Apparently the former was removed from libxfce4panel-4.15.
#include <string.h>
#include <gtk/gtk.h>
#include <libxfce4ui/libxfce4ui.h>
#include <string.h>
#include <gtk/gtk.h>
#include <libxfce4ui/libxfce4ui.h>
-#include <libxfce4panel/xfce-panel-plugin.h>
+#include <libxfce4panel/libxfce4panel.h>
#include "xfce4-hdaps-dialogs.h"
#include "hdaps.h"
#include "xfce4-hdaps-dialogs.h"
#include "hdaps.h"
#define __XFCE4_HDAPS_H__
#include <gtk/gtk.h>
#define __XFCE4_HDAPS_H__
#include <gtk/gtk.h>
-#include <libxfce4panel/xfce-panel-plugin.h>
+#include <libxfce4panel/libxfce4panel.h>
#include <libxfce4util/libxfce4util.h>
G_BEGIN_DECLS
#include <libxfce4util/libxfce4util.h>
G_BEGIN_DECLS