[PATCH v2 3/3] win32u: Return -1 for NUMCOLORS with 8-bit display DCs.

[Zhiyi Zhang]

According to tests, GetDeviceCaps(NUMCOLORS) returns -1 for display DCs when the current display
mode is 8-bit on newer versions of Windows, which makes sense because lower bit depth display modes
are actually emulated with 32-bit modes.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=52679
Signed-off-by: Zhiyi Zhang <zzhang at codeweavers.com>
---
 dlls/user32/tests/monitor.c | 2 +-
 dlls/win32u/driver.c        | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/dlls/user32/tests/monitor.c b/dlls/user32/tests/monitor.c
index e595072c747..02bc6651dd3 100644
--- a/dlls/user32/tests/monitor.c
+++ b/dlls/user32/tests/monitor.c
@@ -3,6 +3,7 @@
  *
  * Copyright 2005 Huw Davies
  * Copyright 2008 Dmitry Timoshkov
+ * Copyright 2019-2022 Zhiyi Zhang for CodeWeavers
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -2314,7 +2315,6 @@ static void test_display_dc(void)
 
             value = GetDeviceCaps(hdc, NUMCOLORS);
             if (bpps[i] > 8 || (bpps[i] == 8 && LOBYTE(LOWORD(GetVersion())) >= 6))
-                todo_wine_if(bpps[i] == 8 && LOBYTE(LOWORD(GetVersion())) >= 6)
                 ok(value == -1, "Expected -1, got %d.\n", value);
             else if (bpps[i] == 8 && LOBYTE(LOWORD(GetVersion())) < 6)
                 ok(value > 16 && value <= 256, "Got %d.\n", value);
diff --git a/dlls/win32u/driver.c b/dlls/win32u/driver.c
index 6b6f1a64ce8..c162a68c924 100644
--- a/dlls/win32u/driver.c
+++ b/dlls/win32u/driver.c
@@ -294,7 +294,8 @@ static INT CDECL nulldrv_GetDeviceCaps( PHYSDEV dev, INT cap )
     case LOGPIXELSY:      return get_system_dpi();
     case NUMCOLORS:
         bpp = NtGdiGetDeviceCaps( dev->hdc, BITSPIXEL );
-        return (bpp > 8) ? -1 : (1 << bpp);
+        /* Newer versions of Windows return -1 for 8-bit and higher */
+        return (bpp > 4) ? -1 : (1 << bpp);
     case COLORRES:
         /* The observed correspondence between BITSPIXEL and COLORRES is:
          * BITSPIXEL: 8  -> COLORRES: 18
-- 
2.32.0