master db1b1f0: Use a new method to determine when to auto-stop image animations

[Lars Ingebrigtsen]

branch: master
commit db1b1f09b820efeefa60a49684c06d511b70eecb
Author: Lars Ingebrigtsen <larsi@gnus.org>
Commit: Lars Ingebrigtsen <larsi@gnus.org>

    Use a new method to determine when to auto-stop image animations
    
    * lisp/image.el (image-animate-timeout): Make the animation
    auto-stop use a decaying average to determine when to stop
    (bug#40685).  The default stop condition will probably require
    some tweaking -- the current default may be too aggressive.
---
 etc/NEWS      |  9 +++++++++
 lisp/image.el | 10 ++++++++--
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/etc/NEWS b/etc/NEWS
index 4c77162..e4d9887 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -490,6 +490,15 @@ more readable text.  Set this variable to nil to get the 
previous
 behavior of rendering as wide as the window-width allows.  If
 'shr-width' is non-nil, it overrides this variable.
 
+** Images
+
+---
+*** Animated images stop automatically under high CPU pressure sooner.
+Previously, an animated image would stop animating if any single image
+took more than two seconds to display.  The new algorithm maintains a
+decaying average of delays, and if this number gets too high, the
+animation is stopped.
+
 ** EWW
 
 +++
diff --git a/lisp/image.el b/lisp/image.el
index 4ea8594..4b2faa9 100644
--- a/lisp/image.el
+++ b/lisp/image.el
@@ -784,6 +784,7 @@ number, play until that number of seconds has elapsed."
       (if (setq timer (image-animate-timer image))
          (cancel-timer timer))
       (plist-put (cdr image) :animate-buffer (current-buffer))
+      (plist-put (cdr image) :animate-tardiness 0)
       (run-with-timer 0.2 nil #'image-animate-timeout
                      image (or index 0) (car animation)
                      0 limit (+ (float-time) 0.2)))))
@@ -848,9 +849,14 @@ The minimum delay between successive frames is 
`image-minimum-frame-delay'.
 
 If the image has a non-nil :speed property, it acts as a multiplier
 for the animation speed.  A negative value means to animate in reverse."
+  ;; We keep track of "how late" image frames arrive.  We decay the
+  ;; previous cumulative value by 10% and then add the current delay.
+  (plist-put (cdr image) :animate-tardiness
+             (+ (* (plist-get (cdr image) :animate-tardiness) 0.9)
+                (float-time (time-since target-time))))
   (when (and (buffer-live-p (plist-get (cdr image) :animate-buffer))
-             ;; Delayed more than two seconds more than expected.
-            (or (time-less-p (time-since target-time) 2)
+             ;; Cumulatively delayed two seconds more than expected.
+             (or (< (plist-get (cdr image) :animate-tardiness) 2)
                 (progn
                   (message "Stopping animation; animation possibly too big")
                   nil)))