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Canvas: new x-fade drawing, two curve widget

This commit is contained in:
Robin Gareus 2014-05-29 03:09:57 +02:00
parent f226ed086b
commit 30f204b90e
6 changed files with 593 additions and 208 deletions
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18
libs/canvas/canvas/curve.h
View File

@ -21,27 +21,25 @@
#include "canvas/visibility.h"
#include "canvas/interpolated_curve.h"
#include "canvas/poly_item.h"
#include "canvas/fill.h"
namespace ArdourCanvas {
class LIBCANVAS_API Curve : public PolyItem, public Fill
class XFadeCurve;
class LIBCANVAS_API Curve : public PolyItem, public Fill, public InterpolatedCurve
{
public:
Curve (Group *);
enum SplineType {
CatmullRomUniform,
CatmullRomCentripetal,
};
enum CurveFill {
None,
Inside,
Outside,
};
void compute_bounding_box () const;
void render (Rect const & area, Cairo::RefPtr<Cairo::Context>) const;
void set (Points const &);
@ -55,14 +53,12 @@ public:
Points samples;
Points::size_type n_samples;
uint32_t points_per_segment;
SplineType curve_type;
InterpolatedCurve::SplineType curve_type;
CurveFill curve_fill;
void interpolate ();
static void interpolate (const Points& coordinates, uint32_t points_per_segment, SplineType, bool closed, Points& results);
};
}
#endif

229
libs/canvas/canvas/interpolated_curve.h Normal file
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@ -0,0 +1,229 @@
/*
Copyright (C) 2013 Paul Davis
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#ifndef __CANVAS_INTERPOLATED_CURVE_H__
#define __CANVAS_INTERPOLATED_CURVE_H__
#include "canvas/visibility.h"
#include "canvas/types.h"
namespace ArdourCanvas {
class LIBCANVAS_API InterpolatedCurve
{
public:
enum SplineType {
CatmullRomUniform,
CatmullRomCentripetal,
};
protected:
/**
* This method will calculate the Catmull-Rom interpolation curve, returning
* it as a list of Coord coordinate objects. This method in particular
* adds the first and last control points which are not visible, but required
* for calculating the spline.
*
* @param coordinates The list of original straight line points to calculate
* an interpolation from.
* @param points_per_segment The integer number of equally spaced points to
* return along each curve. The actual distance between each
* point will depend on the spacing between the control points.
* @return The list of interpolated coordinates.
* @param curve_type Chordal (stiff), Uniform(floppy), or Centripetal(medium)
* @throws gov.ca.water.shapelite.analysis.CatmullRomException if
* points_per_segment is less than 2.
*/
static void
interpolate (const Points& coordinates, uint32_t points_per_segment, SplineType curve_type, bool closed, Points& results)
{
if (points_per_segment < 2) {
return;
}
// Cannot interpolate curves given only two points. Two points
// is best represented as a simple line segment.
if (coordinates.size() < 3) {
results = coordinates;
return;
}
// Copy the incoming coordinates. We need to modify it during interpolation
Points vertices = coordinates;
// Test whether the shape is open or closed by checking to see if
// the first point intersects with the last point. M and Z are ignored.
if (closed) {
// Use the second and second from last points as control points.
// get the second point.
Duple p2 = vertices[1];
// get the point before the last point
Duple pn1 = vertices[vertices.size() - 2];
// insert the second from the last point as the first point in the list
// because when the shape is closed it keeps wrapping around to
// the second point.
vertices.insert(vertices.begin(), pn1);
// add the second point to the end.
vertices.push_back(p2);
} else {
// The shape is open, so use control points that simply extend
// the first and last segments
// Get the change in x and y between the first and second coordinates.
double dx = vertices[1].x - vertices[0].x;
double dy = vertices[1].y - vertices[0].y;
// Then using the change, extrapolate backwards to find a control point.
double x1 = vertices[0].x - dx;
double y1 = vertices[0].y - dy;
// Actaully create the start point from the extrapolated values.
Duple start (x1, y1);
// Repeat for the end control point.
int n = vertices.size() - 1;
dx = vertices[n].x - vertices[n - 1].x;
dy = vertices[n].y - vertices[n - 1].y;
double xn = vertices[n].x + dx;
double yn = vertices[n].y + dy;
Duple end (xn, yn);
// insert the start control point at the start of the vertices list.
vertices.insert (vertices.begin(), start);
// append the end control ponit to the end of the vertices list.
vertices.push_back (end);
}
// When looping, remember that each cycle requires 4 points, starting
// with i and ending with i+3. So we don't loop through all the points.
for (Points::size_type i = 0; i < vertices.size() - 3; i++) {
// Actually calculate the Catmull-Rom curve for one segment.
Points r;
_interpolate (vertices, i, points_per_segment, curve_type, r);
// Since the middle points are added twice, once for each bordering
// segment, we only add the 0 index result point for the first
// segment. Otherwise we will have duplicate points.
if (results.size() > 0) {
r.erase (r.begin());
}
// Add the coordinates for the segment to the result list.
results.insert (results.end(), r.begin(), r.end());
}
}
private:
/**
* Calculate the same values but introduces the ability to "parameterize" the t
* values used in the calculation. This is based on Figure 3 from
* http://www.cemyuksel.com/research/catmullrom_param/catmullrom.pdf
*
* @param p An array of double values of length 4, where interpolation
* occurs from p1 to p2.
* @param time An array of time measures of length 4, corresponding to each
* p value.
* @param t the actual interpolation ratio from 0 to 1 representing the
* position between p1 and p2 to interpolate the value.
*/
static double
__interpolate (double p[4], double time[4], double t)
{
const double L01 = p[0] * (time[1] - t) / (time[1] - time[0]) + p[1] * (t - time[0]) / (time[1] - time[0]);
const double L12 = p[1] * (time[2] - t) / (time[2] - time[1]) + p[2] * (t - time[1]) / (time[2] - time[1]);
const double L23 = p[2] * (time[3] - t) / (time[3] - time[2]) + p[3] * (t - time[2]) / (time[3] - time[2]);
const double L012 = L01 * (time[2] - t) / (time[2] - time[0]) + L12 * (t - time[0]) / (time[2] - time[0]);
const double L123 = L12 * (time[3] - t) / (time[3] - time[1]) + L23 * (t - time[1]) / (time[3] - time[1]);
const double C12 = L012 * (time[2] - t) / (time[2] - time[1]) + L123 * (t - time[1]) / (time[2] - time[1]);
return C12;
}
/**
* Given a list of control points, this will create a list of points_per_segment
* points spaced uniformly along the resulting Catmull-Rom curve.
*
* @param points The list of control points, leading and ending with a
* coordinate that is only used for controling the spline and is not visualized.
* @param index The index of control point p0, where p0, p1, p2, and p3 are
* used in order to create a curve between p1 and p2.
* @param points_per_segment The total number of uniformly spaced interpolated
* points to calculate for each segment. The larger this number, the
* smoother the resulting curve.
* @param curve_type Clarifies whether the curve should use uniform, chordal
* or centripetal curve types. Uniform can produce loops, chordal can
* produce large distortions from the original lines, and centripetal is an
* optimal balance without spaces.
* @return the list of coordinates that define the CatmullRom curve
* between the points defined by index+1 and index+2.
*/
static void
_interpolate (const Points& points, Points::size_type index, int points_per_segment, SplineType curve_type, Points& results)
{
double x[4];
double y[4];
double time[4];
for (int i = 0; i < 4; i++) {
x[i] = points[index + i].x;
y[i] = points[index + i].y;
time[i] = i;
}
double tstart = 1;
double tend = 2;
if (curve_type != CatmullRomUniform) {
double total = 0;
for (int i = 1; i < 4; i++) {
double dx = x[i] - x[i - 1];
double dy = y[i] - y[i - 1];
if (curve_type == CatmullRomCentripetal) {
total += pow (dx * dx + dy * dy, .25);
} else {
total += pow (dx * dx + dy * dy, .5);
}
time[i] = total;
}
tstart = time[1];
tend = time[2];
}
int segments = points_per_segment - 1;
results.push_back (points[index + 1]);
for (int i = 1; i < segments; i++) {
double xi = __interpolate (x, time, tstart + (i * (tend - tstart)) / segments);
double yi = __interpolate (y, time, tstart + (i * (tend - tstart)) / segments);
results.push_back (Duple (xi, yi));
}
results.push_back (points[index + 2]);
}
};
}
#endif

84
libs/canvas/canvas/xfade_curve.h Normal file
View File

@ -0,0 +1,84 @@
/*
Copyright (C) 2013 Paul Davis
Copyright (C) 2014 Robin Gareus <robin@gareus.org>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#ifndef __CANVAS_XFADECURVE_H__
#define __CANVAS_XFADECURVE_H__
#include "canvas/visibility.h"
#include "canvas/curve.h"
namespace ArdourCanvas {
class LIBCANVAS_API XFadeCurve : public Item, public InterpolatedCurve
{
public:
enum XFadePosition {
Start,
End,
};
XFadeCurve (Group *);
XFadeCurve (Group *, XFadePosition);
void set_fade_position (XFadePosition xfp) { _xfadeposition = xfp; }
void compute_bounding_box () const;
void render (Rect const & area, Cairo::RefPtr<Cairo::Context>) const;
void set_points_per_segment (uint32_t n);
void set_inout (Points const & in, Points const & out);
void set_outline_color (Color c) {
begin_visual_change ();
_outline_color = c;
end_visual_change ();
};
void set_fill_color (Color c) {
begin_visual_change ();
_fill_color = c;
end_visual_change ();
}
private:
struct CanvasCurve {
CanvasCurve() : n_samples(0) { }
Points points;
Points samples;
Points::size_type n_samples;
};
Cairo::Path * get_path(Rect const &, Cairo::RefPtr<Cairo::Context>, CanvasCurve const &) const;
void close_path(Rect const &, Cairo::RefPtr<Cairo::Context>, CanvasCurve const &p, bool) const;
uint32_t points_per_segment;
CanvasCurve _in;
CanvasCurve _out;
XFadePosition _xfadeposition;
Color _outline_color;
Color _fill_color;
void interpolate ();
};
}
#endif

197
libs/canvas/curve.cc
View File

@ -74,205 +74,10 @@ void
Curve::interpolate ()
{
samples.clear ();
interpolate (_points, points_per_segment, CatmullRomCentripetal, false, samples);
InterpolatedCurve::interpolate (_points, points_per_segment, CatmullRomCentripetal, false, samples);
n_samples = samples.size();
}
/* Cartmull-Rom code from http://stackoverflow.com/questions/9489736/catmull-rom-curve-with-no-cusps-and-no-self-intersections/19283471#19283471
*
* Thanks to Ted for his Java version, which I translated into Ardour-idiomatic
* C++ here.
*/
/**
* Calculate the same values but introduces the ability to "parameterize" the t
* values used in the calculation. This is based on Figure 3 from
* http://www.cemyuksel.com/research/catmullrom_param/catmullrom.pdf
*
* @param p An array of double values of length 4, where interpolation
* occurs from p1 to p2.
* @param time An array of time measures of length 4, corresponding to each
* p value.
* @param t the actual interpolation ratio from 0 to 1 representing the
* position between p1 and p2 to interpolate the value.
*/
static double
__interpolate (double p[4], double time[4], double t)
{
const double L01 = p[0] * (time[1] - t) / (time[1] - time[0]) + p[1] * (t - time[0]) / (time[1] - time[0]);
const double L12 = p[1] * (time[2] - t) / (time[2] - time[1]) + p[2] * (t - time[1]) / (time[2] - time[1]);
const double L23 = p[2] * (time[3] - t) / (time[3] - time[2]) + p[3] * (t - time[2]) / (time[3] - time[2]);
const double L012 = L01 * (time[2] - t) / (time[2] - time[0]) + L12 * (t - time[0]) / (time[2] - time[0]);
const double L123 = L12 * (time[3] - t) / (time[3] - time[1]) + L23 * (t - time[1]) / (time[3] - time[1]);
const double C12 = L012 * (time[2] - t) / (time[2] - time[1]) + L123 * (t - time[1]) / (time[2] - time[1]);
return C12;
}
/**
* Given a list of control points, this will create a list of points_per_segment
* points spaced uniformly along the resulting Catmull-Rom curve.
*
* @param points The list of control points, leading and ending with a
* coordinate that is only used for controling the spline and is not visualized.
* @param index The index of control point p0, where p0, p1, p2, and p3 are
* used in order to create a curve between p1 and p2.
* @param points_per_segment The total number of uniformly spaced interpolated
* points to calculate for each segment. The larger this number, the
* smoother the resulting curve.
* @param curve_type Clarifies whether the curve should use uniform, chordal
* or centripetal curve types. Uniform can produce loops, chordal can
* produce large distortions from the original lines, and centripetal is an
* optimal balance without spaces.
* @return the list of coordinates that define the CatmullRom curve
* between the points defined by index+1 and index+2.
*/
static void
_interpolate (const Points& points, Points::size_type index, int points_per_segment, Curve::SplineType curve_type, Points& results)
{
double x[4];
double y[4];
double time[4];
for (int i = 0; i < 4; i++) {
x[i] = points[index + i].x;
y[i] = points[index + i].y;
time[i] = i;
}
double tstart = 1;
double tend = 2;
if (curve_type != Curve::CatmullRomUniform) {
double total = 0;
for (int i = 1; i < 4; i++) {
double dx = x[i] - x[i - 1];
double dy = y[i] - y[i - 1];
if (curve_type == Curve::CatmullRomCentripetal) {
total += pow (dx * dx + dy * dy, .25);
} else {
total += pow (dx * dx + dy * dy, .5);
}
time[i] = total;
}
tstart = time[1];
tend = time[2];
}
int segments = points_per_segment - 1;
results.push_back (points[index + 1]);
for (int i = 1; i < segments; i++) {
double xi = __interpolate (x, time, tstart + (i * (tend - tstart)) / segments);
double yi = __interpolate (y, time, tstart + (i * (tend - tstart)) / segments);
results.push_back (Duple (xi, yi));
}
results.push_back (points[index + 2]);
}
/**
* This method will calculate the Catmull-Rom interpolation curve, returning
* it as a list of Coord coordinate objects. This method in particular
* adds the first and last control points which are not visible, but required
* for calculating the spline.
*
* @param coordinates The list of original straight line points to calculate
* an interpolation from.
* @param points_per_segment The integer number of equally spaced points to
* return along each curve. The actual distance between each
* point will depend on the spacing between the control points.
* @return The list of interpolated coordinates.
* @param curve_type Chordal (stiff), Uniform(floppy), or Centripetal(medium)
* @throws gov.ca.water.shapelite.analysis.CatmullRomException if
* points_per_segment is less than 2.
*/
void
Curve::interpolate (const Points& coordinates, uint32_t points_per_segment, SplineType curve_type, bool closed, Points& results)
{
if (points_per_segment < 2) {
return;
}
// Cannot interpolate curves given only two points. Two points
// is best represented as a simple line segment.
if (coordinates.size() < 3) {
results = coordinates;
return;
}
// Copy the incoming coordinates. We need to modify it during interpolation
Points vertices = coordinates;
// Test whether the shape is open or closed by checking to see if
// the first point intersects with the last point. M and Z are ignored.
if (closed) {
// Use the second and second from last points as control points.
// get the second point.
Duple p2 = vertices[1];
// get the point before the last point
Duple pn1 = vertices[vertices.size() - 2];
// insert the second from the last point as the first point in the list
// because when the shape is closed it keeps wrapping around to
// the second point.
vertices.insert(vertices.begin(), pn1);
// add the second point to the end.
vertices.push_back(p2);
} else {
// The shape is open, so use control points that simply extend
// the first and last segments
// Get the change in x and y between the first and second coordinates.
double dx = vertices[1].x - vertices[0].x;
double dy = vertices[1].y - vertices[0].y;
// Then using the change, extrapolate backwards to find a control point.
double x1 = vertices[0].x - dx;
double y1 = vertices[0].y - dy;
// Actaully create the start point from the extrapolated values.
Duple start (x1, y1);
// Repeat for the end control point.
int n = vertices.size() - 1;
dx = vertices[n].x - vertices[n - 1].x;
dy = vertices[n].y - vertices[n - 1].y;
double xn = vertices[n].x + dx;
double yn = vertices[n].y + dy;
Duple end (xn, yn);
// insert the start control point at the start of the vertices list.
vertices.insert (vertices.begin(), start);
// append the end control ponit to the end of the vertices list.
vertices.push_back (end);
}
// When looping, remember that each cycle requires 4 points, starting
// with i and ending with i+3. So we don't loop through all the points.
for (Points::size_type i = 0; i < vertices.size() - 3; i++) {
// Actually calculate the Catmull-Rom curve for one segment.
Points r;
_interpolate (vertices, i, points_per_segment, curve_type, r);
// Since the middle points are added twice, once for each bordering
// segment, we only add the 0 index result point for the first
// segment. Otherwise we will have duplicate points.
if (results.size() > 0) {
r.erase (r.begin());
}
// Add the coordinates for the segment to the result list.
results.insert (results.end(), r.begin(), r.end());
}
}
void
Curve::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) const
{

3
libs/canvas/wscript
View File

@ -54,7 +54,8 @@ canvas_sources = [
'text.cc',
'types.cc',
'utils.cc',
'wave_view.cc'
'wave_view.cc',
'xfade_curve.cc',
]
def options(opt):

270
libs/canvas/xfade_curve.cc Normal file
View File

@ -0,0 +1,270 @@
/*
Copyright (C) 2013 Paul Davis
Copyright (C) 2014 Robin Gareus <robin@gareus.org>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <cmath>
#include <exception>
#include <algorithm>
#include "canvas/utils.h"
#include "canvas/xfade_curve.h"
#include "canvas/interpolated_curve.h"
using namespace ArdourCanvas;
using std::min;
using std::max;
XFadeCurve::XFadeCurve (Group* parent)
: Item (parent)
, points_per_segment (24)
, _xfadeposition (Start)
, _outline_color (0x000000ff)
, _fill_color (0x22448880)
{
}
XFadeCurve::XFadeCurve (Group* parent, XFadePosition pos)
: Item (parent)
, points_per_segment (24)
, _xfadeposition (pos)
, _outline_color (0x000000ff)
, _fill_color (0x22448880)
{
}
void
XFadeCurve::compute_bounding_box () const
{
if (!_in.points.empty() && !_out.points.empty()) {
Rect bbox;
Points::const_iterator i;
if (!_in.points.empty()) {
i = _in.points.begin();
bbox.x0 = bbox.x1 = i->x;
bbox.y0 = bbox.y1 = i->y;
++i;
while (i != _in.points.end()) {
bbox.x0 = min (bbox.x0, i->x);
bbox.y0 = min (bbox.y0, i->y);
bbox.x1 = max (bbox.x1, i->x);
bbox.y1 = max (bbox.y1, i->y);
++i;
}
} else {
i = _out.points.begin();
bbox.x0 = bbox.x1 = i->x;
bbox.y0 = bbox.y1 = i->y;
}
if (!_out.points.empty()) {
i = _out.points.begin();
while (i != _out.points.end()) {
bbox.x0 = min (bbox.x0, i->x);
bbox.y0 = min (bbox.y0, i->y);
bbox.x1 = max (bbox.x1, i->x);
bbox.y1 = max (bbox.y1, i->y);
++i;
}
}
_bounding_box = bbox.expand (1.0);
} else {
_bounding_box = boost::optional<Rect> ();
}
_bounding_box_dirty = false;
}
void
XFadeCurve::set_inout (Points const & in, Points const & out)
{
if (_in.points == in && _out.points == out) {
return;
}
begin_change ();
_in.points = in;
_out.points = out;
_bounding_box_dirty = true;
interpolate ();
end_change ();
}
void
XFadeCurve::set_points_per_segment (uint32_t n)
{
points_per_segment = n;
interpolate ();
redraw ();
}
void
XFadeCurve::interpolate ()
{
_in.samples.clear ();
InterpolatedCurve::interpolate (_in.points, points_per_segment, CatmullRomCentripetal, false, _in.samples);
_in.n_samples = _in.samples.size();
_out.samples.clear ();
InterpolatedCurve::interpolate (_out.points, points_per_segment, CatmullRomCentripetal, false, _out.samples);
_out.n_samples = _out.samples.size();
}
Cairo::Path *
XFadeCurve::get_path(Rect const & area, Cairo::RefPtr<Cairo::Context> context, CanvasCurve const &c) const
{
assert(c.points.size() > 1);
context->begin_new_path ();
Duple window_space;
if (c.points.size () == 2) {
window_space = item_to_window (c.points.front());
context->move_to (window_space.x, window_space.y);
window_space = item_to_window (c.points.back());
context->line_to (window_space.x, window_space.y);
} else {
/* find left and right-most sample */
Points::size_type left = 0;
Points::size_type right = c.n_samples;
for (Points::size_type idx = 0; idx < c.n_samples - 1; ++idx) {
left = idx;
window_space = item_to_window (Duple (c.samples[idx].x, 0.0));
if (window_space.x >= area.x0) break;
}
for (Points::size_type idx = c.n_samples; idx > left + 1; --idx) {
window_space = item_to_window (Duple (c.samples[idx].x, 0.0));
if (window_space.x <= area.x1) break;
right = idx;
}
/* draw line between samples */
window_space = item_to_window (Duple (c.samples[left].x, c.samples[left].y));
context->move_to (window_space.x, window_space.y);
Coord last_x = round(window_space.x);
for (uint32_t idx = left + 1; idx < right; ++idx) {
window_space = item_to_window (Duple (c.samples[idx].x, c.samples[idx].y));
if (last_x == round(window_space.x)) continue;
last_x = round(window_space.x);
context->line_to (last_x - .5 , window_space.y);
}
}
return context->copy_path ();
}
void
XFadeCurve::close_path(Rect const & area, Cairo::RefPtr<Cairo::Context> context, CanvasCurve const &c, bool inside) const
{
Duple window_space;
if (inside) {
window_space = item_to_window (Duple(c.points.back().x, area.height()));
context->line_to (window_space.x, window_space.y);
window_space = item_to_window (Duple(c.points.front().x, area.height()));
context->line_to (window_space.x, window_space.y);
context->close_path();
} else {
window_space = item_to_window (Duple(c.points.back().x, 0.0));
context->line_to (window_space.x, window_space.y);
window_space = item_to_window (Duple(c.points.front().x, 0.0));
context->line_to (window_space.x, window_space.y);
context->close_path();
}
}
void
XFadeCurve::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) const
{
if (!_bounding_box) { return; }
if (_in.points.size() < 2) { return; }
if (_out.points.size() < 2) { return; }
Rect self = item_to_window (_bounding_box.get());
boost::optional<Rect> d = self.intersection (area);
assert (d);
Rect draw = d.get ();
context->save ();
context->rectangle (draw.x0, draw.y0, draw.width(), draw.height());
context->clip ();
/* expand drawing area by several pixels on each side to avoid cairo stroking effects at the boundary.
* they will still occur, but cairo's clipping will hide them.
*/
draw = draw.expand (4.0);
Cairo::Path *path_in = get_path(draw, context, _in);
Cairo::Path *path_out = get_path(draw, context, _out);
Color outline_shaded = _outline_color;
outline_shaded = 0.5 * (outline_shaded & 0xff) + (outline_shaded & ~0xff);
Color fill_shaded = _fill_color;
fill_shaded = 0.5 * (fill_shaded & 0xff) + (fill_shaded & ~0xff);
#define IS (_xfadeposition == Start)
/* fill primary fade */
context->begin_new_path ();
context->append_path (IS ? *path_in : *path_out);
close_path(draw, context, IS ?_in : _out, false);
set_source_rgba (context, _fill_color);
context->fill ();
/* fill background fade */
context->save ();
context->begin_new_path ();
context->append_path (IS ? *path_in : *path_out);
close_path(draw, context, IS ? _in : _out, true);
//context->set_fill_rule (Cairo::FILL_RULE_EVEN_ODD);
context->clip ();
context->begin_new_path ();
context->append_path (IS ? *path_out: *path_in);
close_path(draw, context, IS ? _out : _in, true);
set_source_rgba (context, fill_shaded);
//context->set_fill_rule (Cairo::FILL_RULE_WINDING);
context->fill ();
context->restore ();
/* draw lines over fills */
set_source_rgba (context, IS ? _outline_color : outline_shaded);
context->set_line_width (IS ? 1.0 : .5);
context->begin_new_path ();
context->append_path (*path_in);
context->stroke();
set_source_rgba (context, IS ? outline_shaded :_outline_color);
context->set_line_width (IS ? .5 : 1.0);
context->begin_new_path ();
context->append_path (*path_out);
context->stroke();
context->restore ();
delete path_in;
delete path_out;
}