wined3d: Use lower 8 bits only from _ALPHAREF state.

dlls/wined3d/arb_program_shader.c

@@ -5945,7 +5945,7 @@ static void alpha_test_arbfp(struct wined3d_context *context, const struct wined
         return;
     }
 
-    ref = ((float)state->render_states[WINED3D_RS_ALPHAREF]) / 255.0f;
+    ref = wined3d_alpha_ref(state);
     glParm = wined3d_gl_compare_func(state->render_states[WINED3D_RS_ALPHAFUNC]);
 
     if (glParm)

dlls/wined3d/glsl_shader.c

@@ -2032,7 +2032,7 @@ static void shader_glsl_load_constants(void *shader_priv, struct wined3d_context
 
     if (update_mask & WINED3D_SHADER_CONST_PS_ALPHA_TEST)
     {
-        float ref = state->render_states[WINED3D_RS_ALPHAREF] / 255.0f;
+        float ref = wined3d_alpha_ref(state);
 
         GL_EXTCALL(glUniform1f(prog->ps.alpha_test_ref_location, ref));
         checkGLcall("alpha test emulation uniform");
@@ -12308,7 +12308,7 @@ static void glsl_fragment_pipe_alpha_test_func(struct wined3d_context *context,
 {
     const struct wined3d_gl_info *gl_info = context->gl_info;
     GLint func = wined3d_gl_compare_func(state->render_states[WINED3D_RS_ALPHAFUNC]);
-    float ref = state->render_states[WINED3D_RS_ALPHAREF] / 255.0f;
+    float ref = wined3d_alpha_ref(state);
 
     if (func)
     {

dlls/wined3d/state.c

@@ -681,7 +681,7 @@ void state_alpha_test(struct wined3d_context *context, const struct wined3d_stat
     }
     else
     {
-        ref = ((float)state->render_states[WINED3D_RS_ALPHAREF]) / 255.0f;
+        ref = wined3d_alpha_ref(state);
         glParm = wined3d_gl_compare_func(state->render_states[WINED3D_RS_ALPHAFUNC]);
     }
     if (glParm)

dlls/wined3d/wined3d_private.h

@@ -3100,6 +3100,11 @@ static inline BOOL isStateDirty(const struct wined3d_context *context, DWORD sta
     return context->isStateDirty[idx] & (1u << shift);
 }
 
+static inline float wined3d_alpha_ref(const struct wined3d_state *state)
+{
+    return (state->render_states[WINED3D_RS_ALPHAREF] & 0xff) / 255.0f;
+}
+
 const char *wined3d_debug_resource_access(DWORD access) DECLSPEC_HIDDEN;
 const char *wined3d_debug_bind_flags(DWORD bind_flags) DECLSPEC_HIDDEN;
 const char *wined3d_debug_view_desc(const struct wined3d_view_desc *d,