circuitpython/shared-module/vectorio/Polygon.c

#include "shared-module/vectorio/__init__.h"
#include "shared-bindings/vectorio/Polygon.h"
#include "shared-module/displayio/area.h"

#include "py/runtime.h"
#include "py/gc.h"

#include "stdlib.h"
#include <stdio.h>


#define VECTORIO_POLYGON_DEBUG(...) (void)0
// #define VECTORIO_POLYGON_DEBUG(...) mp_printf(&mp_plat_print __VA_OPT__(,) __VA_ARGS__)


// Converts a list of points tuples to a flat list of ints for speedier internal use.
// Also validates the points.
static void _clobber_points_list(vectorio_polygon_t *self, mp_obj_t points_tuple_list) {
    size_t len = 0;
    mp_obj_t *items;
    mp_obj_list_get(points_tuple_list, &len, &items);
    VECTORIO_POLYGON_DEBUG("polygon_points_list len: %d\n", len);

    if ( len < 3 ) {
        mp_raise_TypeError_varg(translate("Polygon needs at least 3 points"));
    }

    if ( self->len < 2*len ) {
        if ( self->points_list != NULL ) {
            gc_free( self->points_list );
        }
        self->points_list = gc_alloc( 2 * len * sizeof(int), false, false );
    }
    self->len = 2*len;

    for ( size_t i = 0; i < len; ++i) {
        size_t tuple_len = 0;
        mp_obj_t *tuple_items;
        mp_obj_tuple_get(items[i], &tuple_len, &tuple_items);

        if (tuple_len != 2) {
            mp_raise_ValueError_varg(translate("%q must be a tuple of length 2"), MP_QSTR_point);
        }
        if (   !mp_obj_get_int_maybe(tuple_items[ 0 ], &self->points_list[2*i    ])
            || !mp_obj_get_int_maybe(tuple_items[ 1 ], &self->points_list[2*i + 1])
        ) {
            self->len = 0;
            gc_free( self->points_list );
            self->points_list = NULL;
            mp_raise_ValueError_varg(translate("unsupported %q type"), MP_QSTR_point);
        }
    }
}



void common_hal_vectorio_polygon_construct(vectorio_polygon_t *self, mp_obj_t points_list) {
    VECTORIO_POLYGON_DEBUG("%p polygon_construct\n", self);
    self->points_list = NULL;
    self->len = 0;
    self->on_dirty.obj = NULL;
    _clobber_points_list( self, points_list );
}


mp_obj_t common_hal_vectorio_polygon_get_points(vectorio_polygon_t *self) {
    return self->points_list;
}
void common_hal_vectorio_polygon_set_points(vectorio_polygon_t *self, mp_obj_t points_list) {
    _clobber_points_list( self, points_list );
    if (self->on_dirty.obj != NULL) {
        self->on_dirty.event(self->on_dirty.obj);
    }
}

void common_hal_vectorio_polygon_set_on_dirty(vectorio_polygon_t *self, vectorio_event_t notification) {
    if ( self->on_dirty.obj != NULL ) {
        mp_raise_TypeError(translate("polygon can only be registered in one parent"));
    }
    self->on_dirty = notification;
}


void common_hal_vectorio_polygon_get_area(void *polygon, displayio_area_t *area) {
    vectorio_polygon_t *self = polygon;

    area->x1 = SHRT_MAX;
    area->y1 = SHRT_MAX;
    area->x2 = SHRT_MIN;
    area->y2 = SHRT_MIN;
    for (size_t i=0; i < self->len; ++i) {
        int x = self->points_list[i];
        ++i;
        int y = self->points_list[i];
        if (x <= area->x1) area->x1 = x-1;
        if (y <= area->y1) area->y1 = y-1;
        if (x >= area->x2) area->x2 = x+1;
        if (y >= area->y2) area->y2 = y+1;
    }
}


// <0 if the point is to the left of the line vector
//  0 if the point is on the line
// >0 if the point is to the right of the line vector
__attribute__((always_inline)) static inline int line_side( mp_int_t x1, mp_int_t y1, mp_int_t x2, mp_int_t y2, int16_t px, int16_t py ) {
    return (px - x1) * (y2 - y1)
         - (py - y1) * (x2 - x1);
}


uint32_t common_hal_vectorio_polygon_get_pixel(void *obj, int16_t x, int16_t y) {
    VECTORIO_POLYGON_DEBUG("%p polygon get_pixel %d, %d\n", obj, x, y);
    vectorio_polygon_t *self = obj;

    if (self->len == 0) {
        return 0;
    }

    int winding_number = 0;
    int x1 = self->points_list[0];
    int y1 = self->points_list[1];
    for (size_t i=2; i <= self->len + 1; ++i) {
        VECTORIO_POLYGON_DEBUG("  {(%3d, %3d),", x1, y1);
        int x2 = self->points_list[i % self->len];
        ++i;
        int y2 = self->points_list[i % self->len];
        VECTORIO_POLYGON_DEBUG(" (%3d, %3d)}\n", x2, y2);
        if ( y1 <= y ) {
            if ( y2 > y && line_side(x1, y1, x2, y2, x, y) > 0 ) {
                // Wind up, point is to the right of the edge vector
                ++winding_number;
                VECTORIO_POLYGON_DEBUG("    wind:%2d winding_number:%2d\n", 1, winding_number);
            }
        } else if ( y2 <= y && line_side(x1, y1, x2, y2, x, y) < 0 ) {
            // Wind down, point is to the left of the edge vector
            --winding_number;
            VECTORIO_POLYGON_DEBUG("    wind:%2d winding_number:%2d\n", -1, winding_number);
        }

        x1 = x2;
        y1 = y2;
    }
    return winding_number == 0 ? 0 : 1;
}