take into account x11 border_width settings (fixes uxterm border issue)

include/data.h

@@ -297,6 +297,9 @@ struct Con {
     int base_width;
     int base_height;
 
+    /* the x11 border pixel attribute */
+    int border_width;
+
     /* minimum increment size specified for the window (in pixels) */
     int width_increment;
     int height_increment;

src/manage.c

@@ -185,6 +185,8 @@ void manage_window(xcb_window_t window, xcb_get_window_attributes_cookie_t cooki
     nc->window = cwindow;
     x_reinit(nc);
 
+    nc->border_width = geom->border_width;
+
     char *name;
     asprintf(&name, "[i3 con] container around %p", cwindow);
     x_set_name(nc, name);

src/render.c

@@ -51,6 +51,10 @@ void render_con(Con *con) {
         *inset = (Rect){0, 0, con->rect.width, con->rect.height};
         *inset = rect_add(*inset, con_border_style_rect(con));
 
+        /* Obey x11 border */
+        inset->width -= (2 * con->border_width);
+        inset->height -= (2 * con->border_width);
+
         /* Obey the aspect ratio, if any */
         if (con->proportional_height != 0 &&
             con->proportional_width != 0) {