1 files changed, 15 insertions, 6 deletions

diff --git a/src/image.c b/src/image.c
index d9b7101d658..06a8154842c 100644
--- a/src/image.c
+++ b/src/image.c
@@ -3028,6 +3028,7 @@ enum xbm_keyword_index
   XBM_FILE,
   XBM_WIDTH,
   XBM_HEIGHT,
+  XBM_STRIDE,
   XBM_DATA,
   XBM_FOREGROUND,
   XBM_BACKGROUND,
@@ -3049,6 +3050,7 @@ static const struct image_keyword xbm_format[XBM_LAST] =
   {":file",             IMAGE_STRING_VALUE,                     0},
   {":width",            IMAGE_POSITIVE_INTEGER_VALUE,           0},
   {":height",           IMAGE_POSITIVE_INTEGER_VALUE,           0},
+  {":stride",           IMAGE_POSITIVE_INTEGER_VALUE,           0},
   {":data",             IMAGE_DONT_CHECK_VALUE_TYPE,            0},
   {":foreground",       IMAGE_STRING_OR_NIL_VALUE,              0},
   {":background",       IMAGE_STRING_OR_NIL_VALUE,              0},
@@ -3124,7 +3126,7 @@ xbm_image_p (Lisp_Object object)
   else
     {
       Lisp_Object data;
-      int width, height;
+      int width, height, stride;
 
       /* Entries for `:width', `:height' and `:data' must be present.  */
       if (!kw[XBM_WIDTH].count
@@ -3136,6 +3138,11 @@ xbm_image_p (Lisp_Object object)
       width = XFIXNAT (kw[XBM_WIDTH].value);
       height = XFIXNAT (kw[XBM_HEIGHT].value);
 
+      if (!kw[XBM_STRIDE].count)
+        stride = width;
+      else
+        stride = XFIXNAT (kw[XBM_STRIDE].value);
+
       /* Check type of data, and width and height against contents of
          data.  */
       if (VECTORP (data))
@@ -3154,8 +3161,7 @@ xbm_image_p (Lisp_Object object)
 
               if (STRINGP (elt))
                 {
-                  if (SCHARS (elt)
-                      < (width + CHAR_BIT - 1) / CHAR_BIT)
+                  if (SCHARS (elt) < stride / CHAR_BIT)
                     return 0;
                 }
               else if (BOOL_VECTOR_P (elt))
@@ -3169,13 +3175,16 @@ xbm_image_p (Lisp_Object object)
         }
       else if (STRINGP (data))
         {
-          if (SCHARS (data)
-              < (width + CHAR_BIT - 1) / CHAR_BIT * height)
+          if (SCHARS (data) < stride / CHAR_BIT * height)
             return 0;
         }
       else if (BOOL_VECTOR_P (data))
         {
-          if (bool_vector_size (data) / height < width)
+          if (height > 1 && stride != (width + CHAR_BIT - 1)
+              / CHAR_BIT * CHAR_BIT)
+            return 0;
+
+          if (bool_vector_size (data) / height < stride)
             return 0;
         }
       else