path: root/ksvg/impl/libs/art_support/art_render_misc.c

/* This file is part of the KDE project.
 * art_render_misc.c: Here I store some routines I feel should be in libart :)
 *
 * Copyright (C) 2001-2003 KSVG Team
 *
 * This code is adapted from :
 *
 * art_render_gradient.c: Gradient image source for modular rendering.
 *
 * Libart_LGPL - library of basic graphic primitives
 * Copyright (C) 2000 Raph Levien
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 * Authors: Raph Levien <raph@acm.org>
 *          Alexander Larsson <alla@lysator.liu.se>
 */

#include "config.h"
#include "art_render_misc.h"

#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

/* These are in KSVGHelper.cpp */
int linearRGBFromsRGB(int sRGB8bit);
int sRGBFromLinearRGB(int linearRGB8bit);

typedef struct _ArtImageSourceGradRad ArtImageSourceGradRad;

struct _ArtImageSourceGradRad {
  ArtImageSource super;
  const ArtKSVGGradientRadial *gradient;
  double a;
};

#define EPSILON 1e-6

/**
 * art_ksvg_render_gradient_setpix: Set a gradient pixel.
 * @render: The render object.
 * @dst: Pointer to destination (where to store pixel).
 * @n_stops: Number of stops in @stops.
 * @stops: The stops for the gradient.
 * @offset: The offset.
 *
 * @n_stops must be > 0.
 *
 * Sets a gradient pixel, storing it at @dst.
 **/
static void
art_ksvg_render_gradient_setpix (ArtRender *render,
			    art_u8 *dst,
			    int n_stops, ArtGradientStop *stops,
			    double offset, ArtKSVGGradientInterpolation interpolation)
{
  int ix;
  int j;
  double off0, off1;
  int n_ch = render->n_chan + 1;

  for (ix = 0; ix < n_stops; ix++)
    if (stops[ix].offset > offset)
      break;
  /* stops[ix - 1].offset < offset < stops[ix].offset */
  if (ix > 0 && ix < n_stops)
    {
      off0 = stops[ix - 1].offset;
      off1 = stops[ix].offset;
      if (fabs (off1 - off0) > EPSILON)
	{
	  double interp;

	  interp = (offset - off0) / (off1 - off0);
		if(interpolation == ART_KSVG_LINEARRGB_INTERPOLATION)
		{
			for (j = 0; j < n_ch; j++)
				{
					int z0, z1;
					int z;
					int z0_8bit, z0_linearRGB_8bit;
					int z1_8bit, z1_linearRGB_8bit;
					int z_8bit, z_sRGB_8bit;

					/* Note: Using explicit variables for intermediate steps since */
					/* the ART_PIX macros reference the argument more than once. */
					z0 = stops[ix - 1].color[j];
					z0_8bit = ART_PIX_8_FROM_MAX(z0);
					z0_linearRGB_8bit = linearRGBFromsRGB(z0_8bit);
					z0 = ART_PIX_MAX_FROM_8(z0_linearRGB_8bit);

					z1 = stops[ix].color[j];
					z1_8bit = ART_PIX_8_FROM_MAX(z1);
					z1_linearRGB_8bit = linearRGBFromsRGB(z1_8bit);
					z1 = ART_PIX_MAX_FROM_8(z1_linearRGB_8bit);

					z = floor (z0 + (z1 - z0) * interp + 0.5);
					z_8bit = ART_PIX_8_FROM_MAX(z);
					z_sRGB_8bit = sRGBFromLinearRGB(z_8bit);

					if (render->buf_depth == 8)
						dst[j] = z_sRGB_8bit;
					else /* (render->buf_depth == 16) */
						((art_u16 *)dst)[j] = ART_PIX_MAX_FROM_8(z_sRGB_8bit);
				}
		}
		else
		{
			/* sRGB interpolation */
			for (j = 0; j < n_ch; j++)
				{
					int z0, z1;
					int z;
					z0 = stops[ix - 1].color[j];
					z1 = stops[ix].color[j];
					z = floor (z0 + (z1 - z0) * interp + 0.5);
					if (render->buf_depth == 8)
			dst[j] = ART_PIX_8_FROM_MAX (z);
					else /* (render->buf_depth == 16) */
			((art_u16 *)dst)[j] = z;
				}
		}
	  return;
	}
    }
  else if (ix == n_stops)
    ix--;

  for (j = 0; j < n_ch; j++)
    {
      int z;
      z = stops[ix].color[j];
      if (render->buf_depth == 8)
	dst[j] = ART_PIX_8_FROM_MAX (z);
      else /* (render->buf_depth == 16) */
	((art_u16 *)dst)[j] = z;
    }
}

static void
art_ksvg_render_gradient_radial_done (ArtRenderCallback *self, ArtRender *render)
{
  art_free (self);
}

static void
art_ksvg_render_gradient_radial_render (ArtRenderCallback *self, ArtRender *render,
				   art_u8 *dest, int y)
{
  ArtImageSourceGradRad *z = (ArtImageSourceGradRad *)self;
  const ArtKSVGGradientRadial *gradient = z->gradient;
  int pixstride = (render->n_chan + 1) * (render->depth >> 3);
  int x;
  int x0 = render->x0;
  int width = render->x1 - x0;
  int n_stops = gradient->n_stops;
  ArtGradientStop *stops = gradient->stops;
  art_u8 *bufp = render->image_buf;
  double fx = gradient->fx;
  double fy = gradient->fy;
  double dx, dy;
  double *affine = gradient->affine;
  double aff0 = affine[0];
  double aff1 = affine[1];
  const double a = z->a;
  const double arecip = 1.0 / a;
  double b, db;
  double c, dc, ddc;
  double b_a, db_a;
  double rad, drad, ddrad;
  ArtGradientSpread spread = gradient->spread;

  dx = x0 * aff0 + y * affine[2] + affine[4] - fx;
  dy = x0 * aff1 + y * affine[3] + affine[5] - fy;
  b = dx * fx + dy * fy;
  db = aff0 * fx + aff1 * fy;
  c = dx * dx + dy * dy;
  dc = 2 * aff0 * dx + aff0 * aff0 + 2 * aff1 * dy + aff1 * aff1;
  ddc = 2 * aff0 * aff0 + 2 * aff1 * aff1;

  b_a = b * arecip;
  db_a = db * arecip;

  rad = b_a * b_a + c * arecip;
  drad = 2 * b_a * db_a + db_a * db_a + dc * arecip;
  ddrad = 2 * db_a * db_a + ddc * arecip;

  for (x = 0; x < width; x++)
    {
      double z;

      if (rad > 0)
	z = b_a + sqrt (rad);
      else
	z = b_a;

    if (spread == ART_GRADIENT_REPEAT)
	  z = z - floor (z);
    else if (spread == ART_GRADIENT_REFLECT)
    {
	  double tmp;

	  tmp = z - 2 * floor (0.5 * z);
	  z = tmp > 1 ? 2 - tmp : tmp;
    }

      art_ksvg_render_gradient_setpix (render, bufp, n_stops, stops, z, gradient->interpolation);
      bufp += pixstride;
      b_a += db_a;
      rad += drad;
      drad += ddrad;
    }
}

static void
art_ksvg_render_gradient_radial_negotiate (ArtImageSource *self, ArtRender *render,
				      ArtImageSourceFlags *p_flags,
				      int *p_buf_depth, ArtAlphaType *p_alpha)
{
  self->super.render = art_ksvg_render_gradient_radial_render;
  *p_flags = 0;
  *p_buf_depth = render->depth;
  *p_alpha = ART_ALPHA_SEPARATE;
}

/**
 * art_ksvg_render_gradient_radial: Add a radial gradient image source.
 * @render: The render object.
 * @gradient: The radial gradient.
 *
 * Adds the radial gradient @gradient as the image source for rendering
 * in the render object @render.
 **/
void
art_ksvg_render_gradient_radial (ArtRender *render,
			    const ArtKSVGGradientRadial *gradient,
			    ArtFilterLevel level)
{
  ArtImageSourceGradRad *image_source = art_new (ArtImageSourceGradRad, 1);
  double fx = gradient->fx;
  double fy = gradient->fy;

  image_source->super.super.render = NULL;
  image_source->super.super.done = art_ksvg_render_gradient_radial_done;
  image_source->super.negotiate = art_ksvg_render_gradient_radial_negotiate;

  image_source->gradient = gradient;
  /* todo: sanitycheck fx, fy? */
  image_source->a = 1 - fx * fx - fy * fy;

  art_render_add_image_source (render, &image_source->super);
}


/* Hack to find out how to define alloca on different platforms.
 * Modified version of glib/galloca.h.
 */

#ifdef  __GNUC__
/* GCC does the right thing */
	#undef alloca
	#define alloca(size)   __builtin_alloca (size)
#elif defined (HAVE_ALLOCA_H)
/* a native and working alloca.h is there */ 
	#include <alloca.h>
#else /* !__GNUC__ && !HAVE_ALLOCA_H */
	#ifdef _MSC_VER
		#include <malloc.h>
		#define alloca _alloca
	#else /* !_MSC_VER */
		#ifdef _AIX
			#pragma alloca
		#else /* !_AIX */
			#ifndef alloca /* predefined by HP cc +Olibcalls */
char *alloca ();
			#endif /* !alloca */
		#endif /* !_AIX */
	#endif /* !_MSC_VER */
#endif /* !__GNUC__ && !HAVE_ALLOCA_H */

#undef DEBUG_SPEW

typedef struct _ArtImageSourceGradLin ArtImageSourceGradLin;

/* The stops will be copied right after this structure */
struct _ArtImageSourceGradLin
{
	ArtImageSource super;
	ArtKSVGGradientLinear gradient;
	ArtGradientStop stops[1];
};

#ifndef MAX
	#define MAX(a, b)  (((a) > (b)) ? (a) : (b))
#endif /* MAX */

#ifndef MIN
	#define MIN(a, b)  (((a) < (b)) ? (a) : (b))
#endif /* MIN */

static void
art_ksvg_rgba_gradient_run (art_u8 *buf,
														art_u8 *color1,
														art_u8 *color2,
														int len)
{
	int i;
	int r, g, b, a;
	int dr, dg, db, da;

#ifdef DEBUG_SPEW
	printf ("gradient run from %3d %3d %3d %3d to %3d %3d %3d %3d in %d pixels\n",
					color1[0], color1[1], color1[2], color1[3], 
					color2[0], color2[1], color2[2], color2[3],
					len);
#endif

	r = (color1[0] << 16) + 0x8000;
	g = (color1[1] << 16) + 0x8000;
	b = (color1[2] << 16) + 0x8000;
	a = (color1[3] << 16) + 0x8000;
	dr = ((color2[0] - color1[0]) << 16) / len;
	dg = ((color2[1] - color1[1]) << 16) / len;
	db = ((color2[2] - color1[2]) << 16) / len;
	da = ((color2[3] - color1[3]) << 16) / len;

	for(i = 0; i < len; i++)
	{
		*buf++ = (r>>16);
		*buf++ = (g>>16);
		*buf++ = (b>>16);
		*buf++ = (a>>16);

		r += dr;
		g += dg;
		b += db;
		a += da;
	}
}

static void
ksvg_calc_color_at (ArtGradientStop *stops,
										int n_stops,
										ArtGradientSpread spread,
										double offset,
										double offset_fraction,
										int favor_start,
										int ix,
										art_u8 *color)
{
	double off0, off1;
	int j;

	if(spread == ART_GRADIENT_PAD)
	{
		if(offset < EPSILON)
		{
			color[0] = ART_PIX_8_FROM_MAX (stops[0].color[0]);
			color[1] = ART_PIX_8_FROM_MAX (stops[0].color[1]);
			color[2] = ART_PIX_8_FROM_MAX (stops[0].color[2]);
			color[3] = ART_PIX_8_FROM_MAX (stops[0].color[3]);
			return;
		}
		if(offset >= 1.0 - EPSILON)
		{
			color[0] = ART_PIX_8_FROM_MAX (stops[n_stops-1].color[0]);
			color[1] = ART_PIX_8_FROM_MAX (stops[n_stops-1].color[1]);
			color[2] = ART_PIX_8_FROM_MAX (stops[n_stops-1].color[2]);
			color[3] = ART_PIX_8_FROM_MAX (stops[n_stops-1].color[3]);
			return;
		}
	}

	if(ix > 0 && ix < n_stops)
	{
		off0 = stops[ix - 1].offset;
		off1 = stops[ix].offset;
		if(fabs (off1 - off0) > EPSILON)
		{
			double interp;
			double o;
			o = offset_fraction;

			if((fabs (o) < EPSILON) && (!favor_start))
				o = 1.0;
			else if((fabs (o-1.0) < EPSILON) && (favor_start))
				o = 0.0;

			/*
			if (offset_fraction == 0.0  && !favor_start)
				offset_fraction = 1.0;
			*/

			interp = (o - off0) / (off1 - off0);
			for(j = 0; j < 4; j++)
			{
				int z0, z1;
				int z;
				z0 = stops[ix - 1].color[j];
				z1 = stops[ix].color[j];
				z = floor (z0 + (z1 - z0) * interp + 0.5);
				color[j] = ART_PIX_8_FROM_MAX (z);
			}
			return;
		}
		/* If offsets are too close to safely do the division, just
 pick the ix color. */
		color[0] = ART_PIX_8_FROM_MAX (stops[ix].color[0]);
		color[1] = ART_PIX_8_FROM_MAX (stops[ix].color[1]);
		color[2] = ART_PIX_8_FROM_MAX (stops[ix].color[2]);
		color[3] = ART_PIX_8_FROM_MAX (stops[ix].color[3]);
		return;
	}

	/*printf ("WARNING! bad ix %d in calc_color_at() [internal error]\n", ix);
	assert (0);*/
}

static void
art_ksvg_render_gradient_linear_render_8 (ArtRenderCallback *self,
																					ArtRender *render,
																					art_u8 *dest, int y)
{
	ArtImageSourceGradLin *z = (ArtImageSourceGradLin *)self;
	const ArtKSVGGradientLinear *gradient = &(z->gradient);
	int i;
	int width = render->x1 - render->x0;
	int len;
	double offset, d_offset;
	double offset_fraction;
	int next_stop;
	int ix;
	art_u8 color1[4], color2[4];
	int n_stops = gradient->n_stops;
	int extra_stops;
	ArtGradientStop *stops = gradient->stops;
	ArtGradientStop *tmp_stops;
	art_u8 *bufp = render->image_buf;
	ArtGradientSpread spread = gradient->spread;

#ifdef DEBUG_SPEW
	printf ("x1: %d, x2: %d, y: %d\n", render->x0, render->x1, y);
	printf ("spread: %d, stops:", gradient->spread);
	for(i=0;i<n_stops;i++)
	{
		printf ("%f, ", gradient->stops[i].offset);
	}
	printf ("\n");
	printf ("a: %f, b: %f, c: %f\n", gradient->a, gradient->b, gradient->c);
#endif

	offset = render->x0 * gradient->affine[0] + y * gradient->affine[2] + gradient->affine[4];
	d_offset = gradient->affine[0];

	/* We need to force the gradient to extend the whole 0..1 segment,
		 because the rest of the code doesn't handle partial gradients
		 correctly */
	if((gradient->stops[0].offset > EPSILON	/* == 0.0 */) ||
		 (gradient->stops[n_stops-1].offset < (1.0 - EPSILON)))
	{
		extra_stops = 0;
		tmp_stops = stops = alloca (sizeof (ArtGradientStop) * (n_stops + 2));
		if(gradient->stops[0].offset > EPSILON /* 0.0 */)
		{
			memcpy (tmp_stops, gradient->stops, sizeof (ArtGradientStop));
			tmp_stops[0].offset = 0.0;
			tmp_stops += 1;
			extra_stops++;
		}
		memcpy (tmp_stops, gradient->stops, sizeof (ArtGradientStop) * n_stops);
		if(gradient->stops[n_stops-1].offset < (1.0 - EPSILON))
		{
			tmp_stops += n_stops;
			memcpy (tmp_stops, &gradient->stops[n_stops-1], sizeof (ArtGradientStop));
			tmp_stops[0].offset = 1.0;
			extra_stops++;
		}
		n_stops += extra_stops;


#ifdef DEBUG_SPEW
		printf ("start/stop modified stops:");
		for(i=0;i<n_stops;i++)
		{
			printf ("%f, ", stops[i].offset);
		}
		printf ("\n");
#endif

	}

	if(spread == ART_GRADIENT_REFLECT)
	{
		tmp_stops = stops;
		stops = alloca (sizeof (ArtGradientStop) * n_stops * 2);
		memcpy (stops, tmp_stops, sizeof (ArtGradientStop) * n_stops);

		for(i = 0; i< n_stops; i++)
		{
			stops[n_stops * 2 - 1 - i].offset = (1.0 - stops[i].offset / 2.0);
			memcpy (stops[n_stops * 2 - 1 - i].color, stops[i].color, sizeof (stops[i].color));
			stops[i].offset = stops[i].offset / 2.0;
		}

		spread = ART_GRADIENT_REPEAT;
		offset = offset / 2.0;
		d_offset = d_offset / 2.0;

		n_stops = 2 * n_stops;

#ifdef DEBUG_SPEW
		printf ("reflect modified stops:");
		for(i=0;i<n_stops;i++)
		{
			printf ("%f, ", stops[i].offset);
		}
		printf ("\n");
#endif
	}

	offset_fraction = offset - floor (offset);
#ifdef DEBUG_SPEW
	printf ("inital offset: %f, fraction: %f d_offset: %f\n", offset, offset_fraction, d_offset);
#endif
	/* ix is selected so that offset_fraction is
		 stops[ix-1] <= offset_fraction <= stops[ix]
		 If offset_fraction is equal to one of the edges, ix
		 is selected so the the section of the line extending
		 in the same direction as d_offset is between ix-1 and ix.
	*/
	for(ix = 0; ix < n_stops; ix++)
		if(stops[ix].offset > offset_fraction ||
			 (d_offset < 0.0 && fabs (stops[ix].offset - offset_fraction) < EPSILON))
			break;
	if(ix == 0)
		ix = n_stops - 1;
	else if(ix == n_stops)
		ix = n_stops - 1;

#ifdef DEBUG_SPEW
	printf ("Initial ix: %d\n", ix);
#endif
#if 0
	assert (ix > 0);
	assert (ix < n_stops);
	assert ((stops[ix-1].offset <= offset_fraction + EPSILON) ||
					((stops[ix].offset > (1.0 - EPSILON)) && (offset_fraction < EPSILON	/* == 0.0*/)));
	/*assert (offset_fraction <= stops[ix].offset);*/
	/* FIXME: These asserts may be broken, it is for now
		 safer to not use them.  Should be fixed!
		 See bug #121850
	assert ((offset_fraction != stops[ix-1].offset) ||
		(d_offset >= 0.0));
	assert ((offset_fraction != stops[ix].offset) ||
		(d_offset <= 0.0));
	*/
#endif  
	while(width > 0)
	{
#ifdef DEBUG_SPEW
		printf ("ix: %d\n", ix);
		printf ("start offset: %f\n", offset);
#endif
		ksvg_calc_color_at (stops, n_stops,
												spread,
												offset,
												offset_fraction,
												(d_offset > -EPSILON),
												ix,
												color1);

		if(d_offset > 0)
			next_stop = ix;
		else
			next_stop	= ix-1;

#ifdef DEBUG_SPEW
		printf ("next_stop: %d\n", next_stop);
#endif
		if(fabs (d_offset) > EPSILON)
		{
			double o;
			o = offset_fraction;

			if((fabs (o) <= EPSILON) && (ix == n_stops - 1))
				o = 1.0;
			else if((fabs (o-1.0) <= EPSILON) && (ix == 1))
				o = 0.0;

#ifdef DEBUG_SPEW
			printf ("o: %f\n", o);
#endif
			len = (int)floor (fabs ((stops[next_stop].offset - o) / d_offset)) + 1;
			len = MAX (len, 0);
			len = MIN (len, width);
		}
		else
		{
			len = width;
		}
#ifdef DEBUG_SPEW
		printf ("len: %d\n", len);
#endif
		if(len > 0)
		{
			offset = offset + (len-1) * d_offset;
			offset_fraction = offset - floor (offset);
#ifdef DEBUG_SPEW
			printf ("end offset: %f, fraction: %f\n", offset, offset_fraction);
#endif	  
			ksvg_calc_color_at (stops, n_stops,
													spread,
													offset,
													offset_fraction,
													(d_offset < EPSILON),
													ix,
													color2);

			art_ksvg_rgba_gradient_run (bufp,
																	color1,
																	color2,
																	len);
			offset += d_offset;
			offset_fraction = offset - floor (offset);
		}

		if(d_offset > 0)
		{
			do
			{
				ix++;
				if(ix == n_stops)
					ix = 1;
				/* Note: offset_fraction can actually be one here on x86 machines that
		 does calculations with extended precision, but later rounds to 64bit.
		 This happens if the 80bit offset_fraction is larger than the
		 largest 64bit double that is less than one.
				*/
			}
			while(!((stops[ix-1].offset <= offset_fraction &&
							 offset_fraction < stops[ix].offset) ||
							(ix == 1 && offset_fraction > (1.0 - EPSILON)))); 
		}
		else
		{
			do
			{
				ix--;
				if(ix == 0)
					ix = n_stops - 1;
			}
			while(!((stops[ix-1].offset < offset_fraction &&
							 offset_fraction <= stops[ix].offset) ||
							(ix == n_stops - 1 && offset_fraction < EPSILON	/* == 0.0*/)));
		}

		bufp += 4*len;
		width -= len;
	}
}

static void
art_ksvg_render_gradient_linear_done (ArtRenderCallback *self, ArtRender *render)
{
	art_free (self);
}

static void
art_ksvg_render_gradient_linear_render (ArtRenderCallback *self, ArtRender *render,
																				art_u8 *dest, int y)
{
	ArtImageSourceGradLin *z = (ArtImageSourceGradLin *)self;
	const ArtKSVGGradientLinear *gradient = &(z->gradient);
	int pixstride = (render->n_chan + 1) * (render->depth >> 3);
	int x;
	int width = render->x1 - render->x0;
	double offset, d_offset;
	double actual_offset;
	int n_stops = gradient->n_stops;
	ArtGradientStop *stops = gradient->stops;
	art_u8 *bufp = render->image_buf;
	ArtGradientSpread spread = gradient->spread;

	offset = render->x0 * gradient->affine[0] + y * gradient->affine[2] + gradient->affine[4];
	d_offset = gradient->affine[0];

	for(x = 0; x < width; x++)
	{
		if(spread == ART_GRADIENT_PAD)
			actual_offset = offset;
		else if(spread == ART_GRADIENT_REPEAT)
			actual_offset = offset - floor (offset);
		else /* (spread == ART_GRADIENT_REFLECT) */
		{
			double tmp;

			tmp = offset - 2 * floor (0.5 * offset);
			actual_offset = tmp > 1 ? 2 - tmp : tmp;
		}
		art_ksvg_render_gradient_setpix (render, bufp, n_stops, stops, actual_offset, gradient->interpolation);
		offset += d_offset;
		bufp += pixstride;
	}
}

static void
art_ksvg_render_gradient_linear_negotiate (ArtImageSource *self, ArtRender *render,
																					 ArtImageSourceFlags *p_flags,
																					 int *p_buf_depth, ArtAlphaType *p_alpha)
{
	ArtImageSourceGradLin *z = (ArtImageSourceGradLin *)self;

	if(render->depth == 8 &&
		 render->n_chan == 3 &&
		 z->gradient.interpolation == ART_KSVG_SRGB_INTERPOLATION)
	{
		/* The optimised renderer doesn't support linearRGB interpolation at the moment */
		/* so we only use it for sRGB, which is more common anyway. */
		self->super.render = art_ksvg_render_gradient_linear_render_8;
		*p_flags = 0;
		*p_buf_depth = 8;
		*p_alpha = ART_ALPHA_SEPARATE;
		return;
	}

	self->super.render = art_ksvg_render_gradient_linear_render;
	*p_flags = 0;
	*p_buf_depth = render->depth;
	*p_alpha = ART_ALPHA_SEPARATE;
}

/**
 * art_render_gradient_linear: Add a linear gradient image source.
 * @render: The render object.
 * @gradient: The linear gradient.
 *
 * Adds the linear gradient @gradient as the image source for rendering
 * in the render object @render.
 **/
void
art_ksvg_render_gradient_linear (ArtRender *render,
																 const ArtKSVGGradientLinear *gradient,
																 ArtFilterLevel level)
{
	ArtImageSourceGradLin *image_source = art_alloc (sizeof (ArtImageSourceGradLin) +
																									 sizeof (ArtGradientStop) * (gradient->n_stops - 1));

	image_source->super.super.render = NULL;
	image_source->super.super.done = art_ksvg_render_gradient_linear_done;
	image_source->super.negotiate = art_ksvg_render_gradient_linear_negotiate;

	/* copy the gradient into the structure */
	image_source->gradient = *gradient;
	image_source->gradient.stops = image_source->stops;
	memcpy (image_source->gradient.stops, gradient->stops, sizeof (ArtGradientStop) * gradient->n_stops);

	art_render_add_image_source (render, &image_source->super);
}