_gradient_offset(content);
+			else if (strcmp(name, "stop-color") == 0)
+				svgtiny_parse_color(content, &color, state);
+			else if (strcmp(name, "style") == 0) {
+				const char *s;
+				char *value;
+				if ((s = strstr(content, "stop-color:"))) {
+					s += 11;
+					while (*s == ' ')
+						s++;
+					value = strndup(s, strcspn(s, "; "));
+					svgtiny_parse_color(value, &color,
+							state);
+					free(value);
+				}
+			}
+		}
+
+		if (offset != -1 && color != svgtiny_TRANSPARENT) {
+			fprintf(stderr, "stop %g %x\n", offset, color);
+			state->gradient_stop[i].offset = offset;
+			state->gradient_stop[i].color = color;
+			i++;
+		}
+
+		if (i == svgtiny_MAX_STOPS)
+			break;
+	}
+
+	if (i)
+		state->linear_gradient_stop_count = i;
+
+	return svgtiny_OK;
+}
+
+
+float svgtiny_parse_gradient_offset(const char *s)
+{
+	int num_length = strspn(s, "0123456789+-.");
+	const char *unit = s + num_length;
+	float n = atof((const char *) s);
+
+	if (unit[0] == 0)
+		;
+	else if (unit[0] == '%')
+		n /= 100.0;
+	else
+		return -1;
+
+	if (n < 0)
+		n = 0;
+	if (1 < n)
+		n = 1;
+	return n;
+}
+
+
+/**
+ * Add a path with a linear gradient fill to the svgtiny_diagram.
+ */
+
+svgtiny_code svgtiny_add_path_linear_gradient(float *p, unsigned int n,
+		struct svgtiny_parse_state *state)
+{
+	/* determine object bounding box */
+	float object_x0, object_y0, object_x1, object_y1;
+	svgtiny_path_bbox(p, n, &object_x0, &object_y0, &object_x1, &object_y1);
+	#ifdef GRADIENT_DEBUG
+	fprintf(stderr, "object bbox: (%g %g) (%g %g)\n",
+			object_x0, object_y0, object_x1, object_y1);
+	#endif
+
+	/* compute gradient vector */
+	fprintf(stderr, "x1 %s, y1 %s, x2 %s, y2 %s\n",
+			state->gradient_x1, state->gradient_y1,
+			state->gradient_x2, state->gradient_y2);
+	float gradient_x0, gradient_y0, gradient_x1, gradient_y1,
+	      gradient_dx, gradient_dy;
+	if (!state->gradient_user_space_on_use) {
+		gradient_x0 = object_x0 +
+				svgtiny_parse_length(state->gradient_x1,
+					object_x1 - object_x0, *state);
+		gradient_y0 = object_y0 +
+				svgtiny_parse_length(state->gradient_y1,
+					object_y1 - object_y0, *state);
+		gradient_x1 = object_x0 +
+				svgtiny_parse_length(state->gradient_x2,
+					object_x1 - object_x0, *state);
+		gradient_y1 = object_y0 +
+				svgtiny_parse_length(state->gradient_y2,
+					object_y1 - object_y0, *state);
+	} else {
+		gradient_x0 = svgtiny_parse_length(state->gradient_x1,
+				state->viewport_width, *state);
+		gradient_y0 = svgtiny_parse_length(state->gradient_y1,
+				state->viewport_height, *state);
+		gradient_x1 = svgtiny_parse_length(state->gradient_x2,
+				state->viewport_width, *state);
+		gradient_y1 = svgtiny_parse_length(state->gradient_y2,
+				state->viewport_height, *state);
+	}
+	gradient_dx = gradient_x1 - gradient_x0;
+	gradient_dy = gradient_y1 - gradient_y0;
+	#ifdef GRADIENT_DEBUG
+	fprintf(stderr, "gradient vector: (%g %g) => (%g %g)\n",
+			gradient_x0, gradient_y0, gradient_x1, gradient_y1);
+	#endif
+
+	/* show theoretical gradient strips for debugging */
+	/*unsigned int strips = 10;
+	for (unsigned int z = 0; z != strips; z++) {
+		float f0, fd, strip_x0, strip_y0, strip_dx, strip_dy;
+		f0 = (float) z / (float) strips;
+		fd = (float) 1 / (float) strips;
+		strip_x0 = gradient_x0 + f0 * gradient_dx;
+		strip_y0 = gradient_y0 + f0 * gradient_dy;
+		strip_dx = fd * gradient_dx;
+		strip_dy = fd * gradient_dy;
+		fprintf(stderr, "strip %i vector: (%g %g) + (%g %g)\n",
+				z, strip_x0, strip_y0, strip_dx, strip_dy);
+
+		float *p = malloc(13 * sizeof p[0]);
+		if (!p)
+			return svgtiny_OUT_OF_MEMORY;
+		p[0] = svgtiny_PATH_MOVE;
+		p[1] = strip_x0 + (strip_dy * 3);
+		p[2] = strip_y0 - (strip_dx * 3);
+		p[3] = svgtiny_PATH_LINE;
+		p[4] = p[1] + strip_dx;
+		p[5] = p[2] + strip_dy;
+		p[6] = svgtiny_PATH_LINE;
+		p[7] = p[4] - (strip_dy * 6);
+		p[8] = p[5] + (strip_dx * 6);
+		p[9] = svgtiny_PATH_LINE;
+		p[10] = p[7] - strip_dx;
+		p[11] = p[8] - strip_dy;
+		p[12] = svgtiny_PATH_CLOSE;
+		svgtiny_transform_path(p, 13, state);
+		struct svgtiny_shape *shape = svgtiny_add_shape(state);
+		if (!shape) {
+			free(p);
+			return svgtiny_OUT_OF_MEMORY;
+		}
+		shape->path = p;
+		shape->path_length = 13;
+		shape->fill = svgtiny_TRANSPARENT;
+		shape->stroke = svgtiny_RGB(0, 0xff, 0);
+		state->diagram->shape_count++;
+	}*/
+
+	/* invert gradient transform for applying to vertices */
+	float trans[6];
+	svgtiny_invert_matrix(&state->gradient_transform.a, trans);
+	fprintf(stderr, "inverse transform %g %g %g %g %g %g\n",
+			trans[0], trans[1], trans[2], trans[3],
+			trans[4], trans[5]);
+
+	/* compute points on the path for triangle vertices */
+	/* r, r0, r1 are distance along gradient vector */
+	unsigned int steps = 10;
+	float x0, y0, x0_trans, y0_trans, r0; /* segment start point */
+	float x1, y1, x1_trans, y1_trans, r1; /* segment end point */
+	float c0x, c0y, c1x, c1y; /* segment control points (beziers only) */
+	float gradient_norm_squared = gradient_dx * gradient_dx +
+	                              gradient_dy * gradient_dy;
+	struct grad_point {
+		float x, y, r;
+	};
+	struct svgtiny_list *pts = svgtiny_list_create(
+			sizeof (struct grad_point));
+	if (!pts)
+		return svgtiny_OUT_OF_MEMORY;
+	float min_r = 1000;
+	unsigned int min_pt = 0;
+	for (unsigned int j = 0; j != n; ) {
+		int segment_type = (int) p[j];
+
+		if (segment_type == svgtiny_PATH_MOVE) {
+			x0 = p[j + 1];
+			y0 = p[j + 2];
+			j += 3;
+			continue;
+		}
+
+		assert(segment_type == svgtiny_PATH_CLOSE ||
+				segment_type == svgtiny_PATH_LINE ||
+				segment_type == svgtiny_PATH_BEZIER);
+
+		/* start point (x0, y0) */
+		x0_trans = trans[0]*x0 + trans[2]*y0 + trans[4];
+		y0_trans = trans[1]*x0 + trans[3]*y0 + trans[5];
+		r0 = ((x0_trans - gradient_x0) * gradient_dx +
+				(y0_trans - gradient_y0) * gradient_dy) /
+				gradient_norm_squared;
+		struct grad_point *point = svgtiny_list_push(pts);
+		if (!point) {
+			svgtiny_list_free(pts);
+			return svgtiny_OUT_OF_MEMORY;
+		}
+		point->x = x0;
+		point->y = y0;
+		point->r = r0;
+		if (r0 < min_r) {
+			min_r = r0;
+			min_pt = svgtiny_list_size(pts) - 1;
+		}
+
+		/* end point (x1, y1) */
+		if (segment_type == svgtiny_PATH_LINE) {
+			x1 = p[j + 1];
+			y1 = p[j + 2];
+			j += 3;
+		} else if (segment_type == svgtiny_PATH_CLOSE) {
+			x1 = p[1];
+			y1 = p[2];
+			j++;
+		} else /* svgtiny_PATH_BEZIER */ {
+			c0x = p[j + 1];
+			c0y = p[j + 2];
+			c1x = p[j + 3];
+			c1y = p[j + 4];
+			x1 = p[j + 5];
+			y1 = p[j + 6];
+			j += 7;
+		}
+		x1_trans = trans[0]*x1 + trans[2]*y1 + trans[4];
+		y1_trans = trans[1]*x1 + trans[3]*y1 + trans[5];
+		r1 = ((x1_trans - gradient_x0) * gradient_dx +
+				(y1_trans - gradient_y0) * gradient_dy) /
+				gradient_norm_squared;
+
+		/* determine steps from change in r */
+		steps = ceilf(fabsf(r1 - r0) / 0.05);
+		if (steps == 0)
+			steps = 1;
+		fprintf(stderr, "r0 %g, r1 %g, steps %i\n",
+				r0, r1, steps);
+
+		/* loop through intermediate points */
+		for (unsigned int z = 1; z != steps; z++) {
+			float t, x, y, x_trans, y_trans, r;
+			t = (float) z / (float) steps;
+			if (segment_type == svgtiny_PATH_BEZIER) {
+				x = (1-t) * (1-t) * (1-t) * x0 +
+					3 * t * (1-t) * (1-t) * c0x +
+					3 * t * t * (1-t) * c1x +
+					t * t * t * x1;
+				y = (1-t) * (1-t) * (1-t) * y0 +
+					3 * t * (1-t) * (1-t) * c0y +
+					3 * t * t * (1-t) * c1y +
+					t * t * t * y1;
+			} else {
+				x = (1-t) * x0 + t * x1;
+				y = (1-t) * y0 + t * y1;
+			}
+			x_trans = trans[0]*x + trans[2]*y + trans[4];
+			y_trans = trans[1]*x + trans[3]*y + trans[5];
+			r = ((x_trans - gradient_x0) * gradient_dx +
+					(y_trans - gradient_y0) * gradient_dy) /
+					gradient_norm_squared;
+			fprintf(stderr, "(%g %g [%g]) ", x, y, r);
+			struct grad_point *point = svgtiny_list_push(pts);
+			if (!point) {
+				svgtiny_list_free(pts);
+				return svgtiny_OUT_OF_MEMORY;
+			}
+			point->x = x;
+			point->y = y;
+			point->r = r;
+			if (r < min_r) {
+				min_r = r;
+				min_pt = svgtiny_list_size(pts) - 1;
+			}
+		}
+		fprintf(stderr, "\n");
+
+		/* next segment start point is this segment end point */
+		x0 = x1;
+		y0 = y1;
+	}
+	fprintf(stderr, "pts size %i, min_pt %i, min_r %.3f\n",
+			svgtiny_list_size(pts), min_pt, min_r);
+
+	/* render triangles */
+	unsigned int stop_count = state->linear_gradient_stop_count;
+	assert(2 <= stop_count);
+	unsigned int current_stop = 0;
+	float last_stop_r = 0;
+	float current_stop_r = state->gradient_stop[0].offset;
+	int red0, green0, blue0, red1, green1, blue1;
+	red0 = red1 = svgtiny_RED(state->gradient_stop[0].color);
+	green0 = green1 = svgtiny_GREEN(state->gradient_stop[0].color);
+	blue0 = blue1 = svgtiny_BLUE(state->gradient_stop[0].color);
+	unsigned int t, a, b;
+	t = min_pt;
+	a = (min_pt + 1) % svgtiny_list_size(pts);
+	b = min_pt == 0 ? svgtiny_list_size(pts) - 1 : min_pt - 1;
+	while (a != b) {
+		struct grad_point *point_t = svgtiny_list_get(pts, t);
+		struct grad_point *point_a = svgtiny_list_get(pts, a);
+		struct grad_point *point_b = svgtiny_list_get(pts, b);
+		float mean_r = (point_t->r + point_a->r + point_b->r) / 3;
+		/*fprintf(stderr, "triangle: t %i %.3f a %i %.3f b %i %.3f "
+				"mean_r %.3f\n",
+				t, pts[t].r, a, pts[a].r, b, pts[b].r,
+				mean_r);*/
+		while (current_stop != stop_count && current_stop_r < mean_r) {
+			current_stop++;
+			if (current_stop == stop_count)
+				break;
+			red0 = red1;
+			green0 = green1;
+			blue0 = blue1;
+			red1 = svgtiny_RED(state->
+					gradient_stop[current_stop].color);
+			green1 = svgtiny_GREEN(state->
+					gradient_stop[current_stop].color);
+			blue1 = svgtiny_BLUE(state->
+					gradient_stop[current_stop].color);
+			last_stop_r = current_stop_r;
+			current_stop_r = state->
+					gradient_stop[current_stop].offset;
+		}
+		float *p = malloc(10 * sizeof p[0]);
+		if (!p)
+			return svgtiny_OUT_OF_MEMORY;
+		p[0] = svgtiny_PATH_MOVE;
+		p[1] = point_t->x;
+		p[2] = point_t->y;
+		p[3] = svgtiny_PATH_LINE;
+		p[4] = point_a->x;
+		p[5] = point_a->y;
+		p[6] = svgtiny_PATH_LINE;
+		p[7] = point_b->x;
+		p[8] = point_b->y;
+		p[9] = svgtiny_PATH_CLOSE;
+		svgtiny_transform_path(p, 10, state);
+		struct svgtiny_shape *shape = svgtiny_add_shape(state);
+		if (!shape) {
+			free(p);
+			return svgtiny_OUT_OF_MEMORY;
+		}
+		shape->path = p;
+		shape->path_length = 10;
+		/*shape->fill = svgtiny_TRANSPARENT;*/
+		if (current_stop == 0)
+			shape->fill = state->gradient_stop[0].color;
+		else if (current_stop == stop_count)
+			shape->fill = state->
+					gradient_stop[stop_count - 1].color;
+		else {
+			float stop_r = (mean_r - last_stop_r) /
+				(current_stop_r - last_stop_r);
+			shape->fill = svgtiny_RGB(
+				(int) ((1 - stop_r) * red0 + stop_r * red1),
+				(int) ((1 - stop_r) * green0 + stop_r * green1),
+				(int) ((1 - stop_r) * blue0 + stop_r * blue1));
+		}
+		shape->stroke = svgtiny_TRANSPARENT;
+		#ifdef GRADIENT_DEBUG
+		shape->stroke = svgtiny_RGB(0, 0, 0xff);
+		#endif
+		state->diagram->shape_count++;
+		if (point_a->r < point_b->r) {
+			t = a;
+			a = (a + 1) % svgtiny_list_size(pts);
+		} else {
+			t = b;
+			b = b == 0 ? svgtiny_list_size(pts) - 1 : b - 1;
+		}
+	}
+
+	/* render gradient vector for debugging */
+	#ifdef GRADIENT_DEBUG
+	{
+		float *p = malloc(7 * sizeof p[0]);
+		if (!p)
+			return svgtiny_OUT_OF_MEMORY;
+		p[0] = svgtiny_PATH_MOVE;
+		p[1] = gradient_x0;
+		p[2] = gradient_y0;
+		p[3] = svgtiny_PATH_LINE;
+		p[4] = gradient_x1;
+		p[5] = gradient_y1;
+		p[6] = svgtiny_PATH_CLOSE;
+		svgtiny_transform_path(p, 7, state);
+		struct svgtiny_shape *shape = svgtiny_add_shape(state);
+		if (!shape) {
+			free(p);
+			return svgtiny_OUT_OF_MEMORY;
+		}
+		shape->path = p;
+		shape->path_length = 7;
+		shape->fill = svgtiny_TRANSPARENT;
+		shape->stroke = svgtiny_RGB(0xff, 0, 0);
+		state->diagram->shape_count++;
+	}
+	#endif
+
+	/* render triangle vertices with r values for debugging */
+	#ifdef GRADIENT_DEBUG
+	for (unsigned int i = 0; i != pts->size; i++) {
+		struct grad_point *point = svgtiny_list_get(pts, i);
+		struct svgtiny_shape *shape = svgtiny_add_shape(state);
+		if (!shape)
+			return svgtiny_OUT_OF_MEMORY;
+		char *text = malloc(20);
+		if (!text)
+			return svgtiny_OUT_OF_MEMORY;
+		sprintf(text, "%i=%.3f", i, point->r);
+		shape->text = text;
+		shape->text_x = state->ctm.a * point->x +
+				state->ctm.c * point->y + state->ctm.e;
+		shape->text_y = state->ctm.b * point->x +
+				state->ctm.d * point->y + state->ctm.f;
+		shape->fill = svgtiny_RGB(0, 0, 0);
+		shape->stroke = svgtiny_TRANSPARENT;
+		state->diagram->shape_count++;
+	}
+	#endif
+
+	/* plot actual path outline */
+	if (state->stroke != svgtiny_TRANSPARENT) {
+		svgtiny_transform_path(p, n, state);
+
+		struct svgtiny_shape *shape = svgtiny_add_shape(state);
+		if (!shape) {
+			free(p);
+			return svgtiny_OUT_OF_MEMORY;
+		}
+		shape->path = p;
+		shape->path_length = n;
+		shape->fill = svgtiny_TRANSPARENT;
+		state->diagram->shape_count++;
+	} else {
+		free(p);
+	}
+
+	svgtiny_list_free(pts);
+
+	return svgtiny_OK;
+}
+
+
+/**
+ * Get the bounding box of path.
+ */
+
+void svgtiny_path_bbox(float *p, unsigned int n,
+		float *x0, float *y0, float *x1, float *y1)
+{
+	*x0 = *x1 = p[1];
+	*y0 = *y1 = p[2];
+
+	for (unsigned int j = 0; j != n; ) {
+		unsigned int points = 0;
+		switch ((int) p[j]) {
+		case svgtiny_PATH_MOVE:
+		case svgtiny_PATH_LINE:
+			points = 1;
+			break;
+		case svgtiny_PATH_CLOSE:
+			points = 0;
+			break;
+		case svgtiny_PATH_BEZIER:
+			points = 3;
+			break;
+		default:
+			assert(0);
+		}
+		j++;
+		for (unsigned int k = 0; k != points; k++) {
+			float x = p[j], y = p[j + 1];
+			if (x < *x0)
+				*x0 = x;
+			else if (*x1 < x)
+				*x1 = x;
+			if (y < *y0)
+				*y0 = y;
+			else if (*y1 < y)
+				*y1 = y;
+			j += 2;
+		}
+	}
+}
+
+
+/**
+ * Invert a transformation matrix.
+ */
+void svgtiny_invert_matrix(float *m, float *inv)
+{
+	float determinant = m[0]*m[3] - m[1]*m[2];
+	inv[0] = m[3] / determinant;
+	inv[1] = -m[1] / determinant;
+	inv[2] = -m[2] / determinant;
+	inv[3] = m[0] / determinant;
+	inv[4] = (m[2]*m[5] - m[3]*m[4]) / determinant;
+	inv[5] = (m[1]*m[4] - m[0]*m[5]) / determinant;
+}
+
+
+/**
+ * Find an element in the document by id.
+ */
+
+xmlNode *svgtiny_find_element_by_id(xmlNode *node, const char *id)
+{
+	xmlNode *child;
+	xmlNode *found;
+
+	for (child = node->children; child; child = child->next) {
+		if (child->type != XML_ELEMENT_NODE)
+			continue;
+		xmlAttr *attr = xmlHasProp(child, (const xmlChar *) "id");
+		if (attr && strcmp(id, (const char *) attr->children->content)
+				== 0)
+			return child;
+		found = svgtiny_find_element_by_id(child, id);
+		if (found)
+			return found;
+	}
+
+	return 0;
+}
+