A colour wheel for N_GUI: one point in a disc, dragged. More...

#include <math.h>
#include <stdlib.h>
#include <string.h>
#include <allegro5/allegro_color.h>
#include <allegro5/allegro_primitives.h>
#include "nilorea/n_common.h"
#include "nilorea/n_log.h"
#include "nilorea/n_gui_colorwheel.h"

Include dependency graph for n_gui_colorwheel.c:

Data Structures
struct	_N_GUI_COLORWHEEL
	a wheel's state, owned by its custom widget More...
struct	_N_GUI_COLORWHEEL_BLOCK
	a wheel's state and its mouse callback's context in one allocation, because a custom widget owns one pointer More...
struct	_N_GUI_COLORWHEEL_MOUSE
	what a wheel's mouse callback needs: the context and the state More...

Macros
#define	N_GUI_COLORWHEEL_PI 3.14159265358979f
	pi, not taken from math.h's M_PI, which strict C does not have
#define	N_GUI_COLORWHEEL_RINGS 8
	rings and sectors the disc is drawn with: enough to look smooth at the sizes a panel gives it
#define	N_GUI_COLORWHEEL_SECTORS 48
	rings and sectors the disc is drawn with: enough to look smooth at the sizes a panel gives it

Functions
static void	_wheel_block_destroy (void *user_data)
	destroy callback for the block
static void	_wheel_clamp (float u, float v)
	helper: the point kept inside the unit circle
static void	_wheel_draw (N_GUI_WIDGET widget, float x, float y, ALLEGRO_FONT font, void *user_data)
	custom draw callback
static void	_wheel_geometry (float x, float y, float w, float h, float cx, float cy, float *radius)
	helper: the disc's centre and radius in a widget of w by h at x, y
static int	_wheel_mouse (int widget_id, const N_GUI_MOUSE_EVENT ev, void user_data)
	custom mouse callback
static _N_GUI_COLORWHEEL *	_wheel_of (N_GUI_CTX *ctx, int widget_id)
	helper: find the wheel behind a widget id, or NULL
int	n_gui_colorwheel_get (N_GUI_CTX ctx, int widget_id, float u, float *v)
	Read the point.
ALLEGRO_COLOR	n_gui_colorwheel_hue (float u, float v, void *user_data)
	The default disc colour: HSV, hue by angle with red to the right and going counter clockwise, saturation by distance from the centre, value one.
int	n_gui_colorwheel_new (N_GUI_CTX ctx, int window_id, float x, float y, float w, float h, N_GUI_COLORWHEEL_CHANGE on_change, void user_data)
	Add a colour wheel, its point in the centre.
int	n_gui_colorwheel_set (N_GUI_CTX *ctx, int widget_id, float u, float v)
	Set the point.
void	n_gui_colorwheel_set_colour (N_GUI_CTX ctx, int widget_id, N_GUI_COLORWHEEL_COLOUR colour, void user_data)
	Paint the disc with the caller's colours.

Detailed Description

A colour wheel for N_GUI: one point in a disc, dragged.

Author: Castagnier Mickael

Version: 1.0

Date: 28/09/2026

Definition in file n_gui_colorwheel.c.

Data Structure Documentation

◆ _N_GUI_COLORWHEEL

struct _N_GUI_COLORWHEEL

a wheel's state, owned by its custom widget

Definition at line 51 of file n_gui_colorwheel.c.

Collaboration diagram for _N_GUI_COLORWHEEL:

Data Fields
N_GUI_COLORWHEEL_COLOUR	colour	the disc's colour, the caller's or the default
void *	colour_user_data	handed back to colour
int	dragging	non-zero while the button is held
N_GUI_COLORWHEEL_CHANGE	on_change	the caller's change callback
double	press_time	time of the last left press, al_get_time(), for the double click
float	press_x	where it was, in the widget
float	press_y	where it was, in the widget
float	u	the point, across
void *	user_data	handed back to on_change
float	v	the point, up