weston/libweston/vertex-clipping.h

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/*
* Copyright © 2012 Intel Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice (including the
* next paragraph) shall be included in all copies or substantial
* portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#ifndef _WESTON_VERTEX_CLIPPING_H
#define _WESTON_VERTEX_CLIPPING_H
#include <stddef.h>
#include <stdbool.h>
#include <pixman.h>
struct clipper_vertex {
float x, y;
};
struct clipper_quad {
struct clipper_vertex polygon[4];
struct clipper_vertex bbox[2]; /* Valid if !axis_aligned. */
bool axis_aligned;
};
/*
* Initialize a 'quad' clipping context. 'polygon' points to an array of 4
* vertices defining a convex quadrilateral of any winding order. Call
* 'clipper_quad_clip()' to clip an initialized 'quad' to a clipping box.
* Clipping is faster if 'polygon' is an axis-aligned rectangle with edges
* parallel to the axes of the coordinate space. 'axis_aligned' indicates
* whether 'polygon' respects the conditions above.
*/
void
clipper_quad_init(struct clipper_quad *quad,
const struct clipper_vertex polygon[4],
bool axis_aligned);
/*
* Compute the boundary vertices of the intersection of a convex quadrilateral
* stored into a 'quad' clipping context and a clipping 'box'. 'box' points to
* an array of 2 vertices where the values of the 1st vertex are less than or
* equal to the values of the 2nd vertex. Either 0 or [3, 8] resulting vertices,
* with the same winding order than the 'polygon' passed to
* 'clipper_quad_init()', are written to 'vertices'. The return value is the
* number of vertices created.
*/
int
clipper_quad_clip(struct clipper_quad *quad,
const struct clipper_vertex box[2],
struct clipper_vertex *restrict vertices);
/*
* Utility function calling 'clipper_quad_clip()' but taking a pixman_box32
* pointer as clipping box.
*/
int
clipper_quad_clip_box32(struct clipper_quad *quad,
const struct pixman_box32 *box,
struct clipper_vertex *restrict vertices);
float
clipper_float_difference(float a, float b);
#endif