/*
 * overlap.c - Overlap two parallel faces
 *
 * Written 2010 by Werner Almesberger
 * Copyright 2010 by Werner Almesberger
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */


#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <limits.h>
#include <gtk/gtk.h>

#include "face.h"
#include "overlap.h"


#define	UNDEF_F	HUGE_VAL


static double ramp(int z0, double w0, int z1, double w1)
{
	if (z0 != UNDEF && z1 != UNDEF)
		return w0 == 0 && w1 == 0 ? z0 : z0*w0+z1*w1;
	if (z0 == UNDEF && z0 == UNDEF)
		return UNDEF_F;
	if (z0 == UNDEF && w0 < w1)
		return z1;
	if (z1 == UNDEF && w0 > w1)
		return z0;
	return UNDEF_F;
}


static double zmix(struct face *f, double x, double y)
{
	int xa, xb, ya, yb;
	double zx0, zx1;

	xa = floor(x);
	xb = ceil(x);
	ya = floor(y);
	yb = ceil(y);

	zx0 = ramp(
	    get_bounded(f->a, xa, ya), yb-y,
	    get_bounded(f->a, xa, yb), y-ya);
	zx1 = ramp(
	    get_bounded(f->a, xb, ya), yb-y,
	    get_bounded(f->a, xb, yb), y-ya);

	return ramp(zx0, xb-x, zx1, x-xa);
}


static void draw_image(GtkWidget *widget, struct face *f)
{
	guchar *rgbbuf, *p;
	int x, y;
	double z;

	rgbbuf = p = calloc(f->sx*f->sy, 3);
	if (!rgbbuf) {
		perror("calloc");
		exit(1);
	}
	for (y = f->sy-1; y >= 0; y--)
		for (x = 0; x != f->sx ; x++) {
			int xa = x+f->a->min_x;
			int ya = y+f->a->min_y;

			z = zmix(f,
			    xa*f->m.a[0][0]+ya*f->m.a[0][1]+f->m.b[0],
			    xa*f->m.a[1][0]+ya*f->m.a[1][1]+f->m.b[1]);
			if (z == UNDEF_F) {
				p += 3;
				continue;
			}
			z = 256.0*(z-f->a->min_z)/(f->a->max_z-f->a->min_z);
			if (z < 0)
				z = 0;
			if (z > 255)
				z = 255;
			*p++ = z;
			*p++ = z;
			*p++ = z;
		}
	gdk_draw_rgb_image(widget->window,
	    widget->style->fg_gc[GTK_STATE_NORMAL],
	    0, 0, f->sx, f->sy, GDK_RGB_DITHER_MAX, rgbbuf, f->sx*3);
	free(rgbbuf);
}


/*
 * Rotate such that a point at distance "r" moves one unit. Rotate
 * counter-clockwise for r > 1, clockwise for r < 0.
 */

static void rotate(struct matrix *m, double r)
{
	struct matrix t;
	double s, c;

	s = 1/r;
	c = sqrt(1-s*s);
	t.a[0][0] = m->a[0][0]*c-m->a[1][0]*s;
	t.a[0][1] = m->a[0][1]*c-m->a[1][1]*s;
	t.a[1][0] = m->a[1][0]*c+m->a[0][0]*s;
	t.a[1][1] = m->a[1][1]*c+m->a[0][1]*s;
	t.b[0] = m->b[0]*c-m->b[1]*s;
	t.b[1] = m->b[0]*s+m->b[1]*c;
	*m = t;
}


static gboolean scroll_event(GtkWidget *widget, GdkEventScroll *event,
    gpointer data)
{
	GtkWidget *da = gtk_bin_get_child(GTK_BIN(widget));
	struct face *f = data;
	int dx = event->x-f->sx/2;
	int dy = event->y-f->sy/2;
	double r = hypot(dx, dy);

	if (r < 1)
		return TRUE;
	switch (event->direction) {
	case GDK_SCROLL_UP:
		rotate(&f->m, r);
		draw_image(da, f);
		break;
	case GDK_SCROLL_DOWN:
		rotate(&f->m, -r);
		draw_image(da, f);
		break;
	default:
		/* ignore */;
	}
	return TRUE;
}


static gboolean expose_event(GtkWidget *widget, GdkEventExpose *event,
    gpointer user_data)
{
	draw_image(widget, user_data);
	return TRUE;
}



static void make_screen(GtkWidget *root, struct face *f)
{
	GtkWidget *evbox, *da;

	da = gtk_drawing_area_new();
	gtk_widget_set_size_request(da, f->sx, f->sy);
	evbox = gtk_event_box_new();
	gtk_container_add(GTK_CONTAINER(evbox), da);
	gtk_container_add(GTK_CONTAINER(root), evbox);
	gtk_widget_show_all(root);
	draw_image(da, f);

	g_signal_connect(G_OBJECT(evbox), "scroll-event",
	    G_CALLBACK(scroll_event), f);
	g_signal_connect(G_OBJECT(da), "expose-event",
	    G_CALLBACK(expose_event), f);
}

void overlap(struct face *face)
{
	GtkWidget *root;

	root = gtk_window_new(GTK_WINDOW_TOPLEVEL);
	gtk_window_set_position(GTK_WINDOW(root), GTK_WIN_POS_CENTER);

	g_signal_connect(G_OBJECT(root), "destroy",
	    G_CALLBACK(gtk_main_quit), NULL);
	make_screen(root, face);
	gtk_main();
}