/*
 *  Rainbow
 *  -------
 *  Display a rainbow of colours in a window. This program demonstrates the
 *  use of colours, drawings, scrollbars and labels.
 */

#include <graphapp.h>

#define CUBE_SIZE 6	/* colour cube edge length */
window w = NULL;        /* the main window */
scrollbar s = NULL;     /* to control the intensity */
label t = NULL;         /* to display the intensity */
drawing d = NULL;       /* where to draw the rainbow */
checkbox c[3];          /* colour axis checkboxes */
label v[3];             /* colour value displays */

int axis = 2;           /* 0 = Red, 1 = Green, 2 = Blue axis */
int intensity = 255;    /* intensity along colour axis */

char *name[3] = { "Red", "Green", "Blue" };

/* use the colour axis value to determine which colour (a,b,c) represents */
rgb axis_colour(int a, int b, int c)
{
	rgb result = Black;

	/* the 'axis' variable determines which colour's intensity is */
	/* controlled by the 'intensity' variable, here given as 'a' */
	switch(axis) {
		case 0: result = rgb(a, b, c); break;
		case 1: result = rgb(c, a, b); break;
		case 2: result = rgb(b, c, a); break;
	}
	return result;
}

/* draw the rainbow on the drawing area */
void draw_rainbow(drawing d, rect r)
{
	int x, y;
	int a, b, c;
	int size = 256/CUBE_SIZE;

	/* step through one 'face' of the 'colour cube' */
	/* the 'a' colour is the chosen 'axis' colour */
	/* the 'b' colour increases as x increases across the drawing */
	/* the 'c' colour increases as y increases down the drawing */
	/* the axis_colour function determines what 'a', 'b' and 'c' mean */

	a = intensity;
	for (x=0; x < CUBE_SIZE; x++) {
		b = x * 255/(CUBE_SIZE-1);
		for (y=0; y < CUBE_SIZE; y++) {
			c = y * 255/(CUBE_SIZE-1);
			setcolour(axis_colour(a, b, c));
			fillellipse(rect(x*size, y*size, size, size));
		}
	}
}

/* handle a mouse movement over the window */
void clear_colour_display(drawing d, int buttons, point p)
{
	/* clear the display of colour component values */
	/* red component */
	settext(v[0], "");
	/* green component */
	settext(v[1], "");
	/* blue component */
	settext(v[2], "");
}

/* handle a mouse movement over the drawing area */
void set_colour_display(drawing d, int buttons, point p)
{
	int a, b, c;
	rgb colour;
	char str[40];

	a = intensity;
	b = p.x;
	c = p.y;

	/* find out what colour the mouse is over */
	colour = axis_colour(a, b, c);

	/* determine and display the values of each colour component */

	/* red component */
	sprintf(str, "%d", (colour >> 16) & 255);
	settext(v[0], str);
	/* green component */
	sprintf(str, "%d", (colour >> 8) & 255);
	settext(v[1], str);
	/* blue component */
	sprintf(str, "%d", (colour) & 255);
	settext(v[2], str);
}

/* handle a scrollbar event which changes the intensity value */
void change_intensity(scrollbar s, int value)
{
	int new_intensity;
	char str[40];

	/* the top of the scrollbar represents 100%, the bottom 0% intensity */
	new_intensity = 255 - value;
	/* if the new intensity is the same, we ignore the change */
	if (new_intensity == intensity)
		return;
	/* change the intensity of the axis colour */
	intensity = new_intensity;
	/* change the percentage displayed in the intensity label */
	sprintf(str, "%d%%", (int)((long)intensity)*100/255);
	settext(t, str);
	/* draw the new rainbow */
	draw(d);
}

/* handle a checkbox event which changes the colour axis */
void change_axis(checkbox chk)
{
	/* uncheck the previously checked checkbox */
	if (chk != c[axis])
		uncheck(c[axis]);
	/* set the new colour axis from the 'value' stored in this checkbox */
	axis = getvalue(chk);
	/* ensure the correct checkbox is checked */
	check(c[axis]);
	/* draw the new rainbow */
	draw(d);
}

/* the window's redraw function merely draws a box around the edge */
void draw_window(window w, rect r)
{
	setcolour(Black);
	drawrect(rect(5,5,480,270));
}

/* starting point of the program */
void main(void)
{
	int i;

	/* create the window */
	w = newwindow("Rainbow", rect(50,50,490,280),
			Titlebar + Closebox + Minimize + UsePalette);
	setredraw(w, draw_window);
	//setmousemove(w, clear_colour_display);

	/* create the drawing area and set a mouse movement callback */
	d = newdrawing(rect(10,10,256,256), draw_rainbow);
	setmousemove(d, set_colour_display);

	/* create the scrollbar which controls colour intensity */
	s = newscrollbar(rect(280,10,20,256), 255, 15, change_intensity);

	/* create the colour axis checkboxes */
	newlabel("Colour Axis", rect(320,10,100,35), AlignLeft + Underline);
	for (i=0; i < 3; i++) {
		c[i] = newcheckbox(name[i], rect(330,50+i*40,90,35),
				change_axis);
		setvalue(c[i], i);
		v[i] = newlabel("0", rect(430,50+i*40,40,35), AlignRight);
	}
	check(c[axis]);

	/* create the intensity display */
	newlabel("Intensity", rect(320,180,90,35), AlignLeft + Underline);
	t = newlabel("100%", rect(330,220,90,35), AlignLeft);

	/* show the window */
	show(w);
	mainloop();
}