From 20e8da9dfd9bd10a6531369b1f675a2f7de0a2e5 Mon Sep 17 00:00:00 2001
From: ManoloFLTK <41016272+ManoloFLTK@users.noreply.github.com>
Date: Mon, 11 Mar 2024 11:36:47 +0100
Subject: Fix: Filechooser preview of XML file shows it as a corrupt image
 (#926)

---
 src/fl_images_core.cxx | 36 ++++++++++++------------------------
 1 file changed, 12 insertions(+), 24 deletions(-)

(limited to 'src')

diff --git a/src/fl_images_core.cxx b/src/fl_images_core.cxx
index de34fe3e9..d9f8d41a5 100644
--- a/src/fl_images_core.cxx
+++ b/src/fl_images_core.cxx
@@ -36,7 +36,6 @@
 #include <FL/fl_utf8.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
 #include "flstring.h"
 #if defined(HAVE_LIBZ)
 #include <zlib.h>
@@ -126,22 +125,12 @@ fl_check_images(const char *name,               // I - Filename
   // SVG or SVGZ (gzip'ed SVG)
 
 #ifdef FLTK_USE_SVG
-  uchar header2[300];     // buffer for decompression
+  uchar header2[64];      // buffer for decompression
   uchar *buf = header;    // original header data
   int count = headerlen;  // original header data size
 
   // Note: variables 'buf' and 'count' may be overwritten subsequently
-  // if the image data is xml or gzip'ed *and* we can decompress the data
-  
-  if (count >= 5 && memcmp(header, "<?xml", 5) == 0) {
-    FILE *in = fl_fopen(name, "r");
-    if (in) {
-      buf = header2;
-      count = sizeof(header2);
-      count = fread(header2, 1, count, in);
-      fclose(in);
-    }
-  }
+  // if the image data is gzip'ed *and* we can decompress the data
 
 # if defined(HAVE_LIBZ)
   if (header[0] == 0x1f && header[1] == 0x8b) { // gzip'ed data
@@ -169,18 +158,17 @@ fl_check_images(const char *name,               // I - Filename
   }
 
   // Check svg or xml signature
-  bool found_svg = false;
-  if (count >= 4 && memcmp(buf, "<svg", 4) == 0) found_svg = true;
-  else if (count >= 5 && memcmp(buf, "<?xml", 5) == 0) {
-    uchar *p = buf;
-    do {
-      if (memcmp(p, "<svg", 4) == 0) {
-        found_svg = true;
-        break;
-      }
-    } while (++p < buf + count - 4);
+
+  while (count && isspace(buf[0])) { buf++; count--; }
+  if ((count >= 5 &&
+       (memcmp(buf, "<?xml", 5) == 0 ||
+        memcmp(buf, "<svg", 4) == 0  ||
+        memcmp(buf, "<!--", 4) == 0))) {
+    Fl_SVG_Image *image = new Fl_SVG_Image(name);
+    if (image->w() && image->h())
+      return image;
+    delete image;
   }
-  if (found_svg) return new Fl_SVG_Image(name);
 #endif // FLTK_USE_SVG
 
   // unknown image format
-- 
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