mesa: Add helper function _mesa_is_alpha_test_enabled()

Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>

src/mesa/main/framebuffer.c

@@ -1005,3 +1005,14 @@ _mesa_is_multisample_enabled(const struct gl_context *ctx)
           ctx->DrawBuffer &&
           _mesa_geometric_nonvalidated_samples(ctx->DrawBuffer) > 1;
 }
+
+/**
+ * Is alpha testing enabled and applicable to the currently bound
+ * framebuffer?
+ */
+bool
+_mesa_is_alpha_test_enabled(const struct gl_context *ctx)
+{
+   bool buffer0_is_integer = ctx->DrawBuffer->_IntegerBuffers & 0x1;
+   return (ctx->Color.AlphaEnabled && !buffer0_is_integer);
+}

src/mesa/main/framebuffer.h

@@ -149,4 +149,7 @@ _mesa_is_front_buffer_drawing(const struct gl_framebuffer *fb);
 extern bool
 _mesa_is_multisample_enabled(const struct gl_context *ctx);
 
+extern bool
+_mesa_is_alpha_test_enabled(const struct gl_context *ctx);
+
 #endif /* FRAMEBUFFER_H */