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;;; scroll-tests.el --- tests for scrolling -*- lexical-binding: t -*-
;; Copyright (C) 2017-2025 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:
;; These are mostly automated ert tests, but they don't work in batch
;; mode which is why they are under test/manual.
;;; Code:
(require 'ert)
(eval-when-compile (require 'cl-lib))
(defun scroll-tests-up-and-down (margin &optional effective-margin)
(unless effective-margin
(setq effective-margin margin))
(erase-buffer)
(insert (mapconcat #'number-to-string
(number-sequence 1 200) "\n"))
(goto-char 1)
(sit-for 0)
(let ((scroll-margin margin)
(wstart (window-start)))
;; Stopping before `scroll-margin' so we shouldn't have
;; scrolled.
(let ((current-prefix-arg (- (window-text-height) 1 effective-margin)))
(call-interactively 'next-line))
(sit-for 0)
(should (= wstart (window-start)))
;; Passing `scroll-margin' should trigger scrolling.
(call-interactively 'next-line)
(sit-for 0)
(should (/= wstart (window-start)))
;; Scroll back to top.
(let ((current-prefix-arg (window-start)))
(call-interactively 'scroll-down-command))
(sit-for 0)
(should (= 1 (window-start)))))
(defun scroll-tests-display-buffer-with-height (buffer alist)
(let ((height (alist-get 'window-height alist)))
(when height
(let* ((window (or (get-buffer-window buffer) (selected-window)))
(lines (floor height))
(partial (round (* (- height lines) (default-line-height)))))
(setq window (cond ((window-in-direction 'above window nil +1))
((or (window-in-direction 'below window nil -1)
(split-window-below lines))
window)))
(set-window-buffer window buffer)
(set-window-text-height window lines)
(adjust-window-trailing-edge window partial nil t)
window))))
(defmacro scroll-tests-with-buffer-window (&optional height &rest body)
(declare (debug t) (indent defun))
`(with-temp-buffer
(with-selected-window (display-buffer (current-buffer)
'(scroll-tests-display-buffer-with-height
. ,(if (numberp height)
`((window-height . ,height))
(push height body)
nil)))
,@body)))
(ert-deftest scroll-tests-scroll-margin-0 ()
(skip-when noninteractive)
(scroll-tests-with-buffer-window
(scroll-tests-up-and-down 0)))
(ert-deftest scroll-tests-scroll-margin-negative ()
"A negative `scroll-margin' should be the same as 0."
(skip-when noninteractive)
(scroll-tests-with-buffer-window
(scroll-tests-up-and-down -10 0)))
(ert-deftest scroll-tests-scroll-margin-max ()
(skip-when noninteractive)
(scroll-tests-with-buffer-window
(let ((max-margin (/ (window-text-height) 4)))
(scroll-tests-up-and-down max-margin))))
(ert-deftest scroll-tests-scroll-margin-over-max ()
"A `scroll-margin' more than max should be the same as max."
(skip-when noninteractive)
(scroll-tests-with-buffer-window 7
(let ((max-margin (/ (window-text-height) 4)))
(scroll-tests-up-and-down (+ max-margin 1) max-margin)
(scroll-tests-up-and-down (+ max-margin 2) max-margin))))
(ert-deftest scroll-tests-conservative-show-trailing-whitespace ()
"Test for Bug#25792."
;; Note: requires partial line to trigger problem.
(scroll-tests-with-buffer-window 20.5
(let ((show-trailing-whitespace t)
(scroll-conservatively 101)
(scroll-margin 5))
(insert (mapconcat #'number-to-string
(number-sequence 1 200) "\n"))
(goto-char 1)
(forward-line 15)
(sit-for 0)
(let ((window-line (count-lines (window-start) (window-point))))
(dotimes (_ 10)
(call-interactively 'next-line)
(sit-for 0)
(should (= window-line (count-lines (window-start)
(window-point)))))))))
(defun scroll-tests--point-in-middle-of-window-p ()
(= (count-lines (window-start) (window-point))
(/ (1- (floor (window-screen-lines))) 2)))
(cl-defun scroll-tests--scroll-margin-whole-window (&key with-line-spacing)
"Test `maximum-scroll-margin' at 0.5.
With a high `scroll-margin', this should keep cursor in the
middle of the window."
(let ((maximum-scroll-margin 0.5)
(scroll-margin 100))
;; Choose an odd number of lines, so there is a middle line.
(scroll-tests-with-buffer-window 7
(setq-local line-spacing with-line-spacing)
;; `set-window-text-height' doesn't count `line-spacing'.
(when with-line-spacing
(window-resize nil (* line-spacing 8) nil nil 'pixels))
(erase-buffer)
(insert (mapconcat #'number-to-string
(number-sequence 1 200) "\n"))
(goto-char 1)
(sit-for 0)
(call-interactively 'scroll-up-command)
(sit-for 0)
(should (scroll-tests--point-in-middle-of-window-p))
(call-interactively 'scroll-up-command)
(sit-for 0)
(should (scroll-tests--point-in-middle-of-window-p))
(call-interactively 'scroll-down-command)
(sit-for 0)
(should (scroll-tests--point-in-middle-of-window-p)))))
(ert-deftest scroll-tests-scroll-margin-whole-window ()
(skip-when noninteractive)
(scroll-tests--scroll-margin-whole-window))
(ert-deftest scroll-tests-scroll-margin-whole-window-line-spacing ()
;; `line-spacing' has no effect on tty displays.
(skip-unless (display-graphic-p))
(scroll-tests--scroll-margin-whole-window :with-line-spacing 3))
;;; scroll-tests.el ends here
|
