Subject: Re: xwidget-webkit-scroll-behaviour = image is non-functional

From: Paul Eggert <[email-masked]>
Date: Sat, 7 May 2016 17:21:45 -0700

[email-masked] wrote:
> Perhaps someone still prefers the 'image method though.

This seems unlikely, given that it recurses infinitely whenever it scrolls left
or right. Anyway, thanks for following up. If nobody objects I would like to
install the attached patch to emacs-25 to remove xwidget-webkit-scroll-behavior
and therefore fix the bug.
>From 58b7ecc4bcba46c775a7edca209587f034185861 Mon Sep 17 00:00:00 2001
From: Paul Eggert <[email-masked]>
Date: Sat, 7 May 2016 17:17:55 -0700
Subject: [PATCH] Remove buggy non-native image scrolling

This never worked, and could cause infinite recursion.
Problem reported by Glenn Morris (Bug#22465).
* lisp/xwidget.el (xwidget-webkit-scroll-behavior): Remove.
All uses removed.
---
 lisp/xwidget.el | 43 +++++++++----------------------------------
 1 file changed, 9 insertions(+), 34 deletions(-)

diff --git a/lisp/xwidget.el b/lisp/xwidget.el
index 19f631f..7a0ca8b 100644
--- a/lisp/xwidget.el
+++ b/lisp/xwidget.el
@@ -34,13 +34,6 @@
 (require 'cl-lib)
 (require 'bookmark)
 
-(defcustom xwidget-webkit-scroll-behavior 'native
-  "Scrolling behavior of the webkit instance.
-The possible values are: `native' or `image'."
-  :version "25.1"
-  :group 'frames   ; TODO add xwidgets group if more options are added
-  :type '(choice (const native) (const image)))
-
 (declare-function make-xwidget "xwidget.c"
                   (type title width height arguments &optional buffer))
 (declare-function xwidget-set-adjustment "xwidget.c"
@@ -141,40 +134,24 @@ xwidget-webkit-mode-map
   "Keymap for `xwidget-webkit-mode'.")
 
 (defun xwidget-webkit-scroll-up ()
-  "Scroll webkit up.
-Depending on the value of `xwidget-webkit-scroll-behavior',
-this scrolls in `native' fashion, or like `image-mode' would."
+  "Scroll webkit up."
   (interactive)
-  (if (eq xwidget-webkit-scroll-behavior 'native)
-      (xwidget-set-adjustment (xwidget-webkit-last-session) 'vertical t 50)
-    (image-scroll-up)))
+  (xwidget-set-adjustment (xwidget-webkit-last-session) 'vertical t 50))
 
 (defun xwidget-webkit-scroll-down ()
-  "Scroll webkit down.
-Depending on the value of `xwidget-webkit-scroll-behavior',
-this scrolls in `native' fashion, or like `image-mode' would."
+  "Scroll webkit down."
   (interactive)
-  (if (eq xwidget-webkit-scroll-behavior 'native)
-      (xwidget-set-adjustment (xwidget-webkit-last-session) 'vertical t -50)
-    (image-scroll-down)))
+  (xwidget-set-adjustment (xwidget-webkit-last-session) 'vertical t -50))
 
 (defun xwidget-webkit-scroll-forward ()
-  "Scroll webkit forwards.
-Depending on the value of `xwidget-webkit-scroll-behavior',
-this scrolls in `native' fashion, or like `image-mode' would."
+  "Scroll webkit forwards."
   (interactive)
-  (if (eq xwidget-webkit-scroll-behavior 'native)
-      (xwidget-set-adjustment (xwidget-webkit-last-session) 'horizontal t 50)
-    (xwidget-webkit-scroll-forward)))   ; FIXME infloop!
+  (xwidget-set-adjustment (xwidget-webkit-last-session) 'horizontal t 50))
 
 (defun xwidget-webkit-scroll-backward ()
-  "Scroll webkit backwards.
-Depending on the value of `xwidget-webkit-scroll-behavior',
-this scrolls in `native' fashion, or like `image-mode' would."
+  "Scroll webkit backwards."
   (interactive)
-  (if (eq xwidget-webkit-scroll-behavior 'native)
-      (xwidget-set-adjustment (xwidget-webkit-last-session) 'horizontal t -50)
-    (xwidget-webkit-scroll-backward))) ; FIXME infloop!
+  (xwidget-set-adjustment (xwidget-webkit-last-session) 'horizontal t -50))

 ;; The xwidget event needs to go into a higher level handler
@@ -417,9 +394,7 @@ xwidget-webkit-adjust-size-to-content
 (defun xwidget-webkit-adjust-size-dispatch ()
   "Adjust size according to mode."
   (interactive)
-  (if (eq xwidget-webkit-scroll-behavior 'native)
-      (xwidget-webkit-adjust-size-to-window)
-    (xwidget-webkit-adjust-size-to-content))
+  (xwidget-webkit-adjust-size-to-window)
   ;; The recenter is intended to correct a visual glitch.
   ;; It errors out if the buffer isn't visible, but then we don't get
   ;; the glitch, so silence errors.
-- 
2.7.4