/*
 * level.c - Interactively align a nearly horizontal plane with a face
 *
 * 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 <gtk/gtk.h>

#include "array.h"
#include "face.h"
#include "level.h"


#define	NEAR	1


static void draw_image(GtkWidget *widget, struct face *f)
{
	int x, y, z;
	double z0;
	guchar *rgbbuf, *p;

	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++) {
			z = get(f->a, x+f->a->min_x, y+f->a->min_y);
			if (z == UNDEF) {
				p += 3;
				continue;
			}
			z0 = f->z_ref+f->fx*(x-f->sx/2)+f->fy*(y-f->sy/2);
			if (fabs(z-z0) < NEAR) {
				*p++ = 255*fabs(z-z0);
				*p++ = 255*fabs(z-z0);
				*p++ = 255;
				continue;
			}
			if (z < z0) {
				z = z > z0-2*NEAR ? 255*(z-z0)/NEAR :
				    255.0*(z-z0)/(z0-f->a->min_z);
				*p++ = 255;
				*p++ = z;
				*p++ = z;
			} else {
				z = z < z0+2*NEAR ? 255*(z0-z)/NEAR :
				    255.0*(z0-z)/(f->a->max_z-z0);
				*p++ = z;
				*p++ = 255;
				*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);
}


static void scroll_z(GtkWidget *da, struct face *f, int up)
{
	if (up) {
		if (f->z_ref < f->a->max_z)
			f->z_ref++;
	} else {
		if (f->z_ref > f->a->min_z)
			f->z_ref--;
	}
	draw_image(da, f);
}


static void scroll_xy(GtkWidget *da, struct face *f, int dx, int dy, int up)
{
	double d;

	d = (double) (up ? 1 : -1)/(dx*dx+dy*dy)/2.0;
	f->fx += d*dx;
	f->fy += d*dy;
	draw_image(da, f);
}


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;
	int center = hypot(dx, dy)/hypot(f->sx, f->sy) < 0.25;

	switch (event->direction) {
	case GDK_SCROLL_UP:
		if (center)
			scroll_z(da, f, 0);
		else
			scroll_xy(da, f, dx, dy, 1);
		break;
	case GDK_SCROLL_DOWN:
		if (center)
			scroll_z(da, f, 1);
		else
			scroll_xy(da, f, dx, dy, 0);
		break;
	default:
		/* ignore */;
	}
	return TRUE;
}


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


void level(GtkWidget *canvas, struct face *f)
{
	GtkWidget *evbox, *da;

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

	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);
}