* xfns.c (Fx_display_color_cells): Use number of planes to calculate

how many colors can be displayed.

2 files changed, 16 insertions, 2 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 742e2c3dabc..bd641e8f6fb 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2004-03-01  Jan Dj,Ad(Brv  <jan.h.d@swipnet.se>
+
+        * xfns.c (Fx_display_color_cells): Use number of planes to calculate
+        how many colors can be displayed.
+
 2004-03-01  Kenichi Handa  <handa@m17n.org>
 
         * editfns.c (Ftranslate_region): Handle multibyte chars in TABLE
diff --git a/src/xfns.c b/src/xfns.c
index a3e885bac74..3028a61018c 100644
--- a/src/xfns.c
+++ b/src/xfns.c
@@ -3758,8 +3758,17 @@ If omitted or nil, that stands for the selected frame's display.  */)
 {
   struct x_display_info *dpyinfo = check_x_display_info (display);
 
-  return make_number (DisplayCells (dpyinfo->display,
-                                    XScreenNumberOfScreen (dpyinfo->screen)));
+  int nr_planes = DisplayPlanes (dpyinfo->display,
+                                 XScreenNumberOfScreen (dpyinfo->screen));
+
+  /* Truncate nr_planes to 24 to avoid integer overflow.
+     Some displays says 32, but only 24 bits are actually significant.
+     There are only very few and rare video cards that have more than
+     24 significant bits.  Also 24 bits is more than 16 million colors,
+     it "should be enough for everyone".  */
+  if (nr_planes > 24) nr_planes = 24;
+
+  return make_number (1 << nr_planes);
 }
 
 DEFUN ("x-server-max-request-size", Fx_server_max_request_size,