;;; touch-screen.el --- Touchscreen support for GNU Emacs. -*- lexical-binding: t -*-

;; Copyright (C) 2020 Free Software Foundation, Inc.

;; This file is part of GNU Emacs.

;; GNU Emacs 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.

;; GNU Emacs 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 GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; This package provides touch-screen support for GNU Emacs on GTK 4 terminals.
;; This relies on several GTK 4-specific event handling changes, and is unlikely
;; to work well on other platforms.

;;; Code:

(unless (and (or (string-prefix-p "3.98" gtk-version-string)
                 (string-prefix-p "4." gtk-version-string)))
  (error "Trying to load touch-screen.el on an incompatible terminal"))

(require 'widget)

(defvar touch-screen--idle-timer nil
  "The timer that will be used for action popovers.")

(defun touch-screen-pop-up-actions-frame ()
  "Display the selection items popover."
  (interactive)
  (pgtk-show-selection-options (selected-frame)))

(define-minor-mode touch-screen-mode
  "A mode for touchscreen device that displays
several graphical elements suitable for use on touchscreens."
  :global t
  :lighter nil)

(defun touch-screen--after-mark-set ()
  "Internal function for `touch-screen-after-mark-set'."
  (when (and pgtk-last-event-from-touchscreen
             touch-screen-mode
             (region-active-p)
             (window-system)
             (> (abs (- (mark) (point))) 5))
    (touch-screen-pop-up-actions-frame)))

(defun touch-screen-after-mark-set ()
  "This function will be run after the mark is set.
It will display the pop-up frame if `pgtk-last-event-from-touchscreen'
is non-nil."
  (when (window-system)
    (when touch-screen--idle-timer
      (cancel-timer touch-screen--idle-timer))
    (setq touch-screen--idle-timer
          (run-with-idle-timer 1 nil #'touch-screen--after-mark-set))))

(defun touch-screen--safe-kill ()
  "Kill the region, without raising errors if it is not possible."
  (when (not (and buffer-read-only
                  (not inhibit-read-only)
                  (not (get-text-property (point) 'inhibit-read-only))))
    (unwind-protect
        (kill-region (mark) (point))
      nil)))

(add-hook 'activate-mark-hook #'touch-screen-after-mark-set)
(add-hook 'post-command-hook #'touch-screen-after-mark-set)

(provide 'touch-screen)
;;; touch-screen.el ends here