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