A curve editor for N_GUI: control points on a curve over [0,1]. More...

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

Include dependency graph for n_gui_curve.c:

Data Structures
struct	_N_GUI_CURVE
	an editor's state, owned by its custom widget More...
struct	_N_GUI_CURVE_BLOCK
	an editor's state and its mouse callback's context in one allocation, because a custom widget owns one pointer More...
struct	_N_GUI_CURVE_MOUSE
	what an editor's mouse callback needs: the context, to find the widget and mark the GUI dirty, and the editor's state More...

Macros
#define	N_GUI_CURVE_MIN_GAP (1.0f / 1024.0f)
	how close in x two points may come, so neither is ever a zero width segment
#define	N_GUI_CURVE_SEGMENTS 64
	segments the drawn curve is made of: fine enough to look smooth at any size an editor has on a screen

Functions
static void	_curve_block_destroy (void *user_data)
	destroy callback for the block holding both
static float	_curve_clamp (float v)
	helper: clamp to [0,1]
static void	_curve_draw (N_GUI_WIDGET widget, float x, float y, ALLEGRO_FONT font, void *user_data)
	custom draw callback
static int	_curve_insert (_N_GUI_CURVE *cv, float px, float py)
	helper: insert a point in x order; returns its index or -1 when full
static int	_curve_mouse (int widget_id, const N_GUI_MOUSE_EVENT ev, void user_data)
	custom mouse callback
static _N_GUI_CURVE *	_curve_of (N_GUI_CTX *ctx, int widget_id)
	helper: find the editor state behind a widget id, or NULL
static int	_curve_point_at (const _N_GUI_CURVE cv, const N_GUI_WIDGET wgt, float lx, float ly)
	helper: the point within grab distance of a widget-local position, or -1
static float	_curve_value (const _N_GUI_CURVE *cv, float x)
	helper: the editor's curve at x, the caller's or the built-in one
float	n_gui_curve_eval (N_GUI_CTX *ctx, int widget_id, float x)
	The editor's curve at `x`, as it is drawn.
float	n_gui_curve_eval_points (const float xs, const float ys, int count, float x)
	A monotone cubic Hermite spline through points.
int	n_gui_curve_get_points (N_GUI_CTX ctx, int widget_id, float xs, float *ys, int max)
	Read the points.
int	n_gui_curve_new (N_GUI_CTX ctx, int window_id, float x, float y, float w, float h, int max_points, N_GUI_CURVE_CHANGE on_change, void user_data)
	Add a curve editor to a window.
void	n_gui_curve_set_background (N_GUI_CTX ctx, int widget_id, N_GUI_CURVE_BACKGROUND draw, void user_data)
	Draw something behind the grid and the curve.
void	n_gui_curve_set_eval (N_GUI_CTX ctx, int widget_id, N_GUI_CURVE_EVAL eval, void user_data)
	Draw the caller's own curve through the points.
void	n_gui_curve_set_point_radius (N_GUI_CTX *ctx, int widget_id, float radius)
	Size of the drawn points, for a display scale.
int	n_gui_curve_set_points (N_GUI_CTX ctx, int widget_id, const float xs, const float *ys, int count)
	Replace the points.

Detailed Description

A curve editor for N_GUI: control points on a curve over [0,1].

Author: Castagnier Mickael

Version: 1.0

Date: 24/09/2026

Definition in file n_gui_curve.c.

Data Structure Documentation

◆ _N_GUI_CURVE

struct _N_GUI_CURVE

an editor's state, owned by its custom widget

Definition at line 48 of file n_gui_curve.c.

Collaboration diagram for _N_GUI_CURVE:

Data Fields
N_GUI_CURVE_BACKGROUND	background	drawn behind everything, or NULL
void *	background_user_data	handed back to background
int	count	how many points
int	dragging	the point being dragged, or -1
N_GUI_CURVE_EVAL	eval	the caller's curve, or NULL for the built-in one
void *	eval_user_data	handed back to eval
int	id	the widget
int	max	room in xs and ys
N_GUI_CURVE_CHANGE	on_change	the caller's change callback
float	radius	drawn point radius, pixels
void *	user_data	handed back to on_change
float *	xs	points' x, ascending
float *	ys	points' y