Get positions of menus and tooltips right on HiDPI

* src/gtkutil.c (xg_get_scale): New function.
(xg_show_tooltip): Use it.

* src/xmenu.c (create_and_show_popup_menu): Put menus in the
right place.

src/gtkutil.c

@@ -204,6 +204,14 @@ xg_display_open (char *display_name, Display **dpy)
   *dpy = gdpy ? GDK_DISPLAY_XDISPLAY (gdpy) : NULL;
 }
 
+/* Scaling/HiDPI functions. */
+int
+xg_get_scale (struct frame *f)
+{
+  if (FRAME_VISIBLE_P (f) && FRAME_GTK_WIDGET (f))
+    return gtk_widget_get_scale_factor (FRAME_GTK_WIDGET (f));
+  return 1;
+}
 
 /* Close display DPY.  */
 
@@ -724,7 +732,8 @@ xg_show_tooltip (struct frame *f, int root_x, int root_y)
   if (x->ttip_window)
     {
       block_input ();
-      gtk_window_move (x->ttip_window, root_x, root_y);
+      gtk_window_move (x->ttip_window, root_x / xg_get_scale (f),
+		       root_y / xg_get_scale (f));
       gtk_widget_show_all (GTK_WIDGET (x->ttip_window));
       unblock_input ();
     }

src/gtkutil.h

@@ -156,6 +156,7 @@ extern void xg_frame_resized (struct frame *f,
 extern void xg_frame_set_char_size (struct frame *f, int width, int height);
 extern GtkWidget * xg_win_to_widget (Display *dpy, Window wdesc);
 
+extern int xg_get_scale (struct frame *f);
 extern void xg_display_open (char *display_name, Display **dpy);
 extern void xg_display_close (Display *dpy);
 extern GdkCursor * xg_create_default_cursor (Display *dpy);

src/xmenu.c

@@ -1271,6 +1271,11 @@ create_and_show_popup_menu (struct frame *f, widget_value *first_wv,
 
                              /* Child of win.  */
                              &dummy_window);
+#ifdef HAVE_GTK3
+      /* Use window scaling factor to adjust position for hidpi screens. */
+      x /= xg_get_scale (f);
+      y /= xg_get_scale (f);
+#endif
       unblock_input ();
       popup_x_y.x = x;
       popup_x_y.y = y;