added note about _TriangleCaps
diff --git a/docs/RELNOTES-5.1 b/docs/RELNOTES-5.1
index f002cb0..5029b86 100644
--- a/docs/RELNOTES-5.1
+++ b/docs/RELNOTES-5.1
@@ -161,6 +161,13 @@
If a bit is set in the ctx->Texture._EnabledUnits bitmask is set, the
same bit MUST be set in ctx->Texture._EnabledCoordUnits.
+The ctx->_TriangleCaps field is deprecated.
+ Instead of testing the DD_* bits in _TriangleCaps, you should instead
+ directly test the relevant state variables, or use one of the helper
+ functions like NEED_SECONDARY_COLOR() at the bottom of context.h
+ While testing _TriangleCaps bits was fast, it was kludgey, and setting
+ the bits in the first place could be error prone.
+
To Do