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;;; -*- lexical-binding: t -*-
;;; touch.el --- Touch input support
;; Copyright (C) 2017 Free Software Foundation, Inc.
;; Keywords: mouse touch
;; Package: emacs
;; 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 <http://www.gnu.org/licenses/>.
;;; Commentary:
;; This mode enables the use of `touch gestures' on compatible
;; systems.
;; The available gestures are:
;; * scroll/pan :: Scroll the buffer.
;; * pinch :: Change the text scale factor.
;; * rotate
;; * swipe
;; Aside from scroll/pan, I'm not sure that it's worth having default
;; actions. I can't think of any use for rotate, and swipe seems like
;; it would best be assigned to user actions. Pinch is a natural for
;; resizing, but is `text scale' the right thing?
;;; Code:
(defvar touch-gesture-mode)
(defun touch-gesture--scroll (event)
"Scroll up or down according to EVENT."
(interactive (list last-input-event))
;;; FIXME: Handle horizontal scrolling too. Scroll the window under
;;; the mouse pointer, not the last one selected.
(let (;;(delta-x (caaddr event))
(delta-y (cadr (caddr event)))
(line-height (save-excursion
(goto-char (window-start))
(line-pixel-height))))
(let ((num-lines (% (floor delta-y) line-height)))
(if (not (= num-lines 0))
(scroll-down num-lines)))))
(defun touch-gesture--pinch (event)
"Increase or decrease the text scale according to EVENT."
(interactive (list last-input-event))
(let ((delta (caddr event)))
(if (not (= delta 0))
(text-scale-increase delta))))
(define-minor-mode touch-gesture-mode
"Enable default actions for some touch gestures.
`touch-scroll' will act like a mouse-wheel, and scroll the
buffer.
`touch-pinch' will `zoom' in and out by changing the text-scale
factor.
"
:init-value t
:global t
:group 'mouse
(global-unset-key [touch-scroll])
(when touch-gesture-mode
(global-set-key [touch-scroll] 'touch-gesture--scroll)
(global-set-key [touch-pinch] 'touch-gesture--pinch)))
;;; Compatibility entry point
;; preloaded ;;;###autoload
(defun touch-gesture-install (&optional uninstall)
"Enable touch gesture support."
(touch-gesture-mode (if uninstall -1 1)))
(provide 'touch)
;;; touch.el ends here
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