Improve image cache clearing logic (Bug#6230).

* xdisp.c (redisplay_internal): Clear caches even if redisplaying
just one window.

* image.c (Vimage_cache_eviction_delay): Decrease to 300.
(clear_image_cache): If the number of cached images is unusually
large, decrease the cache eviction delay.

3 files changed, 75 insertions, 33 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index d74fb712e6d..f0613a57405 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,12 @@
+2010-05-21  Chong Yidong  <cyd@stupidchicken.com>
+
+        * xdisp.c (redisplay_internal): Clear caches even if redisplaying
+        just one window.
+
+        * image.c (Vimage_cache_eviction_delay): Decrease to 300.
+        (clear_image_cache): If the number of cached images is unusually
+        large, decrease the cache eviction delay (Bug#6230).
+
 2010-05-21  Glenn Morris  <rgm@gnu.org>
 
         * Makefile.in (${ns_appdir}, ${ns_appbindir}Emacs, ns-app):
diff --git a/src/image.c b/src/image.c
index 030e06ad77a..5d4f50ee85e 100644
--- a/src/image.c
+++ b/src/image.c
@@ -1582,29 +1582,56 @@ clear_image_cache (struct frame *f, Lisp_Object filter)
 {
   struct image_cache *c = FRAME_IMAGE_CACHE (f);
 
-  if (c && (!NILP (filter) || INTEGERP (Vimage_cache_eviction_delay)))
+  if (c)
     {
-      EMACS_TIME t;
-      unsigned long old;
-      int i, nfreed;
-
-      EMACS_GET_TIME (t);
-      old = EMACS_SECS (t) - XFASTINT (Vimage_cache_eviction_delay);
+      int i, nfreed = 0;
 
       /* Block input so that we won't be interrupted by a SIGIO
          while being in an inconsistent state.  */
       BLOCK_INPUT;
 
-      for (i = nfreed = 0; i < c->used; ++i)
+      if (!NILP (filter))
+        {
+          /* Filter image cache.  */
+          for (i = 0; i < c->used; ++i)
+            {
+              struct image *img = c->images[i];
+              if (img && (EQ (Qt, filter)
+                          || !NILP (Fmember (filter, img->dependencies))))
+                {
+                  free_image (f, img);
+                  ++nfreed;
+                }
+            }
+        }
+      else if (INTEGERP (Vimage_cache_eviction_delay))
         {
-          struct image *img = c->images[i];
-          if (img != NULL
-              && (NILP (filter) ? img->timestamp < old
-                  : (EQ (Qt, filter)
-                     || !NILP (Fmember (filter, img->dependencies)))))
+          /* Free cache based on timestamp.  */
+          EMACS_TIME t;
+          unsigned long old;
+          int delay, nimages = 0;
+
+          for (i = 0; i < c->used; ++i)
+            if (c->images[i])
+              nimages++;
+
+          /* If the number of cached images has grown unusually large,
+             decrease the cache eviction delay (Bug#6230).  */
+          delay = XFASTINT (Vimage_cache_eviction_delay);
+          if (nimages > 40)
+            delay = max (1, 1600 * delay / (nimages*nimages));
+
+          EMACS_GET_TIME (t);
+          old = EMACS_SECS (t) - delay;
+
+          for (i = 0; i < c->used; ++i)
             {
-              free_image (f, img);
-              ++nfreed;
+              struct image *img = c->images[i];
+              if (img && img->timestamp < old)
+                {
+                  free_image (f, img);
+                  ++nfreed;
+                }
             }
         }
 
@@ -8520,11 +8547,14 @@ A cross is always drawn on black & white displays.  */);
   Vx_bitmap_file_path = decode_env_path ((char *) 0, PATH_BITMAPS);
 
   DEFVAR_LISP ("image-cache-eviction-delay", &Vimage_cache_eviction_delay,
-    doc: /* Time after which cached images are removed from the cache.
-When an image has not been displayed this many seconds, remove it
-from the image cache.  Value must be an integer or nil with nil
-meaning don't clear the cache.  */);
-  Vimage_cache_eviction_delay = make_number (30 * 60);
+    doc: /* Maximum time after which images are removed from the cache.
+When an image has not been displayed this many seconds, Emacs
+automatically removes it from the image cache.  If the cache contains
+a large number of images, the actual eviction time may be shorter.
+The value can also be nil, meaning the cache is never cleared.
+
+The function `clear-image-cache' disregards this variable.  */);
+  Vimage_cache_eviction_delay = make_number (300);
 }
 
 void
diff --git a/src/xdisp.c b/src/xdisp.c
index 6b3097c9a1a..2ff12730b8a 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -12499,22 +12499,25 @@ redisplay_internal (preserve_echo_area)
   if (windows_or_buffers_changed && !pause)
     goto retry;
 
-  /* Clear the face cache eventually.  */
-  if (consider_all_windows_p)
+  /* Clear the face and image caches.
+
+     We used to do this only if consider_all_windows_p.  But the cache
+     needs to be cleared if a timer creates images in the current
+     buffer (e.g. the test case in Bug#6230).  */
+
+  if (clear_face_cache_count > CLEAR_FACE_CACHE_COUNT)
     {
-      if (clear_face_cache_count > CLEAR_FACE_CACHE_COUNT)
-        {
-          clear_face_cache (0);
-          clear_face_cache_count = 0;
-        }
+      clear_face_cache (0);
+      clear_face_cache_count = 0;
+    }
+
 #ifdef HAVE_WINDOW_SYSTEM
-      if (clear_image_cache_count > CLEAR_IMAGE_CACHE_COUNT)
-        {
-          clear_image_caches (Qnil);
-          clear_image_cache_count = 0;
-        }
-#endif /* HAVE_WINDOW_SYSTEM */
+  if (clear_image_cache_count > CLEAR_IMAGE_CACHE_COUNT)
+    {
+      clear_image_caches (Qnil);
+      clear_image_cache_count = 0;
     }
+#endif /* HAVE_WINDOW_SYSTEM */
 
  end_of_redisplay:
   unbind_to (count, Qnil);