genode/repos/gems/include/polygon_gfx/polygon_painter_base.h

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/*
* \brief Common base of polygon painters
* \author Norman Feske
* \date 2015-06-19
*/
/*
* Copyright (C) 2015-2017 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU Affero General Public License version 3.
*/
#ifndef _INCLUDE__POLYGON_GFX__POLYGON_PAINTER_BASE_H_
#define _INCLUDE__POLYGON_GFX__POLYGON_PAINTER_BASE_H_
/* Genode includes */
#include <base/allocator.h>
#include <util/geometry.h>
#include <util/misc_math.h>
#include <polygon_gfx/clipping.h>
namespace Polygon { class Painter_base; }
class Polygon::Painter_base
{
private:
/**
* Interpolate linearly between start value and end value
*/
static inline void _interpolate(int start, int end, int *dst,
unsigned num_values)
{
/* sanity check */
if (num_values == 0) return;
int const ascent = ((end - start)<<16)/(int)num_values;
for (int curr = start<<16; num_values--; curr += ascent)
*dst++ = curr>>16;
}
/**
* Clip polygon against boundary
*
* \param src Array of unclipped source-polygon points
* \param src_num_points Number of source-polygon points
* \param dst Destination buffer for clipped polygon points
* \param clip Clipping boundary
* \return Number of resulting polygon points
*/
template <typename CLIPPER, typename POINT>
static inline int _clip_1d(POINT const *src, unsigned src_num_points,
POINT *dst, int clip)
{
/*
* Walk along the polygon edges. Each time when crossing the
* clipping border, a new polygon point is created at the
* intersection point. All polygon points outside the clipping area
* are discarded.
*/
unsigned dst_num_points = 0;
for (unsigned i = 0; i < src_num_points; i++) {
POINT curr = *src++;
POINT next = *src;
bool curr_inside = CLIPPER::inside(curr, clip);
bool next_inside = CLIPPER::inside(next, clip);
/* add current point to resulting polygon if inside clipping area */
if (curr_inside)
dst[dst_num_points++] = curr;
/* add point of intersection when walking outside of the clipping area */
if (curr_inside && !next_inside)
dst[dst_num_points++] = CLIPPER::clip(curr, next, clip);
/* add point of intersection when walking inside to the clipping area */
if (!curr_inside && next_inside)
dst[dst_num_points++] = CLIPPER::clip(curr, next, clip);
}
/* store coordinates of the first point also at the end of the polygon */
dst[dst_num_points] = dst[0];
return dst_num_points;
}
public:
typedef Genode::Rect<> Rect;
typedef Genode::Area<> Area;
/**
* Buffers used for storing interpolated attribute values along a left
* or right polygon edges.
*
* The edge buffers are partitioned into subsequent sub buffers with a
* size corresponding to the maximum y range of the polygon, which is
* the surface height. The different sub buffers are used to hold the
* interpolated edge values for the different polygon-point attributes.
*
* \param N number of attributes
*/
template <unsigned N>
class Edge_buffers
{
private:
Genode::Allocator &_alloc;
unsigned const _edge_len;
Genode::size_t _edges_size() { return N*2*_edge_len*sizeof(int); }
int * const _edges = (int *)_alloc.alloc(_edges_size());
/**
* Noncopyable
*/
Edge_buffers(Edge_buffers const &);
Edge_buffers &operator = (Edge_buffers const &);
public:
Edge_buffers(Genode::Allocator &alloc, unsigned edge_len)
:
_alloc(alloc), _edge_len(edge_len)
{ }
~Edge_buffers() { _alloc.free(_edges, _edges_size()); }
/**
* Return size of a single edge buffer
*/
unsigned edge_len() const { return _edge_len; }
/**
* Return left edge buffer for Nth attribute
*/
int *left(unsigned n) { return _edges + n*2*_edge_len; }
/**
* Return right edge buffer for Nth attribute
*/
int *right(unsigned n) { return _edges + (n*2 + 1)*_edge_len; }
};
/**
* Calculate maximum number of points needed for clipped polygon
*
* When clipping the polygon with 'num_points' points against
* the canvas boundaries, the resulting polygon will have a
* maximum of 'num_points' + 4 points - in the worst case one
* additional point per canvas edge. To ease the further
* processing, we add the coordinates of the first point as an
* additional point to the clipped polygon.
*/
static unsigned max_points_clipped(unsigned num_points)
{
return num_points + 4 + 1;
}
/**
* Clip polygon against clipping rectangle
*
* \param src_points Array of unclipped polygon points
* \param num_points Number of unclipped polygon points
* \param dst_points Buffer for storing the clipped polygon
* \return Number of points of resulting polygon
*
* During the clipping computation, the destination buffer 'dst_points'
* is used to store two polygons. Therefore, the buffer must be
* dimensioned at 2*'max_points_clipped()'. The end result of the
* computation is stored at the beginning of 'dst_points'.
*/
template <typename POINT>
static int clip_polygon(POINT const *src_points, unsigned num_points,
POINT *dst_points, Rect clip)
{
POINT *c0 = dst_points,
*c1 = dst_points + max_points_clipped(num_points);
for (unsigned i = 0; i < num_points; i++)
c0[i] = src_points[i];
/* last point is connected to the first point */
c0[num_points] = c0[0];
/* clip against top, left, bottom, and right clipping boundaries */
typedef Clipper_2d<POINT> Clipper;
num_points = _clip_1d<typename Clipper::Top> (c0, num_points, c1, clip.y1());
num_points = _clip_1d<typename Clipper::Left> (c1, num_points, c0, clip.x1());
num_points = _clip_1d<typename Clipper::Bottom>(c0, num_points, c1, clip.y2());
num_points = _clip_1d<typename Clipper::Right> (c1, num_points, c0, clip.x2());
return num_points;
}
/**
* Determine bounding box of the specified polygon points
*
* \height maximum bounds
*/
template <typename POINT>
static Rect bounding_box(POINT const points[], int num_points, Area area)
{
int x_min = area.w() - 1, x_max = 0;
int y_min = area.h() - 1, y_max = 0;
for (int i = 0; i < num_points; i++) {
x_min = Genode::min(x_min, points[i].x());
x_max = Genode::max(x_max, points[i].x());
y_min = Genode::min(y_min, points[i].y());
y_max = Genode::max(y_max, points[i].y());
}
return Rect(Point_base(x_min, y_min), Point_base(x_max, y_max));
}
/**
* Calculate edge buffers for a polygon
*
* \param N number of edge attributes
*/
template <unsigned N, typename POINT>
void fill_edge_buffers(Edge_buffers<N> &edges,
POINT points[], unsigned num_points)
{
/* for each edge attribute */
for (unsigned i = 0; i < N; i++) {
int * const l_edge = edges.left(i);
int * const r_edge = edges.right(i);
for (unsigned j = 0; j < num_points; j++) {
POINT const p1 = points[j];
POINT const p2 = points[j + 1];
/* request attribute values to interpolate */
int const p1_attr = p1.edge_attr(i);
int const p2_attr = p2.edge_attr(i);
/* horizontal edge */
if (p1.y() == p2.y());
/* right edge */
else if (p1.y() < p2.y())
_interpolate(p1_attr, p2_attr, r_edge + p1.y(), p2.y() - p1.y());
/* left edge */
else
_interpolate(p2_attr, p1_attr, l_edge + p2.y(), p1.y() - p2.y());
}
}
}
};
#endif /* _INCLUDE__POLYGON_GFX__POLYGON_PAINTER_BASE_H_ */