nuclear@5: #include "config.h"
nuclear@5: #include <string.h>
nuclear@6: #include <assert.h>
nuclear@5: #include "polyfill.h"
nuclear@5: #include "fixed.h"
nuclear@5: #include "gbasys.h"
nuclear@5: 
nuclear@5: static void fill_scanline(int y, int x0, int x1, uint16_t color);
nuclear@5: 
nuclear@5: void draw_poly(int num, const pvec3 *verts, uint16_t color)
nuclear@5: {
nuclear@5: 	int i, topidx = 0, botidx = 0;
nuclear@5: 	int lidx[2], ridx[2];
nuclear@5: 	int32_t y, topy, boty;
nuclear@5: 	int32_t ldy, rdy, ldxdy, rdxdy;
nuclear@5: 	int32_t lx, rx;
nuclear@5: 	int start, end;
nuclear@5: 
nuclear@5: 	topy = boty = verts[0].y;
nuclear@5: 	for(i=1; i<num; i++) {
nuclear@5: 		int32_t y = verts[i].y;
nuclear@5: 		if(y < topy) {
nuclear@5: 			topy = y;
nuclear@5: 			topidx = i;
nuclear@5: 		}
nuclear@5: 		if(y > boty) {
nuclear@5: 			boty = y;
nuclear@5: 			botidx = i;
nuclear@5: 		}
nuclear@5: 	}
nuclear@5: 
nuclear@5: 	lidx[0] = ridx[0] = topidx;
nuclear@5: 	lidx[1] = topidx ? topidx - 1 : num - 1;
nuclear@5: 	ridx[1] = (topidx + 1) % num;
nuclear@5: 
nuclear@6: 	if(verts[ridx[1]].x < verts[lidx[1]].x) {
nuclear@5: 		return;	/* backface (CCW) */
nuclear@5: 	}
nuclear@5: 
nuclear@5: 	lx = rx = verts[lidx[0]].x;
nuclear@5: 
nuclear@6: 	/* TODO handle ldy == 0 or rdy == 0 */
nuclear@5: 	ldy = verts[lidx[1]].y - verts[lidx[0]].y;
nuclear@5: 	ldxdy = x16div(verts[lidx[1]].x - lx, ldy);
nuclear@5: 
nuclear@6: 	rdy = verts[ridx[1]].y - verts[ridx[0]].y;
nuclear@5: 	rdxdy = x16div(verts[ridx[1]].x - rx, rdy);
nuclear@5: 
nuclear@5: 	start = topy >> 16;
nuclear@5: 	end = boty >> 16;
nuclear@5: 
nuclear@6: 	if(end >= HEIGHT) end = HEIGHT - 1;
nuclear@6: 
nuclear@5: 	y = topy;
nuclear@5: 	for(i=start; i<end; i++) {
nuclear@5: 		unsigned short x0, x1;
nuclear@5: 
nuclear@5: 		x0 = lx < 0 ? 0 : (lx >> 16);
nuclear@6: 		x1 = (rx >> 16) >= WIDTH ? WIDTH - 1 : (rx >> 16);
nuclear@5: 
nuclear@6: 		if(i >= 0 && x1 > x0) {
nuclear@6: 			fill_scanline(i, x0, x1, color);
nuclear@6: 		}
nuclear@5: 
nuclear@5: 		if(y >= verts[lidx[1]].y) {
nuclear@5: 			lidx[0] = lidx[1];
nuclear@5: 			lidx[1] = lidx[1] ? lidx[1] - 1 : num - 1;
nuclear@5: 			ldy = verts[lidx[1]].y - verts[lidx[0]].y;
nuclear@5: 			if(ldy < 0) {
nuclear@5: 				break;
nuclear@5: 			}
nuclear@5: 			ldxdy = x16div(verts[lidx[1]].x - lx, ldy);
nuclear@5: 		}
nuclear@5: 		if(y >= verts[ridx[1]].y) {
nuclear@5: 			ridx[0] = ridx[1];
nuclear@5: 			ridx[1] = (ridx[1] + 1) % num;
nuclear@5: 			rdy = verts[ridx[1]].y - verts[ridx[0]].y;
nuclear@5: 			if(rdy < 0) {
nuclear@5: 				break;
nuclear@5: 			}
nuclear@5: 			rdxdy = x16div(verts[ridx[1]].x - rx, rdy);
nuclear@5: 		}
nuclear@5: 
nuclear@5: 		lx += ldxdy;
nuclear@5: 		rx += rdxdy;
nuclear@6: 		y += 65536;
nuclear@5: 	}
nuclear@5: }
nuclear@5: 
nuclear@5: static void fill_scanline(int y, int x0, int x1, uint16_t color)
nuclear@5: {
nuclear@5: 	int i;
nuclear@5: 	uint16_t *pixels = (uint16_t*)back_buffer->pixels + y * WIDTH + x0;
nuclear@5: 
nuclear@5: 	for(i=x0; i<x1; i++) {
nuclear@5: 		*pixels++ = color;
nuclear@5: 	}
nuclear@5: }