bug#10397: [PATCH] Under Remote Desktop, NUMCOLORS is unreliable; workaround

[Daniel Colascione]

Under remote desktop, Windows returns the wrong number of colors from
GetDeviceCaps (hdc, NUMCOLORS).  I hit this bug myself, and MSDN
comments seem to indicate that others hit it as well.  The workaround
seems harmless: on non-palettized displays, calculating the number of
display colors based on display bitness should produce good results.
---
 src/w32fns.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/src/w32fns.c b/src/w32fns.c
index 822e353..4b94f16 100644
--- a/src/w32fns.c
+++ b/src/w32fns.c
@@ -4510,7 +4510,10 @@ If omitted or nil, that stands for the selected frame's 
display.  */)
   if (dpyinfo->has_palette)
     cap = GetDeviceCaps (hdc, SIZEPALETTE);
   else
-    cap = GetDeviceCaps (hdc, NUMCOLORS);
+    // GetDeviceCaps (NUMCOLORS) is buggy under remote desktop and sometimes
+    // returns the number of system reserved colors (20) instead of
+    // the actual number of available colors.
+    cap = -1;
 
   /* We force 24+ bit depths to 24-bit, both to prevent an overflow
      and because probably is more meaningful on Windows anyway */
-- 
1.7.5.1