Generate and paint any polygon using cairo

Data de publicació: Mar 15, 2018 8:19:37 AM

//gcc cairo_poligon.c -lm `pkg-config --cflags gtk+-3.0 --libs gtk+-3.0` -o cairo_poligon

#include <gtk/gtk.h>

#include <math.h>

//Screen dimension in pixels

#define WIDTH 500

#define HEIGHT 500

//Polygon type and radius dimension

#define N_POL 8

#define RADI ( WIDTH / 2 )

typedef struct punt{

    int x;

    int y;

} t_punt;

t_punt POLIGON[N_POL];

int _genera_poligon(t_punt POLIGON[], int n, int r){

int i;

for (i = 0; i < n; i++) {

    POLIGON[i].x = (int)(r - r * sinf(2 * M_PI * i / n));

    POLIGON[i].y = (int)(r - r * cosf(2 * M_PI * i / n));

}

}

gboolean draw_callback(GtkWidget *widget,cairo_t *cr,gpointer data){

guint width, height;

GdkRGBA color;

GtkStyleContext *context;

int i;

context = gtk_widget_get_style_context(widget);

width = gtk_widget_get_allocated_width(widget);

height = gtk_widget_get_allocated_height(widget);

gtk_render_background(context, cr, 0, 0, width, height);

//Constructing and painting the polygon

 _genera_poligon(POLIGON, N_POL, RADI);

 for ( i = 0; i < N_POL; i++ ){

   cairo_move_to (cr, POLIGON[i].x, POLIGON[i].y);

   cairo_line_to (cr, POLIGON[(i+1)%N_POL].x, POLIGON[(i+1)%N_POL].y);

 } 

//Set source color black, and the line width    

cairo_set_source_rgb (cr, 0, 0, 0);

cairo_set_line_width (cr, 1.0);

//Paint the polygon

cairo_stroke (cr);

gtk_style_context_get_color(context,gtk_style_context_get_state(context),&color);

gdk_cairo_set_source_rgba(cr,&color);

//gdk_cairo_set_source_rgba(cr,&color);

cairo_fill (cr);

return FALSE;

}

gint main(int argc,char *argv[])

{

GtkWidget *window,*drawing_area;

gtk_init(&argc,&argv);

window = gtk_window_new(GTK_WINDOW_TOPLEVEL);

g_signal_connect(window,"destroy",G_CALLBACK(gtk_main_quit),NULL);

drawing_area=gtk_drawing_area_new();

gtk_container_add (GTK_CONTAINER (window),drawing_area);

gtk_widget_set_size_request(drawing_area, WIDTH, HEIGHT);

g_signal_connect(G_OBJECT(drawing_area),"draw", G_CALLBACK(draw_callback),NULL);

gtk_widget_show_all(window);

gtk_main();

return 0;

}