Somme de deux vecteurs

Il s'agit dans cet exemple de créer trois points A, B et C qu'on peut déplacer à l'aide de la souris puis de tracer les vecteurs u = AB, v = BC et w = u + v = AC.

vect.cpp

/**
 * vect.cpp
 *
 */

#include "geo2D/geo2D.h"

#define W 800
#define H 600
#define W0 400
#define H0 300

class Donnees {

public:
    GdkCursor *fleche;
    GdkCursor *hand;
    bool presse;

    repere *R;
    point_libre *A, *B, *C;
    vecteur *u, *v, *w;
};

static void paint (GtkWidget *widget, GdkEventExpose *event, Donnees *D) {

    cairo_t *cr;
    cr = gdk_cairo_create (widget->window);
    cairo_select_font_face (cr, "Sans", CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_NORMAL);
    cairo_set_font_size (cr, 12.0);

    cairo_set_source_rgb (cr, 1,1,1);
    cairo_paint (cr);
    cairo_stroke (cr);

    cairo_set_source_rgb (cr, 1, 0, 0);
    cairo_set_line_width (cr, 1.0);
    D->R->trace (cr);

    cairo_set_source_rgb (cr, 0, 0, 1);
    cairo_set_line_width (cr, 1.0);
    D->A->trace_nom (cr);
    D->B->trace_nom (cr);
    D->C->trace_nom (cr);
    D->u->trace (cr);
    D->v->trace (cr);
    D->w->trace (cr);
    cairo_stroke (cr);
    cairo_destroy (cr);
}

static void event_press (GtkWidget *widget, GdkEventButton *event, Donnees *D) {
    int X = event->x;
    int Y = event->y;
    D->presse = D->A->select (X, Y) || D->B->select (X, Y) || D->C->select (X, Y);
    if (D->presse)
        gdk_window_set_cursor (widget->window, D->hand);
}


static void event_motion (GtkWidget *widget, GdkEventMotion *event, Donnees *D) {
    int X = event->x;
    int Y = event->y;
    if (D->presse) {
        D->A->bouge (X, Y);
        D->B->bouge (X, Y);
        D->C->bouge (X, Y);
        D->u->vecteur_pt_pt (D->A, D->B);
        D->u->fixe_origine (D->A);
        D->v->vecteur_pt_pt (D->B, D->C);
        D->v->fixe_origine (D->B);
        D->w->somme (D->u, D->v);
        gtk_widget_queue_draw (widget);
    } else {
        bool proche = D->A->zone (X, Y) || D->B->zone (X, Y) || D->C->zone (X, Y);
        gdk_window_set_cursor (widget->window, (proche) ? D->hand : D->fleche);
    }
}

static void event_release (GtkWidget *widget, GdkEventButton *, Donnees *D) {
    D->A->stop ();
    D->B->stop ();
    D->C->stop ();
    D->presse = FALSE;
    gdk_window_set_cursor (widget->window, D->fleche);
}

int main (int argc, char *argv []) {
    GtkWidget * fenetre;
    Donnees *D;

    D = new Donnees;

    D->R = new repere (W0, H0, W, H, 100.0, 100.0, 1.0, 1.0);
    D->A = new point_libre (-3.0, -1.0, "A", D->R);
    D->B = new point_libre (-2.0, 1.0, "B", D->R);
    D->C = new point_libre (-1.0, 0.0, "C", D->R);
    D->u = new vecteur (D->A, D->B, NULL, D->R);
    D->u->fixe_origine (D->A);
    D->v = new vecteur (D->B, D->C, NULL, D->R);
    D->v->fixe_origine (D->B);
    D->w = new vecteur (NULL, D->R);
    D->w->somme (D->u, D->v);
    D->presse = false;

    gtk_init (&argc, &argv);

    D->fleche = gdk_cursor_new (GDK_LEFT_PTR);
    D->hand = gdk_cursor_new (GDK_HAND1);

    fenetre = gtk_window_new (GTK_WINDOW_TOPLEVEL);

    g_signal_connect (fenetre, "expose-event", G_CALLBACK (paint), D);
    g_signal_connect (fenetre, "destroy", G_CALLBACK (gtk_main_quit), NULL);

    gtk_widget_add_events (fenetre, GDK_POINTER_MOTION_MASK | GDK_POINTER_MOTION_HINT_MASK
                                    | GDK_BUTTON_PRESS_MASK | GDK_BUTTON_RELEASE_MASK);
    g_signal_connect (G_OBJECT (fenetre), "button_press_event", G_CALLBACK (event_press), D);
    g_signal_connect (G_OBJECT (fenetre), "button_release_event", G_CALLBACK (event_release), D);
    g_signal_connect (G_OBJECT (fenetre), "motion_notify_event", G_CALLBACK (event_motion), D);

    gtk_window_set_position (GTK_WINDOW (fenetre), GTK_WIN_POS_CENTER);
    gtk_window_set_default_size (GTK_WINDOW (fenetre), W, H);
    gtk_widget_set_app_paintable (fenetre, TRUE);
    gtk_widget_show_all (fenetre);

    gtk_main ();

    return 0;
}