conky/src/text_object.h

/*
 *
 * Conky, a system monitor, based on torsmo
 *
 * Any original torsmo code is licensed under the BSD license
 *
 * All code written since the fork of torsmo is licensed under the GPL
 *
 * Please see COPYING for details
 *
 * Copyright (c) 2004, Hannu Saransaari and Lauri Hakkarainen
 * Copyright (c) 2005-2019 Brenden Matthews, Philip Kovacs, et. al.
 *	(see AUTHORS)
 * All rights reserved.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
#ifndef _TEXT_OBJECT_H
#define _TEXT_OBJECT_H

#include <stdint.h> /* uint8_t */
#include "config.h" /* for the defines */
#include "exec.h"
#include "specials.h" /* enum special_types */

/* text object callbacks */
struct obj_cb {
  /* text object: print obj's output to p */
  void (*print)(struct text_object *obj, char *p, unsigned int p_max_size);

  /* ifblock object: return zero to trigger jumping */
  int (*iftest)(struct text_object *obj);

  /* meter objects:
   * The following functions return the current meter-type value
   * in a range between 0 and the value passed to the appropriate
   * scan_* function. Or, if named function has been called with
   * a value of 0, make use of auto-scaling (i.e., scaling to the
   * maximum value seen so far). */
  double (*barval)(struct text_object *obj);
  double (*gaugeval)(struct text_object *obj);
  double (*graphval)(struct text_object *obj);

  /* percentage object: return value in range [0, 100] */
  uint8_t (*percentage)(struct text_object *obj);

  /* free obj's data */
  void (*free)(struct text_object *obj);
};

/* generic free opaque callback
 * can be used to simply free obj->data.opaque or obj->data.s */
void gen_free_opaque(struct text_object *);

/* generic iftest returning false (i.e. trigger jumping)
 * used for the else object */
int gen_false_iftest(struct text_object *);

/* generic nothing printer callback printing nothing
 * used for the endif object */
void gen_print_nothing(struct text_object *, char *, unsigned int);

/* generic obj->data.s printer
 * used by the $text object */
void gen_print_obj_data_s(struct text_object *, char *, unsigned int);

class legacy_cb : public conky::callback<void *, int (*)()> {
  typedef conky::callback<void *, int (*)()> Base;

 protected:
  virtual void work() { std::get<0>(tuple)(); }

 public:
  legacy_cb(uint32_t period, int (*fn)())
      : Base(period, true, Base::Tuple(fn)) {}
};

typedef conky::callback_handle<legacy_cb> legacy_cb_handle;
typedef conky::callback_handle<exec_cb> exec_cb_handle;

/**
 * This is where Conky collects information on the conky.text objects in your
 * config
 *
 * During startup and reload, objects are parsed and callbacks are set. Note
 * that there are currently two types of callback: obj_cb (old style) and
 * conky::callback (new style). On each update interval,
 * generate_text_internal() in conky.cc traverses the list of text_objects and
 * calls the old callbacks. The new style callbacks are run separately by
 * conky::run_all_callbacks().
 */
struct text_object {
  struct text_object *next, *prev;  /* doubly linked list of text objects */
  struct text_object *sub;          /* for objects parsing text into objects */
  struct text_object *ifblock_next; /* jump target for ifblock objects */

  union {
    void *opaque; /* new style generic per object data */
    char *s;      /* some string */
    int i;        /* some integer */
    long l;       /* some long integer */
  } data;

  void *special_data;
  long line;
  bool parse;  /* if true then data.s should still be parsed */
  bool thread; /* if true then data.s should be set by a separate thread */

  struct obj_cb callbacks;

  /* Each _cb_handle is a std::shared_ptr with very tight restrictions on
   * construction. For now, it is necessary to store them here as regular
   * pointers so we can instantiate them later. */
  exec_cb_handle *exec_handle;
  legacy_cb_handle *cb_handle;
};

/* text object list helpers */
int append_object(struct text_object *root, struct text_object *obj);

/* ifblock helpers
 *
 * Opaque is a pointer to the address of the ifblock stack's top object.
 * Calling clients should pass the address of a defined void pointer which
 * was initialised to nullptr (empty stack).
 * */
int obj_be_ifblock_if(void **opaque, struct text_object *);
int obj_be_ifblock_else(void **opaque, struct text_object *);
int obj_be_ifblock_endif(void **opaque, struct text_object *);
int ifblock_stack_empty(void **opaque);

/* make the given object be a plain text object printing given string */
void obj_be_plain_text(struct text_object *, const char *);

#endif /* _TEXT_OBJECT_H */