ex_gui_custom_mouse.c

a custom widget that takes the mouse, and one that owns its state

a custom widget that takes the mouse, and one that owns its state

Author

Castagnier Mickael

Version

1.0

Date

24/09/2026

Headless: events are made by hand and fed to n_gui_process_event(). A custom widget with n_gui_custom_set_mouse() is told of a move over it, a press of either button, a drag that leaves it, the release, and the wheel, in its own coordinates; a press elsewhere, or on a widget drawn over it, tells it nothing. n_gui_custom_set_destroy() hands it a heap pointer that n_gui_destroy_ctx() frees.

 
#define ALLEGRO_UNSTABLE 1
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
 
#include "nilorea/n_common.h"
#include "nilorea/n_log.h"
#include "nilorea/n_gui.h"
 
static int log_level = LOG_ERR;
static int failures = 0;

static N_GUI_MOUSE_EVENT last;
static int told = 0;
static int wheel_answer = 1;
static int destroyed = 0;

static void expect_true(const char* what, int ok) {
    if (!ok) {
        n_log(LOG_ERR, "FAIL: %s", what);
        failures++;
    } else {
        n_log(LOG_INFO, "ok: %s", what);
    }
}

static int process_args(int argc, char** argv) {
    int opt = 0;
 
    while ((opt = getopt(argc, argv, "V:")) != -1) {
        if (opt == 'V') {
            log_level = atoi(optarg);
        } else {
            return -1;
        }
    }
    return 0;
}

static int on_mouse(int widget_id, const N_GUI_MOUSE_EVENT* ev, void* user_data) {
    (void)widget_id;
    (void)user_data;
    last = *ev;
    told++;
    return ev->type == N_GUI_MOUSE_WHEEL ? wheel_answer : 1;
}

static void destroy_state(void* state) {
    destroyed++;
    free(state);
}

static int feed(N_GUI_CTX* gui, int type, int x, int y, int button, int dz) {
    ALLEGRO_EVENT ev;
 
    memset(&ev, 0, sizeof(ev));
    ev.type = (ALLEGRO_EVENT_TYPE)type;
    ev.mouse.x = x;
    ev.mouse.y = y;
    ev.mouse.dx = (type == ALLEGRO_EVENT_MOUSE_AXES && dz == 0) ? 1 : 0;
    ev.mouse.dz = dz;
    ev.mouse.button = (unsigned int)button;
    return n_gui_process_event(gui, ev);
}

static int was(int type, int button, float x, float y) {
    return last.type == type && last.button == button && last.x == x && last.y == y;
}
 
int main(int argc, char** argv) {
    int before = 0;
 
    set_log_level(LOG_ERR);
    if (process_args(argc, argv) != 0) {
        fprintf(stderr, "Usage: %s [-V LOG_LEVEL]\n", argv[0]);
        return 2;
    }
    set_log_level(log_level);
    if (!al_init() || !al_init_font_addon()) {
        n_log(LOG_ERR, "allegro init failed");
        return 1;
    }
    ALLEGRO_FONT* font = al_create_builtin_font();
    if (!font) return 1;
    N_GUI_CTX* gui = n_gui_new_ctx(font);
    if (!gui) {
        al_destroy_font(font);
        return 1;
    }
    n_gui_set_display_size(gui, 400.0f, 300.0f);
    int win = n_gui_add_window(gui, "W", 0.0f, 0.0f, 400.0f, 300.0f);
    n_gui_window_set_flags(gui, win, N_GUI_WIN_FRAMELESS);
    n_gui_open_window(gui, win);
 
    int area = n_gui_add_custom(gui, win, 50.0f, 50.0f, 100.0f, 80.0f, NULL, NULL);
    n_gui_custom_set_mouse(gui, area, on_mouse, NULL);
 
    feed(gui, ALLEGRO_EVENT_MOUSE_AXES, 60, 70, 0, 0);
    expect_true("a move over it is a MOVE, in its coordinates", told == 1 && was(N_GUI_MOUSE_MOVE, 0, 10.0f, 20.0f));
    feed(gui, ALLEGRO_EVENT_MOUSE_BUTTON_DOWN, 60, 70, 1, 0);
    expect_true("a left press is a DOWN with button 1", was(N_GUI_MOUSE_DOWN, 1, 10.0f, 20.0f));
    feed(gui, ALLEGRO_EVENT_MOUSE_AXES, 200, 200, 0, 0);
    expect_true("a drag out of it is still reported, as a DRAG", was(N_GUI_MOUSE_DRAG, 1, 150.0f, 150.0f));
    /* Allegro reports a move before a release somewhere new, so the pointer
       is where the last move left it */
    feed(gui, ALLEGRO_EVENT_MOUSE_AXES, 210, 190, 0, 0);
    expect_true("so is the next move of the drag", was(N_GUI_MOUSE_DRAG, 1, 160.0f, 140.0f));
    feed(gui, ALLEGRO_EVENT_MOUSE_BUTTON_UP, 210, 190, 1, 0);
    expect_true("the release is an UP where the pointer is", was(N_GUI_MOUSE_UP, 1, 160.0f, 140.0f));
    before = told;
    feed(gui, ALLEGRO_EVENT_MOUSE_AXES, 220, 220, 0, 0);
    expect_true("a move elsewhere after it is not reported", told == before);
 
    feed(gui, ALLEGRO_EVENT_MOUSE_BUTTON_DOWN, 70, 60, 2, 0);
    expect_true("a right press is a DOWN with button 2", was(N_GUI_MOUSE_DOWN, 2, 20.0f, 10.0f));
    feed(gui, ALLEGRO_EVENT_MOUSE_BUTTON_UP, 70, 60, 2, 0);
 
    before = told;
    expect_true("a wheel it takes is consumed", feed(gui, ALLEGRO_EVENT_MOUSE_AXES, 60, 70, 0, 1) == 1);
    expect_true("and reported with its steps", told == before + 1 && last.type == N_GUI_MOUSE_WHEEL && last.dz == 1);
    wheel_answer = 0;
    before = told;
    feed(gui, ALLEGRO_EVENT_MOUSE_AXES, 60, 70, 0, -1);
    expect_true("a wheel it declines is still reported", told == before + 1 && last.dz == -1);
 
    before = told;
    feed(gui, ALLEGRO_EVENT_MOUSE_BUTTON_DOWN, 300, 250, 1, 0);
    feed(gui, ALLEGRO_EVENT_MOUSE_BUTTON_UP, 300, 250, 1, 0);
    expect_true("a press elsewhere tells it nothing", told == before);
 
    /* a widget drawn over part of it takes the press there */
    n_gui_add_button(gui, win, "over", 50.0f, 50.0f, 30.0f, 20.0f, N_GUI_SHAPE_RECT, NULL, NULL);
    before = told;
    feed(gui, ALLEGRO_EVENT_MOUSE_BUTTON_DOWN, 55, 55, 1, 0);
    feed(gui, ALLEGRO_EVENT_MOUSE_BUTTON_UP, 55, 55, 1, 0);
    expect_true("a press on a widget over it does not reach it", told == before);
 
    n_gui_custom_set_mouse(gui, area, NULL, NULL);
    before = told;
    feed(gui, ALLEGRO_EVENT_MOUSE_BUTTON_DOWN, 100, 100, 1, 0);
    feed(gui, ALLEGRO_EVENT_MOUSE_BUTTON_UP, 100, 100, 1, 0);
    expect_true("with the callback taken away it is told nothing", told == before);
 
    /* ownership */
    int* state = malloc(sizeof(int));
    int owner = n_gui_add_custom(gui, win, 200.0f, 10.0f, 20.0f, 20.0f, NULL, state);
    n_gui_custom_set_destroy(gui, owner, destroy_state);
    n_gui_custom_set_destroy(gui, area, NULL);
    n_gui_destroy_ctx(&gui);
    expect_true("owned state is destroyed with the widget, once", destroyed == 1);
 
    al_destroy_font(font);
    if (failures) {
        fprintf(stderr, "ex_gui_custom_mouse: %d failure(s)\n", failures);
        return 1;
    }
    printf("ex_gui_custom_mouse: ok\n");
    return 0;
}