Add new touch gesture mode

* lisp/touch.el: New file.

1 files changed, 89 insertions, 0 deletions

diff --git a/lisp/touch.el b/lisp/touch.el
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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