From 0b0e0cbc947e357c8053c2837622094b00a422d5 Mon Sep 17 00:00:00 2001
From: Manuel Giraud <manuel@ledu-giraud.fr>
Date: Mon, 25 Nov 2024 17:04:03 +0100
Subject: [PATCH] An on-disk image modification does a cache miss

* src/dispextern.h: Add modification time to an image.
* src/image.c (make_image): Get the modification time from the
image file.
(lookup_image): Make a modified image on disk results in a cache
miss.
* lisp/startup.el (fancy-splash-head): Remove a non full-path
image file spec (XXX is there more?).
---
 lisp/startup.el  |  2 +-
 src/dispextern.h |  4 ++++
 src/image.c      | 26 ++++++++++++++++++++++++++
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/lisp/startup.el b/lisp/startup.el
index 3436409a35e..42f6e70f05d 100644
--- a/lisp/startup.el
+++ b/lisp/startup.el
@@ -1957,7 +1957,7 @@ fancy-splash-image-file
 (defun fancy-splash-head ()
   "Insert the head part of the splash screen into the current buffer."
   (let* ((image-file (fancy-splash-image-file))
-	 (img (create-image image-file))
+         (img (create-image (image-search-load-path image-file)))
 	 (image-width (and img (car (image-size img))))
 	 (window-width (window-width)))
     (when img
diff --git a/src/dispextern.h b/src/dispextern.h
index 9df6eaf623a..0f91568db99 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -3170,6 +3170,10 @@ reset_mouse_highlight (Mouse_HLInfo *hlinfo)
      in prepare_image_for_display.  */
   struct timespec timestamp;
 
+  /* The modification time of the file of this image.  Set in
+     make_image.  */
+  struct timespec mtime;
+
   /* Pixmaps of the image.  */
   Emacs_Pixmap pixmap, mask;
 
diff --git a/src/image.c b/src/image.c
index db7f6acd171..c5bddaf5985 100644
--- a/src/image.c
+++ b/src/image.c
@@ -37,6 +37,7 @@ Copyright (C) 1989-2024 Free Software Foundation, Inc.
 #include <stdint.h>
 #include <c-ctype.h>
 #include <flexmember.h>
+#include <stat-time.h>
 
 #include "lisp.h"
 #include "frame.h"
@@ -1744,6 +1745,7 @@ make_image (Lisp_Object spec, EMACS_UINT hash)
 {
   struct image *img = xzalloc (sizeof *img);
   Lisp_Object file = image_spec_value (spec, QCfile, NULL);
+  struct stat st;
 
   eassert (valid_image_p (spec));
   img->dependencies = NILP (file) ? Qnil : list1 (file);
@@ -1754,6 +1756,9 @@ make_image (Lisp_Object spec, EMACS_UINT hash)
   img->ascent = DEFAULT_IMAGE_ASCENT;
   img->hash = hash;
   img->corners[BOT_CORNER] = -1;  /* Full image */
+  /* Retrieve file mtime.  */
+  if (! NILP (file) && (emacs_fstatat (AT_FDCWD, SSDATA (file), &st, 0) == 0))
+    img->mtime = get_stat_mtime (&st);
   return img;
 }
 
@@ -3513,6 +3518,27 @@ lookup_image (struct frame *f, Lisp_Object spec, int face_id)
       img = NULL;
     }
 
+  /* If the on-disk image file has changed, this is also a cache
+     miss.  */
+  if (img)
+    {
+      Lisp_Object file;
+      bool found;
+
+      file = image_spec_value (spec, QCfile, &found);
+      if (found && STRINGP (file))
+	{
+	  struct stat st;
+
+	  if (emacs_fstatat (AT_FDCWD, SSDATA (file), &st, 0) != 0
+	      || timespec_cmp (get_stat_mtime (&st), img->mtime) != 0)
+	    {
+	      free_image (f, img);
+	      img = NULL;
+	    }
+	}
+    }
+
   /* If not found, create a new image and cache it.  */
   if (img == NULL)
     {
-- 
2.47.0