Work around Xlib 64-bit "specialness"

When putting 32-bit properties into longs on 64-bit architectures,
XGetWindowProperty assumes the values are supposed to be signed, and
so it sign-extends values greater than 0x7fffffff. So if they *aren't*
supposed to be signed, we need to chop off the high bits ourselves.

(Most CARDINAL-valued properties only end up using small values
anyway, so it doesn't matter, but _NET_WM_WINDOW_OPACITY uses the full
range, and so was previously failing on 64-bit machines.)

https://bugzilla.gnome.org/show_bug.cgi?id=605678

1 files changed, 14 insertions, 0 deletions

diff --git a/src/core/xprops.c b/src/core/xprops.c
index f9b4578a..82d28046 100644
--- a/src/core/xprops.c
+++ b/src/core/xprops.c
@@ -264,6 +264,16 @@ cardinal_list_from_results (GetPropertyResults *results,
   *n_cardinals_p = results->n_items;
   results->prop = NULL;
 
+#if GLIB_SIZEOF_LONG == 8
+  /* Xlib sign-extends format=32 items, but we want them unsigned */
+  {
+    int i;
+
+    for (i = 0; i < *n_cardinals_p; i++)
+      (*cardinals_p)[i] = (*cardinals_p)[i] & 0xffffffff;
+  }
+#endif
+
   return TRUE;
 }
 
@@ -608,6 +618,10 @@ cardinal_with_atom_type_from_results (GetPropertyResults *results,
     return FALSE;
 
   *cardinal_p = *(gulong*) results->prop;
+#if GLIB_SIZEOF_LONG == 8
+  /* Xlib sign-extends format=32 items, but we want them unsigned */
+  *cardinal_p &= 0xffffffff;
+#endif
   XFree (results->prop);
   results->prop = NULL;